CSG 15
MINISTRY OF AGRICULTURE, FISHERIES AND FOOD
Research and Development
Final Project Report
(Not to be used for LINK projects)
Two hard copies of this form should be returned to:
Research Policy and International Division, Final Reports Unit
MAFF, Area 6/01
1A Page Street, London SW1P 4PQ
An electronic version should be e-mailed to c.csgfinrep@csg.maff.gsi.gov.uk
Project title
Methods of accelerating development of chalk grassland on ex-arable land
MAFF project code
BD1434
Contractor organisation
and location
CABI Bioscience
Silwood Park
Ascot
Berks
SL5 7TA
Total MAFF project costs
Project start date
£ 36574
01/04/99
Project end date
31/03/00
Executive summary (maximum 2 sides A4)
The EU-funded CLUE project, (Changing Land Usage: Enhancement of biodiversity and ecosystem
development) involved studying novel methods of enhancing the development of plant and animal communities
associated with species-rich grasslands on land taken out of intensive arable cultivation. Since 1996, the
development of chalk grassland on ex-arable land at Bradenham in the Chilterns has been studied. However,
funding under the EU-TERI scheme ceased in March 1999. This one-year MAFF-funded project allowed
continuation of the study and provided supplementary information on two issues of agronomic importance,
namely the impact of the treatments on weed suppression and soil fertility.
The main objective of this project was to allow continuation of the study of the development of chalk
grassland communities in relation to two sets of experimental treatments. Firstly, the use of seed mixtures of
different levels of diversity was compared with allowing natural colonisation. Secondly, the efficacy of using
small-scale turf transplants and soil translocation as a means of accelerating the colonisation of the site by
species characteristic of local chalk grassland was assessed.
Management of the treatment plots continued as for the period 1996-1999, with the exception of the
‘continued cultivation’ (CC) plots. Management of these plots, which had been to subjected to continued arable
cropping during the initial 3-year period, ceased, producing a set of plots at a younger successional age than the
natural colonisation plots established in 1996. The permanent quadrats in the plots of the main sowing
experiment and the stepping stone experiment were recorded in July-August 1999, the fourth summer after
sowing. Changes in the relative abundance of the sown species were apparent, with a general decrease in
abundance of leguminous species and an increase in the abundance of perennial grasses. Some, less
competitive, species amongst those sown are starting to be excluded, particularly from the high diversity plots.
CSG 15 (Rev. 12/99)
1
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Weed suppression was found to be greatest in the high diversity treatments (15 species sown), probably
related to the greater production of standing crop in these plots. The degree of weed suppression in the low
diversity plots (4 species sown) was highly variable, depending on the identity of species sown in the mixture.
The performance of sown species in the high diversity plots was found to be a good indicator of their
performance in the low diversity mixture, so the low diversity mixtures with the greatest weed suppression
were those with the best performing sown species. The consistency of performance of sown species is likely to
vary between sites, years and sowing times. Therefore, it will be difficult to predict the identity of species
likely to perform well in low diversity treatments. The use of high diversity mixtures is likely to offer a greater
probability of successful weed suppression.
The sowing treatments were very effective at suppressing pernicious grass weed species. Early stages of
succession at the site in the natural colonization and continued cultivation plots were dominated by black grass
(Alopecurus myosurioides), with sterile brome (Anisantha sterilis) becoming dominant in later years. Neither
species contributed significantly to the sward in the sown plots in 1999. The sowing treatments were also
effective at suppressing pernicious broad-leaved weeds, notably creeping thistle (Cirsium arvense) and spear
thistle (Cirsium vulgare). The abundance of ragwort (Senecio jacobaea) increased in 1999. However, the
abundance of this species in the sown plots was low (<0.5%) in comparison with its abundance in the natural
colonization and continued cultivation plots.
The stepping stone treatment (consisting of turf and soil translocation from a neighbouring chalk grassland)
was found to effectively enhance the colonisation of the site by chalk grassland plant species. Many of the
species introduced by this restoration treatment have started to colonise the untreated areas, so that the stepping
stone plots are successfully acting as ‘focal points for colonisation’ of the rest of the field. The plant species
that are most successfully introduced using this method are those with a persistent seed bank, especially shortlived chalk grassland species associated with disturbed soil conditions. Several short-lived ‘turf-compatible’
species have also colonised (e.g. Euphrasia nemorosa, Blackstonia perfoliata), as have several species of
perennial forb (Viola hirta, Centaurea scabiosa). Colonisation of the plots with the stepping stone treatment by
chalk grassland graminoids has been limited.
An experiment was carried out to assess the invasibility of the plots of the main sowing experiment to
different plant species. Set numbers of seeds were sown in the autumn, to mimic the timing of natural seed fall.
In total, seeds of 4 weed species and 12 chalk grassland species were sown. Some chalk grassland species have
established well (e.g. Primula veris, Ranunculus bulbosus), for other species no seedlings have been found (e.g.
Hippocrepis comosa, Thymus polytrichus). Establishment of the weed species has been poor. Establishment
success has been greatest for both weed and chalk grassland species in the natural colonisation and continued
cultivation plots, and lowest in the high diversity plots.
The insect assemblages present in the plots of main experiment and the stepping stone experiment were
sampled using a Vortis suction sampler, as were two neighbouring chalk grassland sites (one of which was the
site of origin for the soil and turf for stepping stone treatment). Significant treatment differences were found in
the Coleoptera and Hemiptera (Heteroptera, Auchenorrhyncha) faunas of sowing and natural colonisation
treatments. In addition, a significant effect of the stepping stone treatment was found on the Coleoptera
assemblages present in the plots.
The study reported here showed clear differences in the invertebrate assemblages in natural colonisation
plots compared with those that had been sown. For many groups of invertebrate, abundances were significantly
higher in the sown plots. The diversity of species assemblages was also found to be significantly higher in the
high diversity sown plots than the natural colonisation plots, with the low diversity sown plots having
intermediate values. The stepping stone treatment was also found to have significant effects on the composition
of two insect groups, the Auchenorrhyncha (hoppers) and the Coleoptera (beetles).
In spite of the significant differences between treatments, the insect assemblages in the experimental plots
were composed largely of fairly common species characteristic of a range of herbaceous vegetation. Many of
the species which have habitat affinities restricted to chalk grassland were absent from the plots. It is likely that
development of the invertebrate communities of arable reversion sites will be a slow process, the speed of
CSG 15 (1/00)
2
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
development related to the proximity of established chalk grasslands to act as sources of colonists.
Notwithstanding this, it is clear from the results of this study that development of the assemblages of certain
insect groups towards those that resemble established chalk grassland was promoted by the sowing of plant
species typical of such communities.
Soil cores were taken from the plots of the main experiment, from the adjacent cropped field and from 2
established chalk grassland sites. Levels of N were significantly higher in the continued cultivation plots than
in the sown plots, but no difference was found between the natural colonisation and the sown plots. Levels of P
were significantly higher in the natural colonisation and continued cultivation plots than in the high diversity
sowing treatment. These differences probably reflect the result of the management of the plots by mowing in
late summer and removing clippings. Productivity is highest in high diversity plots, so offtake is likely to be
greatest. This will be especially true for P, as leguminous species are present in sown plots, but almost absent
from natural colonisation plots.
The soils from the high diversity sowing treatment plots showed no significant difference in the levels of P
compared with one of the chalk grassland sites (ADAS index 1). However, major differences between the
experimental plots in general and the established chalk grassland sites were found for pH, N, K and organic
matter. For these factors, the experimental plots had significantly different values when compared with the
chalk grassland soils, but were not significantly different from the soils of the adjacent cropped field.
The implications of the results in terms of techniques for arable reversion are considerable. These
discussed (pages 20–23) in terms of sward characteristics and soil properties. Methods of enhancing
suppression of weed species and enhancing the colonisation by plants and invertebrates characteristic of
target community are provided and critically assessed. Avenues for further research and development
forthcoming.
CSG 15 (1/00)
3
are
the
the
are
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Scientific report (maximum 20 sides A4)
1
INTRODUCTION
Large areas of species-rich grassland have been lost in the past 50 years, primarily as the result of agricultural
intensification. Land has either been converted to arable systems, or remaining areas of grassland have had
their biological diversity diminished as a result of increased inputs of fertilisers, herbicides and pesticides.
These changes in agricultural practice have not only led to the loss of botanical diversity, but have had similar
effects on the range of invertebrates associated with such grassland communities.
Large areas of former arable land are now being managed to promote the development of species-rich
grassland communities. This is the result of the introduction of incentive payments available through MAFF’s
ESA and Countryside Stewardship Schemes, together with the activities of other government agencies, local
authorities and non-governmental organisations.
