PECKIANA ·
Volume 3 (2004)
·
47 – 67
ISSN 1618-1735
Possibilities of biological soil-quality assessment in reclaimed land
WOLFRAM DUNGER
Abstract
The reclamation of post-mining landscapes is linked with the origin of self-sustaining, naturally
developing ecosystems. Lignite opencast mine sites offer a complex experimental field for science,
especially for soil biology, to study the new development of soils and the primary immigration of soil
organisms. Our investigations on the fauna of lignite mines reported here began 1953 in the »Central
German District« (Böhlen) at the University of Leipzig. As of 1960, they were continued, with the
»Upper Lusatian District« (Berzdorf) as central study area and some additional sites of the »Lower
Lusatian District«, on the Saxon State Museum of Natural History Görlitz up to 1999.
As suitable approaches to find determining parameters for biological soil-quality assessment, we
established (1) the soil fauna in general as well as at the species-level, (2) the sustainability of the
developing ecosystems after primary production and potential zoogenic decomposition, and (3) the
diversity of organisms and habitat structures.
1. We studied macrofaunal (earthworms) and mesofaunal (microarthropods; springtails) decomposer
communities at the Berzdorf district over a period of 40 years. Mine sites with deciduous tree
afforestation and without special handicaps were regarded as an »average optimal developmental
series (AOD-series)« of soil fauna succession. That provides the opportunity to compare the
biological soil quality reached so far by the succession of an actual mine site as »actual values«
with the AOD-series as »aspected values«.
2. To get a quantified insight in the decomposition processes, we compared the yield of dead organic
matter by primary production with the ability of the saprophagous soil fauna to decompose that
amount, related to an actual site. The knowledge of the potential level of zoogenic decomposition
opens the possibility to assess the biological activity reached at any other special mine site by
comparison.
3. Using soil faunal and ecological parameters as indicators of the quality of restored soils, the
studied groups should easily be sampled, do not have fewer than 20 or more than 100 species in
the region and show clear reactions to ecosystem development. Therefore, special information
was obtained for Centipedes and Collembola. The results of both groups allow characterisation of
the actual soil biological situation and the trend of ecosystem evolution of mine sites under study.
Post-mining landscapes represent an object of soil biological study that shows remarkable features
because of their extreme ecological conditions and high importance due to the large extent of areas
being affected. The progress in soil zoological studies offers the possibility to examine the selfsustaining condition of the newly developing ecosystems.
48
Wolfram Dunger
1. Introduction
Reclamation of post-mining landscapes is linked with the origin of self-sustaining,
naturally developing ecosystems (Majer 1989, Wali 1999). In the most favourable case,
this can occur by natural succession with human influence being restricted to process
protection. Active recultivation (or renaturation) by man demands a complex managing
programme, including the biological improvement of soils (Broll et al. 2000, Bell 2001,
Bradshaw & Hüttl 2001).
Lignite opencast mine sites offer a complex experimental field for science to study the
new development of soils and the primary immigration of soil organisms. Freshly heaped
substratum from overburden is not only free from soil organisms, but also lacks biogenic
soil structures and substances (except for fossil ones).
Post-mining landscapes represent an object of soil biological study that shows remarkable
features because of their extreme ecological conditions and high importance due to the
large extent of areas being affected. During the last five decades, intensive as well as
extensive soil zoological studies were carried out by us at mine sites in the lignite mining
districts of Eastern Germany (Central Germany, Lower Lusatia and Upper Lusatia).
The aim of our studies was to investigate, based on results gained above all from mine
sites of the Berzdorf lignite mining district, which soil zoological parameters allow
characterisation of the actual soil biological situation and the trend of ecosystem evolution
of mine sites.
Our soil-biological investigations focused on three aspects:
1. quantitatively recording the successive settlement of groups of soil organisms,
2. evaluating the increase in diversity of soil fauna and (micro) flora and of habitat
structures by using soil biota as indicators for ecosystem development,
3. checking habitat structures (e.g. humus profile) as a result of soil-organism activity.
