Phosphorus distribution, forms and dynamics of
riparian zone peat wetland in Kristianstad district,
Southern Sweden
Fosfordistribution, former och dynamik i torvvåtmark i
Kristiandstadsområdet, södra Sverige
Master of Science Thesis (Examensarbete) 140, 2004
Ann Fristedt
Supervisors:
Professor Erasmus Otabbong
Department of Soil Sciences
Swedish University of Agricultural Sciences (SLU)
P.O. Box 7014,
SE 750 07 UPPSALA Sweden
Dr. Elve Lode
Department of Forest Soils (SLU)
P.O. Box 7001
SE 750 07 UPPSALA, Sweden
Abstract
Fristedt, A. 2004. Phosphorus distribution forms and dynamics of riparian zone peat wetland
in Kristianstad district, Southern Sweden. MSc Thesis.
The objectives of this study were to determine total phosphorus (P) status and distribution in
the soil profile and to evaluate the impact of season on P dynamics. The soil was taken from a
riparian zone peat wetland in Kristianstad district, Southern Sweden. The wetland is adjacent
to the nutrient rich-stream Vinneå, which inundates the site regularly, especially during winter
and spring. The soil samples were taken at 20 cm intervals down to a depth of 1 m. Three
replicates were taken in each layer. Samples were taken on five occasions (September,
October, November 2000 and April, June 2001). The samples were air-dried, crushed and
sieved (≤ 2mm). A sequential fractionation was then conducted in four stages using: anion
exchanger (resin) → 0.5 M NaHCO3 → 0.1 M NaOH → 1 M HCl. Furthermore, Total-P was
determined by fusion and P extracted by NaHCO3 and NaOH was broken into organic P (OP)
and inorganic P (IP). By subtracting P extracted by resin, NaHCO3, NaOH and HCl from
Total-P, a value for Residual-P was obtained.
The Total-P content varied between 1434 and 4319 mg/kg in the profile and most P was
organically bound (66-79% of Total-P). The highest amounts of P (2553-4319 mg/kg) were
found in the upper 40 cm of the profile. The Total-P content decreased during the winter. The
results show that P extracted by NaOH and NaHCO3 and Residual-P made up about 95-97%
of Total-P. Most transformations seemed to occur in spring and early summer. pH varied
between 3.9 and 5.3. Pearson’s linear correlation coefficient suggested significant
redistribution among NaHCO3-P into NaOH-P and Residual-P or vice versa. It also suggested
significant redistribution among HCl-P into Residual-P and NaOH-P or vice versa.
In this study, only soil samples were examined but it would be interesting to investigate
inflows and outflows of P via the inundating river or percolating groundwater. The uptake in
plants and the input via the large flocks of geese that spend the winter in southern Sweden
also require investigation.
Key words: phosphorus forms, fractionation, riparian wetland, peat, season, Southern Sweden
2
Sammanfattning (Swedish summary)
Fosfor (P) är en begränsande faktor för primärproduktionen, speciellt i vattensystem. En
överbelastnig av näringsämnen (eutrfiering) i tex sjöar kan orsaka obalans i ekosystemet med
ökad primärproduktion. I slutändan kan detta orsaka snabbare igenväxning och syrebrist på
botten. Eutrofiering kan leda till förändring av artsamhällets sammansättning där blågrönalger
tar över. Dessa alger är ofta toxinbildande och många arter har dessutom den
konkurrensfördelen att kunna fixera luftkväve (N2). Sjöar övergår naturligt till ett eutrofierat
stadie i dess succession. Mänskliga aktiviteter påskyndar denna succession genom diverse
utsläpp, så kallad kulturell eutrofiering. En del av den överflödiga näringen har sitt ursprung i
jordbrukslandskapet, där P lakas ut genom marken eller via partiklar och ytavrinning. Få P
undersökningar har dock gjorts på mark som inte brukas och som är vegetationstäckta året
om. Denna studie gick ut på att undersöka jorden på en obrukad äng med avseende på P.
Studien utfördes inom EU-projektet PROWATER på en provplats i Kristianstad området i
södra Sverige. Platsen som valdes är en slåtteräng där jorden består av torv. Ängen
översvämmas årligen under vinter och vår av den intill liggande näringsrika Vinneå.
Hypotesen för studien var: Markfosfor omvandlas och dess former omfördelas i varandra
beroende på säsong. Hypotesen prövades genom att 1) Bestämma totalfosfor status och
distribution i marksprofilen; 2) Dela upp totalfosfor i olika fraktioner; 3) Utvärdera
säsongernas påverkan på fosfordynamik. Jordprover togs på olika djup med 20 cm intervall
ner till ett djup på 1 m. Tre replikat togs vid varje djup och prover togs vid fem tillfällen
(September, Oktober, November 2000 och April, Juni 2001). Proverna lufttorkades, maldes
och silades (≤2 mm). En stegvis fraktionering med avseende på P gjordes: anjon bytare (resin)
→ 0,5 M NaHCO3 → 0,1 M NaOH → 1 M HCl. Total-P bestämdes genom föraskning och
uppslutning. Fraktionerna utlösta av NaHCO3 och NaOH delades dessutom upp i oorganiskt P
(IP) och organiskt P (OP). P som inte gick att lösa ut i fraktioneringen, kallad Residual-P,
erhölls genom att subtrahera P extraherat med resin, NaHCO3, NaOH och HCl från Total-P.
Total-P varierade mellan 1434 och 4319 mg/kg i profilen. Den största mängden P (2553 –
4319 mg/kg) fanns i de översta 40 cm i profilen. P var till största delen organiskt bundet (6679 % av Total-P). Resultaten visar att P extraherat med NaHCO3, NaOH och Residual-P
utgjorde 95-97% av Total-P. Under vintern sjönk mängden Total-P och de största
omvandlingarna verkade ske under våren och tidig sommar. pH varierade mellan 3,9 och 5,3.
Vid en korrelationsberäkning mellan P fraktionerna visade det sig att P extraherat av NaHCO3
verkade övergå i Residual-P och i P extraherat med NaOH och vice versa. Likadant var det
för P extraherat med HCl som verkade övergå i Residual-P och i P extraherat med NaOH och
vice versa. Den här studien innefattade bara prover tagna i jord, därför skulle det vara mycket
intressant att vidare undersöka in- och utflödet av P via tex den näringsrika Vinneå och via
markvattnet. Växternas upptag skulle också vara intressant att undersöka.
3
Contents
ABSTRACT........................................................................................................................................................... 2
SAMMANFATTNING (SWEDISH SUMMARY)............................................................................................. 3
CONTENTS........................................................................................................................................................... 4
INTRODUCTION................................................................................................................................................. 6
1. WETLANDS...................................................................................................................................................... 7
1.1 STREAMS AND RIPARIAN ZONE WETLANDS .................................................................................................... 7
1.2 WETLAND HYDROLOGY................................................................................................................................. 8
1.2.1 Climatic factors for Scandinavia .......................................................................................................... 9
1.3 WETLAND VEGETATION .............................................................................................................................. 10
1.4 HUMAN IMPACT ON RIPARIAN ZONE WETLANDS .......................................................................................... 10
2. WETLAND SOILS ......................................................................................................................................... 12
3. NUTRIENT UPTAKE BY PLANTS............................................................................................................. 14
3.1 PLANT NUTRITION ....................................................................................................................................... 14
3.2 FUNCTION OF THE ROOT SYSTEM ................................................................................................................. 14
3.2.1 Microorganisms in soil....................................................................................................................... 14
3.2.2 Root hairs and mycorrhizae................................................................................................................ 15
4. PHOSPHORUS ............................................................................................................................................... 16
4.1 PHOSPHORUS IN SOIL ................................................................................................................................... 16
4.1.1 Phosphorus in soil solution ................................................................................................................ 16
4.1.2 Phosphorus adsorption....................................................................................................................... 16
4.1.3 Phosphorus in minerals ...................................................................................................................... 17
4.1.4 Phosphorus in organic matter ............................................................................................................ 17
4.2 PHOSPHORUS RELEASE BY MICROORGANISMS AND ENZYMES...................................................................... 17
4.3 PHOSPHORUS-CYCLE IN WATERLOGGED SOILS ............................................................................................ 18
5. MATERIALS AND METHODS.................................................................................................................... 20
5.1. SITE DESCRIPTION ...................................................................................................................................... 20
5.1.1 History ................................................................................................................................................ 20
5.1.2 Streams influencing the site area........................................................................................................ 20
5.1.2.1. Water level fluctuation............................................................................................................... 21
5.1.3 Vegetation........................................................................................................................................... 22
5.1.4 Soil profile at the site.......................................................................................................................... 23
5.2 CLIMATE DURING THE STUDY PERIOD.......................................................................................................... 23
5.3. METHOD FOR PHOSPHORUS FRACTIONATION AND ANALYSIS ..................................................................... 24
5.3.1. Phosphorus fractionation and fraction description ........................................................................... 24
5.3.2. Phosphorus analysis .......................................................................................................................... 26
5.3.3. pH analysis ........................................................................................................................................ 27
5.3.4. Statistics............................................................................................................................................. 27
6. RESULTS AND DISCUSSION ..................................................................................................................... 28
6.1 PHOSPHORUS FRACTIONS AND PH ............................................................................................................... 28
6.1.1. Bicarbonate Organic and Inorganic Phosphorus.............................................................................. 29
6.1.2. Hydroxide Organic and Inorganic Phosphorus ................................................................................ 30
6.1.3. Total Organic and Inorganic Phosphorus......................................................................................... 31
6.1.4. pH ...................................................................................................................................................... 32
6.2. PHOSPHORUS FRACTIONS AND PH AT DIFFERENT DEPTHS AND DATES ........................................................ 33
6.2.1. Total Phosphorus............................................................................................................................... 33
6.2.2. Resin-extractable Phosphorus ........................................................................................................... 34
6.2.3. Bicarbonate-soluble Phosphorus....................................................................................................... 34
6.2.3.1. Bicarbonate-soluble Organic and Inorganic Phosphorus ......................................................... 35
6.2.4. Hydroxide-soluble Phosphorus ......................................................................................................... 36
6.2.4.1. Hydroxide-soluble Organic and Inorganic Phosphorus............................................................ 37
4
6.2.5 Hydrochloric acid-soluble Phosphorus .............................................................................................. 38
6.2.6. Residual Phosphorus ......................................................................................................................... 39
6.2.7. pH ...................................................................................................................................................... 40
6.3 CORRELATIONS ........................................................................................................................................... 41
6.4. GENERAL DISCUSSION ................................................................................................................................ 42
7. CONCLUSIONS ............................................................................................................................................. 44
7.1. CONCLUDING REMARKS ............................................................................................................................. 44
8. ACKNOWLEDGEMENTS............................................................................................................................ 45
9. REFERENCES................................................................................................................................................ 46
10. APPENDICES ............................................................................................................................................... 49
APPENDIX 1. TABLES A1-A36: RAW DATA ....................................................................................................... 49
APPENDIX 2. FIGURES A1-A5: PHOSPHORUS FRACTIONS AS A PERCENTAGE OF TOTAL PHOSPHORUS .............. 58
APPENDIX 3. FIGURES A6-A13: BICARBONATE AND HYDROXIDE INORGANIC AND ORGANIC PHOSPHORUS .... 61
APPENDIX 4. TABLE A37: WEATHER DATA ....................................................................................................... 65
APPENDIX 5. FIGURES A14-A19: PHOTOS OF THE SITE AREA ............................................................................ 66
5
Introduction
Phosphorus (P) is a limiting factor for primary production (Horne & Goldman, 1994; Havlin
et al., 1999). An unnatural load of P may disturb the balance in e.g. lake ecosystems. Natural
lakes usually go through different trophic stages, from oligotrophic (low nutrient levels) to
eutrophic (high nutrient levels, high primary production), during the succession phase. During
ageing, lakes finally become overgrown with grass and trees and may turn into a marsh or
even dry land. The rate of natural eutrophication depends on the mean depth of the lake and
the size and fertility of the drainage basin. Human activity, such as lowering of the water
level, discharge of sewage into lakes and excessive use of fertilisers in agriculture may
increase this rate. The discharge of nutrients, whether they come from agriculture or from
sewage (cultural eutrophication) disrupt the balance in the lake ecosystem and perhaps causes
overproduction of algae, plants and fish (Horne & Goldman, 1994). This eventually leads to
thick layers of organic matter at the bottom of the lake. The decomposition of this material
causes oxygen depletion at the bottom of the water body and may cause dead lake bottoms
and even fish death
(http://www.naturvardsverket.se/index.php3?main=/document/lagar/bedgrund/sjo/sjo.html ).
Blooms of blue-green algae are often the first sign of cultural eutrophication, and occur in late
summer or autumn. These types of algae compete successfully with other species for nutrients
and have developed other self-promoting features. They may regulate their position vertically
during the day so that they always are at the most favourable position for sunlight and
nutrition and also shade out other species. Some blue-green algae have the advantage of being
able to fix atmospheric N2 gas. To avoid grazing by zooplankton, they produce toxins similar
to those produced by many terrestrial plants. These toxins pose a great problem when the lake
is used as water supply or for recreational purposes (Horne & Goldman, 1994).
The use of P fertiliser has decreased recently in the Nordic countries. Even though Denmark
uses the highest amounts, they do not have the largest losses. This is due to climatic factors
such as temperature, which affects crop yield. Factors that affect nutrient losses include
radiation and precipitation, which affect the annual runoff. These factors vary both on an
annual and seasonal basis with, for instance, peak flows in spring and autumn. High runoff
volumes may result in losses of high amounts of particulate and dissolved P. In spring, when
the snow starts to melt, ground frost may prevent infiltration, leading to high erosion capacity
of the snowmelt water. Other important factors affecting P losses include various agricultural
structures, soils and topography (Rekolainen et al., 1997).
Studies have been carried out on P cycling in cultivated soils and in freshwater lake
ecosystems and the process involved are well understood, but less is understood about P
cycling in freshwater wetlands (Amador, Richany & Jones, 1992). The present study was
carried out within the EU project PROWATER with the aim of investigating what happens to
P in a soil that is not cultivated and that is covered with vegetation all year round. Our
hypothesis was that ‘soil phosphorus is transformed and its forms redistribute into various
compartments depending on season’. The specific objectives of this study were to: 1)
Determine total phosphorus status and distribution in the soil profile; 2) Break down total
phosphorus into various compartments; 3) Evaluate impact of season on phosphorus
dynamics.
6
1. Wetlands
A wetland ecosystem requires that the land be kept wet during all or part of the year. This can
be a result of high rates of water supply or/and water retention depending on the interaction
between climate and landscape topography (Wheeler, 1999). Wetlands often form the
boundary between terrestrial and aquatic ecosystems and include animal and plant
communities of both systems. Therefore a small change in hydrology may cause a dramatic
change in biota (Mitsch & Gosselink, 2000).
In 1971, the importance of wetlands was internationally noted in the RAMSAR Convention
on wetlands. According to this convention, wetlands are defined as ‘areas of marsh, fen, peat
land or water, whether natural or artificial, permanent or temporary, with water that is static or
flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide
does not exceed six metres’ (http://www.ramsar.org/key_conv_e.htm, 2003).
However there are many different types of wetlands with different characteristics caused by
factors such as hydrology, salt or freshwater, climate, etc. Therefore various classification
systems are used to describe wetlands, using different specific parameters such as vegetation,
chemistry, hydrology, geology, etc. These systems reflect the interest of different researchers
and the aims of their studies (Hughes & Heathwaite, 1995).
Wetlands offer a variety of useful functions that are essential for animals and plants and for
maintaining the quality of the environment. They function for example as wildlife habitats
and dispersal corridors, they trap and deposit sediments and function as a nutrient source and
sink. They provide riverbank stabilisation, counteract erosion and assimilate and immobilise
environmental contaminants. From a societal point of view they are important for recreational
and educational purposes. They are also economically important, as hay and peat may be
harvested (Hughes & Heathwaite, 1995).
1.1 Streams and riparian zone wetlands
All watercourses are similar in that they flow from higher altitudes toward lower ones. Water
flow erodes the stream bank, releasing and transporting inorganic and organic materials and
depositing them further downstream. There are basic types of stream reaches - rapids and
slow-flowing stretches. Rapids, with channels of gravel, stones or bedrock, have very
turbulent water flow and temporary sedimentation. Slow-flowing reaches have turbulent water
flow only during floods. They have a higher continuous sedimentation of fine materials
consisting of sand transported along bottoms, and suspend materials like silt, clay and organic
matter. Vegetation along these stretches is completely different from that along rapids.