The creation of species-rich grassland on ex-arable land is hindered by the conditions of the site, which are
the products of intensive arable husbandry, notably high soil fertility and the presence of competitive weed
species in the soil seed bank. In addition, the low frequency of remnant patches of species-rich grassland in
many landscapes means that potential sources of colonising species are widely spaced and consequently the
dispersal of plants and invertebrates to new sites may occur very infrequently.
For many plant species, it is possible to manipulate the colonisation of new grassland through the sowing of
seed. However, certain plant species may establish poorly from seed and typically regenerate by vegetative
means, or have specific requirements for interactions (e.g. with mycorrhizal fungi). Manipulation of the
colonisation of a site by such species of plant and other groups, such as invertebrates and soil fungal and
microbial communities, is more problematic.
This project sought to study the effect of the diversity of the sown seed mixture on the performance of weed
species, the colonisation by desirable species and soil properties was studied and compared to management of
the site by ‘natural colonisation’. In addition, the success of turf and soil translocation from existing areas of
species-rich grassland (the so-called ‘stepping stone’ treatment), as a means of enhancing the colonisation of
new sites by the full range of organisms associated with established grassland communities, was investigated.
The project used two field experiments established as part of the EU-funded CLUE (Changing Land Usage:
Enhancement of biodiversity and ecosystem development) project. This project involved studying novel
methods of enhancing the development of plant and animal communities associated with species-rich
grasslands on land taken out of intensive arable cultivation. Since 1996, the development of chalk grassland on
ex-arable land at Bradenham in the Chilterns has been studied. The experiments, with a range of treatments,
had started to show the potential of using ‘stepping stones’ as focal points for the colonisation of such land by
desirable species.
2
SCIENTIFIC OBJECTIVES
The scientific objectives of the project were as follows:
• To follow the development of the sward in relation to the different sowing treatments and addition of
stepping stones.
• To investigate the relationship between the diversity of the seed mixture and the suppression of weed
species.
• To investigate the colonisation by desirable chalk grassland species of sown and unsown plots.
• To study the invertebrate communities which develop on sown and unsown plots.
• To determine the effects of the sowing treatments on soil properties.
CSG 15 (1/00)
4
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
3
METHODS
3.1
Approach
MAFF
project code
BD1434
The approach involved continuing the programme of measurements carried out at the experimental site during
the period 1996-99 as part of the CLUE project. The sampling protocols for these measurements were wellestablished and had been used in identical experimental sites in 4 other locations across Europe. In addition,
the effects of the sowing and natural colonisation treatments on the suppression of weed species and the
promotion of colonisation by chalk grassland species was assessed using newly-established experiments.
3.2
Study site
The study was carried out on the Bradenham Estate in the Chiltern Hills, 50 km north-west of London, on land
owned by the National Trust. Parts of the estate comprising woodland and species-rich calcareous grassland
are managed as a nature reserve by the Trust; this area is a currently designated a Site of Special Scientific
Interest and is a candidate Special Area of Conservation. The remainder of the estate is managed by a tenant
farmer and comprises arable land and permanent pasture. Several areas of arable land have been taken out of
cultivation over the last 30 years and are being managed for the re-establishment of calcareous grassland.
The field experiment was set up along the upper edge of an arable field in an area measuring approximately
230 m x 35 m. The site is bounded on the east by an open plantation of Fagus sylvatica that was planted about
30 years ago, to the south by an improved permanent pasture and the north and west by arable land. The site is
fenced on three sides, the boundary with the rest of the field is unfenced. The soil is a grey rendzina over
Cretaceous Chalk bed rock. The average annual precipitation is about 750 mm. The area was sown to winter
barley in 1994 and was harvested in August 1995. The site was cultivated in the autumn of 1995 and harrowed
in March 1996 before the start of the experiment.
Two areas of existing chalk grassland on the Bradenham Estate were sampled in order to allow comparison
of the plant and insect assemblages typical of the ‘target’ community. Small Dean Bank is an area of
calcareous grassland with no history of agricultural improvement. The tussocky vegetation is dominated by
Festuca rubra, with abundant Arrhenatherum elatius and tall forbs, such as Origanum vulgare. Butterfly Bank
was cultivated for a short period approximately 30 years ago, and supports a more open vegetation with Festuca
rubra, Leontodon hispidus and Lotus corniculatus. Both sites fall into the Arrhenatherum elatius grassland
(MG1) of the National Vegetation Classification (Rodwell 1992). Such vegetation is typical of many small
fragments of chalk grassland remaining on steep banks in the Chilterns. The target sites are lightly grazed by
sheep for short periods each year. In addition, Butterfly Bank is occasionally mown.
3.3
Main experiment
Within each of 5 replicate blocks, four plots measuring 10 m x 10 m were marked out. The four treatments
(continued cultivation, CC; natural colonisation, NC; low diversity seed mixture, LD and high diversity seed
mixture, HD) were randomly allocated to the plots in each block. The treatments were as follows:
Continued cultivation
Plots cultivated and sown with the same crop as adjacent field, with
equivalent applications of fertilizer and herbicides. Plots left to natural
colonisation Autumn 1998.
Natural colonisation
Plots left to natural colonisation after cultivation in March 1996
Low diversity seed mix
Plots sown with seed mixture containing 4 species
High diversity seed mix
Plots sown with seed mixture containing 15 species
5
Methods of accelerating development of chalk grassland on
ex-arable land
Project
title
MAFF
project code
BD1434
The species chosen for the low and high diversity sowing treatments occur with high frequency in calcareous
grasslands in the surrounding region. In the high diversity plots, 5 grass, 5 legume and 5 other forb species
were sown. The species sown were as follows:
Grasses
Legumes
Other Forbs
Cynosurus cristatus
Anthyllis vulneraria
Centaurea nigra
Festuca rubra
Lotus corniculatus
Galium verum
Holcus lanatus
Medicago lupulina
Leontodon hispidus
Phleum pratense
Trifolium dubium
Plantago lanceolata
Trisetum flavescens
Trifolium pratense
Sanguisorba minor
In the low diversity plots, 2 grass species were sown with one legume and one other forb species. The
identity of the species sown in each replicate differed between blocks, with species being allocated to each LD
mixture by random allocation. This design was adopted to ensure that differences between the LD and HD
treatments were not confounded by the effects of species choice for the LD mixture. The species combinations
used were as follows:
Grasses
Legumes
Other Forbs
A Festuca rubra
Phleum pratense
Lotus corniculatus
Plantago lanceolata
B
Phleum pratense
Trifolium pratense
Centaurea nigra
C Cynosurus cristatus
Holcus lanatus
Trifolium dubium
Galium verum
D Cynosurus cristatus
Trisetum flavescens
Medicago lupulina
Leontodon hispidus
E
Trisetum flavescens
Anthyllis vulneraria
Sanguisorba minor
Holcus lanatus
Festuca rubra
In the high diversity treatment, the grass species were sown at a density of 500 seeds/m2 and the legumes
and other forbs at 100 seeds/m2. Seed densities for the low diversity treatments were 1250 seeds/m2 for grasses
and 500 seeds/m2 for legumes and other forbs. The total densities of sown seeds were therefore consistent
between low and high diversity treatments at 3500 seeds/m2. Sowing took place between 26th and 30th April
1996.
Twelve permanently-marked quadrats were set out within each main plot and have been monitored annually
in July since 1996. Values of estimated percentage cover were assigned to each species of vascular plant
present in the quadrat.
3.4
Stepping stone experiment
Six plots, measuring 2 m x 2 m were marked out in each of 5 replicate blocks. Two plots in each block were
randomly assigned to the natural colonisation (NC), low diversity (LD) and high diversity (HD) treatments.
One plot of each sowing treatment was assigned to the stepping stone treatment (+SS), whilst the other plots
received no stepping stone treatment (-SS). The six plots thereby comprised a full factorial design with 3
sowing treatments and 2 stepping stone treatments.
On 23th-24th April 1996, soil was collected from Butterfly Bank, an adjacent field that was last cultivated in
1970. The soil was collected at 15 points on a regular grid within the field. The soil from each sampling point
was kept separately and each sample randomly allocated to one of the stepping stone treatment plots.
6
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Before application of the soil to the stepping stone plots, the top 5 cm of soil in each 2 x 2 m plot was
temporarily removed. The 10 litres of soil were then spread evenly over the area of the plot and the top layer
then replaced. The topsoil was also removed from the plots with no stepping stone treatment and then replaced
in order to mimic the disturbance caused by this treatment. After application of the soil inoculation, sowing
was carried out as described for the main experiment between 26th and 30th April 1996.