These objectives are linked with the German Federal Soil Protection Act (1998) that
protects the habitat function of soils together with the inhabiting soil organisms. In order
to meet this legal task for developing soils at mine sites as well, compatible methods have
to be developed. Therefore, this view deals with the adaptation of the investigations
published so far (Römbke et al. 2000, Höper & Ruf 2003) for the evaluation of the biological
soil quality to soils in post-mining landscapes.
2. Mine sites investigated
Mine soils of the Central German and the Lower Lusatian mining districts mainly consist
of sandy to loamy Tertiary substratum with a high content of lignite and pyrite. Nevertheless,
there are very high geographical divergences in the conditions of soil development. The
overburden in the Upper Lusatian mining district contained mainly Pleistocene substrata
with low to medium content of lignite and pyrite. These conditions seemed to be the best
for our purposes; therefore we concentrated our investigations to the region of Berzdorf
south of Görlitz (Fig. 1).
Biological soil-quality assessment in reclaimed land
Fig. 1
49
Lignite mining districts in Germany (hatched areas), box: Berzdorf district, Oberlausitz.
Abbreviations for studied sites see Tab. 1
50
Wolfram Dunger
The advantages of the Berzdorf mine sites were a substratum with an adequate to high
water capacity without a dominance of toxic substances, enabling a very rapid biological
development (details see Dunger et al. 2001). According to this, the amelioration could be
made at a low level, and the silvicultural recultivation, done with Alnus, Populus and
Robinia or with Pinus and Larix, was possible with a minimum forest effort. Therefore, a
continuous development of the mine sites as defined by renaturation could take place
(Tab. 1).
Tab. 1 Signs, years of study and characterisation of the mine sites investigated in the Berzdorf and
Böhlen district
Biological soil-quality assessment in reclaimed land
Fig. 2
51
Diagram of processes of technogenesis and ecogenesis during primary succession on mine sites
52
Wolfram Dunger
3. Methods of studying primary succession in mine sites
Studying technogenetic primary ecological successions requires considering the aspects
of the pedogenetic and biogenetic processes (Dunger & Wanner 1999). The heaping of
dumps by the mining company (the technical process introducing a primary succession,
named »technogenesis«) gives rise to a primary sterile »pre-biotope« (Fig. 2). Its suitability
as habitat for organisms (or its environmental capacity) is determined by the physicochemical quality of the substratum heaped at the mine-site surface (mineral contents,
texture, technogenetic heterogeneity, acids and toxins) and by geographic-climatic factors
as well, but not by biological competition which cannot yet act in this situation.
The »ecogenesis« (the biologically dominated part of the primary succession) starts
with the first real settlement. That process is determined on the one hand by the immigration
(natural immigration or introduction by man; organismic groups involved; intensity), on
the other hand by the ability to overcome the immigration barrier (prebiotope selection)
during the initial phase.
With the successful settlement of organisms at the initial biotope, the starting point is
given for an intensive enlargement of the environmental capacity by biocoenotical regulation. As this is the biological motor of ecogenesis, thus the factors of biocoenological
regulation are the decisive biological parameters of the actual soil biological situation and
of the trend of ecosystem evolution of mine sites. As a result of these processes, new
immigrants find a changed biotope and changed conditions of the biotope selection.
On the basis of the nutrient balance as well as of the settlement behaviour of selected
species a pioneer phase can be identified (Dunger et al. 2002). The transition to the
»organisation phase« is characterised by a high development of the regulation processes
with increasing importance of competition within the ecosystem, combined with a decreasing importance of immigration and elimination. Under optimal conditions, this transition
can start as early as after 15 – 25 years after recultivation. This is the beginning of the
development of an entirely new, site-typical ecosystem.
4. Soil zoological methods
The soil-zoological methods applied are described in the basic literature (Dunger &
Fiedler 1997). To calculate yearly averages for each site, results from soil cores, area
samples as well as traps were used. For edaphic microarthropods soil cores were extracted
by thermoeclectors in the laboratory. Epedaphic micro- and macroarthropods were collected
by pitfall-traps and by area samples as well. The earthworm colonisation was ascertained
from area samples of 0.25 cm2 using diluted formalin for excitation combined with hand
sorting of macrocores. Details for the collection of the soil fauna as well as for checking
the biological production parameter are given in Dunger et al. (2001) and Dunger &
Voigtländer (in press).
