Evaluation of different restoration
methods for heathland vegetation.
Department of Agricultural Ecology
Introduction
The increase in agricultural area and intensity
since the Green Revolution has largely been
at the expense of natural and semi-natural
habitats. Increased awareness of the loss of
biodiversity has stimulated considerable
interest in the functional benefits of
biodiversity. As the consequences of
biodiversity loss become better understood,
there is increased momentum for the
protection of rare and threatened habitats and
species. Correspondingly, there has been a
surge of attempts to extend existing wildlife
habitats, and to reconvert intensively
managed land to wildlife habitat (e.g. Burch,
F.M., 1996; Hansson and Hagelfors 1998;
Van der Putten et al. 2000).
A prominent theme in restoration ecology is
the development of natural or semi-natural
vegetation on land with habitat that is of
degraded quality, or has previously been used
for agricultural production. Temporal
changes in the species composition of
vegetation depend on a variety of factors that
include the availability of propagules (Bakker
& Berendse, 1999; Van der Putten et al.
2000), changes in soil fertility (Marrs 1993),
presence or absence of mutualistic symbionts
(Clay and Holah, 1999), and grazing or
mowing regimes.
Throughout the 1970’s and 1980’s,
agriculture schemes and payments
concentrated on the stimulation of
agricultural output. A combination of sheep
hedage payments and the Ewe Premium
scheme lead to a huge increase in sheep
numbers in Ireland over the period 19801995. One of the main environmental
problems in upland and heathland areas is
overgrazing, which is associated with an
increase in soil erosion, water pollution and
loss of biological diversity.
In the present study, we focus on the impacts
of overgrazing on heathland areas, and
investigate possible ameliorative measures
for the effects of overgrazing on heathlands.
The overall objectives of the study were to
compare different restorative measures that
may be implemented to restore habitat quality
(via vegitation cover and species diversity) of
heathland areas. In addition, the restoration
methods must be practically feasible.
Ultimately, many thousands of hectares may
benefit from a successful method of
heathland restoration. Here, we investigate a
number of restoration methods that may be
used to promote the vegetation recovery on
heathland areas. We consider the effect of
seed storage on seed viability as well as
optimul seed application rates required to
promote vegetation recovery.
Methods
Comparison of restoration methods
In 1997, three different restoration methods
were experimentally applied to heathland
areas that had been overgrazed for over five
years. Vegetation growth over the subsequent
12 month period was measured. Generally,
bare ground cover in the experimental area
was 90-95%. The first method involved an
experimental hay-spreading (H) of ‘hay’ that
had been harvested from a nearby heathland
area with bare ground cover of not more than
10%. The second method involved the direct
spreading of seed (Ss) from a commercil
supplier of seeds. The third method (T)
involved the transfer of volumes of
vegetation and soil from the same heathland
area where hay was harvested. Each volume
was 1m X 1m X 0.4m deep.
There were four replicates of each of the
three treatments. Each replicate plot was 6m
X 6m, and there was a 2m border between
adjacent plots.
Percentage cover was assessed in 1998,
approximately one year after applying the
treatments. Percentage cover was assessed in
both a central 1m X 1m quadrat, and a larger
4m X 4m quadrat. The 4m X 4m quadrat had
the 1m X 1m quadrat area at its centre.
Seed viability
In 1997, two experiments were conducted to
investigate the viability of seed samples from
heathland vegetation after storage in both
laboratory and field conditions. The seed
was collected from hay spreading (H)
samples that were used in experiment 1.
In the laboratory experiment, seed was stored
at constant temperature (5oC) and humidity
(5%). After certain periods of time (1 week,
2 weeks, 1 month, 2 months, 3 months, 4
months, 6 months and 12 months), samples
were removed from storage, each replicate
sown in a separate potting tray (12 inches X
12 inches) with a soil layer of 5cm.