(Nilsson, 1999).
The land adjacent to a river, stream or other body of water is called the riparian zone. This
zone is composed of mosaics of landforms and communities, of which riparian wetland is one
type. These wetland ecosystems are unique because of their linear form and because they
process large fluxes of energy and materials from the upstream system. The soil and soil
moisture in these ecosystems are influenced by the adjacent water body through at least
periodic flooding (Mitsch & Gosselink, 2000).
The riparian zone changes along the course of a river system from its headwaters to its mouth
through three major geomorphic zones: erosion, transport, and sediment deposition. The zone
7
of erosion is in the headwaters and upper reaches of low-order1 streams. Depending on the
precipitation, there is a great variation in frequency and duration of the flood. Below the zone
of erosion is the zone of sediment, nutrient and water transport. The extent of flooding
depends on the precipitation and the size of the watershed. The zone of deposition is
characteristic of high-order and low-gradient streams. Sedimentation is greater than transport
and erosion and the valley slopes are gentle. This leads to broad floodplains and meandering
stream channels. Seasonal flooding is characterised by one or a few long- or short-duration
floods. It deposits fine sediments at the periphery of the floodplain and leaves the more coarse
sediments in the channel (Mitsch & Gosselink, 2000).
The slope of the stream and the elevation and area of the watershed determine the local
flooding regime of the riparian zone. A stream with steep slopes floods with sharper peaks but
less frequently than streams with gentle slopes (Mitsch & Gosselink, 2000). River topography
also affects current velocity, soil conditions and microclimate, and is an important reason for
vegetation heterogeneity (Nilsson, 1999).
Both productivity and biodiversity in riparian zones are enhanced by the exchange of
resources between riparian zones and the main channel (Figure 1) caused by seasonal floods.
The composition and relative width of the vegetation zone differ between small streams and
large rivers, due to differences in flood duration and channel topography (Nilsson, 1999).
Riparian vegetation
Provides
terrestrial
habitat
Supplies detritus
(energy) to stream
Shades stream
Controls
primary
production
Food, rest and
hiding for
emergent adults
Some eggs
laid on foliage
Food for
aquatic
invertebrates
Alters water
quality and
quantity
Controls stream
temperature
Habitat space
& quality for
aquatic
invertebrates
Growth rates &
life cycles of
aquatic
invertebrates
Figure 1. Example of functional relationship between riparian vegetation and stream aquatic
communities (after Knight & Bottorff (1984) in Mitsch & Gosselink (2000)).
1.2 Wetland hydrology
Hydrology is probably the single most important determinant of establishment and
maintenance of specific types of wetlands and wetland processes. The first two important
factors affecting the hydrology in wetlands are the climate and geomorphology of the
1
Rivers and streams may be classified by their order. Low-order streams are small and have no larger branches.
When first-order streams join they become a second-order stream. The order will not increase if more first-order
streams join. If second-order streams join, they become a third-order stream, and the process continues (Horne
& Goldman, 1994).
8
landscape and basin. In wet or cool climates there are more wetlands than in hot or dry
climates, as a result of higher precipitation in wet climates and lower evapotranspiration in
cool climates. Flat or gently sloping landscape tends to have more wetlands than steep terrain
(Mitsch & Gosselink, 2000).
Each type of wetland is characterised by the hydroperiod, which is the seasonal pattern of the
water level. The hydroperiod is the result of the water budget (sum of inflows and outflows)
as influenced by physical character of the terrain and the closeness to adjacent water bodies.
The major components of water budget in riparian wetland include precipitation,
evapotranspiration, over-bank flooding and groundwater fluxes. The determination of water
budget and hydroperiod may contribute to a better understanding of wetland function (Mitsch
& Gosselink, 2000).
The physiochemical environment of a wetland is directly modified by the hydrology,
especially the oxygen availability and related chemistry such as nutrient availability, pH and
toxicity. It is also influenced by hydrological inflows and outflows of nutrients, toxins,
sediments, detritus, etc. The physiochemical environment may in turn affect hydrology, in
that the build-up of sediments, for example, may affect the hydrological inflows and outflows.
Changes in physiochemical environment may in turn have a direct impact on the wetland
biota. Even a small change in water balance may affect productivity and species composition
greatly. Some animal and plant species are adapted to anoxia and will benefit in these
conditions. Microbes able to metabolise in anoxic conditions dominate the reduced sediments,
while aerobic microorganisms survive in a thin layer of oxidised sediments and in the water
layers if oxygen is present. When hydrological patterns remain similar from year to year,
wetland biotic structure and functional integrity may persist for many years (Mitsch &
Gosselink, 2000).
1.2.1 Climatic factors for Scandinavia
The climate in Scandinavia is affected by the inflow of mild air from the Atlantic Ocean
caused by the Gulf Stream. This leads to relatively mild winters compared to other parts of the
globe at similar latitudes. The climate in Sweden is highly seasonal. In southern Sweden,
snowfall may occasionally occur but may also be absent or replaced by rainfall in any part of
the winter. In central and northern Sweden, a lasting snow cover persists for 4-6 months. Ice
and snowmelt usually occur in April or early May, as does the seasonal ground frost which in
most winters occur all over Sweden (Sjörs, 1999).
Precipitation in Sweden, which is highest in the south-west, is mainly caused by moist air
from the Atlantic. Rainfall is often high in July and August and often also in the autumn, and
low in the spring and early summer. However, this is rather irregular and may vary from year
to year, which may lead to a large seasonal river discharge fluctuation (Nilsson, 1999).
Evaporation depends on the summer heat and the length of the warm period, which is longer
in the south and is thus greater in summer. However the remaining surplus of water varies
more than the precipitation itself, leading to different groundwater conditions (Sjörs, 1999).
There is a distinct zonation of the temperature climate as it affects the vegetation. This is
mainly due to stronger south to north temperature differences in spring and autumn than in
summer, which leads to different lengths of the climatic growing season. In the Kristianstad
area, the growing period is about 210 days, whereas in the north it is between 100-150 days
9
(Sjörs, 1999). The growing season is defined as the period between the last killing frost of
spring and the first killing frost of autumn, when the daily mean air temperature is above
+5oC (www-markinfo.slu.se/sve/klimat/vegper.html;
www.bartleby.com/65/gr/growings.html).
1.3 Wetland vegetation
Wetland plant composition and community boundaries in floodplains are dependent on the
amplitude of the flooding. When flooded, the soil may be just saturated or wetland plants may
be completely submerged. When the water level is low, it may be just below the soil surface
or well below the rooting zone. The impact these changing conditions have on plants and
plant communities depends on their magnitude and duration, as well as the identity and stature
of the plant species concerned (Wheeler, 1999). However, the soil moisture may be a more
important factor for plant growth than the position of the watertable. Due to different soil
types, the moisture content of the upper soil layer at any low water level can vary between
wetlands. This is mainly because of different capillary properties and removal of evapotranspiration (Wheeler, 1999).
Plants colonising wetlands show a considerable variation in their tolerance of, and adaptation
to, different water regimes and duration of flooding or droughts. Some plants have developed
different strategies to avoid the effect of waterlogging or drought, for example by surviving as
seeds or other perennating organs such as roots, tubers or rhizomes. Another way to survive in
wet conditions is to develop anatomical structures (lacunae, aerenchyma and respiratory
roots). These are used to maintain aerobic respiration by assisting the diffusion of atmospheric
oxygen to the underground parts of the plant. Some plants have adapted to these conditions by
accelerated shoot growth, to extend above the level of flooding. With this in mind, three broad
types of wetlands can be recognised from a plant ecology point of view: Permanent wetlands
- low water level fluctuations do not drive floristic change. Seasonal wetlands - fluctuation
amplitude of the watertable is so great that only opportunistic plants, if any, colonise the
wetland. Fluctuation wetland - great long-term watertable fluctuations and duration, causing a
change in composition of perennial plants or periods when perennial plants cannot grow
(Wheeler, 1999).
Different vegetation types and contrasting habitat conditions can vary greatly within a single
wetland site. Peat as a soil substrate can accumulate where the watertable remains close to the
soil surface much of the year, especially in temperate and boreal regions. Sites strongly
influenced by fluctuating watertables may have a main composition of minerals because of
alluvial depositions and the prevention of peat accumulation caused by low water levels
(Wheeler, 1999).
As a result of climatic factors and the fact that the watercourse becomes larger downstream,
the plant community composition changes dramatically from the upstream to the downstream
reaches. Watercourses play a large role as dispersal corridors, which lead to a distribution of
species beyond their normal range (Nilsson, 1999).
1.4 Human impact on riparian zone wetlands
When people started to optimise their farming, there was no use for wetlands any more.
Farmers were encouraged by the government to drain or fill this wet non-productive land so it
could be used as farmland or used in other ways, as the only policy for managing wetlands.
10
This led to a dramatic decrease in wetlands in a short period of time (Mitsch & Gosselink,
2000).
When an wetland area is drained, the water is led away and the hydrology of the area is
modified. The purpose of drainage is to dry the land out for agricultural or industrial use,
although ditches are sometimes installed as transportation canals across wetlands. Roads may
also be built across wetlands, which alters the hydrology, promotes sediment loading and may
destroy the wetland totally (Mitsch & Gosselink, 2000).
Surface peat mining in wetlands is common in several European countries. Peat is used as fuel
in electric power plants, as potting compost and garden soil, but also as a filtering medium to
remove toxic materials and pathogens from wastewater (Mitsch & Gosselink, 2000).
The great loss of wetlands in the world and the recognition of wetland values have stimulated
the restoration and creation of these systems, which may be carried out in several ways. An
existing wetland may be restored from a condition caused by human activities or it may be
altered on purpose to increase one or several functions. Conversion of previous upland or
shallow-water areas may create new wetlands (Mitsch & Gosselink, 2000). These wetlands
are often used to remove contaminants and pollution from wastewater (Maltby, 1986; Mitsch
& Gosselink, 2000).
Natural wetland usually receives non-polluted water. If a wetland receives polluted water
from local or upstream runoff, or if sewage water is led through such wetland, the quality of
the water flowing out of the wetland may change. However, the polluted water may in turn
change the wetland by eutrophication and altered biological composition. If toxic compounds
reach the wetland, biological life may be destroyed (Lönngren, 1995; Mitsch & Gosselink,
2000).
Sweden has about 10 million hectares of wetlands, or about 25% of the national land area.
Therefore Sweden is one of the top ten wetland-richest countries in the World. However about
25% of the original wetlands in Sweden have disappeared through drainage since the end of
the Nineteenth Century (Naturvårdsverket & SCB, 2000). Riparian zones in Sweden have
been used by humans for a long time. The lower parts of the zones have been used for haymaking by harvesting helophytes such as Carex and Equisetum, whereas the upper parts of the
zones, from which trees and shrubs have been cleared, have been used as meadows. The
meadows were fertilised by annual flooding and usually harvested each year (Nilsson, 1999).
11
2. Wetland soils
Biogeochemical cycling, chemical transformation and transportation in ecosystems involve
several chemical, physical and biological processes. These processes are markedly influenced
by waterlogged conditions (as mentioned in 1.2). Biogeochemical cycling in wetlands may be
divided into two main systems - the exchange of chemicals between the wetland and its
surroundings; and the cycling within the wetland through various transformation processes. If
the wetland has no or little exchange with its surroundings, as for example ombrotrophic
bogs, the system is considered closed. Wetlands adjacent to rivers and lakes may, on the other
hand, have abundant exchange with their surroundings and are considered open. Even if few
transformation processes are unique to wetlands, certain transformation processes tend to be
more dominant in wetlands than in either upland or deep aquatic ecosystems, due to
permanent or intermittent flooding (Mitsch & Gosselink, 2000).
Wetland soils may be divided into organic soils and mineral soils, the latter containing less
than 20-35% organic matter (dry weight). Mineral wetland soils usually have a soil profile
made up of horizons. Organic soils differ further from mineral soils in several physiochemical
features (Table 1). The porosity in organic soils is generally 80% pore space or more, whereas
mineral soil porosity ranges between 45-55% pore space. The porosity affects the bulk
density, which is defined as the dry weight of soil materials per unit volume. Organic soils
have low bulk density due to high porosity, usually ranging between 0.2-0.3 g/cm3, whereas
the bulk density of mineral soils ranges between 1.0-2.0 g/cm3. Both mineral soils and organic
soils have a wide range of possible hydraulic conductivity values. Organic soils may hold
more water due to high porosity, but do not necessarily allow water to pass through more
rapidly compared with mineral soils. Minerals soils often contain more nutrients than organic
soils. The nutrient content in organic soils may be bound in organic forms and unavailable to
plants (Mitsch & Gosselink, 2000).
Table 1. Comparison of mineral and organic soils in wetlands, after Mitsch & Gosselink, 2000
Parameter
Organic content (%)
Organic carbon (%)
pH
Bulk density
Porosity
Hydraulic conductivity
Water holding capacity
Nutrient availability
Cation exchange capacity
Mineral soil
Less than 20-35
Less than 12-20
Usually around neutral
High
Low (45-55%)
High (except for clays)
Low
Generally high
Low, dominated by major cations
Organic soil
Greater than 20-35
Greater than 12-20
Acid
Low
High (80%)
Low to high
High
Often low
High, dominated by hydrogen ions
Organic wetland soils consist mainly of plant residuals in various stages of decomposition.
The organic matter is accumulated because of the anaerobic conditions due to waterlogging
(Mitsch & Gosselink, 2000). Organic matter can be divided into non-humic and humic
substances. The non-humic substances consist of amino acids, proteins, carbohydrates, fats,
waxes, alkanes and low-molecular-weight organic acids. Humic substances comprise the
majority of organic matter and are chemically complex compounds with high molecular
weight. Non-humic substances are decomposed faster than humic substances. The chemical
composition of organic matter can vary from soil to soil, but is in general approximately 50%
C, 5% N, 0.5% P, 0.5% S, 39% O and 5% H (w/w). Some functional groups in humic
substances are carboxy, phenolic, hydroxyl, alcohol hydroxyl, and carbonyl groups (Barber,
1995). Two important characteristics of organic soils are the plant origin and degree of
decomposition. Many properties such as bulk density, cation exchange capacity, hydraulic
12
conductivity and porosity are often dependent on these characteristics. The origin of the plant
residuals varies from mosses to herbaceous materials and wood and leaf litter. The herbaceous
material may be sedges like Carex and Cladium or reed grass Phragmites, or other non-grass
or non-sedges such as Typha. During decomposition, the plant material changes both
physically and chemically until it does not resemble the original material. As the
decomposition proceeds, the bulk density increases, hydraulic conductivity decreases and the
amount of fibric particles larger than 1.5 mm decreases. The relative amount of waxes and
lignin increases due to a decrease in plant pigments and cellulose, which are more easily
decomposed (Mitsch & Gosselink, 2000).
Flooded mineral soils develop certain characteristics called redoximorphic features. These
features are formed by reduction, translocation, and/or oxidation of iron and manganese
oxides. It is microorganisms that cause these features to develop, and there are three obligate
conditions determining the rate of development. First, there must be continuous anaerobic
conditions. Secondly, there must be a temperature (normally above +5oC) sufficient for
biological processes. Thirdly, the microbes need an organic substrate to support their activity.
Under aerobic conditions, iron and manganese are in the solid forms Fe3+ and Mn3+ or Mn4+
and colour the soil red and black respectively. Iron and manganese reduce to their soluble
forms Fe2+ and Mn2+ when the soil is waterlogged and anaerobic conditions occur. When the
soil becomes aerobic again, chemosynthesising bacteria oxidise iron and manganese from
their soluble forms to their insoluble forms. This also occurs non-biologically at neutral or
alkaline pH. When soluble, these ions may leach and the soil regains its natural colour of grey
and black depending on the colour of the parent material. In a similar way, clay may
selectively deplete along root channels to redeposit as a clay coating on soil particles further
down. In some wetlands an oxidised rhizosphere may occur. This is caused by the capacity of
many hydrophytes to transport oxygen from the stem above ground to the roots below. The
oxygen not needed for root metabolism diffuses into the surrounding soil. In this oxidised
zone, soluble iron may oxidise into its solid form and deposit around small roots (Mitsch &
Gosselink, 2000).