5.
Results and Discussion
5.1. Development of test groups: Edaphic Microarthropods
In contrast to epedaphic soil arthropods that are mainly recorded using their migration
Biological soil-quality assessment in reclaimed land
53
activity (by pitfall trapping; Dunger et al. 2002), the (eu)edaphic arthropods, especially
microarthropods, can easily be sampled in their specific small habitat by soil cores. Important groups of soil microarthropods are Collembola, Protura, and mites with Gamasida
(Parasitiformes), Prostigmata (Trombidiformes s.l.; Actinedida), Oribatida, and Acaridida.
As Prostigmata and Acaridida are hardly to discern under the preparation microscope for
non-specialists, soil mites are registered for survey purposes as Gamasida, Oribatida and
»remaining mites«. Most of the soil microarthropods immigrate to mine sites as aerial
plankton (Dunger et al. 2002).
Fig. 3
Development (abundances) of microarthropod populations at mine sites of the Berzdorf mining
district during 46 years. Abbreviations of mine sites see Tab. 1. The lines combine developmental
stages of identical (or very similar) mine sites
54
Wolfram Dunger
Fig. 3 shows the population density of edaphic microarthropods at mine sites of the
Berzdorf district from the first to the 46th year after recultivation. The investigations are
focused to two real-time series (chronosequences) of the deciduous-afforested site A and
the primarily pine-afforested site L from the 10th to the 46th year. Results for L10 are not
demonstrated because we have no whole-year observation from this site at a ten-year
age. For the first to the 7th year a »false time series« (out of the real chronosequence) of
nearly identical sites NA, T, and H was investigated. For the aberrant mine site NB24 see
below.
During the first years, the population density of edaphic microarthropods rises rapidly
beneath a quickly growing shrub vegetation and comes to a very high pioneer maximum
as soon as the 3rd year. During the following years the competition of earthworms arises
and microarthropods show a decreasing density and a changing species inventory. For
the period 15 to 25 years after recultivation, short checks (limited to few samplings each)
allow assumption of a slow and continuous increasing of the density up to a site age of
30 years. At this time the increasing proportion of k-adapted species shows that the
organisation phase of the ecogenesis begins. During the next 15 years of our observations,
the microarthropod density and species inventory adapt to the more and more developed
drilosphere and mull-humus in the mine soil. Nevertheless, even after 46 years it does not
gain any more similarity to a neighbouring native deciduous wood site W, investigated
for comparison. Of course, the mine site A will never become »nearly identical« with any
natural wood-site (Dunger et al. 2004b). A real »predisturbance point« (Majer 1989) does
not exist because the dump was heaped upon a pond.
As could be shown, the microarthropods at the mine sites with Alnus, Populus and
Robinia (NA, T, A) discussed so far, pass through an »average optimal evolution«. In
contrast identical, except for afforestation with pine, mine sites (L) show quite another
settlement. For the first 10 years we find from »short checks« of neighbouring young pine
mine sites that the population density increased more slowly and without a »pioneer
optimum«. After that the augmentation of the needle litter layer and the minimal earthworm
activity lead to a strong, but typical increasing microarthropod abundance up to a maximum
of 400 000 ind. / m2. A specific feature of site L is that more than 50 % of the pine trees died
after 20 – 30 years because of the lack of forestry cultivation and spontaneous growth of
deciduous trees gave the site step by step a mixed-forest character. That caused a decrease
of the needle layer thickness and an increase of earthworm activity, resulting in lower
microarthropod density (25–) 46 years after afforestation.
Fig. 4 shows that single groups of microarthropods (here: Collembola) do not behave
completely identically. Beneath deciduous trees, springtails are as abundant after 46 years
as after 33 years, and the change of site L into a mixed wood even caused a significant
increase of their density. Groups of mites show an alternative development.
On acid Tertiary mine sites of the mining district of Böhlen (Central Germany), the
population density during the first 10 years was investigated for microarthropods in
general and for Collembola in particular in a »false-time series« of sites under different
melioration and recultivation conditions (Fig. 5).
