WETLAND SERVICES AND MANAGEMENT

Differential responses of abandoned wet grassland plantcommunities to reinstated cutting management

Maureen Berg • Chris Joyce • Niall Burnside

Received: 25 November 2010 / Accepted: 15 July 2011 / Published online: 19 August 2011

� Springer Science+Business Media B.V. 2011

Abstract The nature of ecological stability is still

debated, and there is a need to establish which types

of communities show resistance to environmental

change and to explore community responses in

relation to their environmental context. This study

aims to investigate the effects of reinstating cutting

management on abandoned wet grasslands by com-

paring responses in two different communities with

contrasting environmental conditions, to elucidate the

restoration potential of wet grasslands. Two coastal

wet grassland plant communities in Estonia were

monitored over 5 years: a species-poor lower shore

grassland and a more diverse tall grassland. Piezom-

eters and soil samples were used to characterise the

hydrology, while cutting effects and ongoing aban-

donment were compared using replicate quadrats in

both grasslands. Annual changes and significant

differences in community composition were analysed

using Detrended and Canonical Correspondence

Analyses, diversity indices, and inferential statistics.

The results showed that cutting produced greater

changes in composition and species abundance in the

lower shore community compared to the tall grass-

land, including a greater proportion of significant

differences. The increased responsiveness of the

lower shore community may be related to its variable

hydrological regime, especially flooding, which cre-

ates a dynamic environment favouring adaptable

species. In contrast, the tall grassland featured a more

stable water regime and species that responded less to

perturbation, and manifested resistance to cutting

management. Thus, restoring abandoned wet grass-

lands through vegetation management may be a

slow process, especially where there is residual

diversity, and the importance of hydrological regime

in determining wet grassland communities should be

considered.

Keywords Abandonment � Ecological stability �Diversity � Management � Restoration � Wetland

Introduction

Understanding the dynamics and stability of ecolog-

ical systems has had a long and controversial history

(e.g. May, 1973; Pimm, 1984), and more recently has

been associated with a debate about the role of

Electronic supplementary material The online version ofthis article (doi:10.1007/s10750-011-0826-x) containssupplementary material, which is available to authorized users.

Guest editor: Chris B. Joyce / Wetland services and

management

M. Berg

School of Pharmacy and Biomolecular Sciences,

University of Brighton, Brighton, UK

C. Joyce (&) � N. Burnside

School of Environment and Technology,

University of Brighton, Brighton, UK

e-mail: C.B.Joyce@brighton.ac.uk

123

Hydrobiologia (2012) 692:83–97

DOI 10.1007/s10750-011-0826-x

diversity in ecosystem functioning (e.g. Kinzig et al.,

2001; Loreau et al., 2002; Naeem et al., 2009). A key

mechanism for increased functioning and stability in

biological systems is believed to be niche comple-

mentarity, which relates to the greater efficiency of

resource use by a community of species whose

functional traits are different. Compensatory dynam-

ics exist when increases in the abundance of one

species are associated with decreases of another

species (Gonzalez & Loreau, 2009). Thus, it is

suggested that species-rich communities are more

capable of buffering environmental variability than

species-poor communities and that a loss of biodiver-

sity can reduce ecosystem resistance against ecolog-

ical perturbation (Naeem et al., 1994). Plant strategies

may also be important, with some species being able

to gain a competitive advantage from disturbance,

while others are favoured by undisturbed conditions

(Grime, 1979). However, there is still a need to

establish which types of communities show resistance

to environmental change and to explore community

responses in relation to their environmental context

(Kinzig et al., 2001; Grman et al., 2010).

Wet grassland ecosystems combine wetland and

semi-natural grassland properties, with plant commu-

nity composition largely determined by hydrological

regime and management practices, such as grazing or

mowing for agriculture (Joyce & Wade, 1998).