In November 1996, 60 turf monoliths measuring 25 cm x 25 cm x 25 cm were taken from Butterfly Bank.
The turves were taken at points on a grid with 15 m spacing between rows and columns. The turves were
randomly-allocated to the stepping stone treatment plots. Four turves were placed in each of the stepping stone
plots at the corners of the central 1m2 sampling area, being buried so that the top of each turf was level with the
surrounding soil.
The vegetation development in these plots has been recorded in a central 1m2 permanent plot by estimation
of percentage cover of each species of vascular plant present.
3.5
Colonisation of plots by undesirable weed species and chalk grassland plants
A new experiment was established in order to assess differences in the invasibility of the plots of the main
sowing experiment to different plant species. Seeds of 4 weed species and 12 chalk grassland species were
sown in October 1999. Sixteen sub-plots measuring 20 x 20 cm were marked out in four positions within each
10 x 10 m plot of the main experiment. The sixteen species were randomly-allocated to sub-plots within each
grid and 100 seeds of each species sown. The plots were monitored and the number of seedlings counted for 10
months.
3.6
Colonisation of plots by invertebrates
Coleoptera assemblages were sampled by the suction method, using a Vortis sampler (Burkhard Manufacturing,
Rickmansworth, UK). Samples were taken on three dates, mid-June, late-July and mid-September. On each
occasion, an area of 0.155 m-2 was sampled in each plot, corresponding to 8 positions of the Vortis sampler. In
addition, five samples of 0.155 m-2 were collected from the target sites of Butterfly Bank and Small Dean Bank,
the 5 sample locations being evenly spaced across each field. Invertebrates were extracted from the samples
and the specimens stored in alcohol prior to identification to species. Invertebrate species were identified to
taxonomic order and key groups (Heteroptera, Auchenorrhyncha, Coleoptera) identified to species.
3.7
Characterisation of soil properties
Soil cores were taken from the plots of the main experiment, from the adjacent cropped field and from 2
established chalk grassland sites. A total of 25 cores were taken on a regularly-spaced grid within each 10 m x
10 m plot and the cores from each main plot thoroughly mixed. A similar procedure was used to collect soil
samples from the adjacent field and target chalk grassland sites. For these, five ‘dummy’ 10 x 10 m plots were
laid out at random positions within each field and 25 cores taken from each dummy plot. A 500 g sub-sample
was taken from the bulk sample for each plot (or dummy plot) and forwarded to the ADAS Laboratories,
Wolverhampton for analysis. The following analyses were carried out:
pH
Loss on ignition (for soil organic matter)
Total N (Dumas method)
Total P, K and Mg (aqua regia soluble method)
7
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
4
RESULTS
4.1
Development of sward in relation to main treatments
MAFF
project code
BD1434
The permanent quadrats in the plots of the main sowing experiment and the stepping stone experiment were
recorded in July-August 1999, the fourth summer after sowing. Changes in the relative abundance of the sown
species were apparent, with a general decrease in abundance of leguminous species and an increase in the
abundance of perennial grasses since 1998 (Figure 1). Some of the forb species sown in 1996 established very
effectively and dominated the vegetation of the sown plots in the early years of the experiment, most notable
amongst these species are Anthyllis vulneraria, Plantago lanceolata and Medicago lupulina. In the year of the
study reported here (1999), the relative abundance of these early dominants has decreased as the abundance of
the sown perennial grasses has increased.
Some of those species sown in 1996 established poorly and remain present in the sward only at low
abundance. Of these, Trifolium dubium, which was present with low abundance but high frequency in the high
diversity sown plots in earlier years, was only recorded from 3% of the quadrats in 1999. Other poorlyestablishing species have slowly increased in abundance (some perennial grasses and Leontodon hispidus).
Ten of the sown species were found to have established in the natural colonization plots in 1999, and six of
these were also recorded in the continued cultivation plots (Table 1). The species that established rapidly after
the LD and HD plots were sown in 1996 are the same species which are now successfully colonizing the natural
colonization and continued cultivation plots (Anthyllis vulneraria, Plantago lanceolata and Medicago
lupulina). Others are starting to colonise the unsown NC and CC plots.
Table 1
Frequency (%) of sown species in the permanent quadrats of the treatment plots in 1999.
Grasses
Legumes
Other forbs
4.2
TREATMENT:
Cynosurus cristatus
Festuca rubra
Holcus lanatus
Phleum pratense
Trisetum flavescens
Anthyllis vulneraria
Lotus corniculatus
Medicago lupulina
Trifolium dubium
Trifolium pratense
Centaurea nigra
Galium verum
Leontodon hispidus
Plantago lanceolata
Sanguisorba minor
CC
0
0
1
0
0
10
0
18
0
0
3
0
0
42
7
NC
0
10
8
0
7
45
0
65
0
0
27
1
1
72
3
LD
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
HD
93
100
100
100
100
100
100
100
3
38
100
100
87
100
100
Development of sward in relation to ‘stepping stone’ treatments
The stepping stone treatment (consisting of turf and soil translocation from a neighbouring chalk grassland)
resulted in a significant increase in plant species richness (Figure 2). The number of unsown species was
highest in the natural colonization plots and lower in the sown plots, as was found to be the case for the main
experiment. The magnitude of this effect was greater in previous years, probably because the more open
conditions in the natural colonization plots allowed more successful establishment of species from the
translocated soil. In 1999, addition of the stepping stone treatment resulted in an increase of about 5 species per
quadrat, regardless of whether the plots were sown or undergoing natural colonisation.
8
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Figure 1 Changes in abundance (percentage cover) of the fifteen sown species in the high diversity (˜) and
low diversity (˜) plots. Error bars show ± 1 s.e.m. (NB error bars are not shown for legumes and
other forbs in the LD treatment as each species was sown in only one replicate.
GRASSES
100
LEGUMES
Cynosurus cristatus
100
OTHER FORBS
Anthyllis vulneraria
100
80
80
80
60
60
60
40
40
40
20
20
20
0
0
96
97
100
98
99
Festuca rubra
0
96
97
100
98
99
Lotus corniculatus
96
80
80
60
60
60
40
40
40
20
20
20
0
96
97
98
100
99
Holcus lanatus
97
100
98
99
Medicago lupulina
60
60
60
40
40
40
20
20
20
0
98
100
99
Phleum p ratense
97
98
100
99
Trifolium dubium
60
60
60
40
40
40
20
20
20
0
100
98
99
Trisetum flavescens
97
100
98
99
Trifolium p ratense
60
60
60
40
40
40
20
20
20
0
98
99
97
100
80
97
99
Plantago lanceolata
96
80
96
98
0
96
80
0
97
100
80
97
99
Leontodon hispidus
96
80
96
98
0
96
80
0
97
100
80
97
99
Galium verum
96
80
96
98
0
96
80
0
97
100
80
0
Centaurea nigra
98
99
Sanguisorba m inor
0
96
97
98
9
99
96
97
98
99
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Figure 2 Number of unsown species per quadrat for the natural colonization (£), low diversity (˜) and high
diversity (˜) sown plots, with and without the addition of the stepping stone treatment. Error bars
show ± 1 s.e.m.
30
number of unsown species
25
20
NC SS
15
NC
10
LD SS
HD SS
5
LD
HD
0
1996
1997
1998
1999
The stepping stone treatment has effectively enhanced the colonisation of the site by chalk grassland plant
species. Many of the species introduced by this restoration treatment have started to colonise the untreated
areas, so that the stepping stone plots are successfully acting as focal points for colonisation of the rest of the
field. The plant species that are most successfully introduced using this method are those with a persistent seed
bank, especially short-lived chalk grassland species associated with disturbed soil conditions (Figure 3).
Several short-lived ‘turf-compatible’ species have also colonised (e.g. Euphrasia nemorosa, Blackstonia
perfoliata), as have several species of perennial forb (Viola hirta, Centaurea scabiosa). Colonisation of the
plots with the stepping stone treatment by chalk grassland graminoids has been limited.
Comparison of the vegetation developing in the plots of the stepping stone experiment with that of sites in
the chronosequence sites at Bradenham (i.e. the replicated set of fields of different successional age) was
carried out using multivariate techniques. The first two axes of the detrended correspondence analysis are both
correlated with successional age (Figure 4). Axis 1 separates the samples taken at the start of the experiment, in
very early stages of the colonization of ex-arable land, from sites with established vegetation cover. Axis 2
separates vegetation dominated by weed species from that composed of grassland species.