13
3. Nutrient uptake by plants
3.1 Plant nutrition
Plants get the raw material for their maintenance and growth from the soil and the
atmosphere. Almost all plants can transform CO2 and H2O and sunlight into organic
compounds for their energy source. They use inorganic compounds from their environment to
synthesise the vitamins and amino acids they require. Over 60 chemical elements have been
identified in plants, but only a few are essential for them to complete their lifecycle. Today
seventeen such elements have been identified and are divided into micronutrients and
macronutrients. The micronutrients are required in very small amounts (less than 100 mg/kg
of dry matter) whereas macronutrients are required in large amounts (1000 mg/kg of dry
matter or more) (Raven, 1999). Phosphorus (P) is considered to be a macronutrient. The most
essential function of phosphorus in plants is energy storage and transfer, but it also acts as an
important structural component of nucleic acids, coenzymes, nucleotides, phosphorus
proteins, phospholipids and sugar phosphate (Havlin et al., 1999; Raven, 1999). Plants
contain about 0.1 to 0.5% phosphorus (Havlin et al., 1999).
The main P source for plants is the two inorganic forms of orthophosphate ions, H2PO4- and
HPO42-. The uptake of HPO42- is slower than the uptake of H2PO4-. Plants can also absorb
certain soluble organic phosphates such as nucleic acids and phytin, but this P source is
limited, especially to higher plants, in the presence of an active microbial population which
decomposes these compounds rapidly (Havlin et al., 1999).
3.2 Function of the root system
Roots have many tasks and their main functions are absorption, anchorage, storage and
conduction. Most of the essential nutrients are absorbed via roots. Several kinds of root
system can be recognised, e.g. a taproot system and a fibrous root system. The taproot system
has one taproot, which grows directly downwards, giving rise to lateral roots. Fibrous root
systems develop from many adventitious roots raised from the stem, and produce lateral roots.
Several factors, such as moisture, temperature and soil composition, determine how deep and
how far laterally the root system grows (Raven, 1999).
3.2.1 Microorganisms in soil
The rhizosphere is the layer of mucigel covering the epidermis in the absorptive part of some
roots and the soil particles bound to it. This layer provides an environment for a variety of
microorganisms and may affect ion availability to the root. The rhizosphere may also, in the
short-term, prevent the root from drying out (Raven, 1999). One major reason for the high
microbial activity in the rhizosphere may be the organic exude from the root, consisting of
root cap cells, old root hairs etc., which serves as an energy source (Barber, 1995).
The general breakdown of organic matter in soil is generated by heterotrophic bacteria, fungi
and actinomycetes. Under anaerobic conditions, bacterial decomposition dominates (Brady &
Weil, 1996).
Soil bacteria are divided in groups depending on their oxygen requirement, nutritional pattern
and symbiotic relationship (Donahue et al., 1983). Autotrophic bacteria obtain their energy
from sunlight (photoautotrophs) or from oxidation of inorganic constituents (chemo-
14
autotrophs), for example iron and sulphur. They obtain most of their carbon from CO2 and
carbonates. These bacteria are not a large group but they play an important role in controlling
nutrient availability to higher plants. Heterotrophic bacteria, which represent the biggest
group of soil bacteria, obtain their energy and carbon from organic matter in the soil
(Donahue et al., 1983; Brady & Weil, 1996).
Soil bacteria can digest most naturally-occurring materials and also a diversity of toxic
element such as insecticides and other organic toxins, due to their broad range of enzymatic
capability. Bacteria also dominate several basic enzymatic transformations, for example the
oxidation and reduction of selected chemical elements in soil. Some chemoautotrophic
bacteria obtain their energy from such oxidations. Anaerobic and facultative bacteria reduce a
number of substances other than oxygen gas. Many of these biochemical reactions play a
great role for environmental quality, as well as for plant nutrition (Brady & Weil, 1996).
Actinomycetes are classified in the kingdom Monera, as are bacteria, and they are generally
aerobic heterotrophs. They get their energy from decomposing organic materials but also from
compounds supplied by certain plant species in a parasitic or symbiotic relationship. Many
actinomycetes species produce antibiotic compounds that kill other microorganisms.
Actinomycetes are numerous in soils high in humus, for example old meadows and pastures.
They are sensitive to acidic soil conditions and optimum pH value is between 6.0-7.5.
Actinomycetes often dominate the late stages of decomposition because they also reduce
resistant compounds such as lignin, cellulose, and phospholipids (Brady & Weil, 1996).
Fungi represent a diverse group of heterotrophic and generally aerobic microorganisms.
However some fungi tolerate rather low oxygen concentrations found in wet or compacted
soils. Fungi may be divided in three groups, yeasts, moulds and fungi. Yeasts, which are
single celled-organisms, live mostly in waterlogged, anaerobic soils. Moulds and fungi are
both filamentous characterised by hyphae. Moulds play a greater role in decomposing organic
matter than do fungi. They develop vigorously in acid, neutral and alkaline soils and are
therefore abundant in acidic soils where both bacteria and actinomycetes are few. Although
fungi are not as widely distributed as moulds, they are important in the breakdown of woody
tissue and the formation of symbiotic relationships (mycorrhizae) with plants (Brady & Weil,
1996).
3.2.2 Root hairs and mycorrhizae
To obtain better nutrient and water uptake, roots can develop root hairs or live in symbiosis
with fungi (mycorrhizae). Root hairs are tubular lateral extensions of the epidermal cells of
the root. They increase the absorptive surface of the root by a factor of 2 to 10 (Barber, 1995).
Root hairs are relatively short lived but new hairs are developed almost at the same rate as the
old ones die (Raven et al., 1999).
Mycorrhizae have a mutualistic symbiosis between fungi and root. The fungi provide the root
with water and some essential elements, especially phosphorus. The fungi increase the P
availability to plants, not only by extension of hyphae into the soil, but also through the
secretion of organic acids (Stevenson, 1986). The root provides the fungi with carbohydrates
and vitamins essential for their growth. Mycorrhizae can be found in most soils in symbiosis
with most plant species. Mycorrhizae can be classified into five groups: ecto-, endo-, ericoid-,
arbutoid and orchidaceous. The major groups are endo- and ecto-mycorrhizae (Barber, 1995;
Raven et al., 1999).
15
4. Phosphorus
4.1 Phosphorus in soil
Phosphorus occurs in both inorganic and organic forms in soil. The content of P in the soil
ranges between 100 and 2 500 kg/ha, with an average of 1000 kg/ha in the top 20 cm
(Mitchell et al., 1986). Phosphorus in soil may be divided into four main categories: (1) P as
ions and compounds in the soil solution; (2) P adsorbed on the surface of inorganic soil
constituents; (3) P minerals, both crystalline and amorphous; and (4) P as a component of soil
organic matter (Barber, 1995).
4.1.1 Phosphorus in soil solution
The concentration of P in soil solution varies among soils, but the concentration required by
plant ranges between 0.003 and 0.3 ppm and depends on the type of vegetation. As roots from
the soil solution absorb P, additional P is transported toward the roots via diffusion and mass
flow. Soluble inorganic P is in the form of orthophosphate, H2PO4- and HPO42- and the
predominant form depends on the pH (Table 2). Normally soil pH ranges between 4.4 and 8.5
and at pH 7.2 the amounts of the two phosphate ions are generally equal (Barber, 1995;
Havlin et al., 1999). As much as half the phosphate in soil solution may be as soluble organic
compounds, especially in soils with a high content of organic matter (Barber, 1995).
Table 2. Predominant forms of soluble inorganic phosphorus depending on pH (after Barber,
1995)
pH value
pH 7.2
pH< 7.2
pH> 7.2
Predominant form
H2PO4- = HPO42H2PO4- < HPO42H2PO4- > HPO42-
4.1.2 Phosphorus adsorption
Surface adsorption and precipitation reactions are collectively called P fixation or retention.
Inorganic P that is not absorbed by plants or by microorganisms can be adsorbed to mineral
surfaces (labile P) or precipitate as secondary P compounds. The most important factor
affecting the extent to which P is fixed is pH. In soils with a pH of 7.2, inorganic P
precipitates as Ca-P secondary minerals and/or is adsorbed to clay minerals and CaCO3. In
soils with a pH<7.2, inorganic P is adsorbed to clay minerals and Fe/Al-oxides and/or is
precipitated as Fe/Al-P secondary minerals (Barber, 1995; Havlin et al., 1999).
Hydroxy minerals and Al and Fe oxides are primarily involved in the adsorption of inorganic
P in acidic soils. Although both positive and negative sites exist, positive sites dominate and
give a net positive charge. These sites attract anions such as H2PO4- and HPO42-. When
adsorbed, OH- and OH2+ sites on the Fe/Al-oxide interact with the P ion. When the P ion is
bound through one Al-O-P bond, the ions are considered labile and are desorbed readily to the
soil solution. When two Al-O bonds occur with one P ion, the orthophosphate is considered
non labile and desorption is more difficult (Havlin et al., 1999).
Both Fe/Al-oxides and clay are capable of adsorbing large amounts of P in soil solution.
However, the amount of P adsorbed depends on the amount of clay and Fe/Al-oxides in soils
16
and the pH. Adsorption of P by Fe/Al-oxides decreases with increasing pH. Bloom (1981)
suggests that Al-substituted peat has a high affinity for the adsorption of phosphate ions in the
pH range 3 to 6. Phosphorus may also compete with both inorganic and organic anions for
bonding sites. Anions such as H3SiO4-, SO42-, OH-, COOH- and MoO42- can be competitive
with P. Humus acid may also compete for bonding sites on Fe/Al-oxides and create a
protective cover, thereby decreasing P adsorption. Organic anions such as citric oxalate,
tartate and malate may form stable chelate complexes with Fe and Al ions from Fe-P and Al-P
complexes, and thereby solubilise P (Havlin et al., 1999). Anaerobic conditions occur when
the soil moisture increases up to the extent of flooding. This results in reduction of FePO4 to
Fe3(PO4)2, which is soluble. Similar reactions occur with Mn3(PO4)4 which reduces to soluble
Mn3(PO4)2 (E. Otabbong, pers. comm. 2003).
4.1.3 Phosphorus in minerals
Many minerals in the soil may be potential P sources, particularly minerals of P combined
with calcium, aluminium and iron (Barber, 1995). Some secondary minerals of P are wavellite
[Al3(PO4)2(OH)3 x 5H2O], vivianite [Fe3(PO4)2 x 8H2O], dufrenite [FePO4 x Fe(OH)3] and
variscite [Al(PO4) x 2H2O] (Stevenson, 1986). Most rocks contain P (P2O5) in amounts of
0.15-0.2%, predominantly in the form of silicate and apatite minerals, which are relatively
stable in surface environment. The local availability of P from rocks depends on three factors.
Firstly, the soil may contain uncommon rocks that contain high amounts of P, like basaltic
volcanic rocks and P-rich sedimentary rocks. Secondly, rocks may be more or less easy
weathered. Thirdly, the environment itself in terms of e.g. climate or water acidity may affect
the P availability (McKelvey, 1973).
4.1.4 Phosphorus in organic matter
Organic soil P varies typically between 15 and 80% of the total P in most soils. The
distribution of P with depth also varies among soils. Inositol phosphate, phospholipids and
nucleic acids are esters of orthophosphoric acid (H2PO4-), of which most organic P
compounds consist. Of the total P, the approximate proportion of inositol is 10-50%,
phospholipids 1-5% and nucleic acid 0.2-2.5%. Phospholipids and nucleic acids are broken
down more quickly than inositol, hence the large difference in concentration. Microbial
residues, which contain stabile esters, are believed to make up the remaining P compounds
(Barber, 1995; Havlin et al., 1999).
4.2 Phosphorus release by microorganisms and enzymes
Immobilisation and mineralisation occur simultaneously in soil and may be described as
follows:
Mineralisation
Organic P
Immobilisation
Inorganic P (H2PO4-/HPO42-)
Microorganisms mineralise P through the degradation of organic residues into other organic
compounds which release inorganic P. However, some organic compounds, such as humic
acids, are resistant to microbial degradation (Havlin et al., 1999). Phosphatase is an important
enzyme that catalyses the mineralisation of organic P into inorganic P by the reaction:
R-PO4- + H2O → HPO42- + ROH (Stevenson, 1986; Havlin et al., 1999). Phosphatase may be
present both intracellularly and in the soil solution after being released by the lysis of
microbial cells (Stevenson, 1986).
17
Microorganisms may also immobilise available phosphates into cellular material and promote
the solubilisation of fixed or insoluble mineral forms of P, for example through the production
of chelating agents. Organic chelates form complexes with Ca, Fe or Al and thereby release
the phosphate in water-soluble forms as follows:
CaX2 x 3Ca(PO4)2 + chelate → soluble PO42- + Ca-chelate complex (where X = OH or F)
and
Al(Fe) x (H2O)3(OH)2H2PO4 + chelate → soluble PO42- + Al(Fe)-chelate complex
Total organic P is, in most soils, highly correlated with soil total organic C. Therefore,
mineralisation would be expected to increase with increasing total organic C, in the way
nitrogen does2. However, the situation for P is different because of the fact that total organic P
is present in compounds with different solubilities. Moreover, organic P can be bound by the
soil and is thereby less accessible to microorganisms. When organic P decreases, P
immobilisation increases. The C/P ratio of the decomposition residues regulates the
predominance of P mineralisation over immobilisation. Other factors affecting the quantity of
P mineralisation/immobilisation are temperature, moisture, aeration and pH (Stevenson, 1986;
Havlin et al., 1999)
Table 3. Phosphorus mineralisation and immobilisation (after Stevenson, 1986)
C/P ratio
<200
200-300
>300
Mineralisation/Immobilisation
Net mineralisation of organic P
No gain or loss of inorganic P
Net immobilisation of inorganic P
4.3 Phosphorus-cycle in waterlogged soils
The phosphorus cycle in wetland soil is shown in Figure 2 (after Mitch and Gosselink, 2000).
When soils are inundated with water, reduced (anaerobic) conditions usually occur due to
oxygen diffusing much more slowly through water-filled pores than air-filled pores. However,
there usually is an oxidised (aerobic) soil layer, sometimes only a few millimetres thick, at the
soil-water interface. The thickness of this layer is determined by the oxygen transport rate
over the atmosphere-surface water interface, the amount of oxygen-consuming
microorganisms present, the oxygen production by algae within the free water and the mixing
of the water caused by convection currents and wind action. There may also be transport of
excess oxygen by wetland plants to their roots. This oxidised layer is often important for the
chemical transformation and nutrient cycling that occur in wetlands.
Particulate organic P from plant and microbial residues may transform into soluble organic P
(SOP) and further into inorganic soluble P in both the free water and the oxidised and reduced
soil layers. In the oxidised soil layer, however, iron may be oxidised from its soluble form
Fe2+ to its insoluble form Fe3+ and precipitate P as FePO4 . Manganese also behaves in this
way and precipitates P as Mn3(PO4)4. In the anaerobic layers, the reaction proceeds in the
opposite direction and releases P again. Inorganic P and soluble organic P may diffuse
2
If the C/N ratio is <20-25 there is a net mineralisation of organic N. If the C/N ratio is >2025 there is a net immobilisation of inorganic N (Persson, 2003).
18
upwards to the oxidised layer and may also diffuse to the free water. However, inorganic
soluble P from the free water may precipitate in the oxidised soil layer.
Inflows (runoff, tides etc.)
Air
Surface
water
Oxidized
soil layer
Reduced
soil layer
Plant/microbial uptake
Particulate
organic P
Particulate
organic P
Sedimentation
SOP
PO43-
SOP
PO43-
Adsorption
Precipitation
Upward diffusion
Anaerobic
Anaerobic
release of
of PP
release
SOP
PO43-
Particulate
inorganic P
including Ca-P,
Al-P, Fe-P
Plant uptake
Figure 2. Phosphorus transformations in wetlands. SOP indicates soluble organic phosphorus
(redrawn from Mitsch and Gosselink, 2000).
19
5. Materials and methods
5.1. Site description
5.1.1 History
The Kristianstad plain was covered with ice during the last glacial period. About 13 000 years
BP, the ice started to melt and the plain was inundated. The sea level was about 50 m above
the current level. As the ice melting proceeded northwards, the suppressed earth crust started
to rise and the plain was drained and the sea level sank 30 m below the current sea level. The
area around Lake Hammarsjön became covered with a forest of alder (Alnus glutinosa)
(Magnusson & Vägren, 1994). During the period 7 500- 4 000 years BP the sea level rose and
fell several times, and the alder forest was immersed. Some of these 7 500-year-old alder logs
are still found today on the bottom of Lake Hammarsjön. The last sea level rise took place
about 4 000 years BP and the watertable reached 8-10 m above the current sea level. When
the water retreated, lakes were formed. The strong sea currents created a bank of sand, which
in turn made a large lagoon. The lagoon was overgrown with vegetation and gradually a large
area of marsh was created and only a few open water surfaces were left (Magnusson, 1981).
