Recreating species rich grasslands
using the hemiparasitic plant
Rhinanthus minor
Name: Harriet Cuthbert
Project supervisors: Tracey Hamston and Dave Ellacott
Whitley Wildlife Conservation Trust
The University of York
2007- 2008
Contents
Abstract i
1 Introduction 1 1.1 Grassland classification and mesotrophic grasslands 1 1.2 Intensification 1 1.3 Grassland management techniques 2 1.4 Grassland restoration techniques 3 1.5 Rhinanthus minor L 4 1.6 The use of seed in meadow restoration 7 1.7 Aims 7 1.8 Hypothesis 8
2 Study area, materials and methods 9 2.1 Study area 9 2.2 Materials 10 2.3 Methods 11
3 Results – site one 15 3.1 Biodiversity 15 3.2 R. minor 16 3.3 Grass productivity 17 3.4 Wildflower establishment 19
4 Results – site two 21
4.1 R. minor 21 4.2 Wildflower establishment 21
5 Discussion 23 5.1 Site one 23 5.2 Site two 25 5.3 Limitations and management 26 5.4 Future management 27
6 References 28
7 Acknowledgements 34
8 Appendix 35
i
Abstract
Since 1930, unimproved lowland grassland has suffered great losses throughout
England and Wales because of farming intensification and high levels of artificial
fertiliser application. The rise in nutrient supply has allowed nutrient-demanding
coarse grass species to thrive and has led to an overall decline in plant species
diversity which, in turn, has directly affected the faunal assemblages supported. It has
been suggested that Rhinanthus minor, a hemiparasitic annual plant, can be used to
restore such grasslands by parasitising and reducing the vigour of the dominant grass
species allowing the less competitive species to colonise.
Primley meadow, South Devon, is a south facing, mesotrophic area of grassland with
low biological diversity. In August 2005, 60 permanent quadrats were established and
various treatments applied in a randomised block design (site one). These included all
combinations of two ground preparation methods (short cut and rotovation) and three
sowing regimes (R. minor only, a wildflower mix only and both). Results from site
one indicate that R. minor significantly reduced grass height and biomass but as yet
has had no overall effect on biodiversity, although sown wildflower species had
increased in abundance. In October 2007, a larger field trial of R. minor was
established (site two). A plot (90 m x 90 m) was created using the most successful
treatment from the previous two years i.e. the vegetation was short cut and both R.
minor and wildflower mix were sown together. Results from site two show some of
the wildflowers sown to have established; however, R. minor appears not to have
germinated.
Keywords: Rhinanthus minor; restoration; mesotrophic; biodiversity
1
Recreating species rich grasslands using the hemiparasitic plant
Rhinanthus minor
1. Introduction
1.1 Grassland classification
Habitat conversion from natural or semi-natural vegetation to intensive agriculture is
at the heart of the present biological diversity crisis (Walker, 2004). In 1992,
environmental targets for 2010 were set up at the convention on biological diversity
for all the countries involved (CEH1, 2007). In the United Kingdom, lowland
grassland was highlighted as a particular habitat in need of assistance (JNCC, 2006).
Action plan objectives for the UK include halting depletion of lowland meadow and
attempting to re-establish 500 ha of lowland meadow of wildlife value (BAP, 2008).
Rodwell (1998) has developed a comprehensive classification system, the National
Vegetation Classification (NVC), to recognise and describe plant communities in
Britain. Thus, grassland in the UK has been categorised into 14 calcareous
communities, 21 acid communities and 13 mesotrophic communities (e.g. MG1-13).
Mesotrophic grasslands consist of sites of neutral soil pH, but due to farming
intensification have experienced insufficient grazing and application of high levels of
fertiliser. This has resulted in great losses of grassland with significant biodiversity
value. Mentioned below in 1.2.
1.2 Intensification
Between 1930 and 1984, unimproved lowland grassland in England and Wales was
reduced by 97 % (Fuller, 1987). This is a result of increasing agricultural efficiency,
where a high proportion of lowland grassland in the UK has been subjected to
artificial fertiliser application (Jefferson, 2005) and farming intensification. Berendse
et al. (1997) has shown a rise in nutrient supply leads to a decline in species diversity.
This is because high nutrient supplies generate a much more limited grassland species
list where a few nutrient demanding species that thrive in productive, human altered
environments (Walker, 2004) dominate the area and out compete softer grasses and
dicots abbr., in particular, because of their high seed production (Bullock et al., 1994).
2
Plant species most vulnerable with the decline of lowland grassland include greater
butterfly orchid Platanthera chlorantha and wood bitter vetch Vicia orobus (BAP,
2008). The decrease in wildflowers and overall species diversity of grassland directly
impacts the faunal assemblages it supports (Pywell et al., 2004; Vickery et al., 2001).
Lowland meadows are important habitats for farmland birds; the curlew Numenius
arquata, in particular, has experienced a major range contraction and was highlighted
by the Biodiversity Action Plan (BAP) as a UK priority species (BAP, 2008). In
Devon there are only 30 breeding pairs remaining as agricultural improvement has
resulted in a loss and fragmentation of breeding sites for this species (Devon BAP,
2008).
Although the majority of land in the UK is grassland, most mesotrophic grasslands are
less than 10 ha in size (Jefferson and Robertson, 1996) and the total extent of
unimproved mesotrophic grassland in England and Wales is between 7500 ha and
15000 ha (Blackstock et al., 1999). This results in these grassland areas being small,
fragmented and highly localised (BAP, 2008). Therefore, it is necessary to protect and
expand existing lowland grassland habitats and reverse recent successional traits
(Blackstock et al., 1999).