It is remarkable that shortly after recultivation high abundances (»pioneer optimum«)
can be shown at Böhlen with nearly the same densities as on »better«, more Pleistocene
and pyrite-poor mine sites of the Berzdorf district (Figs 3, 4), followed by a decreasing of
the same degree, though there was no earthworm activity (except site V with a cover of
Biological soil-quality assessment in reclaimed land
55
»culturable substratum«). In this case, the decrease of the microarthropod density after
the pioneer optimum does not indicate an earthworm competition but reflects with high
sensibility a weakening growth of the vegetation that has exhausted the starting supply
of nutrients from the melioration.In Fig. 5, the site BöII – showing a very low microarthropod density – cannot be compared with the other sites because of its agricultural
recultivation.
Fig. 4
Development (abundances) of collembolan populations at mine sites of the Berzdorf mining
district during 46 years. Abbreviations of mine sites see Tab. 1, for further explanation see Fig. 3
56
Fig. 5
Wolfram Dunger
Development (abundances) of microarthropod and collembolan populations at mine sites of
the Böhlen mining district (Central Germany). Abbreviations of mine sites see Tab. 1
5.2. Earthworms and other macrofauna
Without doubt, earthworms (Lumbricidae) are the most important group both for faunal
colonisation of mine sites and its identification. Other than microorganisms and even
microarthropods that are mostly distributed by air transport, earthworms have to overcome
several complications in immigration. Except for opencast mines with an important
proportion of loess in the overburden (e.g. Rhenish lignite district; Topp et al. 2001),
Biological soil-quality assessment in reclaimed land
57
earthworms normally do not come with the initial dumping of substrates into the mine-site
soils. As sources of the first occurrence of earthworms, plantation of seedlings, transport
by man with boots, by cars in treads of tires, or by birds and deer have been identified
(Dunger et al. 2004a). In this way, earthworms are found at the earliest three years after
dumping. Settlement caused by active movement of earthworms takes much longer, depending upon the local conditions.
At mine sites of the Berzdorf district, the earthworm population (biomass per m2) increases
nearly continuously from the third to the 46th year after recultivation (Fig. 6). Mine sites
with deciduous tree afforestation and without special handicaps (e.g. acidity) exhibit an
»average optimal evolution« as shown by a »false time series« of the sites NA 1 and NA
4 as well as T 3 and T 6 and the following real time series of A 10 to A 46. More sandy mine
sites (H 6, 7) have a lower population. Quite more deviation is shown by the site NB 24
(see below). At mine sites primarily planted with conifers (Pinus), the settlement by
earthworms starts later and more slowly and was expected to become hardly more dense
than after 10 years (L 10). However, the natural change of this site to a mixed forest after
approximately 20 years led to an increase of earthworm population that came in the 46th year
near to the level of deciduous sites.
Fig. 6
Development of earthworms (Lumbricidae) at mine sites of the Berzdorf mining district
(biomass, species numbers and proportion (%) of epigeic life forms). Abbreviations of mine
sites see Tab. 1, further explanation see Fig. 2
58
Wolfram Dunger
To consider this development in a more qualified manner, the proportion of life types
give a good indication. The specimens of Dendrobaena, Dendrodrilus and Lumbricus
rubellus can be united as litter dwellers (epigeic life forms) and listed against the deep
burrowers (anecic life form; Lumbricus terrestris) and the mineral soil dwellers (endogeic
life forms; species of Allolobophora, Aporrectodea, Octolasion) (Fig. 6). Though the
first earthworm found in NA 4 was an endogeic mineral soil dweller (Aporrectodea
caliginosa), the litter dwellers soon reached the highest proportion of biomass with 45 %
after 6 years (T 6), which, however, decreased to about 25 % after 46 years (A 46) in the
»average optimal developmental series« of deciduous tree afforestation. The deviating
development of sites with predomination of sand (H 6, 7) and other special characters
(NB 24, see below) become even more clear by the differing proportions of epedaphic
earthworms. The settlement of coniferous sites (L 10) starts nearly exclusively with
epedaphic earthworms (some 85 %). In the course of change into a mixed forest this
proportion decrease up to some 35 % after 46 years and thus comes near to the developmental
line of primarily deciduous trees sites.