Today, the area around Kristianstad holds one of the largest marsh areas in Sweden, in spite
of the fact that the marsh has been altered during the past 400 years. These alterations were
due to human desire to control this ‘water-sick’ land and use it as arable land. Up to the
1700s, the marsh was only used for haymaking and as grazing land for animals. Later, rivers
and streams were straightened, areas were filled with rocks, and ditches were made for
drainage. Lakes were drained and the river Helgeå was regulated through a power plant dam
further up in the basin. Sewage from fast-growing villages, lowering of the watertable in the
river-lake system and regulation of the river Helgeå all contributed to the eutrophication of
Lake Araslövssjön and Lake Hammarsjön. Today efficient sewage treatment plants are
minimising the nutrient supply to these lakes (Magnusson, 1981).
The marsh that was left untouched forms an internationally valuable area, included in the
wetlands list of the Ramsar Convention. This marsh area of ~ 5 500 hectares represents the
lower part of the river Helgeå from the village Torsebro to the Baltic Sea at Åhus. The
riparian zone meadows are the most valuable areas, which have been harvested, grazed and
flooded regularly over a long period of time. This has created a specialised flora and fauna
adapted to these conditions. These meadows are valuable resting sites for migratory birds
such as ducks, geese and waders. If the regular harvesting and grazing ceases, the area will
become overgrown and high herbs, reeds, shrubs and trees will take over (Cronert, 1996).
5.1.2 Streams influencing the site area
The stream Vinneå with its length of 33.5 km has its origin in Hässleholm municipality on the
Nävlinge ridge and stretches out to the Kristianstad plain in Kristianstad municipality. On the
Nävlinge ridge, forest and pasture dominate and the stream meanders. When the stream has
passed the village of Vinlsöv, the nature of the surrounding area changes into farmland on the
Kristianstad plain and the river is straightened and remains so until it reaches its outflow in
the river Helgeå. The river Vinneå basin is about 197 km2 in area and is depicted in Figure 3.
About 35% of this area consists of farmland, located mainly on the intensively farmed
Kristianstad plain. Forest and pasture area constitute 44% and 9% respectively, located
20
mainly on the Nävlinge ridge. Built-up areas and remaining land constitute 3% and 9%
respectively (Fristedt, 1999). An air photo of the sampling area is shown in Figure A14.
N
Figure 3. Drainage area of stream Vinneå (Lantmäteriverket, ur GSD Röda kartan). The star
indicates the sampling site.
5.1.2.1. Water level fluctuation
The water in the river Helgeå flows slowly due to the low fall of about a couple of metres
from Torsebro to the sea. The water amplitude varies during the year between 1.3 m above
sea level to 0.1 m below the sea level, with its peaks after snowmelt in spring and after heavy
rain in late autumn (Cronert, 1996).
Water level fluctuation was not monitored during the sampling period for the stream Vinneå.
However Kristianstad municipality continuously monitors the water level fluctuations in the
river Helgeå in Kristianstad town and the water level fluctuations in the Baltic Sea at Åhus
(Figure 4). The stream Vinneå is a tributary to the river Helgeå, and is thereby influenced by
21
m above a fix sealevel
the water level fluctuations of the Helgeå, which may cause flooding in the adjacent area
(Figure A15-A18).
0,8
0,6
0,4
0,2
0
-0,2
-0,4
August 2000 September
2000
River Helgeå
October
2000
November
2000
December
2000
January
2001
February
2001
March 2001
April 2001
Baltic sea
Figure 4 . Water level fluctuations of the river Helgeå in Kristianstad town and of the Baltic
Sea at the mouth of the river Helgeå in Åhus.
(http://www.weather.vattenriket.kristianstad.se/cgi-win/vader.exe), Zero is in Åhus = +0.05 m
above a standard sea level in RH70 (Karin Magntorn; Barry Broman, pers. comm. 8/12/2004).
5.1.3 Vegetation
The sampling site was a meadow covered mainly by Deschampsia cespitosa spp. cespitosa
and Alopecurus pratensis. In the wetter parts Juncus effusus was found. This meadow is not
fertilised directly. It is harvested in years when it is dry enough to use agricultural machines,
and is sometimes grazed by cattle.
22
5.1.4 Soil profile at the site
The soil in the site area is classified as a Eutic Histosol, according to Troedsson and Wiberg
(1986). The soil profile at the site is shown in Table 4.
Table 4. Soil profile at the site (Otabbong & Fristedt, 2005)
Depth
(cm)
0-30
pH
(H2O)
5.41
Bulk density
(gcm-3)
0.27-0.35
30-60
4.47
0.15-0.2
H5- Moderately decomposed peat, which when squeezed
releases very small amounts of amorphous granular peat
escaping between the fingers. The structure of the plant
remains is quite indistinct although it is possible to
recognize certain features. The residue is very pasty.
60-90
4.79
0.09-0.12
H2- Almost entirely undecomposed peat which when
squeezed releases clear or yellowish water. Plant remains
still easily identifiable. The plant remains are yellowish.
Degree of humification (H) according to von Post (1922)
H7- Highly decomposed peat. Contains a lot of
amorphous material with very faintly recognizable plant
structure. When squeezed, about ½ of the peat escapes
between the fingers. The water is dark and almost pasty.
5.2 Climate during the study period
Precipitation and air temperature dynamics for the sampling period are depicted in Figure 5.
The chart shows an approximately 270-day-long vegetative period in the year 2000, starting
in the middle of March and ending in the middle of December. The winter lasted for about 3.5
months and the vegetative period started again in the beginning of April 2001.
The annual precipitation and air temperature for 1998 – 2000 is shown in Table 5. During
those years the amount of precipitation was between 697 and 955 mm. The number of days
with precipitation decreased from 162 in 1998 to 148 in 2000. The air temperature increased
during these three years from 8.3 in 1998 to 9.7 in 2000.
Table 5. Precipitation and air temperature for the sampling area during the three years,
including the first study year (2000) (http://www.weather.vattenriket.kristianstad.se/cgiwin/vader.exe)
Year
1998
1999
2000
Precipitation (mm)
Precipitation Number of days
with precipitation
831
162
955
154
697
148
Air temperature (◦C)
Maximum
Average
Minimum
temperature temperature temperature
26.9
8.3
-11.9
29.9
9.1
-13.7
32.9
9.7
-13.9
The monthly precipitation and average air temperature for the sampling period close to the
site are presented in Table A37. The precipitation during the sampling period ranged between
20 and 122 mm. The lowest precipitation period was during February and March in 2001,
23
45
1
40
35
2
4
3
30
5
20
10
temp limit for growing period
30
0
f reezing point
-10
20
◦
-20
15
precipitation
9-7 2001
24-7 2001
9-6 2001
24-6 2001
25-5 2001
10-5 2001
25-4 2001
10-4 2001
26-3 2001
11-3 2001
9-2 2001
24-2 2001
25-1 2001
10-1 2001
26-12 2000
11-12 2000
26-11 2000
11-11 2000
27-10 2000
27-9 2000
12-10 2000
12-9 2000
28-8 2000
13-8 2000
29-7 2000
14-7 2000
29-6 2000
14-6 2000
30-5 2000
-50
15-5 2000
0
30-4 2000
-40
15-4 2000
5
31-3 2000
-30
1-3 2000
10
16-3 2000
Precipitation (mm)
25
Air temperatur ( C)
with about 20 mm for each month. The wettest month was June 2000, with a precipitation
amount of 122 mm, but during the autumn (September – November) the amount of
precipitation varied between 61 and 95 mm. The average air temperature during the summer
(June – August) 2000 ranged between 15.5 and 16.8 ◦C and the autumn temperature ranged
between 7.6 and 13.0 ◦C. The winter (December 2000- March 2001) had an average air
temperature ranging between 0.2 and 3.4 ◦C. From April to 5th June, the temperature ranged
between 9.3 and 13.3 ◦C.
temp
Figure 5. Dynamics of precipitation and air temperature over the sampling period close to the
sampling site (N 56◦ 02’ 05,0825’, O 14◦ 09’ 11,1474’), where 1, 2…5 =dates of sampling
occasions (1=5th September 2000, 2=8th October 2000, 3=11th November 2000, 4=15th April
2001 and 5=5th June 2001) (http://www.weather.vattenriket.kristianstad.se/cgi-win/vader.exe).
5.3. Method for phosphorus fractionation and analysis
5.3.1. Phosphorus fractionation and fraction description
To separate P forms from the total P content, a sequential fractionation was conducted
according to the method established by Hedley et al. (1982) and modified by Otabbong &
Persson (1994).
The fractionation was conducted in four stages where each stage was given a P fraction name
depending on the agent used (resin (an anion exchanger), bicarbonate, hydroxide and
hydrochloride) to extract P from the soil. The fractions in this study are therefore referred to
as Resin-P, Bicarbonate-P, Hydroxide-P and HCl-P. To obtain the fraction referred as
Residual-P in this study, Resin-P, Bicarbonate-P, Hydroxide-P and HCl-P were subtracted
from Total-P.
As reviewed by Otabbong & Persson (1994), Resin-P and Bicarbonate-P consist of inorganic
P and organic P and are labile. When adsorbed to surfaces of crystalline compounds,
sesquioxides and carbonates, P is readily available to plants. Bicarbonate-P also includes
fulvic acid P, humic acid P and microbial P, which all must be mineralised before P can be
absorbed by plants. Hydroxide-P, however, is non labile and is sparingly available to plants.
24
This fraction consists of P occluded by Fe oxides, stegnite P and P in fulvic and humic acids.
HCl-P is also non labile and this fraction consists mainly of apatite mineral which becomes
available as the soil becomes acidified. The final fraction is Residual-P, which consists partly
of P occluded primarily by silicate minerals and partly of very resistant and non-extractable P
trapped in mineral materials.
Soil samples taken at the depths 0-20, 20-40, 40-60, 60-80 and 80-100 cm within an area of
10 m2 on five occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th
April 2001 and 5th June 2001) were used. Three replicates were taken at each depth on each
occasion.
The samples were air-dried at 40◦C and then crushed and passed through a sieve of 2 mm.
A scheme of fractionation is depicted in Figure 6. Thus, 1g of the sample of ≤2mm was
suspended in 60 ml deionised water. A bag of resin (Cl- anion exchanger) was added and the
sample shaken for 16 h (Stage 1). The resin bag was removed from the solution. The soil
particles on the bag were carefully washed off with deionised water into the solution. The
solution was centrifuged at 3500 rpm for 10 min. The liquid was then carefully decanted off
and thrown away, leaving a ‘soil cake’. This ‘cake’ was used in the next fractionation stage.
The bag of resin was extracted with 60 ml of 0.5 M HCl, shaken for 1 h and the solution was
then used for P analysis (Resin-P).
To the ‘cake’, 60 ml 0.5 M NaHCO3 at pH 8.5 was added (Stage 2). The solution was shaken
for 16 h, then centrifuged at 3500 rpm for 10 min. The liquid was decanted off and saved for
P analysis (Bicarbonate-P).
To the remaining ‘cake’, 60 ml of 0.1 M NaOH at pH above 12 was added (Stage 3). The
solution was shaken for 16 h, then centrifuged at 3500 rpm for 10 min. The liquid was
decanted off and saved for P analysis (Hydroxide-P).
To the remaining ‘cake’, 60 ml of 1 M HCl was added (Stage 4). The solution was shaken for
16 h, then centrifuged at 3500 rpm for 10 min. The liquid was decanted off and saved for P
analysis (HCl-P).
A separation into inorganic-P and organic-P of the fractions Bicarbonate-P and Hydroxide-P
was conducted. Two samples from the solution saved for P analysis (Stages 2 and 3) were
taken from each of the two fractions. One was used for measurement of Total-P (BicarbonateP and Hydroxide-P) and one for measurement of Inorganic-P (Bicarbonate-IP and HydroxideIP). Organic-P (Bicarbonate-OP and Hydroxide-OP) was then obtained by subtracting
Inorganic-P from Total-P, as shown in Figure 6. To analyse Inorganic-P, the organic colloids
were coagulated by adding 1 ml 0.9 M H2SO4 to 10 ml extractant. The solution was then
centrifuged at 3500 rpm for 10 min and the liquid was decanted off and used for P analysis.
To analyse Total-P, a sample of 5 ml solution was digested in a mixture of 2 ml of 97%
H2SO4 and 1 ml of 25% H2O2 until clear. The digestate was used for P analysis.
To obtain Total-P of the soil, a new sample from the dried, crushed and sieved soil consisting
of 2 g of the fraction ≤ 2 mm was incinerated and the ash was dissolved in 10 ml of 1 M HCl
and then analysed.
25
Stage 1
Stage 2
Resin-P
1g soil +
HCO3- (resin)
bag in H2O
Shake
Centrif.
Stage 3
Stage 4
Bicarbonate-P
Hydroxide-P
Soil
0.5 M NaHCO3
Shake
Centrifuge
Soil
0.1 M NaOH
Shake
Centrifuge
HCl-P
Soil
1 M HCl
Shake
Centrifuge
Stage 5
Residual-P
Soil
Digest (97%
H2SO4 –
25% H2O2)
Discard
Solution
Bag
+
0.5 M HCl
Shake 1 h
Separation
of P forms
Separation
of P forms
P-analysis
P-analysis in
digestate
Bag washed
in 0.5 M HCl
and preserved
in 0.1 M HCl
P-analysis
Digest (97%
H2SO4 – 25%
H2O2)
Remove
organics with
0.9 M H2SO4
Digest (97%
H2SO4 – 25%
H2O2)
Remove
organics with
0.9 M H2SO4
P-analysis
P-analysis
Total-P Inorganic-P
Total-P Inorganic-P
Total-P- Inorganic-P = Organic-P
Figure 6. A scheme for fractionating P, redrawn from Otabbong & Persson, 1994. The soil
used was air-dried and passed through a sieve of ≤ 2 mm. The samples were shaken for 16 h
and centrifuged at 3500 rpm. In this study, the extraction was ended at the HCl-stage. The
Total-P was determined by fusion. Residual-P was obtained by subtracting Resin-P,
Bicarbonate-P, Hydroxide-P and HCl-P from Total-P.
5.3.2. Phosphorus analysis
To determine P from the different stages, the molybdate ascorbic acid procedure (Murphy &
Riley, 1962) was used colorimetrically on the saved solutions. To enable solutions with high
concentrations to be analysed, some had to be diluted before analysis. The principle of the
method is as follows: 5 ml of the saved solution was transferred into a 25 ml bottle, 2 drops of
methyl orange was added and the solution was titrated to a weak yellowish colour. Two ml of
ascorbic molybdate were added and the solution was diluted to 25 ml with deionised water.
The colour intensity was then measured at 880 nm on a colorimeter. The result was then
compared with a standard curve and P was subsequently determined.
26
5.3.3. pH analysis
A soil sample of 1 g was suspended in 10 ml deionised water and shaken for 30 min and pH
was determined on a pH-meter at accuracy of ± 0.01 units.
5.3.4. Statistics
The results were subjected to statistical analysis of variance and Pearson’s correlation, using
the SAS Institute software (2000). Means for depth and seasons were separated at the
Student’s t-test (p<0.05) and relationships among the fractions was based on Pearson’s linear
correlation coefficients (r) at 95% probability.
27
6. Results and discussion
6.1 Phosphorus fractions and pH
The results as mean values for the five sampling occasions of each P fraction and pH at
different depths are depicted in Figures 7-12, with more information listed in the Appendices,
Tables A1- A6.
The three dominant fractions were Bicarbonate-P, Hydroxide-P and Residual-P, which
together made up about 95-97% of Total-P (TP). As a general observation the upper layers (020, 20-40 cm) tended to have the highest amounts of P, which decreased with depth (40-60,
60-80, 80-100 cm).
The fraction Resin-P ranged between 1.0 and 1.3% of TP and formed the smallest part of TP
(Figure 7 and Table A2). In absolute values Resin-P ranged between 21 and 33 mg/kg (Figure
8 and Table A1) and tended to decrease down the profile whereas Resin-P as a percentage did
not show such a trend.
Bicarbonate-P ranged between 19 and 42% of TP (Figure 7 and Table A2) and between 295
and 1190 mg/kg (Figure 8 and Table A1). Bicarbonate-P showed the same trend as a
percentage as it did in absolute values, with the highest values being recorded in the upper
layers (0-20, 20-40 cm) whereafter the values decreased with depth (40-60, 60-80, 80-100
cm).