It can be seen on the ordination diagram that, whereas trajectory for the natural colonization plots is towards
the mid-successional sites of the chronosequence, the trajectory for the high diversity sown plots is towards the
target of chalk grassland. The low diversity sown plots are intermediate between the natural colonization and
high diversity sown treatments. The stepping stone treatment has resulted in a significant acceleration in the
development of the vegetation within the plots towards mid- and late-successional sites on the chronosequence,
this effect being most pronounced in the natural colonization treatment.
10
Methods of accelerating development of chalk grassland on
ex-arable land
Project
title
MAFF
project code
BD1434
Figure 3 Ordination of plant species from treatment plots of the stepping stone experiment using Redundancy
Analysis. Species introduced by the stepping stone treatment are shown in bold (®), species
occurring in all plots are shown in normal text (¯). The centroids for the different treatment
combinations are shown thus: natural colonization (£), low diversity sown (˜) and high diversity
sown (˜) plots. Species codes are listed in Appendix 1.
NC
1.0
Crep capi
Clem vita
Tara offi
Epil parv
Crep vesi
Cirs arve Inul cony
Poa prat
0.5
Alop myos
Plan majo
Sonc aspe
Vero arve
Anis ster
Rese lute
Cirs vulg
Agro stol
Epil tetr
Euph nemo
Sene jaco
Brom hord
Odon vern
Picr hier
-0.5
LD
Sonc arve
Rume cris
Trif repe
Vici sati
Dact glom
Leuc vulg
Malu sylv
HD
Dauc caro
Hera spho Hype hirs
Vici hirs
1.0
Meli alti
Blac perf
Viol hirt
Cent scab
NCSS
Arrh
elat
Knau arve
Clin vulg Ranu repe
Cera font
Orig vulg
Vero cham
Prun vulg
LDSS
Gali moll
Hype perf
HDSS
-0.5
Figure 4 Ordination of samples from treatment plots and chronosequence sites using Detrended
Correspondence Analysis. Each point represents the mean score for 5 replicates. Treatment codes as
for Figure 3.
DCA Axis 2
EARLY SUCCESSIONAL
3
Chronosequence
sites
2
Experimental plots
1996
1999
1
CHALK
GRASSLAND
DCA Axis 1
0
0
1
2
3
4
11
NC
NC SS
LD
LD SS
HD
HD SS
5-year old
15-year old
30-year old
Chalk Grassland
Project
title
4.3
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Suppression of weed species
Weed suppression was found to be greatest in the high diversity treatments (15 species sown), probably related
to the greater production of standing crop in these plots. The degree of weed suppression in the low diversity
plots (4 species sown) was highly variable, depending on the identity of species sown in the mixture. The
performance of sown species in the high diversity plots is a good indicator of their performance in the low
diversity mixture, so the low diversity mixtures with the greatest weed suppression were those with the best
performing sown species. The consistency of performance of sown species is likely to vary between sites,
years and sowing times, so high diversity mixtures offer a greater likelihood of successful weed suppression.
Changes in abundance (percentage cover) of the selected pernicious weed species in the continued
cultivation (¯), natural colonization (£), low diversity (˜) and high diversity (˜) plots. Error
bars show ± 1 s.e.m.
4
Senecio jacobaea
% cover
3
2
1
0
96
8
98
99
Cirsium vulgare
3
% cover
% cover
97
4
Cirsium arvense
6
4
2
2
1
0
0
96
20
97
98
96
99
97
20
Alopecurus myosurioides
98
99
Anisantha sterilis
15
% cover
15
% cover
Figure 5
10
10
5
5
0
0
96
97
98
99
12
96
97
98
99
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
The sowing treatments were very effective at suppressing pernicious grass weed species. Early stages of
succession at the site in the natural colonization and continued cultivation plots were dominated by black grass
(Alopecurus myosurioides), with sterile brome (Anisantha sterilis) becoming dominant in later years (Figure 5).
Neither species contributed significantly to the sward in the sown plots in 1999. The sowing treatments were
also effective at suppressing pernicious broad-leaved weeds, notable creeping thistle (Cirsium arvense) and
spear thistle (Cirsium vulgare). The abundance of ragwort (Senecio jacobaea) increased in 1999. However,
the abundance of this species in the sown plots was low (<0.5%) in comparison with its abundance in the
natural colonization and continued cultivation plots.
The invasibility of the vegetation present in the treatments of the main experiment was investigated by
sowing seed of a number of weed species into the sward and monitoring establishment. Levels of establishment
of all four species sown were low (Table 2), and there were few significant effects. Differences between the
treatments were only found for charlock (Sinapis arvensis), with higher numbers of seedlings establishing in the
autumn and spring in the continued cultivation and natural colonization plots than in the sown plots (Figure 6).
This treatment effect was not found on the final recording data in late July 2000, many of the seedlings having
died in the spring and summer months.
Table 2
Mean numbers of seedlings per plot for weed species in the continued cultivation (CC), natural
colonization (NC), low diversity (LD) and high diversity (HD) sown plots in March and July 2000.
Treatment effects tested using ANOVA on log-transformed data (1), or the Friedman test for data not
conforming to the requirement of homogeneity of variances (2).
March
CC
Cirsium vulgare
Papaver rhoeas
Rumex crispus
Sinapis arvensis
4.4
0.40
0.00
1.03
1.60
NC
0.40
0.24
0.37
1.20
LD
0.24
0.00
1.44
0.00
HD
0.00
0.00
0.60
0.20
1
ns
ns 2
ns 1
P=0.0322
July
CC
NC
LD
HD
0.40
0.00
0.00
0.20
0.20
0.20
0.86
0.00
0.20
0.00
0.45
0.00
0.00
0.00
0.20
0.00
ns 2
ns 2
ns 1
ns 2
Colonisation by chalk grassland plants
The invasibility of the vegetation present in the treatments of the main experiment was investigated by sowing
seed of a number of chalk grassland species into the sward and monitoring establishment. Species were
grouped according to seed weight. Levels of establishment varied between species (Table 3), but there were
few significant effects and no obvious patterns in relation to seed weight. For species showing significant
treatment effects, establishment success has been greatest in the continued cultivation and natural colonisation
plots, and lowest in the high diversity sown plots (Figure 6).
Some of the chalk grassland species sown have established well (e.g. Primula veris, Prunella vulgaris),
whilst for other species establishment has been absent or poor (Campanula rotundifolia, Hippocrepis comosa,
Thymus polytrichus). The species sown when the experiment was established in 1996 and those sown in the
invisibility experiment in 1999 are all characteristic of the target chalk grassland community. Other species
found in chalk grasslands are also colonizing the experimental plots spontaneously. Many of these species are
present in the hedgebank surrounding the experimental site, so colonization is probably occurring through local
seed dispersal.
The grassland species colonizing the experimental plots spontaneously are characteristic of the Pastinaca
sativa sub-community of Arrhenatherum elatius grassland (MG1d), vegetation typical of abandoned arable land
on shallow chalky soils. The abundance of these species is greatest in the natural colonization plots, their
contribution to the sward of the sown plots is limited (Figure 7). The species are more or less absent from the
continued cultivation plots. Of these species, the perennial grass Arrhenatherum elatius is the only species
which contributes significantly to cover, and then only in the natural colonization plots.
13
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
Table 3
Mean numbers of seedlings per plot for chalk grassland species in the continued cultivation (CC),
natural colonization (NC), low diversity (LD) and high diversity (HD) sown plots in March and July
2000. Abbreviations as in Table 2.
March
CC
Light seed weight (<0.3 mg)
Achillea millefolium
32.0
Campanula rotundifolia
0.2
Pilosella officinarum
0.4
Thymus polytrichus
0.0
Medium seed weight (0.3-1.0 mg)
Filipendula vulgaris
2.0
Plantago media
36.4
Primula veris
126.8
Prunella vulgaris
64.6
Heavy seed weight (>1.0 mg)
Hippocrepis comosa
0.0
Pimpinella saxifraga
0.0
Ranunculus bulbosus
17.6
Scabiosa columbaria
3.0
NC
LD
HD
9.4
0.2
0.0
0.0
6.2
0.2
0.0
0.0
4.0
0.0
0.0
0.0
1.0
23
92.4
46
0.6
2.5
6.4
33.8
0.8
9.8
47.6
25.4
0.0
0.2
14
1.2
0.0
0.6
12.0
0.6
0.0
0.0
8.4
0.0
MAFF
project code
BD1434
July
CC
NC
LD
HD
ns 1
ns 1
ns 2
8.2
0.8
0.0
0.0
32.2
0.0
0.8
0.0
6.6
0.6
0.0
0.0
0.0 P=0.009
0.2
ns 2
1.8
ns 2
0.0
ns 2
ns 1
P=0.003
ns 1
1.6
10.0
79.0
77.2
10.2
31.2
88.1
81.3
0.8
22.0
51.8
45.2
1.2 P=0.023
5.2
ns 1
37.2
ns 1
29.2
ns 1
1.2
0.6
12.4
8.0
1.0
5.6
16.8
13.4
0.2
5.0
6.4
3.4
1
ns
ns 1
ns 2
ns 2
ns 1
ns 1
ns 1
0.0
0.6
1.8
0.0
Figure 6 Establishment of selected species sown in the invasibility experiment in the continued cultivation
(¯), natural colonization (£), low diversity (˜) and high diversity (˜) plots. Error bars show ± 1
s.e.m.