Fig. 7
Average development of earthworm biomass on individual or series of mine sites of the
Berzdorf mining district. For explanation see text
Biological soil-quality assessment in reclaimed land
59
A further qualification is brought about by considering the species numbers, though
there is only a total of seven species involved (Fig. 6). The number of earthworm species
clearly increases continuously with site age, i.e. they show another development as seen
in microarthropods with a pioneer optimum in species numbers.
The results shown above allow the description of trend series of the development of
earthworm biomass (Fig. 7). The trend series I (shaded area) marks the »average optimal
developmental series« of deciduous mine sites. Poorer sites with predomination of sand
(II, H 6, 7, 10), the primarily coniferous plantation (IV, L 10), and the older site stages
changing to a mixed forest (V, L 33, 46) show a slower development, dominated by other
species. A similarly poor situation shows the deciduous tree series III (NB 24), where the
immigration of anecic earthworms (Lumbricus species) was entirely prevented by a
surrounding zone of pine plantation.
The same observation was made with the Geophilids (endogean Chilopods). Only the
endogean pioneer Schendyla nemorensis could be detected. Necrophloeophagus flavus,
the most frequent species of Geophilids at mine sites with deciduous trees older than 15
years, is entirely lacking in NB 24, most probably for the same reason as in the earthworm
genus Lumbricus (Dunger et al. 2004a).
Fig. 8
Annual energy input (as derived from litter sampling and field layer harvesting) and potential
level of zoogenic decomposition (DLZpot; see text) at deciduous mine sites of the Berzdorf
mining district during 46 years. L 10, L 46 = DLZpot 10 resp. 46 years after pine afforestation
at mine site L (Berzdorf)
60
Wolfram Dunger
5.3. Participation of soil fauna in the decomposition of SOM
The importance of soil fauna for the development of mine sites is based on their activity
in metabolism as well as in bioturbation. The metabolism of the saprophagous soil fauna
indicates their participation in the decomposition of soil organic matter. To obtain a
quantified insight into this process, a comparison can be made between the yield of dead
soil organic matter (SOM) by primary production and the ability of the saprophagous soil
fauna to decompose that amount, related to an actual site. As a »best estimation« of the
yearly production of dead organic matter, the method of litter sampling and harvesting the
soil and herb layer throughout the year is introduced (Dunger & Fiedler 1997). At the
Berzdorf mine sites, litter production has been measured for a chronosequence of mine
sites with deciduous tree plantation from the first to the 46th year and the mixed forest in
the 46th year (Fig. 8). It can be seen that the nutrients available in the initial situation are
quickly used by the vegetation giving rise to a »pioneer optimum«. The litter layer increases
rapidly, thereby offering an optimal habitat for the immediately immigrating microarthropods. Later on, an essential zoogenic decomposition is done mostly by the later immigrating
earthworms. The litter production by vegetation exceeds the amount measured during the
pioneer maximum only about 20 years after recultivation.
5.4. The role of different groups of the soil fauna
To calculate the role played by different soil faunal groups (e.g. microarthropods,
earthworms) in the decomposition of soil organic matter, individual numbers or even
biomass are not adequate dimensions. A »best estimation« is possible based on a simple
metabolic parameter, e.g. the inactive respiration related to the individual biomass under
standard conditions. Basic data are tabelled in methodological literature (Dunger & Fiedler
1997). From this the metabolic equivalent (ME) is deduced as ME= B’ * k * 102 * Y/X;
where B’ is the mean biomass (g wet mass/m2, k is the caloric equivalent factor, X is the
mean living mass per individual (g), and Y is the oxygen consumption (laboratory data, ml
O2 ind-1 h-1 at 10°C). The quotient »sum of ME (saprophage soil fauna to energy yield
(yearly litter production)«, introduced as potential level of zoogenic decomposition
(DLZpot), can be used to compare the potential capacity of soil fauna in litter decomposition. Until the pre-wood stage is reached (A 10), DLZpot is low at the deciduous mine
sites of the Berzdorf district, and even decreases in the first years slightly because of the
disproportion of the quick development of vegetation and the slow increase of the
saprophagous ME (Fig. 8). During the first ten years, decomposition acts at the level of
the »arthropod humus formation«. Afterwards, the DLZpot increases suddenly, based on
the quick augmentation of the earthworm activity (level of lumbricid humus formation).