Hydroxide-P ranged between 32 and 42% of TP (Figure 7 and Table A2) and in absolute
values between 648 and 1201 mg/kg (Figure 8 and Table A1). Hydroxide-P showed the same
trend in absolute values as Bicarbonate-P, with the highest values recorded in the upper layers
(0-20, 20-40 cm) and a decreasing trend with depth (40-60, 60-80, 80-100 cm). However
when expressed as a percentage, the opposite trend was observed.
HCl-P also formed a small part of TP and ranged between 1.7 and 3.3% of TP (Figure 7 and
Table A2). In absolute values, HCl-P ranged between 27 and 97 mg/kg (Figure 8 and Table
A1). In general, HCl-P tended to decrease down the profile.
Residual-P ranged between 22 and 37% of TP (Figure 7 and Table A2) or between 554 and
919 mg/kg (Figure 8 and Table A1).
28
P content of TP, %
45
a
a
40
a
35
a
ab
b
a
a
b
30
ab
ab
b
25
b
b
b
20
15
10
5
a
bc
a
a
ab
a
bc
a
c
a
0
0-20
Resin-P
20-40
Bicarbonate-P
40-60
Hydroxide-P
HCl-P
60-80
80-100
Depth (cm)
Residual-P
P content, mg/kg
Figure 7. Distribution of phosphorus (P) content as a percentage of Total-P (TP) in the soil
profile, as mean values based on the results on five sampling occasions (5th September 2000,
8th October 2000, 11th November 2000, 15th April 2001 and 5th June 2001). Mean values with
similar letters within the same P fraction are not statistically different at 95% probability.
1400
a
1200
a
a
a
1000
a
ab
800
b
600
b
ab
b
b
b
ab
b
400
b
200
b
a
ab
a
ab
b
b
c
b
c
0
0-20
Resin-P
Bicarbonate-P
20-40
Hydroxide-P
40-60
HCl-P
Residual-P
60-80
80-100
Depth (cm)
Figure 8. Distribution of phosphorus (P) content in mg/kg in the soil profile, as mean values
based on the results on five sampling occasions (5th September 2000, 8th October 2000, 11th
November 2000, 15th April 2001 and 5th June 2001). Mean values with similar letters within
the same P fraction are not statistically different at 95% probability.
6.1.1. Bicarbonate Organic and Inorganic Phosphorus
The distributions of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and Bicarbonate
Inorganic Phosphorus (Bicarbonate-IP) are shown in Figure 9 and Tables A3 and A4.
Bicarbonate-IP and Bicarbonate-OP both showed the same trend as Bicarbonate-P, with the
highest values in the upper layers (0-20, 20-40 cm) and a decreasing trend for the other layers
down the profile. Bicarbonate-IP was higher than Bicarbonate-OP in the upper layers (0-20,
20-40 cm) whereas Bicarbonate-OP was slightly higher than Bicarbonate-IP in the layers
below (40-60, 60-80, 80-100 cm) (Figure 9). Bicarbonate-IP ranged between 141 and 744
mg/kg, whereas Bicarbonate-OP ranged between 155 and 516 mg/kg (Figure 9 and Table A3).
Expressed as a percentage, Bicarbonate-IP ranged between 46 and 59% of Bicarbonate-P and
29
Bicarbonate OP and IP content, mg/kg
Bicarbonate-OP ranged between 41 and 53% of Bicarbonate-P (Table A4). Bicarbonate-IP
had the highest percentage, ranging between 55 and 59% of Bicarbonate-P in the upper layers
(0-20, 20-40 cm) and decreasing to about 47% in the layers below (40-60, 60-80, 80-100 cm),
whereas Bicarbonate-OP ranged between 41 and 45 % of Bicarbonate-P in the upper layers
(0-20, 20-40 cm) and increased to about 53% in the layers below (40-60, 60-80, 80-100 cm)
(Table A4).
800
a
a
700
600
500
a
a
400
b
300
b
200
b
b
b
b
100
0
0-20
Bicarbonate-OP
20-40
Bicarbonate-IP
40-60
60-80
80-100
depth (cm)
Figure 9. Distribution of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and Bicarbonate
Inorganic Phosphorus (Bicarbonate-IP) in mg/kg in the soil profile, as mean values based on
the results on five sampling occasions (5th September 2000, 8th October 2000, 11th November
2000, 15th April 2001 and 5th June 2001). Mean values with similar letters within the same P
fraction are not statistically different at 95% probability.
6.1.2. Hydroxide Organic and Inorganic Phosphorus
The distributions of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) are shown in mg/kg in Figure 10 and Tables A3 and
A4. Hydroxide-OP accounted for the largest fraction of Hydroxide-P and ranged between 78
and 84% (Table A4). Hydroxide-OP ranged between 517 and 986 mg/kg, whereas HydroxideIP ranged between 125 and 216 mg/kg (Figure 10 and Table A3). In absolute values
Hydroxide-OP was highest in the uppermost layers (0-20, 20-40 cm) and decreased down the
profile (Figure 10) as did the general trend of Hydroxide-P (Figure 8), whereas Hydroxide-IP
showed a slight decreasing trend down the profile. However as percentages, there were no
differences for either Hydroxide-OP or Hydroxide-IP down the profile (Table A4).
30
Hydroxide OP and IP content, mg/kg
1100
1000
a
900
a
800
700
b
600
b
b
500
400
300
a
200
a
a
100
a
a
0
0-20
Hydroxide-OP
20-40
Hydroxide-IP
40-60
60-80
80-100
Depth (cm )
Figure 10. Distribution of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) in mg/kg in the soil profile, as mean values based on
the results on five sampling occasions (5th September 2000, 8th October 2000, 11th November
2000, 15th April 2001 and 5th June 2001). Mean values with similar letters within the same P
fraction are not statistically different at 95% probability.
6.1.3. Total Organic and Inorganic Phosphorus
As no mineral soil was observed in the studied soil profile, the assumption were made that
Residual-P was organically bound P. Hence, Total Organic Phosphorus (Total-OP) was the
sum of Bicarbonate-OP, Hydroxide-OP and Residual-P. Total Inorganic Phosphorus (TotalIP) was the sum of Resin-P, Bicarbonate-IP, Hydroxide-IP and HCl-P. The distributions of
Total-OP and Total-IP are shown in Figure 11 and Tables A5 and A6. Total-OP made up the
biggest share of TP and ranged between 66 and 79% (Table A6). Total-OP ranged in absolute
values between 1257 and 2421 mg/kg, whereas Total-IP ranged between 321 and 987 mg/kg
(Figure 11 and Table A5). Total-OP and Total-IP showed the same trend with the highest
values in the upper layers (0-20, 20-40 cm) and for the other layers (40-60, 60-80, 80-100 cm)
a decreasing trend down the profile.
31
Total OP and IP content, mg/kg
3000
2500
a
a
2000
b
b
1500
b
a
1000
a
b
500
b
b
0
0-20
Total-OP Total-IP
20-40
40-60
60-80
80-100
Depth (cm)
Figure 11. Distribution of Total Organic Phosphorus (Total-OP) and Total Inorganic
Phosphorus (Total-IP) in mg/kg in the soil profile, as mean values based on the results on five
sampling occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th April
2001 and 5th June 2001), where Total-OP is the sum of Residual-P, Bicarbonate-OP and
Hydroxide-OP, whereas Total-IP is the sum of Resin-P, Bicarbonate-IP, Hydroxide-IP and
HCl-P. Mean values with similar letters within the same P fraction are not statistically
different at 95% probability.
pH
6.1.4. pH
The distribution of pH is shown in Figure 12 and Table A1. The pH ranged between 3.9 and
5.3, with its lowest value in the 40-60 cm layer and its maximum value at in the 80-100 cm
layer.
6
5
ab
a
b
c
d
4
3
2
1
0
0-20
20-40
40-60
60-80
80-100
Depth (cm)
Figure 12. pH in the soil profile, as mean values based on the results on five sampling
occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th April 2001 and
5th June 2001). Mean values with similar letters are not statistically different at 95%
probability.
32
6.2. Phosphorus fractions and pH at different depths and dates
In addition to the results presented in Figures 7 -12, pH changes and P distribution in the soil
profile for each date (5th September 2000, 8th October 2000, 11th November 2000, 15th April
2001 and 5th June 2001) at each depth (0-20, 20-40, 40-60, 60-80 and 80-100 cm) are shown
in Figures 13-21 and Figures A1-A13 and listed in Tables A7-A36.
6.2.1. Total Phosphorus
The distribution of Total-P at different depths is shown for the five sampling occasions in
mg/kg in Figure 13 and in Tables A7, A13, A19, A25 and A31. Total-P ranged between 1434
and 4319 mg/kg. As noted above, the upper layers (0-20, 20-40 cm) tended to have the
highest values (2553-4319 mg/kg). In the layers below (40-60, 60-80, 80-100 cm) the amount
of TP was about the same (1434-2286 mg/kg) down the profile and no change was observed
over the season. However, in the upper layers (0-20, 20-40 cm) the values in September,
October and November were higher (2983-4319 mg/kg) than those in April and June (25533202 mg/kg). The higher values in the autumn coincided with the end of the growing period
(Figure 5). Although the temperature limit for the growing period (5oC air temperature, wwwmarkinfo.slu.se) was not exceeded, growth was slowing down and plants were decaying.
During the winter the sampling site was inundated, causing anaerobic conditions and leaching
could theoretically occur, which was indicated by the lower values in April.
To ta l-P co n te n t, m g /kg
0
1000
2000
3000
4000
5000
D e p th (cm )
0 -2 0
2001-04-15
2000-09-05
2001-06-05
2000-10-08
2 0 -4 0
4 0 -6 0
6 0 -8 0
2000-11-11
8 0 -1 0 0
Figure 13. Distribution of Total-P content in mg/kg in the soil profile on the five sampling
occasions.
33
6.2.2. Resin-extractable Phosphorus
The Resin-P values at different depths are shown for the five sampling occasions in absolute
values in Figure 14 and in Tables A7, A13, A19, A25 and A31 and as a percentage of TP in
Tables A8, A14, A20, A26 and A32 and Figure A1. Resin-P, which is biologically available
and soluble, ranged between 16 and 46 mg/kg (Figure 14 and Tables A7, A13, A19, A25 and
A31) and between 0.39 and 2.00% of TP (Tables A8, A14, A20, A26 and A32 and Figure
A1). The amount of Resin-P varied in the upper part of the profile (0-20, 20-40 cm), ranging
between 17 and 46 mg/kg, and showed a decreasing trend (16-36 mg/kg) with depth (40-60,
60-80, 80-100 cm). The highest values in mg/kg were observed in the upper two layers (0-20,
20-40 cm) in April and June (34-46 mg/kg) whereas the lowest value was observed in
November (17-20 mg/kg). As a percentage of TP (Figure A1), an increasing trend with depth
was observed, ranging between 0.53 and 1.70 % in the top layer (0-20 cm) and between 1.15
and 1.77 % in the bottom layer (80-100 cm). In the upper part of the profile (0-20, 20-40 cm),
the values in April and June were higher (1.15-1.70 % of TP) than those in September,
October and November (0.39-0.94 % of TP).
R e sin -P co n te n t, m g /kg
0
10
20
30
40
50
D e p th (cm )
0 -2 0
2001-04-15
2000-09-05
2001-06-05
2000-10-08
2 0 -4 0
4 0 -6 0
6 0 -8 0
2000-11-11
8 0 -1 0 0
Figure 14. Distribution of Resin-P content in mg/kg in the soil profile on five sampling
occasions.
6.2.3. Bicarbonate-soluble Phosphorus
Bicarbonate-P values at different depths are shown for the five sampling occasions in absolute
values in Figure 15 and Tables A7, A13, A19, A25 and A31 and as a percentage of TP in
Tables A8, A14, A20, A26 and A32 and Figure A2. Bicarbonate-P, which is readily available
to plants, ranged between 289 and 1624 mg/kg (Figure 15 and Tables A7, A13, A19, A25 and
A31) and as a percentage between 17 and 56% of TP (Tables A8, A14, A20, A26 and A32
and Figure A2). Bicarbonate-P showed a decreasing trend down the profile in both absolute
34
values and as a percentage of TP. However, the absolute values in November, April and June
increased in the 20-40 cm layer and then decreased down the profile (Figure 15). As a
percentage only, the values in April and June increased in the 20-40 cm layer (Figure A2).
The highest values were observed in the upper two layers (0-20, 20-40 cm), ranging between
30-55% of TP (A8, A14) and between 819-1624 mg/kg (A7, A13).
0
400
B ica rb o n a te -P co n te n t, m g /kg
800
1200
1600
2000
D e p th (cm )
0 -2 0
2001-04-15
2000-09-05
2001-06-05
2000-10-08
2 0 -4 0
4 0 -6 0
6 0 -8 0
2000-11-11
8 0 -1 0 0
Figure 15. Distribution of Bicarbonate-P content in mg/kg in the soil profile on five sampling
occasions.
6.2.3.1. Bicarbonate-soluble Organic and Inorganic Phosphorus
The distributions of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and Bicarbonate
Inorganic Phosphorus (Bicarbonate-IP) are shown for the five sampling occasions in absolute
values in Tables A9, A15, A21, A27 and A33 and as a percentage of Bicarbonate-P in Figure
16, Tables A10, A16, A22, A28 and A34 and Figures A6-A9. Bicarbonate-OP ranged
between 21 and 64% of Bicarbonate-P. Bicarbonate-OP dominated the layers 40-60, 60-80
and 80-100 cm, ranging between 50 and 64% of Bicarbonate-P, with the exception of the
values in October at 40-60 cm and April and June at 80-100 cm, which all were lower than
50%. The biggest change was in the top layer (0-20 cm) (Table A10), where Bicarbonate-OP
was 21% in September, increased to about 60% in October and November and decreased
again in April and June to around 40%. In the other layers the change between BicarbonateOP and Bicarbonate-IP was not so great (Figures A6-A9).
35
Bicarbonate OP and IP (% of Bicarbonate-P)
100
90
a
c
c
b
a
b
3
4
b
80
70
60
50
40
30
20
10
c
a
b
0
1
Bicarbonate OP
2
Bicarbonate IP
5
Sampling occasions
Figure 16. Distribution of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and
Bicarbonate Inorganic Phosphorus (Bicarbonate-IP) as a percentage of Bicarbonate-P on five
sampling occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November
2000, 4=15th April 2001 and 5= 5th June 2001) at 0-20 cm depth. Mean values with similar
letters within the same P fraction are not statistically different at 95% probability.
6.2.4. Hydroxide-soluble Phosphorus
Hydroxide-P ranged between 521 and 1638 mg/kg (Figure 17 and Tables A7, A13, A19, A25
and A31) and as a percentage between 29 and 48% of TP (Tables A8, A14, A20, A26 and
A32 and Figure A3). Hydroxide-P tended to decrease with depth. The highest values (7781638 mg/kg) were observed in the upper layers (0-20, 20-40 cm) and decreased to 872-521
mg/kg in the layers below (40-60, 60-80, 80-100 cm), where no change was observed over the
season. It might be worth noting that the absolute values in April and June at 0-20 and 20-40
cm were lower (778-918 mg/kg) than those in September, October and November (876-1638
mg/kg). Furthermore, the absolute values increased in the upper layers (0-20, 20-40 cm) from
September (876-1239 mg/kg) to November (1333-1638 mg/kg). As a percentage of TP,
Hydroxide-P tended to increase with depth. In the top layer (0-20 cm) October and November
tended to have the highest values (40-44% of TP), whereas the values in September, April and
June were lower (29-32 % of TP).
36
Hydroxide-P content, mg/kg
0
300
600
900
1200
1500
1800
0-20
2001-04-15
2000-09-05
2001-06-05
2000-10-08
20-40
40-60
60-80
depth (cm)
2000-11-11
80-100
Figure 17. Distribution of Hydroxide-P content in mg/kg in the soil profile on five sampling
occasions.
6.2.4.1. Hydroxide-soluble Organic and Inorganic Phosphorus
The distributions of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) are shown for the five sampling occasions in absolute
values in Tables A9, A15, A21, A27 and A33 and as a percentage of Hydroxide-P in Figure
18, Tables A10, A16, A22, A28 and A34 and Figures A10-A13. In absolute values
Hydroxide-IP ranged between 22 and 388 mg/kg and Hydroxide-OP ranged between 3731002 mg/kg. Hydroxide-OP ranged between 56 and 97% of Hydroxide-P (Figure 18, Tables
A10, A16, A22, A28 and A34 and Figures A10-A13) and hence dominated all layers. The
largest variation was in the top layer (0-20 cm), with Hydroxide-OP ranging between 60-93%
of Hydroxide-P over the seasons.