Typical plant species are functionally adapted to the

prevailing hydroperiod, including any flooding, and

are able to tolerate defoliation. Plants are therefore

good indicators of ecosystem functioning and plant

communities have been used to assess and monitor

environmental perturbations and changes (Diekmann,

2003). Regular wet grassland management favours

open habitats with species-rich, low-growing herba-

ceous vegetation that supports considerable biodiver-

sity (e.g. wading birds and wildfowl) and is of

importance for nature conservation. A lack of man-

agement due to neglect or abandonment will lead to

more competitive species of larger stature forming a

dense canopy, such as Phragmites australis, displac-

ing smaller species and reducing diversity (Burnside

et al., 2007). Abandonment of formerly managed

grasslands is a widespread phenomenon due to

changing economic and social conditions, for exam-

ple, in Europe where approximately 15 million

hectares have been abandoned (Benstead et al.,

1999), resulting in concerns over losses of grassland

communities of nature conservation value and an

urgency to restore degraded grasslands.

Restoration of the wet grassland resource focuses

upon rewetting sites and/or reinstating vegetation

management to encourage characteristic species and

enhance diversity (Toogood & Joyce, 2009). Rein-

stating management, such as cutting, to abandoned

vegetation may increase disturbance levels, provok-

ing responses in plant species richness and abundance

(Gerard et al., 2008). Joyce (1998) found that an

inundation grassland community characterised by

short-lived species responded rapidly to perturbations

while a flood-meadow community comprising peren-

nial plants was resistant to abandonment, but gener-

ally wet grassland community dynamics have not

been well documented in relation to restoration

management. The aim of this study was to investigate

the effects of reinstating cutting management on

abandoned wet grasslands by comparing responses in

two different communities with contrasting environ-

mental contexts, to elucidate the restoration potential

of wet grasslands. The field study was undertaken in

west Estonia, where coastal wet grasslands are of

international conservation significance for their bio-

diversity, including rare plants and breeding and

migratory birds, but are threatened by grazing and

cutting abandonment because of agricultural and

socio-political changes in recent decades (Burnside

et al., 2007). Plant communities were monitored for

5 years by measuring the abundance of species to

interpret changes in diversity and composition.

Methods

Study area

The study area was located within the landscape

reserve of Hosby (58�5900600N, 23�2201200E), on

Vormsi island, west Estonia (Fig. 1). The reserve

comprises 136 ha and is designated for the wet

grassland and other wetland habitats it sustains, and

the protected plants and birds. The topography of the

study area varies between 0.5 and 0.8 m a.s.l. and the

substrate is composed of marine sands covered by

saline littoral soil. The hydrology at Hosby is

dominated by precipitation and the proximity of the

Baltic Sea, which, in western Estonia, has a small

tidal range and a salinity of generally \6% (Tyler,

84 Hydrobiologia (2012) 692:83–97

123

1969); flooding can occur following snow melt,

intense rainfall, storms at sea and on-shore winds.

Since the 1960s, changes in agricultural practices

with grazing abandonment led to the overgrowth and

modification of the coastal grasslands at Hosby. By

2002, the study area was dominated by Phragmites

australis reed swamp, with any remaining patches of

wet grassland encroached by P. australis. Hosby

remains, however, important for nature conservation.

Experimental design

Two contrasting wet grassland plant communities

within the Hosby landscape reserve were selected for

this experiment, namely, lower shore grassland and

tall grassland. Lower shore grasslands tend to estab-

lish on low-lying land where periodic flooding is

influential, while tall grasslands are found at higher

elevations where flooding is less pronounced (Burn-

side et al., 2008; Berg, 2009). Both grassland study

sites were formerly grazed extensively by livestock

but had been abandoned for approximately 40 years.

Lower shore grassland vegetation is of conserva-

tion value for wetland birds as breeding and feeding

habitats (Rannap et al., 2004), although the presence

of saline water may contribute to restricted botanical

diversity. At the start of the experiment, the lower

shore grassland was typified by a relative abundance

of Juncus gerardii, Festuca rubra and Phragmites

australis, and by three halophytic forb species: Glaux

maritima, Plantago maritima and Triglochin mariti-

ma (Table 1). Eighteen plant taxa were identified

within the surveyed community, with a mean species

richness of 10.4 ± 0.6 per 2 m 9 2 m quadrat.