Achillea m illefolium
50
45
14
Num b e r of seedlings
Numbe r o f s e e d l i n g s
Filipendula vulgaris
16
40
35
30
25
20
15
10
12
10
8
6
4
2
5
0
0
0 1
/1
0 /9
9
3
1
/1
0 /9
9
3
0 /1
1
/9
9
3
0 /1
2
/9
9
2
9
/0 1
/0 0
2
8
/0 2
/0 0
2
9
/0 3
/0 0
2
8
/0 4
/0 0
2
8
/0 5
/0 0
2
7
/0 6
/0 0
2
7
/0 7
/0 0
2
6
/0 8
0 1
/0 0
/1
Oct Nov Dec Jan Feb Mar A pr May Jun Jul
9
3
1
/1
0 /9
9
3
0 /1
1
/9
9
3
0 /1
2
/9
9
2
9
/0 1
/0 0
2
8
/0 2
/0 0
2
9
/0 3
/0 0
2
8
/0 4
/0 0
2
8
/0 5
/0 0
2
7
/0 6
/0 0
2
7
/0 7
/0 0
2
6
/0 8
/0 0
2
6
/0 8
/0 0
Oct Nov Dec Jan Feb Mar A pr May Jun Jul
Primula veris
160
0 /9
Sinapis arvensis
3
Num b e r of seedlings
Num b e r of seedlings
140
120
100
80
60
40
2
1
20
0
0
0 1
/1
0 /9
9
3
1
/1
0 /9
9
3
0 /1
1
/9
9
3
0 /1
2
/9
9
2
9
/0 1
/0 0
2
8
/0 2
/0 0
2
9
/0 3
/0 0
2
8
/0 4
/0 0
2
8
/0 5
/0 0
2
7
/0 6
/0 0
2
7
/0 7
/0 0
2
6
/0 8
/0 0
Oct Nov Dec Jan Feb Mar A pr May Jun Jul
0 1
/1
0 /9
9
3
1
/1
0 /9
9
3
0 /1
1
/9
9
3
0 /1
2
/9
9
2
9
/0 1
/0 0
2
8
/0 2
/0 0
2
9
/0 3
/0 0
2
8
/0 4
/0 0
2
8
/0 5
/0 0
2
7
/0 6
/0 0
Oct Nov Dec Jan Feb Mar A pr May Jun Jul
14
2
7
/0 7
/0 0
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Figure 7 Changes in abundance (percentage cover) of the selected pernicious weed species in the continued
cultivation (¯), natural colonization (£), low diversity (˜) and high diversity (˜) plots. Error bars
show ± 1 s.e.m.
0.4
A c hillea m illefolium
% c o ve r
0.3
0.2
0.1
0
96
97
98
99
0.4
0.6
Clinopodium vulgare
Origanum vulgare
0.5
% c over
% c over
0.3
0.4
0.3
0.2
0.2
0.1
0.1
0
0
96
97
98
96
99
15
97
98
99
0.4
A rrhenatherum elatius
Dactylis glomerata
% c over
% c over
0.3
10
5
0.2
0.1
0
0
96
97
98
99
15
96
97
98
99
Project
title
4.5
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Colonisation by invertebrates
Clear effects of the treatments on the abundance of different insect groups were found (Figure 8). For four of
the six groups studied in detail, total numbers per sample (pooled for all sample dates) showed significant
treatment effects (Table 4). In all cases, the total number of individuals sampled followed the pattern
CC<NC<LD<HD.
Table 4
Results of analyses of variance of abundance of invertebrate groups in the continued cultivation
(CC), natural colonization (NC), low diversity (LD) and high diversity (HD) sown plots. Data were
log10(n+1) transformed before analysis. Treatments with the same letter code are not significantly
different (P>0.05 for analyses of total number sampled).
Aphididae
Auchenorrhyncha
Heteroptera
Coleoptera
Isopoda
Araneae
Aphids
Hoppers
True bugs
Beetles
Woodlice
Spiders
Number in sample
June
July
ns
ns
ns
P=0.005
ns
ns
ns
P=0.001
P=0.000
P=0.049
ns
ns
Sept
ns
ns
ns
P=0.001
ns
ns
Treatment comparison
CC
NC
LD
HD
TOTAL
ns
P=0.004
ns
P=0.000
P=0.002
P=0.001
a
a
ab
b
a
a
a
a
a
a
a
a
ab
b
b
b
Three groups were identified to species, the Auchenorrhyncha (hoppers), Heteroptera (true bugs) and
Coleoptera (beetles). Indices of diversity (species number, Shannon Index) and community structure (Shannon
Evenness, Berger Parker Dominance) were calculated for these groups and treatment differences analysed using
analyses of variance (species number, Shannon index) and Friedmann Tests (evenness and dominance). The
results are shown in Table 5.
Table 5
Values of indices of diversity (species per sample, Shannon Index) and community structure
(Shannon Evenness Index, Berger Parker Dominance Index) for Auchenorrhynca, Heteroptera and
Coleoptera, showing the results of analyses of variance or Friedmann tests. Treatments sharing the
same letter code and not significantly different (P>0.05).
CC
AUCHENORRHYNCHA
Species Richness
Diversity (Shannon)
Evenness (Shannon)
Dominance (Berger-Parker)
HETEROPTERA
Species Richness
Diversity (Shannon)
Evenness (Shannon)
Dominance (Berger-Parker)
COLEOPTERA
Species Richness
Diversity (Shannon)
Evenness (Shannon)
Dominance (Berger-Parker)
P=0.009
ns
ns
ns
5.6
1.4
0.82
0.47
ns
ns
P=0.023
P=0.030
4.8
1.27
0.82
0.52
P=0.004
P=0.012
P=0.000
P=0.001
17.4
2.38
0.84
0.31
NC
a
6.4
1.56
0.87
0.41
ab
ab
4.2
0.97
0.66
0.64
a
a
ab
a
23.6
2.86
0.91
0.15
16
LD
a
8.8
1.83
0.84
0.35
a
b
4.8
1.41
0.93
0.38
ab
b
b
b
23.2
2.83
0.91
0.19
HD
ab
10.0
1.94
0.85
0.28
b
b
ab
5.8
1.65
0.95
0.32
b
a
ab
b
a
b
32.4
2.68
0.77
0.35
b
ab
a
a
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Figure 8 Changes in abundance (number per sample) of the selected invertebrate groups in the continued
cultivation (¯), natural colonization (£), low diversity (˜) and high diversity (˜) plots. Error bars
show ± 1 s.e.m.
Aphidida e
250
200
150
100
50
0
Jul-99
Aug-99
350
300
250
200
150
100
50
Jun-99
Sep-99
H e te ropte ra
300
Jul-99
250
200
150
100
50
0
Aug-99
Sep-99
C o l e o p te ra
700
Num b e r p e r s ample
Num b e r p e r s ample
450
400
0
Jun-99
600
500
400
300
200
100
0
Jun-99
Jul-99
Aug-99
Sep-99
Jun-99
Ara n e a e
800
Jul-99
Aug-99
700
600
500
400
300
200
100
0
Sep-99
Isopoda
250
Num b e r p e r s ample
Num b e r p e r s ample
A u c h e n o rrhyncha
500
Num b e r p e r s ample
Num b e r p e r s ample
300
200
150
100
50
0
Jun-99
Jul-99
Aug-99
Sep-99
Jun-99
Jul-99
Aug-99
Sep-99
The number of species of Auchenorrhyncha was significantly higher in the HD plots than the CC and NC
plots. Values for the LD plots were intermediate. However, other indices of diversity did not differ
significantly between treatments. No significant treatment differences in the diversity of Heteroptera were
found, although there were treatment effects on community structure. The HD plots had assemblages with
higher evenness and lower dominance values than the NC plots, suggesting a more even distribution of species
abundances. Values for the CC and LD plots were generally intermediate.