37
Hydroxide OP and IP (% of Hydroxide-P)
100
90
b
ab
b
a
b
a
ab
a
b
a
80
70
60
50
40
30
20
10
0
1
Hydroxide OP
2
Hydroxide IP
3
4
5
Sampling occasions
Figure 18. Distribution of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) as a percentage of Hydroxide-P on five sampling
occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November 2000, 4=15th
April 2001 and 5= 5th June 2001) at 0-20 cm depth. Mean values with similar letters within
the same P fraction are not statistically different at 95% probability.
6.2.5 Hydrochloric acid-soluble Phosphorus
HCl-P ranged between 23 and 128 mg/kg (Figure 19 and Tables A7, A13, A 19, A25 and
A31) and between 1.1 and 4.8% of TP (Figure A4 and Tables A8, A14, A 20, A26 and A32),
and hence accounted for a small part of TP. For all five sampling occasions the same trend
was observed both in absolute values and as a percentage of TP, with an increase from the
upper layer (0-20 cm) (44-71 mg/kg and 1.10-2.15 % of TP) to the second layer (20-40 cm)
(88-128 mg/kg and 2.04-4.84 % of TP) and then a decrease down the profile. It is worth
noting that the absolute value in June for the 20-40 cm increased to 128 mg/kg, whereas the
values from September, October, November and April ranged between 88 and 97 mg/kg
(Figure 19 and Table A13). As a percentage, however, the trend with increased values in the
20-40 cm layer was not so distinct for October and November, whereas in September, April
and June that trend was clear (Figure A4, Table A14).
38
HCl-P content, mg/kg
0
20
40
60
80
100
120
140
Depth (cm)
0-20
20-40
2001-04-15
2000-09-05
2001-06-05
2000-10-08
40-60
60-80
2000-11-11
80-100
Figure 19. Distribution of HCl-P content in mg/kg in the soil profile on five sampling
occasions.
6.2.6. Residual Phosphorus
The fraction Residual-P at different depths is shown for the five sampling occasions in mg/kg
in Figure 20 and Tables A7, A13, A 19, A25 and A31 and as a percentage in Figure A5 and
Tables A8, A14, A 20, A26 and A32. Residual-P ranged between 224 and 1537 mg/kg
(Figure 20 and Tables A7, A13, A 19, A25 and A31) and as a percentage between 8 and 44%
of TP (Figure A5 and Tables A8, A14, A 20, A26 and A32). The biggest change was
observed in the 20-40 cm layer, where the absolute values in April and June decreased to the
same value, 224 mg/kg, whereas the values in November increased to 1537 mg/kg, which was
the highest value for this fraction (Table A13). The values in September and October
increased only slightly at the same layer (20-40 cm). The percentage of TP (Figure A5)
showed the same trend, as did the values in mg/kg in the top layers (0-20, 20-40 cm). In the
layers below (40-60, 60-80, 80-100 cm), however, the values as a percentage slightly
increased whereas the absolute values slightly decreased.
39
Residual-P content, mg/kg
0
400
800
1200
1600
2000
Depth (cm)
0-20
2001-04-15
2000-09-05
2001-06-05
2000-10-08
20-40
40-60
60-80
2000-11-11
80-100
Figure 20. Distribution of Residual-P content in mg/kg in the soil profile on five sampling
occasions.
6.2.7. pH
The pH at different depths is shown for the five sampling occasions in Figure 21 and Tables
A7, A13, A19, A25 and A31. The pH ranged between 3.5 and 5.6. It tended to decrease from
the upper layer (0-20 cm) down to the 40-60 cm layer and then increase again in the layers
below.
40
pH
0
1
2
3
4
5
6
D e p th (cm )
0 -2 0
20 -4 0
2000-09-05
2001-04-15
40 -6 0
2000-10-08
2001-06-05
60 -8 0
2000-11-11
8 0-1 0 0
Figure 21. Distribution of pH in the soil profile on five sampling occasions.
6.3 Correlations
Correlations of P fractions are shown in Tables 6 and 7. Caution should be taken when
interpreting correlations since the number of samples was not large (n=25). However, the
results show some trends of relationship among the P fractions. Most of the correlations based
on the absolute values were positive, whereas negative correlations were obtained when
values were expressed as percentages. In the latter case it is worth noting the relationship
between Residual-P and HCl-P, between Residual-P and Bicarbonate-P, between HCl-P and
Hydroxide-P, and between Hydroxide-P and Bicarbonate-P, which were significant and
negative, implying that either one increases at the expense of the other. Even if the
correlations based on percentages were not significant between Resin-P and Bicarbonate-P, a
negative correlation was noted that theoretically would mean that the fractions transformed
into each other.
Table 6. Correlations among phosphorus (P) fractions based on mean values as a % of TP on
five sampling occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th
April 2001 and 5th June 2001), where n =25
HCl-P
Residual-P
Resin-P
Bicarbonate-P
Hydroxide-P
-0.40*
0.04
0.08
-0.57**
Bicarbonate-P
0.56**
-0.83***
-0.13
Resin-P
0.27
0.02
Residual- P
-0.50**
* p = 0.05; ** 0.05 > p ≥ 0.01; *** 0.01> p
41
Table 7. Correlation between phosphorus (P) fractions based on mean values in mg/kg on
five sampling occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th
April 2001 and 5th June 2001) where n =25
HCl-P
Residual-P
Bicarbonate-IP
Bicarbonate-OP
Hydroxide-IP
Hydroxide-OP
Resin-P
0.45**
-0.06
0.41**
0.36
-0.11
0.09
Hydroxide-OP
0.49**
0.42**
0.61***
0.76***
0.30
Hydroxide-IP
0.05
0.54***
0.28
0.30
Bicarbonate-OP
0.79***
0.18
0.64***
Bicarbonate-IP
0.66***
0.39
Residual P
0.14
* p = 0.05; ** 0.05 > p ≥ 0.01; *** 0.01> p
6.4. General discussion
We are aware that P may have been added to the sampling site, when for example the soil was
inundated by the nutrient-rich stream Vinneå or via animal droppings from e.g. the huge
flocks of geese that spend the winter in southern Sweden. P has most likely been added via
decaying plants, but in this study only soil was examined. We are also aware that P may have
been lost to the soil solution or through leaching, or via plant uptake. These types of features
are important but were not accounted for in this study. We are also aware that the water level
in the stream and the groundwater level are important features but we did not have the
possibility to monitor them.
Soil pH, moisture content, chemical relationships and temperature control the transformation
of P in soils. Theoretically during the vegetative period when the soil is mostly aerobic,
soluble P can be absorbed by plants and microbes or can be precipitated by compounds like
Fe, Al and Mn. When inundation causes anaerobic conditions, however, plant and microbial
activity decreases and P can be released from compounds of Fe, Al and Mn. During the winter
when temperature is low biological activity ceases, leading to decreased biological
transformation of P and no plant uptake. When soil pH is lower than 7.2, soluble P is
adsorbed to clay minerals and Fe/Al-oxides and/or is precipitated as Fe/Al-P secondary
minerals. P also competes with organic and inorganic compounds for bonding sites or can be
adsorbed by organic compounds.
Total-P content in this study was largest in the upper layers (0-20, 20-40 cm) and showed a
variation over the seasons in those layers, whereas in the layers below (40-60, 60-80, 80-100
cm) no great variation was noted. Börling (2003) showed a similar trend with high amounts of
P in the upper 40 cm of fertilized arable land which was not shown for non-fertilized arable
land. In addition, the inundating stream in the present study contains high amounts of P, most
likely originating from upstream arable land (Fristedt, 1999). These facts indicate that high
amounts of P may have been incorporated into the soil over a long period of time, but the
reason is not clear. Generally the upper 30 cm of a soil profile are characterised by high root
density (Richardson & Marshall, 1986; Jackson et al., 1996) and thus high biological activity.
The variation over the season in this study indicated a high biological activity in the upper 40
cm. The highest Total-P content in the upper 40 cm was noted in November, ranging between
3738 and 4319 mg/kg. This is at the end of the growing period, when plants have been
decaying, which may have added P to the soil. According to Richardson & Marshall (1986),
about 35% of aboveground P uptake by plants is returned to the ground surface via litter fall.
42
In April, however, the Total-P content in the upper 40 cm was at its lowest, ranging between
2646 and 3202 mg/kg. This sampling occasion was preceded by a period of high water levels
and leaching may theoretically have occurred. Mahapatra & Patrick (1969) show that iron and
aluminium phosphates increase during waterlogged conditions. They also show that the iron
phosphate originates partly from the reductant soluble iron phosphate. In addition, Diaz,
Anderson & Hanlon (1993) show that an increasing amount of total P is mineralised under
flooded conditions and that flooding significantly increases the amount of Total P released
into the drainage effluents. They also found that the leachate contains soluble inorganic and
organic P and that the amount of leached organic P is greater under flooded conditions.
When the sample in April was taken, the growing period was just starting (Figure 5) and had
been preceded by an inundated and cool period. Theoretically, when the soil becomes more
aerated and the temperature increases, microbial activity increases (Gross et al., 1995).
Microbes promote the transformation of unavailable P to available P. An increased microbial
activity would thereby release more P. This study indicates that the amount of soluble P is
highest in spring and early summer. However, there were no samples taken of the soil
solution, nor was plant material analysed. It is therefore hard to say how much soluble P there
really was. One would expect a high plant uptake during the summer and chemical release
during the anaerobic conditions in winter time.
In this study the soluble pool (Resin-P) behaved differently in the profile over the seasons.
For example most of the transformations seemed to occur in the 0-20 and 20-40 cm layers.
Over the seasons, the soluble pool was largest in April and June and lowest in November.
However, theoretically, an unknown portion of this fraction should be in the soil solution, but
no such study was conducted.
The readily available P pool (Bicarbonate-P) also behaved differently in the profile over the
seasons. In this pool too, most of the transformations seemed to occur in the upper layers (020, 20-40 cm). This pool seemed to have the opposite trend as a percentage of TP compared
with the resistant P pool (Residual-P), in that Bicarbonate-P decreased down the profile
(Figure A2) whereas Residual-P increased down the profile (Figure A5). In April and June
there was a clear trend in the 20-40 cm layer where Bicarbonate-P increased whereas
Residual-P decreased. This, together with the significant correlation based on percentage of
TP (Table 6), indicates that Residual-P transforms into Bicarbonate-P and vice versa.
There was also a significant negative correlation as a percentage of TP between Bicarbonate-P
and the sparingly plant available Hydroxide-P, which together with Figure 7 indicate that
Bicarbonate-P transforms into Hydroxide-P.
The non labile pool HCl-P had significant negative correlations as a percentage of TP (Table
6) with the also sparingly plant available Hydroxide-P and Residual-P, which indicates that
HCl-P increases when Hydroxide-P or Residual-P decreases or vice versa. Figures A5 and A4
also indicate this trend where HCl-P decreases down the profile whereas Residual-P increases
down the profile. Hydroxide-P also shows an increasing trend down the profile (Figure A3)
but is not as clear as the trend shown for Residual-P.
This study indicates that the P forms transform into each other and that most transformations
occur in the upper 40 cm of the profile. The total P content is lower after the winter when the
soil has been inundated, indicating loss of P, most likely through leaching. Most
transformations seem to occur in spring and early summer, although since the loss or gain of P
43
via for example the inundating water and groundwater was not monitored, it is hard to draw
any accurate conclusions on seasonal influences.
7. Conclusions
ƒ
P was mainly organically bound (66-79%)
ƒ
The upper 40 cm of the soil profile contained the largest amount of P (2553-4319
mg/kg)
ƒ
The Total-P content decreased during the winter when the soil was inundated
ƒ
Bicarbonate-extractable P transformed into the resistant P pool and vice versa
ƒ
Bicarbonate-extractable P transformed into Hydroxide-extractable P and vice versa
ƒ
The resistant P pool transformed into HCl-extractable P and vice versa
ƒ
The HCl-extractable P transformed into Hydroxide-extractable P and vice versa
ƒ
The largest transformations occurred in spring and early summer
7.1. Concluding remarks
Riparian wetlands are complex systems, and are influenced by the adjacent water and also by
biological life in the form of plants and animals. It was therefore hard to monitor the real gain
or loss of P. To understand the dynamics of P in such wetland, it is important to examine
crucial features such as loss or gain via the inundating stream or via the groundwater. The
uptake via plants is another interesting feature worth investigating.
44
8. Acknowledgements
This study was conducted within the EU project Prowater ‘Program for Prevention of Diffuse
Pollution with Phosphorus from Degraded and Re-wetted Peat Soils’ (PROWATER-EVICICT-1999-00036) financed by European Union. The Swedish University of Agricultural
Sciences (SLU) supported the MSc studies.
I would like to thank my main supervisor Professor Erasmus Otabbong for introducing me to
the interesting subject of soil science and soil phosphorus. I especially want to thank my
second supervisor Dr. Elve Lode, for her enormous support and for always being there for me.
I also want to thank Per Edenhamn, Gerd Johansson and Brita Sjögren who made it possible
for me to finish this report. To Ragnar Persson, who helped me with all my computer
problems.
Furthermore I would like to thank the owner of the sampling site and the friendly neighbours
in the site area. Thanks to the people at the Department of MNA at the University of
Kristianstad and to Karin Magntorn, Kristianstad vattenrike.
I also would like to thank Dr. Mary McAfee who edited my English.
Finally I would like to thank my family and friends who have supported me, and especially
Emil, who has been there for me unconditionally.
45
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Websites
http://www.ramsar.org/key_conv_e.htm (20030909)
http://www-markinfo.slu.se/sve/klimat/vegper.html (200030915)
http://www.weather.vattenriket.kristianstad.se/cgi-win/vader.exe (200040928)
Maps
Figure A14: Lantmäteriverket, 1998, GSD-Digitalt ortofoto Dnr. 507-98-3015
Figure 4: Lantmäteriverket, ur GSD Röda kartan Dnr. 507-98-4720
Personal communication
Erasmus Otabbong, Supervisor (2004)
Karin Magntorn, Kristianstad Vattenrike, Kristianstad Kommun (08 12 2004)
Barry Broman, SMHI (08 12 2004)
48
10. Appendices
Appendix 1. Tables A1-A36: Raw data
Table A1. pH and Phosphorus (P) fractions in mg/kg as mean values on five sampling
occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th April 2001 and 5th
June 2001) at different depths
Depth (cm)
Total-P
(mg/kg)
pH
Resin-P
(mg/kg)
Bicarbonate -P
(mg/kg)
Hydroxide- P
(mg/kg)
HCl-P
(mg/kg)
Residual-P
(mg/kg)
5,1 ab
3408 a
33 a
1192 a
1201 a
62 b
919 a
0-20
4,8 b
3144 a
30 ab
1259 a
1004 a
97 a
754 ab
20-40
3,9 d
2012 b
27 ab
514 b
731 b
53 b
695 ab
40-60
4,4 c
1760 b
22 b
418 b
727 b
39 c
554 b
60-80
5,3 a
1577 b
21 b
295 b
648 b
27 c
585 ab
80-100
Mean values with similar letters within the same fraction are not statistically different with 95% probability.
Table A2. Phosphorus (P) fractions in percentage of Total-P (TP) as mean values on five
sampling occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th April
2001 and 5th June 2001) at different depths
Depth (cm)
Resin-P %
of TP
Bicarbonate- P %
of TP
Hydroxide-P %
of TP
HCl-P %
of TP
Residual-P %
of TP
1,01 a
34,58 a
34,98 b
1,85 bc
27,58 ab
0-20
1,03 a
41,51 a
31,85 b
3,25 a
22,36 b
20-40
1,34 a
25,67 b
36,26 ab
2,65 ab
34,08 a
40-60
1,28 a
23,85 b
41,28 a
2,22 bc
31,37 ab
60-80
1,34 a
18,84 b
41,33 a
1,74 c
36,75 a
80-100
Mean values with similar letters within the same fraction are not statistically different with 95% probability.