The assumption of a steady development between the tenth and 46th years (A 10, A 46)
is caused by the lack of complete data sets (simultaneously check of the whole-year
earthworm density and litter production). That leads to the question whether there is
indeed no important variation of DLZpot at the »lumbricid-level« over such a long time. A
nearby constancy would mean that the ME-sum of the saprophagous fauna increases and
decreases in parallel to the change of litter production. That is still to be verified, possibly
within five years.
Biological soil-quality assessment in reclaimed land
61
deciduous trees
Pinus plantation
Fig. 9
Metabolic equivalents (ME) of microarthropod and lumbricid populations (sum and proportion)
at mine sites of the Berzdorf mining district during 46 years
ME = B’ (g wm m-2) * k * 102 * Y/K; see text
5.5. Interrelationships between earthworms and soil microarthropods
Interrelationships between the soil macrofauna, especially earthworms, and the soil
mesofauna, especially soil microarthropods, are essentially determined by their position
in the food web. Their overall contribution to the decomposition within the ecosystem
can be established by the energy used by these groups. As an easily available parameter
the ME is used. introduced already. The sum of ME of earthworms and microarthropods
develops on mine sites with deciduous afforestation suddenly after 7 years and reaches
a maximum after about 30 years. Later it can decrease again (dotted line in Fig. 9). Pineneedle litter inhibited the development of the earthworms. Such mine sites show increasing
ME only after changing to mixed forests with enlargement of the deciduous proportion.
A suitable measure of the interrelationships between earthworms and saprophagous microarthropods is the quotient of their ME (full line in Fig. 9). The entire dominance of the
microarthropods is broken with the first settlement of earthworms, becoming dominant
under deciduous afforestation very quickly after 3 years, whereas under coniferous plan-
62
Wolfram Dunger
tations a co-dominance of both groups can be seen at least after 10 years (Fig. 9). In mine
site L 30 the MEMa : MELu-quotient is 18 %. This is relatively high, but it decreases after
another 13 years (L 46) already to nearly 3 %, though the sum of the ME of these groups
is clearly far from the level of primarily deciduous sites.
5.6. Indication on species and society level
Centipedes (Chilopoda)
Soil faunal groups are suitable for the indication of succession stages if they can easily
be sampled, do not have fewer than 20 or more than 100 species in the region and show
clear reactions to ecosystem development. 30 species of Centipedes are known from the
Berzdorf region (K. Voigtländer, verbal information). This group shows different life forms
with ecological behaviour as hunters in the litter layer (Lithobiomorpha) or predators
within the soil pores (Geophilomorpha). From this it is clear that Lithobiomorpha are able
to migrate very early into young mine sites, whereas Geophilomorpha need an at least
minimal development of the soil A-horizon (Dunger & Voigtländer in press). Tab. 2 shows
that four species of Lithobiomorpha immigrated to the mine sites of the Berzdorf district as
pioneers during the first ten years. Of these, Lamyctes emarginatus behaves as a fugitive
pioneer species by disappearing as early as after eight years, the other pioneers are
persistent. Most of the species need 15 and more years to invade. Six of the species found
in the surrounding native woods or forests could not yet settle on the dump even after
50 years.
Some species exhibit special ecological behaviour. Lamyctes emarginatus tends to
return if new open plots appear, other species undertake unsuccessful attempts to settle
sometimes in the early period (Lithobius mutabilis) or for a distinct (probably favourable)
time (Lithobius calcaratus).
The dominance of lithobiid species at Berzdorf mine sites indicates three stages of
primary succession during the first half century (Fig. 10). The initial stage is well
characterised by Lamyctes emarginatus. After ten years, a late pioneer stage is represented
by Lithobius forficatus during the development of a pre-wood vegetation, corresponding
to the ecological preference of this species to inhabit places with open vegetation. About
25 years after afforestation, the closing of the tree canopy supports the dominance of
Lithobius microps, a species being present but recedent together with L. forficatus. Both
species belong to the species inventory of surrounding native deciduous woods, which
are dominated by Lithobius mutabilis. The last species was found to invade the mine
sites several times but was not able to settle continuously or at least to become dominant
for the first half century, thus indicating that the succession to a »regionally typical«
woodland is not yet completed.