Germanation rate of the seed was determined
as the number of seedlings produced per unit
number of seeds, expressed as a percentage
of the germination rate before storage.
of 47 cm with John Innes soil, sown with the
appropriate density of seeds, and covered
with a soil layer of about 3 cm. In the field
experiment, similar containers were sunk into
the ground, filled to a depth of 47 cm with
John Innes soil, sown with the appropriate
density of seeds, and covered with a soil layer
of about 3 cm. The experimental area was
fenced to exclude large herbivores.
There were four replicates per treatment, and
a complete randomised block design was
used in both experiments.
During the harvesting of hay in 1997, twelve
bales of hay (of standard size) were made and
stored in a covered shed. After certain
periods of time (1 week, 2 weeks, 1 month, 2
months, 3 months, 4 months, 6 months and
12 months), three sub-samples were removed
from each bale, and the germination rate was
determined as in the laboratory experiment
above.
Results
(See Figs. 1-4).
Seed application rate
Two experiments were conducted to
investigate whether there is an upper
threshold of density of viable seeds, beyond
which there is no significant increase in the
percentage cover of vegetation.
Seed was collected from 100kg of heathland
vegetation that was mown, and from which
5kg of seed was extracted. Using data from
other experiments, the number of viable seeds
per unit weight of the 5kg seed mass could be
estimated.
In both the glasshouse and field experiment,
the sowing density of viable seeds was
systematically varied (100, 200, 400, 800,
1600, 3200 viable seeds per m sq.) and
vegetation cover measured after a period of
one year.
In the glasshouse experiment, cube-shaped
containers of side 0.5 m were filled to a depth
References
Burch F.M. 1996. Establishing species-rich
grassland on set-aside land: balancing weed
control and species enhancement. Aspects of
Applied Biology 44: 221-226.
Bakker J.P. and Berendse F. (1999).
Constraints in the restoration of ecological
diversity in grassland and heathland
communities. Trends in Ecology and
Evolution, 14, 63-68.
Hansson M. and Hagelfors H. 1998.
Management of permanent set-aside on
arable land in Sweden. Journal of Applied
Ecology 35: 758-771.
Clay K. and Holah J. (1999). Fungal endophyte
symbiosis and plant diversity in successional
fields. Science 285: 1742-1744.
Marrs RH. 1993. Soil fertility and nature
conservation in Europe: theoretical
considerations and practical management
solutions. Advances in Ecological Research,
24, 241-300.
Schulze E.-D. and Mooney H.A. (1993).
Biodiversity and ecosystem function.
Springer.
100
germination rate (%)
100
% cover
80
60
40
20
0
H1 H4
Ss 1 Ss 4
80
60
40
20
0
0
T1 T4
Treatment
6
time
9
12
Fig. 2. Plot of germination rate following
storage of seeds in laboratory conditions for
different periods of time.
Fig. 1. Comparison of vegetation cover following
experimental application of different restoration
methods in Experiment 1.
100
100
80
80
%cover
germination rate (%)
3
60
40
20
60
40
20
0
0
3
6
9
Time (months)
Fig. 3. Germination rate of seeds following
storage in field condiations for different
periods of time.
12
0
0
1000
2000
3000
Seed application (per m sq)
Fig. 4. Vegetation cover resulting from different applications
of seed density. Data are presented for both laboratory
(diamonds) and field (circles) conditions.
Assignment
1. Were the objectives of the experiment adequately addressed?
2. Write a short summary (ten lines) of this report.
3. Using no more than four lines for each Figure, write down the main findings of each of
Figures 1-4.
4. Draw the layout of the field plots that could be used in the ‘comparison of restoration
methods’. Compare your layout of the field plots with a different layout by a classmate. What
are the differences? What are the impacts of those differences on a) experimental rigour of the
design, and b) the logistics of the fieldwork?
5. Provide a written evaluation of the Introduction and Methods sections of this report.
OR
Based on the Introduction, Methods and data provided, complete the Results and Discussion
section.