Table A3. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in mg/kg as mean values on five sampling
occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th April 2001 and 5th
June 2001) at different depths
Depth (cm)
Bicarbonat-IP (mg/kg)
Bicarbonat-OP
(mg/kg)
Hydroxide-IP
(mg/kg)
Hydroxide-OP
(mg/kg)
677 a
516 a
216 a
986 a
0-20
744 a
515 a
176 a
828 a
20-40
240 b
274 b
125 a
606 b
40-60
195 b
223 b
160 a
567 b
60-80
141 b
155 b
132 a
517 b
80-100
Mean values with similar letters within the same fraction are not statistically different with 95% probability.
Table A4. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in percentage of Bicarbonate-P and HydroxideP respectively as mean values on five sampling occasions (5th September 2000, 8th October
2000, 11th November 2000, 15th April 2001 and 5th June 2001) at different depths
Depth (cm)
Bicarbonate-IP % of
Bicarbonate-P
Bicarbonate-OP % of
Bicarbonate-P
Hydroxide-IP % of
Hydroxide-P
Hydroxide-OP % of
Hydroxide-P
55,81 ab
44,19 ab
18,23 a
81,77 a
0-20
59,08 a
40,92 b
15,83 a
84,17 a
20-40
46,77 b
53,23 a
17,68 a
82,33 a
40-60
46,76 b
53,24 a
21,70 a
78,30 a
60-80
47,48 b
52,53 a
20,23 a
79,77 a
80-100
Mean values with similar letters within the same fraction are not statistically different with 95% probability.
49
Table A5. Distribution of Total Organic Phosphorus (Total-OP) and Total Inorganic
Phosphorus (Total-IP) and Extractable Phosphorus (Extractable-P) in mg/kg as mean values
on five sampling occasions (5th September 2000, 8th October 2000, 11th November 2000, 15th
April 2001 and 5th June 2001) at different depths, where Total-OP was the sum of Residual-P,
Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P, BicarbonateIP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus Residual-P
Depth (cm)
Extractable-P (mg/kg)
Total-OP (mg/kg)
Total-IP (mg/kg)
2489 a
2421 a
987 a
0-20
2390 a
2097 a
1047 a
20-40
1325 b
1575 b
445 b
40-60
1206 b
1343 b
417 b
60-80
992 b
1257 b
321 b
80-100
Mean values with similar letters within the same fraction are not statistically different with 95% probability.
Table A6. Distribution of Total Inorganic (Total-IP) and Total Organic (Total-OP)
Phosphorus and Extractable Phosphorus (Extractable-P) in percentage of Total-P (TP) as
mean values on five sampling occasions (5th September 2000, 8th October 2000, 11th
November 2000, 15th April 2001 and 5th June 2001) at different depths where Total-OP was
the sum of Residual-P, Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of
Resin-P, Bicarbonate-IP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P
minus Residual-P
Depth (cm)
Extractable-P % of TP
Total-OP % of TP
Total-IP % of TP
72,42 ab
71,18 bc
28,82 ab
0-20
77,66 a
66,15 c
33,85 a
20-40
65,92 b
77,73 ab
22,27 bc
40-60
68,64 ab
76,42 ab
23,58 bc
60-80
63,26 b
79,77 ab
20,23 c
80-100
Mean values with similar letters within the same fraction are not statistically different with 95% probability.
Table A7. pH and Phosphorus (P) fractions in mg/kg on five sampling occasions at the depth
of 0-20 cm
Date
pH
Total-P
(mg/kg)
Resin-P
(mg/kg)
Bicarbonate-P
(mg/kg)
Hydroxide-P
(mg/kg)
HCl-P (mg/kg)
Residual-P
(mg/kg)
05-sep-00 5,3 a
3938 a
33 c
1624 a
1239 c
44 c
998 ab
08-okt-00
5,2 ab
3474 c
27 d
1300 b
1400 b
71 a
675 d
11-nov-00 4,8 c
3738 b
20 e
1206 b
1638 a
70 a
804 c
15-apr-01 5,0 bc
2688 e
46 a
819 d
865 d
55 b
904 bc
05-jun-01
5,3 a
3202 d
37 b
1058 c
918 d
69 a
1120 a
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A8. Phosphorus (P) fractions in percentage of Total-P (TP) on five sampling occasions
at the depth of 0-20 cm
Date
Resin-P %
of TP
Bicarbonate-P % of
TP
Hydroxide-P %
of TP
HCl-P %
of TP
Residual-P %
of TP
05-sep-00
0,85 c
41,23 a
31,47 c
1,10 c
25,35 b
08-okt-00
0,78 c
37,42 b
40,30 b
2,04 a
19,45 c
11-nov-00
0,53 d
32,27 cd
43,81 a
1,88 b
21,51 c
15-apr-01
1,70 a
30,46 d
32,17 c
2,03 ab
33,65 a
05-jun-01
1,15 b
33,04 c
28,66 d
2,15 a
35 a
Values with similar letters within the same fraction are not statistically different with 95% probability.
50
Table A9. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in mg/kg on five sampling occasions at the
depth of 0-20cm
Date
Bicarbonate-IP
(mg/kg)
Bicarbonate-OP
(mg/kg)
Hydroxide-IP
(mg/kg)
Hydroxide-OP (mg/kg)
05-sep-00
1272 a
353 b
239 a
1000 bc
08-okt-00
550 c
751 a
362 a
1038 b
11-nov-00
491 d
716 a
190 ab
1448 a
15-apr-01
490 d
329 b
349 a
516 d
05-jun-01
629 b
430 b
61 b
857 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A10. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in percentage of Bicarbonate-P and
Hydroxide-P respectively as mean values on five sampling occasions at the depth of 0-20 cm
Date
Bicarbonate-IP % of
Bicarbonate-P
Bicarbonate-OP % of
Bicarbonate-P
Hydroxide-IP % of
Hydroxide-P
Hydroxide OP % of
Hydroxide-P
05-sep-00
78,41 a
21,59 c
19,29 b
80,71 a
08-okt-00
42,30 c
57,70 a
25,88 ab
74,12 ab
11-nov-00
40,67 c
59,33 a
11,60 b
88,40 a
15-apr-01
59,80 b
40,20 b
40,25 a
59,75 b
05-jun-01
59,45 b
40,55 b
6,65 b
93,36 a
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A11. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic (TotalOP) Phosphorus and Extractable Phosphorus (Extractable-P) in mg/kg on five sampling
occasions at the depth of 0-20 cm, where Total-OP was the sum of Residual-P, BicarbonateOP and Hydroxide-OP whereas Total-IP were the sum of Resin-P, Bicarbonate-IP,
Hydroxide-IP and HCl-P and were Extractable P was Total-P minus Residual-P
Date
Extractable-P (mg/kg)
Total-OP (mg/kg)
Total-IP (mg/kg)
05-sep-00
2940 a
2351 b
1587 a
08-okt-00
2798 a
2464 b
1010 b
11-nov-00
2934 a
2967 a
771 c
15-apr-01
1783 c
1749 c
939 bc
05-jun-01
2081 b
2406 b
795 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A12. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic (TotalOP) Phosphorus and Extractable-Phosphorus (Extractable –P) in percentage of Total-P (TP)
on five sampling occasions at the depth of 0-20 cm, where Total-OP was the sum of ResidualP, Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P,
Bicarbonate-IP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus
Residual-P
Date
Extractable-P % of TP
Total-OP % of TP
Total-IP % of TP
05-sep-00
74,65 b
59,67d
40,33 a
08-okt-00
80,55 a
70,93 bc
29,07 bc
11-nov-00
78,49 a
79,38 a
20,62 d
15-apr-01
66,35 c
65,07 cd
34,93 ab
05-jun-01
65,00 c
75,16 ab
24,84 cd
Values with similar letters within the same fraction are not statistically different with 95% probability.
51
Table A13. pH and Phosphorus (P) fractions in mg/kg on five sampling occasions at the
depth of 20-40 cm
Date
pH
Total-P
(mg/kg)
Resin-P
(mg/kg)
Bicarbonate-P
(mg/kg)
Hydroxid-P
(mg/kg)
HCl-P
(mg/kg)
Residual-P
(mg/kg)
05-sep-00 4,5 c
2983 c
25 d
944 c
876 c
96 b
1042 b
08-okt-00
4,8 a
3254 b
31 c
1088 b
1233 b
88 c
816 b
11-nov-00 5,3 a
4319 a
17 e
1345 a
1333 a
88 c
1537 a
15-apr-01 4,9 b
2553 d
34 b
1406 a
792 d
97 b
224 c
05-jun-01
4,8 b
2646 d
44 a
1474 a
778 d
128 a
224 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A14. Phosphorus (P) fractions in percentage of Total-P (TP) on five sampling
occasions at the depth of 20-40 cm
Date
Resin-P %
of TP
Bicarbonate-P % of
TP
Hydroxide-P %
of TP
HCl-P %
of TP
Residual-P %
of TP
05-sep-00
0,84 d
31,74 b
29,42 b
3,21 c
34,79 a
08-okt-00
0,94 c
33,42 b
37,89 a
2,68 d
25,06 b
11-nov-00
0,39 e
31,13 b
30,86 b
2,04 e
35,58 a
15-apr-01
1,33 b
55,06 a
31,04 b
3,79 b
8,77 c
05-jun-01
1,65 a
55,67 a
29,41 b
4,84 a
8,43 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A15. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in mg/kg on five sampling occasions at the
depth of 20-40 cm
Date
Bicarbonate-IP
(mg/kg)
Bicarbonate-OP
(mg/kg)
Hydroxide-IP (mg/kg)
Hydroxide-OP
(mg/kg)
05-sep-00
599 d
345 d
134 c
743 c
08-okt-00
550 e
538 b
232 b
1002 a
11-nov-00
891 b
454 bc
388 a
946 b
15-apr-01
974 a
432 cd
83 d
710 d
05-jun-01
690 c
784 a
52 e
727 cd
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A16. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in percentage of Bicarbonate-P and HydroxideP respectively as mean values on five sampling occasions at the depth of 20-40 cm
Date
Bicarbonate-IP % of
Bicarbonate-P
Bicarbonate-OP % of
Bicarbonate-P
Hydroxide-IP % of
Hydroxide-P
Hydroxide-OP % of
Hydroxide-P
05-sep-00
63,58 b
36,42 b
15,24 c
84,76 c
08-okt-00
50,53 c
49,47 a
18,78 b
81,22 d
11-nov-00
66,31 ab
33,69 bc
29,07 a
70,93 e
15-apr-01
69,36 ab
30,64 c
10,47 d
89,53 b
05-jun-01
46,79 c
53,21 a
6,62 e
93,38 a
Values with similar letters within the same fraction are not statistically different with 95% probability.
52
Table A17. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) and Extractable Phosphorus (Extractable-P) in mg/kg on five
sampling occasions at the depth of 20-40 cm, where Total-OP was the sum of Residual-P,
Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P, BicarbonateIP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus Residual-P
Date
Extractable-P (mg/kg)
Total-OP (mg/kg)
Total-IP (mg/kg)
05-sep-00
1940 c
2129 c
853 d
08-okt-00
2438 b
2356 b
899 c
11-nov-00
2782 a
2936 a
1383 a
15-apr-01
2329 b
1365 e
1188 b
05-jun-01
2424 b
1735 d
913 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A18. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) and Extractable Phosphorus (Extractable-P) in percentage of Total-P
(TP) on five sampling occasions at the depth of 20-40 cm, where Total-OP was the sum of
Residual-P, Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P,
Bicarbonate-IP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus
Residual-P
Date
Extractable-P % of TP
Total-OP % of TP
Total-IP % of TP
05-sep-00
65,21 c
71,35 a
28,66 c
08-okt-00
74,94 b
72,37 a
27,63 c
11-nov-00
64,42 c
67,97 b
32,03 b
15-apr-01
91,23 a
53,47c
46,53 a
05-jun-01
91,57 a
65,51 b
34,49 b
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A19. pH and Phosphorus (P) fractions in mg/kg on five sampling occasions at the
depth of 40-60 cm
Date
pH
Total-P
(mg/kg)
Resin-P
(mg/kg)
Bicarbonate-P
(mg/kg)
Hydroxid-P
(mg/kg)
HCl-P (mg/kg)
Residual-P
(mg/kg)
05-sep-00 3,5 b
2033 b
26 ab
548 b
732 b
45 b
682 c
08-okt-00
4,0 a
2212 a
29 ab
461 c
872 a
54 a
797 b
11-nov-00 4,0 a
1825 c
22 b
607 a
675 bc
58 a
464 e
15-apr-01 4,0 a
2286 a
30 ab
558 b
710 b
53 a
936 a
05-jun-01
4,2 a
1779 c
36 a
427 d
637 c
56 a
623 d
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A20. Phosphorus (P) fractions in percentage of Total-P (TP) on five sampling
occasions at the depth of 40-60 cm
Date
Resin-P %
of TP
Bicarbonate-P %
of TP
Hydroxide-P % of
TP
HCl-P %
of TP
Residual-P %
of TP
05-sep-00
1,29 b
26,95 b
36,00 b
2,19 c
33,58 c
08-okt-00
1,32 b
20,84 d
39,40 a
2,43 b
36,01 b
11-nov-00
1,22 b
33,23 a
36,96 b
3,17 a
25,42 d
15-apr-01
1,30 b
24,39 c
31,05 c
2,33 bc
40,93 a
05-jun-01
2,00 a
23,98 c
35,82 b
3,16 a
35,04 b
Values with similar letters within the same fraction are not statistically different with 95% probability.
53
Table A21. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in mg/kg on five sampling occasions at the
depth of 40-60 cm
Date
Bicarbonate-IP
(mg/kg)
Bicarbonate-OP
(mg/kg)
Hydroxide-IP (mg/kg)
Hydroxide-OP
(mg/kg)
05-sep-00
263 a
285 b
159 a
574 b
08-okt-00
243 b
219 c
62 c
810 a
11-nov-00
271 a
336 a
131 b
544 bc
15-apr-01
239 b
319 a
135 b
575 b
05-jun-01
195 c
232 c
148 a
489 c
Values with similar letters within the same fraction are not statistically different with 95% probability
Table A22. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in percentage of Bicarbonate-P and HydroxideP respectively on five sampling occasions at the depth of 40-60 cm
Date
Bicarbonate-IP % of
Bicarbonate-P
Bicarbonate-OP % of
Bicarbonate-P
Hydroxide-IP % of
Hydroxide-P
Hydroxide-OP % of
Hydroxide-P
05-sep-00
47,95 b
52,05 c
21,68 ab
78,32 cd
08-okt-00
52,61 a
47,39 d
7,11 d
92,89 a
11-nov-00
44,60 cd
55,40 ab
19,35 bc
80,65 bc
15-apr-01
42,90 d
57,10 ab
19,03 c
80,97 b
05-jun-01
45,59 c
54,41 b
23,25 a
76,75 d
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A23. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) and Extractable Phosphorus (Extractable-P) in mg/kg on five
sampling occasions at the depth of 40-60 cm, where Total-OP was the sum of Residual-P,
Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P, BicarbonateIP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus Residual-P
Date
Extractable-P (mg/kg)
Total-OP (mg/kg)
Total-IP (mg/kg)
05-sep-00
1350 a
1541 b
492 a
08-okt-00
1416 a
1825 a
388 d
11-nov-00
1361 a
1344 c
482 ab
15-apr-01
1350 a
1829 a
457 bc
05-jun-01
1155 b
1344 c
434 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A24. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) Extractable Phosphorus (Extractable-P) in percentage of Total-P
(TP) on five sampling occasions at the depth of 40-60 cm, where Total-OP was the sum of
Residual-P, Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P,
Bicarbonate-IP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus
Residual-P
Date
Extractable-P % of TP
Total-OP % of TP
Total-IP % of TP
05-sep-00
66,42 b
75,80 c
24,20 b
08-okt-00
63,99 c
82,48 a
17,52 d
11-nov-00
74,58 a
73,64 d
26,36 a
15-apr-01
59,07 d
80,00 b
20,00 c
05-jun-01
64,96 c
75,59 c
24,41 b
Values with similar letters within the same fraction are not statistically different with 95% probability.