Springtails, Collembola
Using springtails as indicators, about 100 species are to be taken in consideration.
The suitability of single species of this group of soil microarthropods for these purposes
is well documented in the literature (Dunger 1991). Here, the advantage of studying societies
of the springtails should be stressed. For doing so, the springtails have to be separated
63
Biological soil-quality assessment in reclaimed land
into epedaphic and euedaphic dwellers. That means a separation of results from pitfall
trapping and from soil core sampling. Having studied numerous sets of samplings, societies
can be constructed following the method of Braun-Blanquet as customary in plant
sociology.
Tab. 2 Immigration, elimination and species deficits of Chilopoda from Berzdorf mine sites.
L = Lithobiomorpha, epedaphic dwellers, G = Geophilomorpha, euedaphic dwellers. (After
Voigtländer)
Species found in the Berzdorf mine sites
First records
(years after recultivation)
Last records
(years after recultivation)
1
(L) Lamyctes emarginatus
8 (22)
4
(L) Lithobius forficatus
–
5
(L) Lithobius microps
–
7
(L) Lithobius melanops
–
15
(G) Schendyla nemorensis
–
15
(G) Necrophloeophagus flavus
–
22
(L) Lithobius calcaratus
35
33
(L) Lithobius crassipes
–
34
(G) Geophilus electricus
–
45 (4, 11)
(L) Lithobius mutabilis
–
45
(G) Strigamia crassipes
–
45
(G) Strigamia acuminata
–
45
(G) Strigamia transsilvanica
–
45
(G) Geophilus insculptus
–
Species from the surrounding woodland not found in the mine sites over 50 years of
recultivation
Lithobius dentatus
Lithobius nodulipes
Lithobius austriacus
Lithobius macilentus
Lithobius lusitanus valesiacus
Lithobius agilis
Fig. 10 Dominance of lithobiid species at Berzdorf mine-sites during 46 years. (After K. Voigtländer)
64
Wolfram Dunger
Biological soil-quality assessment in reclaimed land
65
Fig. 11 shows societies and subsocieties of Collembola from the mine sites of the Berzdorf
district afforested with deciduous wood. It is noticeable that the succession is more rapid
and varied in the epedaphic stratum, whereas the euedaphic stratum develops more quietly
(Dunger et al. 2002). The initial phase (Fig. 2) is well documented by only one society at
each stratum, but the pioneer phase shows a quick changing in the litter and a long
duration (with two subsocieties) in the mineral soil. In contrast, the transition to the
organisation phase shows more differentiation in the euedaphic stratum. These findings
have to be discussed in more detail, using new data (Dunger et al. 2004b).
Fig. 11 Succession of societies of epedaphic and euedaphic Collembola at deciduous mine sites of the
Berzdorf mining district. Latin typed: subsocieties
6.
Future prospects
The development of post-mining landscapes from the soil biological point of view
Our knowledge about the high importance of soil organisms in the process of origin and
first development of soils necessitates the inclusion of soil biological investigations to
studies on the development of post-mining landscapes (Pflug 1998, Frouz et al. 2001,
Topp et al. 2001, Dunger & Voigtländer 2002). Possible objectives of reclamation are:
– Readaptation to the »predisturbance level«: possible only in exceptional cases
because of the altered physico-chemical conditions of the dump soils.
– Maximisation of the production of biomass as soon as possible: such demands are
today no longer pursued.
66
Wolfram Dunger
– Adaptation to the environmental capacity of native soils according to the mineral
composition: an entirely realistic aim.
– Attainment of high diversity and environmental capacity and transition to a natural
cycle of development: optimal future prospect of post-mining landscapes being not
(or minimally) used by man.
Biotope selection – Main processes of primary succession
In chapter 3, steps of the pedogenetic and biogenetic processes immediately after dump
heaping were shortly presented. Immigration modalities combined with the biotope
selection, though highly important, are not a topic of this paper (see Dunger et al. 2002).