Tall grassland is one of the most species-rich

Estonian wetland plant communities, with a greater

frequency and/or proportion of forbs than lower shore

grassland (Burnside et al., 2007). The tall grassland

community supported a total of 33 plant taxa

(Table 1) and a mean of 14.1 ± 0.8 species per

quadrat. Grass species were the dominant taxonomic

group in terms of cover, with Festuca arundinacea,

F. rubra, Elytrigia repens and P. australis well

represented (Table 1). Forb species were the most

numerous group, with Achillea millefolium, Poten-

tilla anserina, Sonchus arvensis, Valeriana offici-

nalis, Vicia cracca and Peucedanum palustre being

the most abundant.

The vegetation was first surveyed 11–14 August

2003 when 16 permanent 2 m 9 2 m quadrats were

placed in each study site. Four separate fenced

enclosures measuring 10 m 9 10 m, each containing

four quadrats, were installed to prevent any disturbance

by animals such as wild boar. Quadrats were perma-

nently fixed with metal poles so that it was possible to

relocate them using a metal detector for subsequent

Fig. 1 Location of the

study area of Hosby,

Vormsi Island, Estonia

Hydrobiologia (2012) 692:83–97 85

123

sampling, which took place annually between 22 and

28 July until 2007. During the annual survey, the

percentage cover for each plant species present, as well

as bare ground and litter, was visually estimated. The

treatment plots were selected in a stratified random

way to ensure interspersion within each grassland

study site. Eight quadrats at each site had no experi-

mental management, and so acted as control plots,

hereafter termed ‘abandoned’ because of their lack of

management. The other eight plots at each site were cut

annually using shears; cutting was on 14 August in

2003 and 24–28 July during the subsequent years. The

cut vegetation was removed from the plots, leaving

3–4 cm of standing vegetation.