1.3 Grassland management techniques
1.3.1 Grazing
Many areas of lowland grassland have been destroyed by not only ploughing and
excessive fertilisation, but also by the lack of management and abandonment such as
hilly areas where agricultural equipment cannot reach (Jongepierová et al., 2007).
Grazing of livestock, which involves defoliation, treading and manuring (Morris,
2000; Gilbert and Anderson, 1998), is an efficient management technique for
maintaining grasslands (Marriott et al., 2003). Livestock remove new sward growth
continually which restricts the dominant coarse grasses by altering the relative
abundance and competitive ability of different plant species (Vickery et al., 2001).
The trampling effect of stock is also beneficial, creating bare ground and damaging
competitive species (Crofts and Jefferson, 1999). The disturbance caused by grazing
opens up the sward and creates germination gaps; forb seed from hay crop or sown
3
seed are consequently able to colonise the area (Walker, 2004). Grazing increases the
abundance of dicots, in particular, because of their high seed production (Bullock et
al., 1994). Grazing is selective, which therefore results in a more diverse range of
invertebrates surviving intensive grazing than other sward management techniques
(Vickery et al., 2001). The advantage of seasonal grazing over continuous grazing is
the promotion of sward heterogeneity and hence increased invertebrate diversity
(Vickery et al., 2001).
1.3.2 Cutting
In contrast to grazing, cutting is a far more aggressive and controlled management
technique (Morris, 2000) where the sward is non-discriminately cut to a uniform
height (Rodwell, 1998). This technique is considered detrimental to invertebrate
populations (Vickery et al., 2001; Morris, 2000). Therefore, timing of the cut is
critical (Morris, 2000; Baines, 1998). Cutting the grassland in autumn, both reduces
the impact on invertebrates, but also on wildflower populations, enabling seed to set
first and persist for longer in the seed bank (Smith and Jones, 1991). Removal of cut
material avoids the development of thick thatch which suppresses and smothers the
weaker, smaller plants (Gilbert and Anderson, 1998); it can also function as a method
to reduce soil fertility (Schaffers et al., 1998; Walker 2004) as well as optimise
conditions for the colonisation and establishment of target species.
Hayes and Sackville (2001) stated cutting favours coarse grasses whereas grazing
alone encourages the establishment of undesirable weed species. However, cutting
with aftermath grazing has generally been more successful than either cutting or
grazing alone (Walker, 2004), suggesting this is the best management technique.
1.4 Grassland restoration techniques
1.4.1 Direct methods
Restoration of grassland to reduce the negative effects of high soil fertility from the
application of fertiliser can be achieved in a number of ways. The two direct methods
commonly used are 1) the removal of top soil and 2) cropping. As cutting and grazing
do not always reach set targets quickly, top soil removal can accelerate the grassland
4
restoration process. This technique eliminates nutrients from the top layers of soil but
also removes both desirable and undesirable species from the seed bank (Westbury
and Dunnett, 2000). Berendse et al. (1992) showed that removing top soil caused a
sharp fall in productivity which had a positive effect on species diversity. However,
the process is costly and is therefore only worth stripping if the nutrient levels in the
lower horizons of the soil are significantly less than those of the surface (Gilbert and
Anderson, 1998; Bullock and Pywell, 2005). To reduce the price of this technique,
top soil may be re-allocated when sold to recover part of the cost (Gilbert and
Anderson, 1998). Reducing soil nutrients can also be achieved by continuous
cropping. This technique involves cutting of the sward at the end of the growing
season and removing arisings.
1.4.2 Indirect methods
Two indirect methods can also be used to resolve the problems associated with
farming intensification. These are 1) rotovation to scarify the land and 2) the use of
parasitic plants. Rotovation essentially mimics the effects of intensive grazing by
turning the top layer of the soil containing the seed bank. Rotovation, however,
disturbs the soil to a greater depth than grazing. This creates germination gaps for less
competitive species and wildflower seeds that are sown. Furthermore, establishment
of seeds can be enhanced through the disturbance as shown by Westbury et al.
(2006). The introduction of hemi parasitic angiosperms of the genus Rhinanthus has
shown to inhibit the growth of dominant grass species (Davies et al., 1997; Joshi et
al., 2000). Subsequently, hemiparasites have been used in grassland restoration
projects to promote growth of desirable wildflower species that would have
previously been out competed.
1.5 Rhinanthus minor L.
Rhinanthus minor minor (herein referred as R. minor) (figure 1) is one of six
subspecies of Rhinanthus minor recognised in the British Isles and is widespread
throughout most of Europe (Westbury, 2004). R. minor, commonly known as yellow
rattle, is a late summer annual capable of facultative root hemiparasitic growth
(Westbury, 2004; Westbury & Davies, 2005). It is defined as a hemiparasite because
of the presence of chlorophyll (Musselman and Press, 1995), enabling both
5
autotrophic and heterotrophic growth (Joshi et al., 2000; Westbury, 2004). Nutrients
and water are obtained via the vascular system using a structure known as the
haustorium; this is a physiological and morphological bridge that forms between the
host and the parasite (Riopel and Timko, 1995). R. minor sets seed between June and
August (Bullock et al.) resulting in an autumn cut being beneficial by both allowing
the seed to set and assist seed dispersal (Bullock et al., 2003). During the winter, the
seed in the soil surface layers are chilled which results in the breaking of dormancy
for the subsequent spring germination (Smith et al., 2000). Unlike most annuals, it
has no persistent seed bank (Gilbert and Anderson, 1998; Westbury and Davies,
2005) so the population size is dependant on the production and dispersal of the seed
each year (Coulson et al., 2001).