Biocoenotic regulation
Two kinds of parameters being important for the development of the environmental
capacity of young mine-site soils can be distinguished: activities of life of soil organisms
as a contribution to substantial processes and the quantitative and qualitative structure
of organismic groups as biological indicators.
The first group of parameters is linked with the use of energy. Checking the decomposition by microorganisms gives information about actual transformation of soil organic
matter. Studying the role of saprophagous soil macrofauna, especially earthworms, enables
to obtain an insight into the main decomposition strategy at the mine site, i.e. the stimulation
of microbial activity by feeding of earthworm and other soil animals, faeces deposition
and bioturbation. Such information cannot be derived directly from the abundance or
even biomass observation of the saprophagous macrofauna, but requires the determination
of metabolic equivalences. If reliable data of the lumbricid fauna of a site are available, the
level of potential zoogenic decomposition can be calculated from the literature. Compared
with the known yearly litter input, the intensity of zoogenic decomposition provides good
information about the biological quality of the soil under study. Unfortunately, only few
sites are investigated intensively enough to make it possible to draw such comparisons.
Therefore, the examples presented here cannot yet be generally used for the majority of
mine sites.
The attempt to use available information about the soil fauna as a direct indicator is
primarily confronted in nearly all groups with the highly pulsating abundances during the
year and the high patchiness of individual densities. For the soil macrofauna, especially
the earthworms, biomass is a more well-balanced parameter because most of these animals
live longer than one or two years. For the microarthropods, population densities are more
adequate units of measurement. As a basis of indication the dominance of types of feeding
can be used. Here the life forms of earthworms (epigeic, anecic, endogeic) or of
microarthropods (epedaphic, (eu)edaphic) are included. As an interesting strategy being
important in the first steps of succession, the dominance-strategy can be described,
acting according the »inhibition-model« of Connel & Slatyer (1977). The explosive increase
of some species of soil animals during the initial or pioneer phases of succession led to
the question whether a kind of »macrobiostasis« is here in action. The high aggregation
of some microarthropod species may in this way be interpreted as a space-time-strategy;
but without doubt the basis of nutritive sources decides on the duration of such processes.
Biological soil-quality assessment in reclaimed land
67
Summarising the present possibilities to investigate and understand the biocenotical
regulation processes, the ecological characterisation of the important species involved is
to be seen in the key position of necessary knowledge for biological soil quality assessment.
Unfortunately, basic information on ecological demands and the behaviour of such species
are available only for a small part of species, e.g. lumbricids, and should therefore be
enlarged for most of the soil-animal groups.
The soil quality of post-mining landscapes
The meaning of all soil faunal groups for a good restoration of mine-site soils is a
function of their diverse activities. Using soil faunal parameters as indicators of the quality
of restored soils should be primarily linked with direct influences of animals on the
development of the humus soil profile The progress in soil zoological studies offers the
possibility to examine the self-sustaining condition of the newly emerged ecosystems.
Decomposer communities can be described with regional differentiations mainly at the
macrofaunal (earthworms; Graefe 1993, Graefe et al. 2001) or the mesofaunal level
(microarthropods; Beckmann 1988). They exhibit characteristic species compositions
depending on soil properties such as texture, moisture etc. From the faunal development
of mine sites under deciduous forest, studied at the Berzdorf district, an average optimal
developmental series of soil fauna succession can be derived (Dunger & Voigtländer
2002). Compared with this situation as »expected values«, other soil faunal results from
mine sites, e.g. of the Lower Lusatia, can be regarded as »actual values«. There are
obvious differences in the zoogenic decomposition level and/or the abundance of earthworms indicating a minor quality of soil development. These findings enable the recultivation engineers to discuss the »best way for a good restoration« (Higgs 1997).
7. Acknowledgements
I thank the team of the soil zoological department of the Museum of Natural History in
Görlitz, especially Dr Karin Voigtländer, for a very long and splendid cooperation. English
corrections were made by Dr David Russell. This study was partly supported by the
German Federal Ministry of Education and Research (BMBF).
Author’s address:
Prof. Dr Wolfram Dunger
State Museum of Natural History Görlitz, Soil Zoological Department
POB 30 01 54
02806 Görlitz, Germany
e-mail: [email protected]