54
Table A25. pH and Phosphorus (P) fractions in mg/kg on five sampling occasions at the
depth of 60-80 cm
Date
pH
Total-P
(mg/kg)
Resin-P
(mg/kg)
Bicarbonate-P
(mg/kg)
Hydroxid-P
(mg/kg)
HCl-P
(mg/kg)
Residual-P
(mg/kg)
05-sep-00 4,4 ab
1776 bc
21 cd
449 b
700 d
35 b
572 b
08-okt-00
4,7 ab
1718 c
23 bc
382 d
826 a
32 b
456 c
11-nov-00 4,3 b
1843 b
24 b
480 a
784 b
31 b
524 bc
15-apr-01 4,8 a
1968 a
19 d
386 cd
754 c
50 a
760 a
05-jun-01
4,6 ab
1551 d
27 a
399 c
591 e
54 a
481 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A26. Phosphorus (P) fractions in percentage of Total-P (TP) on five sampling
occasions at the depth of 60-80 cm
Date
Resin-P %
of TP
Bicarbonate-P % of
TP
Hydroxide-P %
of TP
HCl-P %
of TP
Residual-P %
of TP
05-sep-00
1,17 b
25,26 a
39,40 c
1,98 c
32,2 b
08-okt-00
1,31 b
22,21 b
48,10 a
1,84 c
26,53 d
11-nov-00
1,31 b
26,03 a
42,56 b
1,68 c
28,43 cd
15-apr-01
0,94 c
19,60 c
38,30 c
2,55 b
38,61 a
05-jun-01
1,73 a
25,69 a
38,07 c
3,47 a
31,03 bc
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A27. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in mg/kg on five sampling occasions at the
depth of 60-80 cm
Date
Bicarbonate-IP
(mg/kg)
Bicarbonate-OP
(mg/kg)
Hydroxide-IP
(mg/kg)
Hydroxide-OP
(mg/kg)
05-sep-00
172 b
277 a
129 c
571 b
08-okt-00
180 b
202 c
136 c
691 a
11-nov-00
238 a
242 b
188 b
570 b
15-apr-01
180 b
206 c
234 a
520 c
05-jun-01
186 b
213 c
59 d
532 c
Values with similar letters within the same fraction are not statistically different with 95% probability
Table A28. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in percentage of Bicarbonate-P and HydroxideP on five sampling occasions at the depth of 60-80 cm
Date
Bicarbonate-IP % of
Bicarbonate-P
Bicarbonate-OP % of
Bicarbonate-P
Hydroxide-IP % of
Hydroxide-P
Hydroxide-OP % of
Hydroxide-P
05-sep-00
38,27 b
61,73 a
18,45 c
81,56 b
08-okt-00
47,18 a
52,82 b
16,40 c
83,60 b
11-nov-00
49,53 a
50,47 b
23,92 b
76,08 c
15-apr-01
46,70 a
53,30 b
31,05 a
68,95 d
05-jun-01
46,67 a
53,33 b
9,91 d
90,09 a
Values with similar letters within the same fraction are not statistically different with 95% probability.
55
Table A29. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) and Extractable Phosphorus (Extractable-P) in mg/kg on five
sampling occasions at the depth of 60-80 cm, where Total-OP was the sum of Residual-P,
Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P, BicarbonateIP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus Residual-P
Date
Extractable- P (mg/kg)
Total-OP (mg/kg)
Total-IP (mg/kg)
05-sep-00
1204 c
1419 ab
356 b
08-okt-00
1362 b
1348 b
370 b
11-nov-00
1319 a
1362 b
480 a
15-apr-01
1208 c
1485 a
483 a
05-jun-01
1070 d
1226 c
325 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A30. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) and Extractable Phosphorus (Extractable-P) in percentage of TotalP (TP) on five sampling occasions at the depth of 60-80 cm, where Total-OP was the sum of
Residual-P, Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P,
Bicarbonate-IP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus
Residual-P
Date
Extractable-P % of TP
Total-OP % of TP
Total-IP % of TP
05-sep-00
67,80 c
79,93 a
20,07 b
08-okt-00
73,47 a
78,47a
21,53 b
11-nov-00
71,58 ab
73,94 b
26,06 a
15-apr-01
61,39 d
75,47 b
24,53 a
05-jun-01
68,97 bc
79,03 a
20,97 b
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A31. pH and Phosphorus (P) fractions in mg/kg on five sampling occasions at the
depth of 80-100 cm
Date
pH
Total-P
(mg/kg)
Resin-P
(mg/kg)
Bicarbonate-P
(mg/kg)
Hydroxid-P
(mg/kg)
HCl-P
(mg/kg)
Residual-P
(mg/kg)
05-sep-00 5,6 a
1826 a
26 a
305 a
682 b
37 a
777 a
08-okt-00
5,5 a
1559 b
28 a
306 a
737 a
25 b
464 bc
11-nov-00 5,0 b
1434 c
16 c
326 a
669 b
34 a
389 c
15-apr-01 5,5 a
1520 b
18 bc
289 a
521 d
25 b
668 a
05-jun-01
5,0 b
1510 b
21 b
304 a
641 c
23 b
520 b
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A32. Phosphorus (P) fractions in percentage of Total-P (TP) on five sampling
occasions at the depth of 80-100 cm
Date
Resin-P %
of TP
Bicarbonate-P %
of TP
Hydroxide-P % of
TP
HCl-P %
of TP
Residual-P %
of TP
05-sep-00
1,41 bc
16,69 b
37,3 c
2,03 ab
42,54 a
08-okt-00
1,77 a
19,60 ab
47,26 a
1,62 b
29,75 b
11-nov-00
1,15 c
22,70 a
46,62 a
2,40 a
27,14 b
15-apr-01
1,16 bc
19,01 ab
34,24 d
1,65 b
43,94 a
05-jun-01
1,42 b
20,10 ab
42,46 b
1,58 b
34,44 b
Values with similar letters within the same fraction are not statistically different with 95% probability.
56
Table A33. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in mg/kg on five sampling occasions at the
depth of 80-100 cm
Date
Bicarbonate-IP
(mg/kg)
Bicarbonat-OP
(mg/kg)
Hydroxide-IP (mg/kg)
Hydroxide-OP
(mg/kg)
05-sep-00
151 b
154 ab
190 a
492 d
08-okt-00
140 b
166 ab
206 a
531 c
11-nov-00
114 c
212 a
104 c
565 b
15-apr-01
146 b
144 ab
148 b
373 e
05-jun-01
168 a
136 b
22 d
619 a
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A34. Distribution of Inorganic Phosphorus (IP) and Organic Phosphorus (OP) within
the fractions Bicarbonate-P and Hydroxide-P in percentage of Bicarbonate-P and HydroxideP respectively on five sampling occasions at the depth of 80-100 cm
Date
Bicarbonate-IP % of
Bicarbonate-P
Bicarbonate-OP % of
Bicarbonate-P
Hydroxide-IP % of
Hydroxide-P
Hydroxide-OP % of
Hydroxide-P
05-sep-00
49,46 ab
50,54 bc
27,88 a
72,12 c
08-okt-00
45,84 b
54,17 b
27,97a
72,03 c
11-nov-00
35,41 c
64,59 a
15,48 b
84,52 b
15-apr-01
50,35 ab
49,65 bc
28,45 a
71,55 c
05-jun-01
55,34 a
44,66 c
3,43 c
96,57 a
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A35. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) and Extractable Phosphorus (Extractable-P) in mg/kg on five
sampling occasions at the depth of 80-100 cm, where Total-OP was the sum of Residual-P,
Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P, BicarbonateIP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus Residual-P
Date
Extractable-P (mg/kg)
Total-OP (mg/kg)
Total-IP (mg/kg)
05-sep-00
1049 ab
1423 a
403 a
08-okt-00
1095 a
1160 c
399 a
11-nov-00
1045 ab
1166 c
268 c
15-apr-01
852 c
1184 c
336 b
05-jun-01
990 b
1275 b
235 c
Values with similar letters within the same fraction are not statistically different with 95% probability.
Table A36. Distribution of Total Inorganic Phosphorus (Total-IP) and Total Organic
Phosphorus (Total-OP) and Extractable Phosphorus (Extractable-P) in percentage of TotalP (TP) on five sampling occasions at the depth of 80-100 cm, where Total-OP was the sum of
Residual-P, Bicarbonate-OP and Hydroxide-OP whereas Total-IP were the sum of Resin-P,
Bicarbonate-IP, Hydroxide-IP and HCl-P and were Extractable-P was Total-P minus
Residual-P
Date
Extractable-P % of TP
Total-OP % of TP
Total-IP % of TP
05-sep-00
57,46 b
77,91 c
22,09 b
08-okt-00
70,25 a
74,41 d
25,59 a
11-nov-00
72,86 a
81,32 b
18,68 c
15-apr-01
56,06 b
77,89 c
22,15 b
05-jun-01
65,56 a
84,41 a
15,59 d
Values with similar letters within the same fraction are not statistically different with 95% probability.
57
Appendix 2. Figures A1-A5: Phosphorus fractions as a percentage of Total
Phosphorus
Resin-P in % of TP
0
0,5
1
1,5
2
2,5
Depth (cm)
0-20
2001-04-15
2000-09-05
2001-06-05
2000-10-08
20-40
40-60
60-80
2000-11-11
80-100
Figure A1. Distribution of Resin-P in percentage of Total-P in the soil profile at five sampling
occasions
Bicarbonate-P in % of TP
0
10
20
30
40
50
60
Depth (cm)
0-20
2001-04-15
2000-09-05
2001-06-05
2000-10-08
20-40
40-60
60-80
2000-11-11
80-100
Figure A2. Distribution of Bicarbonate-P in percentage of Total-P in the soil profile at five
sampling occasions.
58
Hydroxide-P in % of TP
0
10
20
30
40
50
60
Depth (cm)
0-20
2000-09-05
2001-04-15
20-40
40-60
2000-10-08
2001-06-05
60-80
2000-11-11
80-100
Figure A3. Distribution of Hydroxide-P in percentage of Total-P in the soil profile at five
sampling occasions.
HCl-P in % of TP
0
1
2
3
4
5
6
Depth (cm)
0-20
2001-04-15
2000-09-05
2001-06-05
2000-10-08
20-40
40-60
60-80
2000-11-11
80-100
Figure A4. Distribution of HCl-P in percentage of Total-P in the soil profile at five sampling
occasions
59
Residual-P in % of TP
0
10
20
30
40
50
Depth (cm)
0-20
2001-04-15
2000-09-05
2001-06-05
2000-10-08
20-40
40-60
60-80
2000-11-11
80-100
Figure A5. Distribution of Residual-P content in percentage of Total-P in the soil profile at
five sampling occasions
60
Bicarbonate OP and IP (% of Bicarbonate-P)
Appendix 3. Figures A6-A13: Bicarbonate and Hydroxide Inorganic and Organic
Phosphorus
100
90
b
c
ab
ab
b
a
bc
c
2
3
c
80
70
60
50
40
30
20
a
10
0
1
Bicarbonate OP
4
Bicarbonate IP
5
Sampling occasions
Bicarbonate OP and IP (% of Bicarbonate-P)
Figure A6. Distribution of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and
Bicarbonate Inorganic Phosphorus (Bicarbonate-IP) in percentage of Bicarbonate-P on five
sampling occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November
2000, 4=15th April 2001 and 5= 5th June 2001) at the depth of 20-40 cm. Mean values with
similar letters within the same P fraction are not statistically different at 95% probability.
100
90
b
a
c
d
cd
d
c
80
70
60
50
40
30
20
ab
ab
b
10
0
1
Bicarbonate OP
2
Bicarbonate IP
3
4
5
Sampling occasions
Figure A7. Distribution of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and
Bicarbonate Inorganic Phosphorus (Bicarbonate-IP) in percentage of Bicarbonate-P on five
sampling occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November
2000, 4=15th April 2001 and 5= 5th June 2001) at the depth of 40-60 cm. Mean values with
similar letters within the same P fraction are not statistically different at 95% probability.
61
Bicarbonate OP and IP (% of Bicarbonate-P)
100
90
b
a
a
a
b
b
2
3
a
a
80
70
60
50
40
30
20
b
b
10
0
1
Bicarbonate OP
4
5
Sampling occasions
Bicarbonate IP
Bicarbonate OP and IP (% of Bicarbonate-P)
Figure A8. Distribution of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and
Bicarbonate Inorganic Phosphorus (Bicarbonate-IP) in percentage of Bicarbonate-P on five
sampling occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November
2000, 4=15th April 2001 and 5= 5th June 2001) at the depth of 60-80 cm. Mean values with
similar letters within the same P fraction are not statistically different at 95% probability.
100
ab
b
c
ab
bc
b
a
bc
a
90
80
70
60
50
40
30
20
c
10
0
1
Bicarbonate OP
2
Bicarbonate IP
3
4
5
Sampling occasions
Figure A9. Distribution of Bicarbonate Organic Phosphorus (Bicarbonate-OP) and
Bicarbonate Inorganic Phosphorus (Bicarbonate-IP) in percentage of Bicarbonate-P on five
sampling occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November
2000, 4=15th April 2001 and 5= 5th June 2001) at the depth of 80-100 cm. Mean values with
similar letters within the same P fraction are not statistically different at 95% probability.
62
Hydroxide OP and IP (% of Hydroxide-P)
100
c
b
a
d
e
d
e
b
a
2
3
4
90
80
70
60
50
40
30
20
c
10
0
1
Hydroxide OP
Hydroxide IP
5
Sampling occasions
Hydroxide OP and IP (% of Hydroxide-P)
Figure A10. Distribution of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) in percentage of Hydroxide-P on five sampling
occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November 2000, 4=15th
April 2001 and 5= 5th June 2001) at the depth of 20-40 cm. Mean values with similar letters
within the same P fraction are not statistically different at 95% probability.
100
90
d
ab
bc
c
a
bc
b
2
3
4
a
80
70
60
50
40
30
20
cd
d
10
0
1
Hydroxide OP
Hydroxide IP
5
Sampling occasions
Figure A11. Distribution of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) in percentage of Hydroxide-P on five sampling
occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November 2000, 4=15th
April 2001 and 5= 5th June 2001) at the depth of 40-60 cm. Mean values with similar letters
within the same P fraction are not statistically different at 95% probability.
63
Hydroxide OP and IP (% of Hydroxide-P)
100
c
c
b
a
d
c
d
a
3
4
90
80
70
60
50
40
30
20
b
b
10
0
1
Hydroxide OP
2
5
Sampling occasions
Hydroxide IP
Hydroxide OP and IP (% of Hydroxide-P)
Figure A12. Distribution of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) in percentage of Hydroxide-P on five sampling
occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November 2000, 4=15th
April 2001 and 5= 5th June 2001) at the depth of 60-80 cm. Mean values with similar letters
within the same P fraction are not statistically different at 95% probability.
c
100
90
a
a
b
a
c
b
c
80
70
60
50
40
30
20
c
a
10
0
1
Hydroxide OP
2
Hydroxide IP
3
4
5
Sapling occasions
Figure A13. Distribution of Hydroxide Organic Phosphorus (Hydroxide-OP) and Hydroxide
Inorganic Phosphorus (Hydroxide-IP) in percentage of Hydroxide-P on five sampling
occasions (where 1=5th September 2000, 2= 8th October 2000, 3=11th November 2000, 4=15th
April 2001 and 5= 5th June 2001) at the depth of 80-100 cm. Mean values with similar letters
within the same P fraction are not statistically different at 95% probability.
64
Appendix 4. Table A37: Weather data
Table A37. Monthly precipitation and monthly average air temperature close to the sampling
site for the periods of 2000 and 2001 (http://www.weather.vattenriket.kristianstad.se/cgiwin/vader.exe
Month
Precipitation (mm)
Average air
temperature
(◦C)
March 2000
52
1,7
April
42
9,3
May
36
13,3
June
123
15,5
July
51
16,8
August
49
16,2
September
62
13,0
October
67
11,7
November
95
7,6
December
46
3,4
January 2001
30
1,8
Februrary
21
0,2
March
21
1,4
April
42
9,3
May
28
13,3
June*
42
12,9
* The last sampling was 5th June, hence the precipitation
and temperature shown in this table are values from the 1st – 5th June.
65
Appendix 5. Figures A14-A19: Photos of the site area
Figure A15. Photo 1; Inundated sampling
site, January 2001 (Photo by Ann Fristedt).
road
river/ ditch
railroad
photo direction
Figure A14. Air photograph taken over
the sampling site (Lantmäteriverket 1998.
GSD- Digitalt Ortofoto dnr:507-983015). Arrows indicate photo direktions.
Soil samples were taken where the arrow
2 is.
Figure A17. Photo 3; Inundated adjacent
fields, January 2001 (Photo by Ann Fristedt).
66
Figure A16. Photo 2; Knee-deep water at the
sampling site, January 2001 (Photo by Emil
Andersson).
Figure A18. Photo 4; Inundated adjacent
fields, January 2001 (Photo by Ann
Fristedt).