Figure 1. R. minor in flower.
R. minor has been proposed as a management tool for use in restorative grassland
practices to increase botanical diversity (Davies et al., 1997; Pywell et al., 2004;
Bargett et al., 2006; Jefferson, 2005; Westbury et al., 2006) and is most abundantly
found in grassland habitats (Keith et al., 2004). Current grassland restoration methods
to reduce soil fertility and vigour of competitive plants are often unsuccessful or
disruptive and expensive (CEH2, 2007), whereas R. minor establishment can be
achieved relatively easily and cheaply (Bullock and Pywell, 2005). It has been shown
that, like most parasites, R. minor has a broad host range and can parasitise
approximately 50 host species from 18 different families within European grasslands
6
(Westbury, 2004). A single R. minor plant has even been found to parasitise up to
seven different host species simultaneously (Westbury, 2004). However, R. minor is
not a true generalist and has shown host preference (Press and Phoenix, 2005) which
will alter the competitive balance within a community, increasing the competitive
status of non-host species (Joshi et al., 2000; Bardgett et al., 2006). R. minor has
demonstrated considerable host selectivity with preferred hosts being from the
legume family (Gibson and Watkinson 1989). It has been suggested that the most
likely reason for this is special nutrient requirements that can only be supplied by
particular hosts (Gibson and Watkinson, 1989). Rumer et al. (2007) showed that roots
of potential hosts respond differently when R. minor attempts to form haustoria with
them. Fabaceae roots showed a weak connection, where a slight lignification
occurred, and no reaction was observed between the endophyte and cortical tissue of
the host root. In contrast, grass roots react with strong lignification of all cells within
the stele, thus resulting in the potential to serve as a good host (Rumer et al., 2007).
However, Davies et al. (1997) indicates that host choice is non-discriminatory and the
most dominant species tends to be suppressed. Species poor grasslands exhibit high
levels of soil nutrients which lead to a few aggressive grass species then dominating
the area by out competing other species. It has been theorised that R. minor will
parasitise these dominant species (Pywell et al., 2004) reducing both sward height
and vigour, allowing the less competitive species to colonise, which in turn will create
a more diverse grassland. Another added benefit of R. minor is the yearly death of the
annual that will leave colonisation gaps, and therefore, open up the sward (Joshi et
al., 2000). Although there are many benefits of using R. minor to increase
biodiversity in grassland, it has been suggested that the parasite is too unpredictable,
mainly due to variability in composition and differences in productivity, to be an
effective restoration tool (Westbury and Davies, 2005). Evidence also suggests that
R. minor could potentially be harmful to livestock; however, prolonged periods of
exclusive consumption are required for toxicity (Westbury and Davies, 2005).
Nevertheless, despite the potential problems, the parasitic nature of R. minor makes it
a suitable agent for restorative grassland management.
To assess how successful the introduction of R. minor into grassland is, a variety of
methods can be undertaken. These include 1) measuring biomass; 2) measuring sward
7
height throughout the growing season; 3) measuring species richness before and after
introducing R. minor. Biomass of an area of grassland gives an indication of
productivity; coarse grasses will have a high biomass in nutrient rich soils.
Introduction of R. minor in North Yorkshire led to a reduction in biomass that ranged
from 8-73 % within sites, with a noticeable decline in grasses coinciding with an
increase in the proportion of dicotledons (Davies et al., 1997). Bardgett et al. (2006)
also showed that total above-ground biomass reduced significantly over three years,
when R. minor was present. A strong, inverse relationship between the frequency of
R. minor and sward height was shown; there was also evidence of a threshold
frequency of the hemiparasite above which there was a significant reduction in
grassland productivity (Pywell et al., 2004).
1.6 The use of seed in meadow restoration
In the UK, the favoured method for re-creating species-rich grasslands on ex-arable
soils has been direct seeding with mixtures of suitable species (Walker, 2004; Coulson
et al., 2001) as not all seeds can arrive naturally, largely because of habitat
fragmentation and a poor seed bank. The origin of seed also needs to be considered
and choice of seed is dependant on individual species requirements such as soil pH
preference, bio-geographical region and tolerance to intended management practices.
Seeds used in meadow restoration must be of British native origin, but locally
collected seed is more desirable as to maintain local genetic adaptation. To ensure
establishment of meadows with a typical regional character and to avoid introduction
of non-native species and genotypes, it is necessary to select seeds of appropriate
provenance (Jongepierová et al., 2007).
1.7 Aims
The aims of this project are to increase biological diversity at Primley meadow from
the introduction of the hemiparasite R. minor by:
• Monitoring plots, in site one, with and without the introduction of R. minor
and sown wildflower mix and comparing the ground preparation techniques:
short cut and rotovation, to find the best treatment.
• Using data collected from previous years to apply correct management and
restoration techniques to a large scale plot in site two.
8
1.8 Hypothesis
R. minor will reduce coarse grass creating a more favourable habitat for other species
to grow, resulting in an increase in biodiversity.
9
2. Study area, materials and methods
2.1 Study area
2.1.1 Site
Primley meadow is a south facing, mesotrophic meadow located in South Devon (OS
grid reference SX 880601). It is an isolated site, surrounded by woodland and
residential areas, resulting in the source of wildflower to be limited to the seed bank.