Ground water levels were monitored from June

2004 to August 2006, using one piezometer at each of

the two grasslands. The wells were 80–100 cm deep

and of 50-mm diameter, enclosed within a geo-textile

sock to exclude soil particles, and fitted with a cap to

prevent direct entry of surface water, precipitation

and debris. Water level was determined by a pressure

transducer linked to a waterproof logging unit (Model

Table 1 Plant community

composition for the lower

shore and tall grassland

study sites

Values are mean (n = 16,

SE) cover (%) for bare

ground, litter and species

identified pre-treatment in

August 2003 in 2 m 9 2 m

quadrats

Lower shore Tall grassland

Bare 1.95 ± 1.0 Bare 1.4 ± 0.4

Litter 6.2 ± 0.8 Litter 10.0 ± 1.75

Ophioglossum vulgatum 0.05 ± 0.05 Ophiglossum vulgatum 0.9 ± 0.35

Agrostis stolonifera 2.7 ± 0.8 Agrostis gigantea 1.25 ± 0.6

Festuca rubra 14.4 ± 3.8 Alopecurus pratensis 0.05 ± 0.05

Phragmites australis 15.6 ± 2.1 Elymus repens 14.35 ± 3.9

Carex distans 0.2 ± 0.2 Festuca arundinacea 17.7 ± 2.45

Carex nigra 0.05 ± 0.05 Festuca rubra 10.0 ± 2.0

Eleocharis palustris 1.45 ± 0.7 Molinia caerulea 0.3 ± 0.3

Juncus gerardii 25.5 ± 2.6 Phragmites australis 14.05 ± 2.25

Atriplex patula 0.05 ± 0.05 Achillea millefolium 7.0 ± 2.4

Galium palustre 1.05 ± 0.35 Angelica palustris 0.4 ± 0.3

Glaux maritima 15.75 ± 3.9 Atriplex patula 0.2 ± 0.15

Leontodon autumnalis 0.5 ± 0.25 Centaurea jacea 1.0 ± 0.6

Lotus pedunculatus 0.15 ± 0.15 Filipendula ulmaria 0.2 ± 0.2

Odontites vernus 1.05 ± 0.4 Galeopsis tetrahit 0.25 ± 0.15

Plantago maritima 7.55 ± 2.1 Galium boreale 0.3 ± 0.2

Potentilla anserina 1.95 ± 0.75 Galium palustre 0.6 ± 0.3

Triglochin maritima 6.95 ± 1.4 Galium uliginosum 0.25 ± 0.25

Galium verum 0.95 ± 0.6

Lotus pedunculatus 0.05 ± 0.05

Lysimachia vulgaris 0.25 ± 0.25

Mentha aquatica 1.15 ± 1.05

Peucedanum palustre 2.0 ± 0.55

Plantoga lanceolata 0.25 ± 0.2

Potentilla anserina 4.2 ± 0.85

Ranunculus acris 0.3 ± 0.15

Rumex acetosa 0.05 ± 0.05

Rumex crispus 0.05 ± 0.05

Sonchus arvensis 2.65 ± 0.85

Tanacetum vulgare 0.75 ± 0.75

Trifolium pratense 0.5 ± 0.4

Valeriana officinalis 3.9 ± 1.0

Vicia cracca 4.2 ± 1.05

86 Hydrobiologia (2012) 692:83–97

123

740 from Valeport Ltd, Totnes, Devon, UK), which

was permanently installed upon a metallic tripod

1.5 m above-ground to avoid flooding and accumu-

lated snow. During set-up, the transducer probe was

calibrated in situ, with the burst length (length of time

for measurements) set at 60 s and the burst cycle

(time between measurements) at 60 min. Pressure

variations (dBar) were converted into depth below

ground level based upon the existing linear relation-

ship between pressure and depth. Lower shore

grassland showed fluctuating water levels, ranging

from ?20 to -80 cm (mean -34 cm) with four

inundation periods (Sept–Nov 2004; May–June 2005;

July–Sept 2005; June–Aug 2006) totalling 172 days.

In the tall grassland, mean water levels were -74 cm

(0 to -100 cm), and there were no flood events,

although ground water levels reached the surface in

June–July 2005 and the same in 2006. Flooding and

rapid rises in water table in the two communities

were caused by a combination of (i) snow melt (e.g.

in May), (ii) precipitation, and/or (iii) storms and

onshore winds (e.g. in autumn) leading to sea water

ingress. In winter, ground water in the piezometers

was generally frozen, while, in the summer, water

levels may occasionally have fallen below the depth

of the piezometers.

Key soil water parameters were sampled monthly

using a WET sensor soil probe (Delta-T Devices Ltd.,

Cambridge, UK) and a pH electrode (Hanna Instru-

ments, Bedfordshire, UK), with eight replicate read-

ings from control plots at both study sites in June–

August 2006. This indicated that soil moisture was

somewhat higher in the lower shore grassland (mean

60.7%) than the tall grassland (mean 53.8%), while

pH was lower (median 5.9 compared to 7.4, respec-

tively) and soil temperature was higher (mean 23.8�C

compared to 20.8�C, respectively). Conductivity

differences were pronounced, with an overall mean

value for the lower shore of 667 mS m-1 compared

to 272 mS m-1 for the tall grassland, reflecting the

proximity of the Baltic Sea and its saline water source

to the lower shore grassland.

Statistical analysis

Annual changes in the floristic composition in each

plant community were described using species rich-

ness and abundance in abandoned (control) and cut

plots from 2003 to 2007. Percentage cover values for

all the species (and litter and bare ground) were

arcsine transformed to verify the normality assump-

tion necessary for the statistical tests. Multivariate

analysis was performed separately for each commu-

nity with all the species and without down-weighting.

Detrended Correspondence Analysis (DCA) was used

for providing a summary of variation and plant

community dynamics and Canonical Correspondence

Analysis (CCA), and Pearson correlation of case

scores and environmental variables, was used for

testing for treatment and time effects upon commu-

nity composition (using MVSP, Kovach Computing

Services, 2003). Community diversity was assessed

using species richness, the Shannon–Wiener diversity

and evenness indices, and Simpson’s diversity and

evenness indices (see Magurran, 2004). General

Linear Model (GLM), incorporating repeated mea-

sures analysis of variance, and Least Significant

Difference (LSD) post-hoc testing were used for

detecting any significant differences within (i.e.

annual variations) and between (i.e. treatment effects)

the treatments for diversity and abundance, with

significance set at P \ 0.05. Between-treatment

homogeneity at each site was tested before treatment

application to examine species richness and abun-

dance in plots allocated to different treatments. This

indicated that experimental differences were valid, as

there were no significant differences before imple-

mentation of the cutting regime.