17
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Differences in the composition of the species assemblages of the Auchenorrhyncha (hoppers), Heteroptera
(true bugs) and Coleoptera (beetles) in the treatment plots were analysed using Redundancy Analysis followed
by Monte Carlo permutation tests to test for the significance of particular treatment effects. Once the effects of
the main treatments had been tested, comparison of the NC vs. CC treatments and LD vs. HD treatments alone
were carried out to test for the effect of successional age and diversity of the sown seed mixture respectively.
The significance of differences between the sowing treatments and the stepping stone treatment were tested
using data from the stepping stone experiment. The results are shown in Table 6.
Table 6. Results of tests of the significance of treatment effects on the composition of assemblages of
Auchenorrhyncha, Heteroptera and Coleoptera using Redundancy Analysis and Monte Carlo
permutation tests.
Data-set
Test
Auchenorrhyncha
Heteroptera
Coleoptera
Main Experiment
Effect of treatment (CC,
NC, LD, HD)
P=0.005
P=0.035
P=0.005
Effect of successional
age (CC vs. NC)
ns
ns
ns
Effect of diversity of
mixture (LD vs. HD)
ns
ns
ns
Effect of sowing
treatment (NC, LD, HD)
P=0.045
P=0.010
P=0.005
Effect of stepping stone
treatment (with, without)
P=0.015
ns
P=0.035
Stepping Stone Experiment
Significant treatment differences were found in the Auchenorrhyncha, Heteroptera and Coleoptera faunas of
sowing and natural colonisation treatments. In addition, a significant effect of the stepping stone treatment was
found for the Auchenorrhyncha and Coleoptera assemblages present in the plots. However, no significant
effects or either successional age (NC vs. CC) or diversity of sown seed mix (LD vs. HD) were found,
suggesting that treatment differences in the insect assemblages were primarily the result of differences between
the sown and unsown plots. In addition, significant effects of the stepping stone treatment were found for
Auchenorrhyncha and Coleoptera.
The assemblages of Auchenorrhyncha, Heteroptera and Coleoptera found in the treatment plots of the two
experiments were compared with those of two chalk grassland sites situated in the vicinity of the experimental
site. Detrended correspondence analyses (DCA) were used to assess how closely the assemblages present in
the treatment plots resembled those of the target chalk grassland community.
For all three insect groups studied the assemblages present in the experimental plots were clearly different
from those in the two chalk grassland sites. In analyses using the 1997 and 1999 data, a clear development of
the insect fauna of the experimental plots is apparent, with the assemblages sampled in 1999 bearing a closer
resemblance to those of the chalk grasslands (Figure 9). Of the different experimental treatments, the sown LD
and HD plots had assemblages that were more similar to those of the established grasslands. Differences
between treatment plots can be attributed to differences in botanical composition, canopy structure and amount
of litter, but reflect preferences of a range of common frequent grassland species. These may have rapidly
colonised the site through flighted dispersal or moving from hedgebank at field edge. Few species restricted in
their distribution to chalk grasslands were found to have colonised the plots.
18
Methods of accelerating development of chalk grassland on
ex-arable land
Project
title
MAFF
project code
BD1434
Figure 9. Detrended Correspondence Analysis of the composition of assemblages of Auchenorrhyncha and
Heteroptera in the experimental plots (1997 and 1999) and two neighbouring chalk grassland sites
(1999 only). .The following symbols are used for continued cultivation (¯), natural colonization
(£), low diversity (˜) and high diversity (˜) plots.
(a) Auchenorrhyncha
(b) Heteroptera
4 DCA axis 2
(λ=0.60)
1999
¯
3 DCA axis 2
3
(λ=0.32)
¯
1999
2
Chalk
Grassland
¯
¯
2
1997
1997
1
1
DCA axis 1
(λ=0.61)
0
0
4.6
Chalk
Grassland
1
2
3
4
5
DCA axis 1
(λ=0.64)
0
0
1
2
3
4
Effects of treatments on soil properties
Comparison of treatments
Levels of soil organic matter (measured as loss on ignition) were significantly higher in the continued
cultivation plots than in the sown plots, but no difference was found between the natural colonisation and the
sown plots. Levels of phosphorus were significantly higher in the natural colonisation and continued
cultivation plots than in the high diversity sowing treatment. These differences probably reflect the result of the
management of the plots by mowing in late summer and removing cuttings. Biomass productivity is highest in
high diversity plots, so offtake is likely to be greatest when the cuttings are removed. This will be especially
true for P, as leguminous species are present in sown plots, but almost absent from natural colonisation plots.
Table 7. Differences between the treatments in soil phosphorus, nitrogen and organic matter (CC - continued
cultivation, NC - natural colonization, LD - low diversity and HD - high diversity sown plots), and
comparison with values for two neighbouring chalk grassland sites (G1, G2).
pH
Phosphorus
Potassium
Magnesium
Loss on Ig
Total N
mg/l
mg/l
mg/l
%
%
CC
ADAS
index
8.22
15.0
1
52.6
0
17.6
0
3.11
0.23
NC
ADAS
index
8.20
15.8
2
68.0
1
21.4
0
2.70
0.24
19
LD
ADAS
index
8.18
12.6
1
55.0
1
18.2
0
2.38
0.21
HD
ADAS
index
8.20
11.0
1
59.0
0
15.0
0
2.38
0.25
G1
ADAS
index
8.04
9.60
0
97.0
1
81.0
2
5.56
0.47
G2
ADAS
index
8.04
7.60
0
95.2
1
58.4
2
4.50
0.40
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Comparison with established chalk grasslands
The soils from the high diversity sowing treatment plots showed no significant difference in the levels of P
compared with one of the chalk grassland sites (ADAS index 1). However, major differences between the
experimental plots in general and the established chalk grassland sites were found for pH, N, K and organic
matter. For these factors, the experimental plots had significantly different values when compared with the
chalk grassland soils, but were not significantly different from the soils of the adjacent cropped field.
Figure 10. Differences between the treatments in soil phosphorus, nitrogen and organic matter (CC - continued
cultivation, NC - natural colonization, LD - low diversity and HD - high diversity sown plots), and
comparison with values for two neighbouring chalk grassland sites (G1, G2). Treatments with the
same letter code are not significantly different (P>0.05). Error bars show ± 1 s.e.m.
mg/l
Phosphorus
ab
a
abc
c
cd
d
%
0.6
Nitrogen
a
a
a
a
b
b
15
10
5
0
G1 G2
6
0.4
4
0.2
2
0
CC NC LD HD
Treatment
%
Soil organic matter
a
a
a
a
c
b
0
CC NC LD HD
Treatment
5.
MAIN IMPLICATIONS OF THE FINDINGS
5.1
Development of sward in relation to main treatments
G1 G2
CC NC LD HD
Treatment
G1 G2
One of the primary constraints in the creation of species-rich grasslands on ex-arable land is the availability of
seed (Hutchings & Booth 1996, Mortimer et al. 1998). In intensively-managed agricultural landscapes remnant
patches of species-rich grassland, which might act as sources of propagules, occur infrequently. Because of
this, the use of natural colonisation in arable reversion schemes is usually recommended only on land adjacent
to existing areas of species-rich grassland. In other locations, sowing seed of suitable species is recommended.
The results presented here show demonstrate successful establishment of sown species in ex-arable land.
With the exception of one species, all of those sown established in the plots and have persisted for four years.
The exception is Trifolium dubium, the only annual species amongst the 15 sown in the experiment. Many of
the sown species, having established in the plots, are now colonizing the unsown treatment plots and other areas
of the experimental site. Whilst the early stages of vegetation development were dominated by fast-growing
forb species, especially short-lived legumes, in the fourth year after establishment, reported here, the balance
between the perennial grasses and forbs is more equitable. In comparison with the sown plots, the natural
colonization and continued cultivation plots are dominated by early-successional species. Whilst the species
richness is higher than in the sown plots, the majority of the species are ruderals of low conservation value.
The vegetation is characterized by mat forming perennial grasses and rosette forbs, typically species of
Epilobium and Asteraceae. Areas of patch-forming dominants, such as creeping thistle Cirsium arvense and
perennial sow-thistle Sonchus arvensis are expanding.
One of the main implications of the findings of this study concerns the importance of the diversity of the
sown seed mixture. Most arable reversion options within the MAFF-supported Environmental Land
Management Schemes prescribe the use of at least four species from a recommended list. Supplementary
payments are available within the Countryside Stewardship Scheme to support the inclusion of wild flower
20
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
species in the sown mix. There is evidence that sowing a higher diversity seed mixture results in the
development of a sward of greater diversity (Pywell et al. 1997). However, other benefits may also accrue
from the use of seed mixtures of higher diversity. The results presented here demonstrate that high diversity
mixtures lead to the development of vegetation which is stable in composition and productivity, whilst low
diversity mixtures may be prone to large temporal or spatial variability as a result of the failure, or dominance,
of a single species having a proportionally greater impact on the whole community (van der Putten et al. 2000,
Leps et al. 2001). Thus, high diversity mixtures are more likely to contain a few species that will perform well
in the particular conditions of the site (Huston 1997). This is evidence of the so-called ‘insurance hypothesis’,
that more diverse communities are buffered against the effects of stochastic factors, such as weather or
pest/disease outbreak (Heywood & Watson 1995).