The meadow was previously used as horse pasture, the outcome being highly
fertilised soil, dominated by a few coarse grasses resulting in low biological diversity.
Primley meadow is owned by the Whitley Wildlife Conservation Trust (WWCT) and
is an important wildlife habitat. The area is open to the public and frequently visited
by dog walkers. In 1995, fertiliser application stopped and since then, an autumn cut
has taken place and arisings removed to reduce soil nutrients and increase
biodiversity. The meadow is split into seven sections and each year a different area,
determined by a set rota, is not cut which acts as a refuge to invertebrates. The
meadow is dominated by a few coarse-leaved tussock grass species such as
Arrhenatherum elatius, Dactylis glomerata and Holcus lanatus. Two areas of the
meadow chosen for this study are named site one and site two (figure 2). Site one is a
sloped area of grassland near the top of the meadow, whilst site two is an area of
coarser grass which is situated in a slightly more shaded part of the meadow.
10
Figure 2. An aerial view of Primley Park including the woodland (pale yellow) and meadow (pale green). Positions of site one and two are shown in dark green.
2.1.2 NVC community
The NVC provides a suitable framework to recognise and describe the plant
community to classify an area of grassland. In 2005, ten randomly placed quadrats
(2 m x 2 m, subdivided into 100 squares) were placed around site one to determine the
community type before treatments were applied. The results show that vegetation
closely matched that of a MG1c community Arrhenatherum elatius (57.14 %
similarity. This type of grassland is common of road side verges and un-improved
lowland meadows (Rodwell, 1998). In September 2007, ten randomly placed 2 m x
2 m quadrats were placed in site two. All plant species within the quadrats were
identified and rooted percentage cover was determined. Data was inputted into
MAVIS Plot Analyser (v1.0) (Smart, 2000) which concluded that site two, like site
one, also matched a MG1c community Arrhenatherum elatius (54.79 % similarity).
2.2. Materials
2.2.1 Seed selection
To increase floristic diversity a wildflower mix was applied to both site one and two
because the area is isolated so seed cannot arrive through natural causes. A selection
11
of five wildflower species were chosen, using the floristic table for a MG1c
community (Rodwell, 1998), which suited the community already present at Primley
meadow. Species were also selected for their aesthetic value and germination rates.
The wildflower mix included Achillea millefolium, Centaurea nigra, Leucanthemum
vulgare, Prunella vulgaris and Knautia arvensis. R. minor was chosen because of its
hemiparastic growth and compatibility with grassland areas, in particular hay
meadows.
2.3 Methods
2.3.1 Experimental design – site one
In 2005, 60 2 m x 2 m permanent quadrats were set up in site one using metal discs to
allow identification of the plots again using a metal detector and arranged according
to figure 3. Each of the quadrats had a 2 m guard row to reduce contamination of
R. minor and wildflower mix between plots. Twelve different treatments, as shown in
the treatment key (figure 3), each with five replicates were arranged in blocks. The
treatments were arranged in a randomised block design. The two ground preparation
techniques include 1) Short cut; 2) Rotovation; which were both applied in October
2005 and 2006. These were chosen because both were feasible management
techniques for Primley meadow and unlike top soil removal, were inexpensive.
Grazing is not possible because the area is open for public access. Six different seed
treatments were applied in October 2005 and 2006. These include 1) Control; 2)
Wildflower seed mix sown 2005; 3) Wildflower seed mix sown 2006; 4) R. minor
sown 2005; 5) R. minor and wildflower mix sown 2005; 6) R. minor sown 2005 and
wildflower mix sown 2006. Both R. minor and wildflower mix were sown at a rate of
1g/1m2 (Landlife, 2007).
2.3.2 Full vegetation survey
A full vegetation survey took place at both site one and site two. Site one was
surveyed in April, June and August 2008. Site two was surveyed every month from
April to August 2008 because it was a newly prepared plot. This included wildflower
identification to enable rooted percentage cover of each species to be calculated
within each 2 m x 2 m quadrat. Each of the grass species had rooted percentage cover
12
estimated by eye. Bare ground cover was calculated for each quadrat to see how fast
colonisation occurred in the vegetation gaps. To measure grass height, the drop disc
technique (disc 60 g, 240 mm x 264 mm) was used. The disc was thrown randomly
onto the quadrat and a measuring pole was pushed through a hole in the centre to give
a reading of grass height. This allowed grass productivity to be assessed as the
growing season of R. minor developed, enabling measurement of the parasite’s
effectiveness.
2.3.3 Preliminary study
In 2003, a pilot study of Primley meadow was carried out by Gillepsie (2004). This
study analysed the seed bank and concluded that it was limited which therefore, could
be a potential restrictive factor for the restoration of this meadow. This project is a
longitudinal study first started in August 2005. Site one had a full vegetation survey
carried out for each of the 60 quadrats which was conducted in August 2005 (before
treatments had been applied to give baseline data) and February through to August
2006 every month by Cunningham (2006). This survey was continued by Chavner
(2007) from March to August 2007.
2.3.4 Experimental design – site two
In 2007, using data collection from the previous two years, a larger plot (90 m2 (15 m
x 6 m)) in another area of grassland at Primley Meadow (site two) was set up. Data
prior to September 2007 from site one concluded that the treatment YW5 SC
(R. minor and wildflower mix sown in the same year with the short cut ground
preparation) was most successful. The larger plot was marked out using metal discs at
each of the four corners, short cut and raked until bare ground was visible. Both
R. minor and wildflower mix (Achillea millefolium, Centaurea nigra, Leucanthemum
vulgare, Prunella vulgaris and Knautia arvensis) were sown at an increased density of
1.5 g/m2 to raise the colonisation rates shown at site one over the previous two years.
The seed mix was combined with sawdust and scattered manually. This site had
random 2 m x 2 m quadrats throughout the area rather than the permanent quadrats as
to fully assess the whole area.
13
2.3.5 Biomass
Due to time limits, it was impractical to clip all vegetation within the entire quadrat as
would be desired. In September 2007, productivity was assessed by clipping a random
20 cm2 area to soil level using hand shears within each 2 m2 quadrat at site one. Grass
was separated out from all other vegetation, dried at 80 oC and weighed.
2.3.6 Data analyses
Biodiversity was calculated using the Simpson’s Index of Diversity (appendix). This
was chosen as it represented both species richness and evenness. It ranges from zero
to one, with zero being no diversity and one being infinite diversity. Levene’s test for
the homogeneity of variances was used to determine validity of the univariate
ANOVA and independent samples t-test. To analyse data over the years, repeated
measures ANOVA was carried out because each quadrat was surveyed three or more
times. Mauchly’s test of sphericity was used to test the variances of the differences
between conditions was equal. When a significant sphercity result was produced the
Greenhouse-Geisser correction was used. All data analysis was carried out using
SPSS 15.0.
14
Figure 3. Arrangement of plots (2 m2 quadrat with 2 m guard row) within Primley Meadow at site one. Each colour represents a different replicate block
Code Treatment C SC Short cut and control C R Rotovation and control W5 SC Short cut and wildflower seed mix sown in September 2005 W5 R Rotovation and wildflower seed mix sown in September 2005 W6 SC Short cut and wildflower seed mix sown in September 2006 W6 R Rotovation and wildflower seed mix sown in September 2006 Y5 SC Short cut and R. minor sown in September 2005 Y5 R Rotovation and R. minor sown in September 2005 YW5 SC Short cut and R. minor and wildflower seed mix sown in September 2005 YW5 R Rotovation and R. minor and wildflower seed mix sown in September 2005 YW6 SC Short cut and R. minor sown in 2005. Wildflower seed mix sown in September 2006 YW6 R Rotovation and R. minor sown in 2005. Wildflower seed mix sown in September 2006
Q Treatment Q Treatment Q Treatment Q Treatment 1 Y5 SC 16 YW5 R 31 W5 SC 46 Y5 R 2 C SC 17 C R 32 W5 R 47 W5 SC 3 Y5 R 18 YW6 R 33 YW6 R 48 C R 4 YW6 R 19 YW5 SC 34 YW5 R 49 C R 5 W6 R 20 W6 SC 35 C R 50 Y5 R 6 W6 SC 21 Y5 SC 36 W6 SC 51 YW6 SC 7 YW5 SC 22 W6 R 37 YW6 SC 52 W5 R 8 YW6 SC 23 YW6 SC 38 W6 SC 53 W6 SC 9 C R 24 Y5 R 39 Y5 SC 54 YW5 SC 10 YW5 R 25 Y5 R 40 YW5 SC 55 Y5 SC 11 W5 R 26 Y5 SC 41 C SC 56 C SC 12 W5 SC 27 W6 R 42 YW5 R 57 W5 SC 13 W5 R 28 C SC 43 W6 R 58 YW5 R 14 W5 SC 29 YW6 SC 44 YW6 R 59 YW6 R 15 C SC 30 YW5 SC 45 W5 R 60 W6 R
60
59 58
57 56 55
54 53 52
50 49 48
51 47 43
45
42
44
46 40 39
41 36
38 37
35
34
33
24
18
27
32 30
31
23
17
26
22
16
25
29 28
21
15
20
14
19
13
12 11 10
1 6 5 4 3
9 8 7
2
Treatment key
15
3. Results – Site one 3.1 Biodiversity The aim of the project, as a whole, is to increase biodiversity at Primley meadow.
Using Simpson’s Index of Diversity (appendix) biodiversity was calculated using
percentage cover of wildflower species for each quadrat over the three years.
00.10.20.30.40.50.60.70.80.9
1
C SC
C R
W5 S
CW
5 R
W6 S
CW
6 R
Y5 SC
Y5 R
YW5 S
C
YW5 R
YW6 S
C
YW6 R
Treatment
Inde
x of
div
ersi
ty
2005
2006
2007
2008
Figure 4. The mean biodiversity for each treatment across the four years (+S.E). N=5
Figure 4 shows that biodiversity has significantly (F=53.188, p<0.001***) increased
since 2005 (baseline), with the use of ground preparation and seed addition. The
average biodiversity has increased from 0.43 (0.03 S.E) in 2005 to 0.65 (0.02 S.E) in
2008; although biodiversity peaks in 2007 at 0.71 (0.04 S.E). No significant
difference (F=0.537, NS) between treatments was found when analysed using
repeated measures ANOVA. When looking at the values for individual treatments in
August 2008, both controls show the lowest biodiversity (C SC – 0.55 (S.E 0.10); C R
– 0.56 (S.E 0.07)).
16
3.2 R. minor
R. minor has been theorised to reduce grass height and vigour so establishment when
sown was investigated. Data from the June survey each year is presented as this is the
time of year when R. minor is most abundant.