5.2
Development of sward in relation to ‘stepping stone’ treatment
Some plant species do not reproduce easily from seed, either because their main mode of propagation is by
vegetative means or because they have exacting requirements for germination or micro-sites in which to
establish. In addition, the seed of some species is difficult to produce commercially, for example, the orchid
species typical of calcareous grasslands have minute spore-like seeds. Alternative methods are necessary in
order to aid the colonisation of new sites by these species. Plug-plants have been tried as a means of enhancing
the colonisation of newly-created species rich grasslands by some species (Pywell et al. 1997).
The results of the experiment reported here show that small-scale turf and soil translocation can be effective
in providing focal points for colonisation, which may greatly accelerate the colonisation of a new site by
species with particular modes of propagation. The translocation (‘stepping stone’) treatment was effective at
introducing a suite of chalk grassland species, for which commercially seed is not available. The treatment was
most effective for short-lived forbs and few perennial graminoids present in the translocated material spread
into the treated plots. Many of the species that were successfully introduced to the site using this treatment
have now spread to adjacent plots and pathways, some establishing more than 50 m from the nearest treated
plot. This emphasizes the potential for such small scale translocation to provide focal points for colonization.
The effect of this treatment was found to be greatest in the natural colonization plots, suggesting that a
relatively open sward is essential for the establishment of species introduced using this method. Overall, the
stepping stone treatment resulted in a significant acceleration of vegetation development, resulting in
communities resembling mid-successional grasslands in the surrounding area. Such an approach may also have
a beneficial effect on the colonisation of the site by other groups of organisms, such as invertebrates (see
section 5.5) and elements of the soil biota (van der Putten et al. 1997).
5.3
Suppression of weed species
One of the primary problems in arable reversion schemes is the presence of a large, persistent seed bank of
weed species (Hutchings & Booth 1996, Mortimer et al. 1998). Many of these species are poor competitors
and pose no long-term problem, disappearing from the sward after a few years. However, certain competitive
ruderals such as spear thistle Cirsium vulgare and ragwort Senecio jacobaea may be more pernicious
(Silvertown & Smith 1989).
The results presented here show not only greater suppression in the sown plots compared to the natural
colonisation treatments, but also evidence for greater suppression in those plots sown with a high diversity seed
mixtures. This seems to be the result of greater mean standing crop in the high diversity plots. The suppression
of annual grasses such as blackgrass and sterile brome by the sowing treatments was particularly effective. The
suppression of pernicious weeds such as spear thistle Cirsium vulgare and ragwort Senecio jacobaea was less
effective, although problems with these short-lived species may be transient. The results of the supplementary
sowing of weed species showed that levels of establishment of weed species in the plots in the year of the study
were very low. The pernicious weed species present in the plots in the year of the study probably represent
individuals which established when the turf was much more open, in the earlier years of the experiment.
21
Project
title
5.4
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
Colonisation by chalk grassland plants
The colonisation of a new grassland site on ex-arable land is likely to be hindered by problems of seed
availability. The low frequency of species-rich grassland in many intensive agricultural landscapes leads to a
paucity of sources of potential colonists. When species do manage to arrive at a site through dispersal, their
establishment will be affected by the nature of vegetation present.
The experimental plots were colonized as a result of local seed dispersal by a number of species found in
chalk grasslands. Most of the species colonising the plots in this way were species with wide habitat affinities
that are also found in mesotrophic grasslands, field margins and hedgebanks. Most of these species were
present in the along the boundaries of the experimental field. The abundance of these species in the treatment
plots was generally greatest in the natural colonization plots and lowest in the high diversity sown and the
continued cultivation plots (levels were low in the latter as a result of the continued management by annual
cultivation). Similar results were found in the experiment involving supplementary sowing of additional chalk
grassland species. Whilst the levels of establishment of the species introduced by supplementary sowing varied
considerably, where significant effects of the treatments were found, levels of establishment were always
greatest in the natural colonization or continued cultivation plots.
Thus, the same processes which hinder establishment of weed species, may also hinder the establishment of
desirable species (Stevenson et al. 1995; Burch 1996), although grassland species are, by their nature, more
likely to have a ‘turf compatible’ regeneration niche (sensu Fenner 1978) than weed species. These research
findings underline the need for proper aftercare management through appropriate grazing regimes.
Establishment of grassland species in sown swards will be promoted as a result of the small scale disturbances
created by grazing animals.
5.5
Colonisation by invertebrates
The colonisation of new grassland sites by invertebrates is also limited by the same problems of isolation and
dispersal that have been described for plants (Mortimer et al. 1998). Similarly, the successful establishment of
new invertebrate populations will be affected by both the structure and composition of the vegetation
developing at the site (Gibson et al. 1992a, 1992b; Brown & Gibson 1994). Thus, increasing structural and
compositional diversity of the plant community will promote the development of a diverse invertebrate
assemblage. In addition, the use of novel techniques, such as turf transplantation, may assist the colonisation of
invertebrates, particularly of sedentary species.
The study reported here showed clear differences in the invertebrate assemblages in natural colonisation
plots compared with those that had been sown. For many groups of invertebrate, abundances were significantly
higher in the sown plots. The diversity of species assemblages was also found to be significantly higher in the
high diversity sown plots than the natural colonisation plots, with the low diversity sown plots having
intermediate values. The stepping stone treatment was also found to have significant effects on the composition
of two insect groups, the Auchenorrhyncha (hoppers) and the Coleoptera (beetles).
In spite of the significant differences between treatments, the insect assemblages in the experimental plots
were composed largely of fairly common species characteristic of a range of herbaceous vegetation. Many of
the species which have habitat affinities restricted to chalk grassland were absent from the plots. It is likely that
development of the invertebrate communities of arable reversion sites will be a slow process, the speed of
development related to the proximity of established chalk grasslands to act as sources of colonists.
Notwithstanding this, it is clear from the results of this study that development of the assemblages of certain
insect groups towards those that resemble established chalk grassland was promoted by the sowing of plant
species typical of such communities.
5.6
Effects of treatments on soil properties
Land coming out of arable cultivation has high soil nutrient status, especially levels of P and K (Gough &
Marrs 1990). However, recent studies have shown that levels of total N are lower than those of established
22
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
MAFF
project code
BD1434
chalk grassland, and that considerable N immobilisation occurs as grasslands develop on ex-arable soils as N
becomes incorporated into organic forms (MAFF Project BD0327 Final Report). The results of this study
confirm the disparity in levels of total N and soil organic matter between arable reversion sites and mature
chalk grasslands. Management of the site aimed at reducing soil P through cutting and removal of cuttings may
also limit the build up of litter, decomposer assemblages and the accumulation of organic matter in the soil.
The soils of ex-arable land will be impoverished in other ways, for example, the stepping stone treatment
may also aid the colonisation of the site by other beneficial organisms, such as mycorrhizal fungi. Similarly,
other elements of the soil biota will be absent or impoverished in ex-arable soils. Invertebrates, fungi and
bacteria involved in decomposition may increase in response to the stepping stone treatment. Such decomposer
communities will exhibit concurrent development as vegetation develops and will be influenced by the diversity
and nature of the developing plant community.
6
•
•
•
•
•
7
POSSIBLE FUTURE WORK
Assessment of the success of establishment of commercially available seed of wildflower and grass species
in relation to site characteristics and timing of sowing.
Investigation of the use of sequential sowing of different plant types in order to overcome the problems of
poor grass establishment and early dominance by legume species.
Assessment of the effects of the identity of sown species on the ongoing spontaneous colonisation of sites
by species typical of the target vegetation type.
Investigation of factors influencing the lag in invertebrate colonisation of arable reversion sites, in
particular, the relative importance of conditions prevalent at the site (sward structure, botanical
composition) versus dispersal limitation and chance colonisation events.
Assessment of the applicability of these treatments to other grassland types.
ACTION RESULTING FROM RESEARCH
Publications
One paper, based on the findings of this project, has been accepted by the journal Biological Conservation:
Mortimer, S.R., Booth, R.G., Harris, S.J. & Brown, V.K. (in press). Effects of initial site management on the Coleoptera
assemblages colonising newly-established chalk grasslands on ex-arable land. Biological Conservation.