0
10
20
30
40
50
60
2006 2007 2008
Year
Ave
rage
root
ed %
cov
er
Short cut
Rotovation
Figure 5. Mean average rooted percentage cover of R. minor for plots where R. minor was sown and then either short cut or rotovated (+S.E). This data is from the June vegetation survey. N = 15
Figure 5 shows R. minor has successfully established in plots where sown; however,
as shown by the graph, the average rooted percentage cover has significantly
(F=91.108, ***p<0.001 – repeated measures ANOVA) reduced from 2006 to 2008
(42.8 % (3.10 S.E) – 2006 to 17.1 % (4.33 S.E) - 2008). The percentage cover of
R. minor is higher for plots where the ground was short cut rather than rotovated (NS
– Independent samples t-test).
17
0
5
10
15
20
25
30
35
2006 2007 2008Year
Gra
ss h
eig
ht (c
m)
No R.minor
R.minor
Figure 6. The mean grass height (cm) for plots where R. minor was sown and those where no R. minor was sown over the three years in June (+S.E). N = 30
Figure 6 shows grass height was reduced for plots where R. minor had been sown
compared to those where it hadn’t for each of the three years. Using the independent
samples t-test a significant result was found between these treatments for 2006
(T=2.943, *p<0.05) and 2007 (T=3.010, **p<0.005). Repeated measures ANOVA
shows R. minor to significantly reduce grass height (F=27.820, ***p<0.001);
however, ground preparation was non-significant (F=0.019, NS).
3.3 Grass productivity
Grass productivity was measured using the biomass survey in September 2007.
Univariate ANOVA gave a significant result for both R. minor (F=25069.444,
**p<0.005) and ground preparation (F=3640.111, *p<0.05). The average biomass for
plots with R. minor was 12.7 g compared to 14.2 g when R. minor was not applied.
Ground preparation showed rotovation (13.1 g) to reduce biomass by 0.6 g more than
short cut (13.7 g).
** *
18
0
5
10
15
20
25
C SC
C R
W5 S
CW
5 R
W6 S
CW
6 R
Y5 SC
Y5 R
YW5 S
C
YW5 R
YW6 S
C
YW6 R
Treatment
Bio
mas
s (g
)
Figure 7. Mean biomass of grass (+S.E) for each of the different treatments in September 2007. C SC = Control, short cut; C R = Control, rotovation; W5 SC = Wildflower 05, short cut; W5 R = Wildflower 05, rotovation; W6 SC = Wildflower 06, short cut; W6 R = Wildflower 06, rotovation; Y5 SC = R. minor 05, short cut; Y5 R = R. minor 05, rotovation; YW5 SC = R. minor & wildflower 05, short cut; YW5 R = R. minor & wildflower 05, rotovation YW6 SC = R. minor 05, wildflower 06, short cut; YW6 R = R. minor 05, wildflower 05, rotovation. N = 5
The dominance of grasses (table 1) shows how percentage cover and dominance vary
between the five most prevalent species. There is not much change in order
throughout the years, but in 2008, Agrositis stolonifera moves from most abundant to
4th position.
1st 2nd 3rd 4th 5th
2005 A. stolonifera H. lanatus D. glomerata A. elatius A. odoratum
2006 A. stolonifera H. lanatus D. glomerata A. elatius A. odoratum
2007 A. stolonifera H. lanatus A. elatius D. glomerata A. odoratum
2008 H. lanatus D. glomerata A. elatius A. stolonifera A. odoratum
Table 1. The order of dominance of the five most prevalent grasses found at Primley meadow across the years of the study. 1st = most abundant; 5th = least abundant.
19
3.4 Wildflower establishment
August data was used to look at wildflowers as this is when most species were
present. Using all species that were sown in the wildflower mix, total percentage
cover of those which germinated was recorded. Plots were divided into 1) wildflowers
sown in 2005 (same year as R. minor), 2) those sown in 2006 (the following year after
R. minor) and 3) those without wildflower mix applied, and then compared.
Species Total % cover % change from previous year
Achillea millefolium 2005 120
2006 151 26
2007 197 30
2008 187 -5
Centaurea nigra 2005 8 2006 78 875
2007 104 33
2008 271 161
Prunella vulgaris 2005 0
2006 0
2007 6
2008 34 467
Table 2. Total percentage cover of the three most prevalent sown wildflowers Achillea millefolium, Centaurea nigra, Prunella vulgaris for all 60 quadrats across the four years in August.
Table 2 shows the cumulative percentage cover of the three most prevalent sown
wildflower species and the rate they are increasing over the years. Each of the species
has an increasing overall percentage cover from 2005 to 2008, with C. nigra having
increased to the highest density by 2008. Both A. millefolium and C. nigra were
present in the quadrats before the wildflower mix was sown.
20
020406080
100120140160180200
None S
C
None R
2005
SC
2005
R
2006
SC
2006
R
Treatment
Tota
l so
wn
wild
flow
er2005
2006
2007
2008
Figure 8.The total percentage cover of wildflowers (species from wildflower mix) for each different treatment of wildflower application. These include no wildflower sown, wildflower sown in 2005 (same year as R. minor) and wildflower sown in 2006 (the following year after R. minor). SC = Short cut; R = Rotovation. N = 10
Wildflower sown in 2005 with the ground being short cut proved to be the most
successful wildflower application with the highest cumulative percentage cover
(185 % in August 2008). Repeated measures ANOVA showed a significant increase
in wildflowers over the years (F=16.295, p<0.005***). A significant interaction
between year and wildflower application was found (F=3.070, p<0.05*). The post hoc
test (LSD) (table 3) reveals wildflower sown in 2006 is significantly different
(p=0.048*) from that sown in 2005. Wildflower sown in 2005 is almost significantly
different from no wildflower mix application (p=0.077).
Wildflower 1 Wildflower 2 p-value None 2005 0.077
2006 0.827 2005 None 0.077
2006 0.048* 2006 None 0.827
2005 0.048*
Table 3. Post hoc test (LSD) for wildflower application. None = no seed applied; 2005 = wildflower mix sown in 2005; 2006 = wildflower mix sown in 2006.
21
0
2
4
6
8
10
12
2005 2006 2007 2008
Year
No.
of s
peci
esC SC
C R
Y5 SC
Y5 R
Figure 9. The mean number of herb species recorded for the four treatments (C SC – control, short cut; C R – control, rotovation; Y5 SC – R. minor sown in 2005, short cut; Y5 R – R. minor sown in 2005, rotovation) which were not sown with wildflowers (+SE). Data taken from the August survey for each year. N = 5
Figure 9 shows the mean number of different herb species recorded, for the treatments
which were not sown in wildflower mix, to see if R. minor is increasing species
richness by creating a more favourable habitat by reducing grass vigour. The graph
shows that the treatments containing R. minor have a higher number of species
present for each year between 2006 and 2008. The baseline data (2005), before
ground preparation and R. minor application, shows no difference between the control
and R. minor plots. Repeated measures ANOVA does not show a significant result for
ground preparation (F=0.312, NS) or R. minor (F=0.010, NS); however, year was
significant (F=59.524, ***p<0.001).
4. Results – Site two
4.1 R. minor
R. minor was not found in any of the random quadrats over the entire sample period
of April until August 2008 (table 3).
4.2 Wildflowers The full vegetation survey concluded that three out of the five (Achillea millefolium,
Centaurea nigra, and Prunella vulgaris) species of the wildflower mix germinated
22
(table 3). None of the wildflower mix species were found in September 2007 so all
species appear to have come from introducing them; however, random quadrats were
used so this cannot account for the whole area.
Month R.minor A.millefolium C.nigra K.arvensis L.vulgare P.vulgaris September 0 0 0 0 0 0 April 0 14 4 0 0 0 May 0 12 22 0 0 0 June 0 10 28 0 0 0 July 0 1 57 0 0 2 August 0 6 4 0 0 0
Table 3. The total number of each wildflower species germinated in the 10 random quadrats each month.
23
5. Discussion
5.1 Site one
After three years of monitoring for this longitudinal study, results appear to provide a
positive outlook for the future. Biodiversity results show that the trend overall seems
to be heading upwards from 2005 to 2008 (figure 4) for each of the treatments.
However, these results should be treated with caution as the sudden increase from
2005 to 2006 for each of the different treatments (including the two controls) is
unlikely to be caused by ground preparation alone. It is more likely to be because of
differences in identification skills with the various surveyors, as each year of the study
was carried out by a different student. With the rise and fall of biodiversity between
2006 and 2008, this illustrates how these initial results do not provide concrete
evidence for biodiversity change. It should be noted that biodiversity change is a slow
process and can take up to ten years to achieve (Walker et al., 2004) so further
monitoring will be required in the future to supply conclusive results. There appears
to be no significant differences in biodiversity between treatments at this early stage
of the restoration of Primley meadow, but changes are likely to become more apparent
in later years.
As a restoration tool, the theory is that R. minor will establish in the area undergoing
restoration and parasitise the coarse grasses residing there; resulting in a reduction in
grass height The results show R. minor has established well in plots where sown
(figure 5). R. minor has a higher rooted percentage cover for plots where the short cut
was used compared to rotovation so it appears R. minor establishes better with this
ground preparation. There is a significant interaction between year and ground
preparation and the difference of R. minor establishment between short cut and
rotovated plots seems to be increasing over the years (figure 5). Over the three years a
decline in R. minor abundance was observed. Westbury (2004) showed a year-to-year
variation in seed production will take place dependant on environmental conditions,
and given that seed doesn’t stay in the seed bank, next years germination is a direct
result of the previous year’s seed production (Gilbert and Anderson, 1998; Westbury
and Davies, 2005). It has been suggested by Pywell et al. (2004) that R. minor takes
three years to establish so a decline over the initial few years is not unexpected. The
24
overall success of R. minor may be because of the abundance of hosts present, as
grasses are the most common components of communities R. minor is associated with
(such as Primley meadow). Therefore, the probability of locating a suitable host is
high (Gibson and Watkinson, 1989). R. minor successfully reduced sward height each
year (figure 6) as shown by previous studies (Pywell et al., 2004). This indicates that
R. minor is parasitising the grasses and reducing their vigour or stunting their growth.
The difference in grass height between plots containing R. minor and those without it
was significant for both 2006 and 2007. The reduction in R. minor (figure 5) over the
years is likely to account for the non-significance shown by data from 2008. Bardgett
et al. (2006) showed how R. minor density affects biomass, species diversity and forb
composition so it is likely grass height is also affected by density, as a reduced
number of R. minor plants will not parasitise so many hosts.