In addition, the contractors have published two recent papers based on the first three years data from the
experimental site used for this study:
Van der Putten, W.H., Mortimer, S.R., Hedlund, K., van Dijk, C., Brown, V.K., Leps, J., Rodriguez-Barrueco, C., Roy, J, Diaz
Len, T.A., Gormsen, D., Korthals, G.W., Lavorel, S., Santa Regina, I & Smilauer, P. (2000). Plant species diversity as
a driver of early succession in abandoned fields: a multi-site approach. Oecologia, 124, 91-99.
Leps, J., Brown, V.K., Diaz Len, T.A., Gormsen, D., Hedlund, K., Kailova, J., Korthals, G.W., Mortimer, S.R., RodriguezBarrueco, C., Roy, J, Santa Regina, I., van Dijk, C. & van der Putten, W.H. (2001). Separating the chance effect from
other diversity effects in the functioning of plant communities. Oikos, 92, 123-134.
Conferences
The findings of this research project have been presented in two conference papers:
Mortimer, S.R. & Brown, V.K. (1999). Suppression of weed species during restoration of species-rich grasslands: differential
responses of plant functional types. British Ecological Society Winter Meeting, University of Leeds, December 1999.
Mortimer, S.R., Booth, R.G. & Brown, V.K. (2000). Insects as indicators in the restoration of agricultural land. XXI
International Congress of Entomology, Iguassu Falls, Brazil, August 2000.
Other dissemination activities
Dr Mortimer presented the findings of the research on the FRCA/English Nature training day on arable
reversion held in Wiltshire on 20th July 2000. In addition, the experimental site was open to the public at the
National Trust regional open day at Bradenham in September 1999.
23
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
APPENDIX 1
Code
Agro stol
Alop myos
Anis ster
Arrh elat
Blac perf
Brom hord
Cent scab
Cera font
Cirs arev
Cirs vulg
Clem vita
Clin vulg
Crep capi
Crep vesi
Dact glom
Dauc caro
Epil parv
Epil tetr
Euph nemo
Gali moll
Hera spho
Hype hirs
Hype perf
Inul cony
Knau arve
Leuc vulg
Malv sylv
Meli alti
Odon vern
Orig vulg
Picr hier
Plan majo
Poa prat
Prun vulg
Ranu repe
Rese lute
Rume cris
Sene jaco
Sonc arve
Sonc aspe
Tara offi
Trif repe
Vero arve
Vero cham
Vici hirs
Vici sati
Viol hirt
MAFF
project code
BD1434
Species codes used in Figure 3
Scientific name
Agrostis stolonifera
Alopecurus myosurioides
Anisantha sterilis
Arrhenatherum elatius
Blackstonia perfoliata
Bromus hordeaceus
Centaurea scabiosa
Cerastium fontanum
Cirsium arvense
Cirsium vulgare
Clematis vulgare
Clinopodium vulgare
Crepis capillaris
Crepis vesicaria
Dactylis glomerata
Daucus carota
Epilobium parviflorum
Epilobium tetragonum
Euphrasia nemorosa
Galium mollugo
Heracleum sphondylium
Hypericum hirsutum
Hypericum perforatum
Inula conyzae
Knautia arvensis
Leucathemum vulgare
Malva sylvestris
Melilotus altissima
Odontites verna
Origanum vulgare
Picris hieracoides
Plantago major
Poa pratensis
Prunella vulgaris
Ranunculus repens
Reseda lutea
Rumex crispus
Senecio jacobaea
Sonchus arvensis
Sonchus asper
Taraxacum officinale
Trifolium repens
Veronica arvensis
Veronica chamaedrys
Vicia hirsuta
Vicia sativa
Viola hirta
English name
creeping bent
blackgrass
sterile brome
false oat-grass
yellowwort
* if introduced by SS treatment
*
*
greater knapweed
*
creeping thistle
spear thistle
old man’s beard
wild basil
*
cocksfoot
wild carrot
*
*
eyebright
hedge bedstraw
hogweed
*
*
*
*
*
field scabious
ox-eye daisy
*
red bartsia
marjoram
creeping buttercup
wild mignonette
curled dock
ragwort
perennial sow-thistle
prickly sow-thistle
dandelion
white clover
field speedwell
germander speedwell
hairy violet
24
*
*
*
*
*
*
*
*
*
Project
title
Methods of accelerating development of chalk grassland on
ex-arable land
APPENDIX 2
MAFF
project code
BD1434
REFERENCES
Brown, V.K. & Gibson, C.W.D. 1994. Re-creation of species-rich calcicolous grassland communities. In: Haggar, R.J.
& Peel, S. (eds.) Grassland management and nature conservation, pp. 125-136. British Grassland Society,
Reading.
Burch, F.M. 1996. Establishing species-rich grassland on set-aside land: balancing weed control and species
enhancement. Aspects Appl. Biol. 44: 221-226.
Fenner, M. 1978. A comparison of the abilities of colonizers and closed-turf species to establish from seed in artificial
swards. J. Ecol. 66: 953-963.
Gibson, C.W.D., Brown, V.K., Losito, L. & McGavin, G.C. 1992a. The response of invertebrate assemblies to grazing.
Ecography, 15, 166-176.
Gibson, C.W.D., Hambler, C. & Brown, V.K. 1992b. Changes in spider (Araneae) assemblages in relation to succession
and grazing management. J. Appl. Ecol. 29: 132-142.
Gough, M.W. & Marrs, R.H. 1990. A comparison of soil fertility between semi-natural and agricultural plant
communities: implications for the creation of species-rich grassland on abandoned arable land. Biol. Conserv. 51:
83-96.
Heywood, V.H. & Watson, R.T. 1995. Global biodiversity assessment. Cambridge University Press.
Huston, M.A. 1997. Hidden treatments in ecological experiments: re-evaluating the ecosystem function of biodiversity.
Oecologia (Berl.) 110: 449-460.
Hutchings, M.J. & Booth, K.D. 1996a. Studies of the feasibility of re-creating chalk grassland vegetation on ex-arable
land. I. The potential roles of seed bank and seed rain. J. Appl. Ecol. 33: 1171-1181.
Leps, J., Brown, V.K., Diaz Len, T.A., Gormsen, D., Hedlund, K., Kailova, J., Korthals, G.W., Mortimer, S.R.,
Rodriguez-Barrueco, C., Roy, J, Santa Regina, I., van Dijk, C. & van der Putten, W.H. (2001). Separating the
chance effect from other diversity effects in the functioning of plant communities. Oikos, 92, 123-134.
Mortimer, S.R., Hollier, J.A. & Brown, V.K. 1998. Interactions between plant and insect diversity in the restoration of
lowland calcareous grasslands in southern Britain. Appl. Veg. Sci. 1: 101-114.
Pywell, R.F., Peel, S., Hopkins, A. & Bullock, J.M. 1997. Multi-site experiments on the restoration of botanically diverse
grassland in ESAs. In: Sheldrick, R.D. (ed.) Grassland management in Environmentally Sensitive Areas, pp.
160-167. British Grassland Society, Reading.
Rodwell, J.S. (ed.) 1992. British plant communities. Vol. 3. Grasslands and montane communities. Cambridge
University Press, Cambridge.
Silvertown, J. & Smith, B. 1989. Germination and population structure of spearthistle Cirsium vulgare in relation to
experimentally controlled sheep grazing. Oecologia (Berl.) 81: 369-373.
Stevenson, M.J., Bullock, J.M. & Ward, L.K. 1995. Re-creating semi-natural communities: effect of sowing rate on
establishment of calcareous grassland. Rest. Ecol. 3: 279-289.
van der Putten, W.H., Brown, V.K., Dhillion, S.S., van Dijk, C., Gormsen, D., Hedlund, K., Korthals, G.W., Lavorel, S.,
Leps, J., Mortimer, S.R., Rodriguez-Barrueco, C., Roy, J., Rundgren, S. & Smilauer, P. 1997. Interaction
between soil biodiversity, vegetation and ecosystem processes. In: Functional Implications of Biodiversity in
Soil, ed. by V. Wolters. Ecosystems Report Series No. 24. European Commission, Brussels.
Van der Putten, W.H., Mortimer, S.R., Hedlund, K., van Dijk, C., Brown, V.K., Leps, J., Rodriguez-Barrueco, C., Roy, J,
Diaz Len, T.A., Gormsen, D., Korthals, G.W., Lavorel, S., Santa Regina, I & Smilauer, P. (2000). Plant species
diversity as a driver of early succession in abandoned fields: a multi-site approach. Oecologia, 124, 91-99.
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