R. minor is speculated to reduce grass biomass and results from this study coincide
with this hypothesis. The average grass biomass was lower for plots treated with
R. minor (figure 7) which indicates that R. minor successfully parasitises the grass
species reducing their vigour. Rotovation also reduced grass biomass when compared
to plots that were short cut; this was only by 0.6 g, however. The order of dominance
of grasses is almost the same from 2005 to 2008. This may be because R. minor
densities are not large enough for the high density of grasses present. With such
excessive grass densities, small differences in host selectivity could be diluted to such
an extent that they are unseen. R. minor could also have no host preference between
these grass species and be parasitising all species equally. R. minor could potentially
be using a different non-grass host or growing autotrophically; although autotrophic
growth within the field is less common (Gibson and Watkinson, 1989). The order of
dominance of each of the grass species shows A. stolonifera, unlike the other species,
has moved from most dominant to fourth position (table 1). This species was
highlighted by Smith et al. (2000) as showing the greatest reduction from originally
high frequencies (35-40 %). Therefore, A. stolonifera may be a target host for
R. minor at Primley meadow.
It has been suggested that sowing wildflower after R. minor application is beneficial
because of gap creation when R. minor dies allowing seedling colonisation the
subsequent year (Pywell et al., 2004). However, the wildflower mix being sown in the
25
same year as R. minor (2005) proved to be the most successful sowing technique with
the highest total percentage cover recorded for species sown in the wildflower mix
(figure 8). Results also show wildflower sown in 2006 had a significantly lower
percentage cover when compared to both plots without wildflower mix sown and
those when sown in 2005. This suggests that sowing wildflower mix the following
year is not beneficial for wildflower germination. On the other hand, low germination
rates of wildflower when sown in 2006 could be attributed to poor environmental
conditions or a less viable seed mix that year. It must also been taken into account that
seeds sown in 2005 have had longer to establish and are likely to have seeded twice
by 2008, compared to seeds sown in 2006 which will have only seeded once. Nearly
all treatments show an increase in wildflower percentage cover across the years
(figure 8) with particularly large increases in later years, as the wildflowers become
more established and start seeding, for treatments where wildflower mix was sown.
The mean number of species recorded was higher for the treatments with only
R. minor sown: Y5 SC (R. minor application and short cut) and Y5 R (R. minor
application and rotovation) than either of the controls: C SC (control and short cut)
and C R (control and rotovation) (figure 9). This suggests that R. minor is reducing
grass vigour and other dominant species allowing a wider range of species to survive
because the habitat has become more favourable. This shows species richness can
potentially increase with changes in habitat conditions. The results are non-significant
but it is not to be expected that species composition would change dramatically in a
matter of a few years. It also emphasises the need for sowing supplementary
wildflowers because the limited seed bank could potentially delay restoration (Bakker
and Berendse, 1999).
5.2 Site two The results indicate that R. minor appears not to have germinated at site two (table 3).
This may be because of non-viable seeds purchased. Environmental conditions are
unpredictable and as Westbury (2004) states R. minor yield is directly affected by
this. Wet summers are becoming the norm of recent years so as R. minor sets seed
from June onwards this would result in seed quality being reduced. R. minor doesn’t
stay in the seed bank each year (Gilbert and Anderson, 1998; Westbury and Davies,
2005) so more seed will need to be sown the following year. R. minor requires a
26
chilling period to break dormancy over the winter (Smith et al., 2000); Ter Bong
(2005) states Rhinanthus species germination can be effected by both the temperature
and the duration of chilling. The winter of 2007 may have not provided the essential
chilling needed for the lifecycle of R. minor. It is not surprising that the numbers of
wildflower mix that germinated are relatively low (table 3) as this is the first year of
the study and many perennials require at least two years before plants are mature
enough to flower and several growing seasons to properly establish (landlife online).
5.3 Limitations and improvements
One of the problems of a longitudinal study, conducted by different people, is the
inconsistency of identification skills. Identification skills also improved dramatically
over the year with practice. This cannot be quantified but should be taken into
account.
The drop disc technique was a reasonably reliable method to measure grass height.
However, reliability decreased when the grass was longer and folded over in August.
Grass height also varied among the quadrat so the random throwing of the disc onto
the quadrat didn’t always represent the entire area.
The 20 cm2 quadrat used for the biomass sampling was effective at giving a reading
of grass productivity. Even so, only 1 % of the total area was sampled which reduced
accuracy, in particular if large forb species were present within the 20 cm2 quadrat.
Primley Park provides a vital habitat for many invertebrate species, such as the great
green bush cricket Tettigonia viridissima which features in the Devon Biodiversity
Action Plan. To further this project, a logical step to take is to look at the next level in
the food chain i.e. invertebrates. This would provide data on the impact of increasing
species richness on invertebrates. However, this aspect, is clearly long term and not
possible with the size of the small quadrats used for this project at site one.
Additional study into soil temperature and pH could provide answers to why R. minor
did not germinate at site two. Berendse et al. (1992) has also suggested that
restoration of species rich grasslands is affected by various environmental factors
which have not been touched on in this study.
27
5.4 Future management
Restoration of grassland takes many years to achieve so changes in biodiversity are
not expected at these early stages of the project. Primley meadow will continue to be
monitored in the following years to gather data on the long-term changes in
biodiversity. Site one has provided evidence regarding the best treatment (YW5 SC)
so further plots of this treatment will be set up around different parts of the meadow.
Site two will require additional R. minor seed to be sown after the ground is short cut
again in autumn. It is hoped that seed dispersal will occur across the meadow, with
the aid of the continuation of the annual hay cut each autumn, and Primley meadow
will become much more species rich in both flora and fauna in the future.
28
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33
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Word count: 6288
34
7. Acknowledgments Special thanks to Dr Amy Plowman, Dave Ellacott, Tracey Hamston and Andrea
Stacey for all their help, support and advice. Thanks also to the rest of the Field
Conservation and Research team and everyone else at Paignton Zoo for making my
year here such a useful and enjoyable one.
35
8. Appendix Simpson’s Index of Diversity = 1- ((�n (n-1)) / (N (N-1)))