Results

Lower shore grassland

Community changes

Results of the DCA for the lower shore grassland

indicate that both abandoned and cut plots were

similar in community composition in 2003–2004 but

then shifted in subsequent years, as shown by the

increasing point scores for both treatments along axis

1 (Fig. 2). Axis 1 accounted for 31% of the variation

in species composition, which showed a greater

dispersion (0.7 standard deviation units) and eigen-

value (0.073) than axis 2, which accounted for 12%

of community variation. Correlations of CCA results

showed that axis 1 was significantly positively related

to time (r = 0.8, P = 0.000) and axis 2 to treatment

Hydrobiologia (2012) 692:83–97 87

123

(r = 0.585, P = 0.000), with no significant interac-

tions. Treatment effects apparently increased between

2005 and 2007, indicated by diverging point scores

for cut and abandoned plots in the DCA (Fig. 2).

Temporal community changes were therefore pro-

nounced, but standard error values for mean point

values were relatively small, indicating little varia-

tion within the community at any one point in time

irrespective of treatment (Fig. 2).

Species changes

Key drivers of temporal community change were

similar in both abandoned and cut plots (Table 2),

with the cover of bare ground and Agrostis stolonif-

era increasing, Festuca rubra, Phragmites australis,

Glaux maritima, and Plantago maritima declining

overall, and Juncus gerardii and Triglochin maritima

fluctuating with no overall trend. Litter fluctuated but

decreased ultimately in the cut plots. A substantial

community change between 2004 and 2005, apparent

in the higher mean values along axis 1 of the DCA

(Fig. 2), was expressed by a significant decrease in

litter, F. rubra and G. maritima, and a significant

expansion of J. gerardii and P. australis, in both

treatments (Table 2).

Five species, as well as the cover of bare ground

and litter, showed significant differences between cut

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Axis 1 Eigen value 0.073

Axi

s 2

Eig

en v

alue

0.0

2

Abandoned Cut

Ct 03

A 03

A 04

Ct 04

A 07

Ct 07

Ct 05

A 05

Ct 06A 06

s.d

s.dFig. 2 Detrended

Correspondence Analysis of

plant community cover in

lower shore grassland

between 2003 and 2007.

Mean values ± 1 SE

(n = 8) are shown, with

each point labelled

according to the treatment

(Ct cut and A abandoned)

and year of survey

(03 = 2003, 04 = 2004,

05 = 2005, 06 = 2006 and

07 = 2007)

Table 2 Summary of significant (GLM, LSD post hoc, P value \ 0.05) temporal changes in abundance in the lower shore grassland

for abandoned and cut treatments

Variable 2003–2004 2004–2005 2005–2006 2006–2007

Ab. Cut Ab. Cut Ab. Cut Ab. Cut

Bare ground 0.094 0.107 0.091 0.000 (?) 0.046 (?) 0.088 0.156 0.003 (?)

Litter 0.000 (?) 0.000 (?) 0.011 (-) 0.024 (-) 0.534 0.608 0.727 0.002 (-)

Agrostis stolonifera 0.000 (?) 0.000 (?) 0.194 0.091 0.003 (?) 0.005 (?) 0.001 (?) 0.041 (?)

Festuca rubra 0.616 0.691 0.000 (-) 0.000 (-) 0.234 0.106 0.593 0.006 (-)

Glaux maritima 0.000 (-) 0.001 (-) 0.036 (-) 0.004 (-) 0.389 0.038 (?) 0.652 0.108

Juncus gerardii 0.026 (-) 0.481 0.000 (?) 0.001 (?) 0.029 (-) 0.003 (-) 0.147 0.297

Phragmites australis 0.003 (-) 0.000 (-) 0.013 (?) 0.004 (?) 0.553 0.642 0.016 (-) 0.238

Plantago maritima 0.078 0.185 0.724 0.060 0.004 (-) 0.009 (-) 0.000 (?) 0.190

Triglochin maritima 0.055 0.002 (-) 0.742 0.356 0.026 (?) 0.002 (?) 0.346 0.202

Variables with greater than 5% mean cover and results from the post hoc pairwise comparisons are shown. Significant P values are in

bold with (?) = significant increase and (-) = significant decrease. See Appendix—Electronic supplementary material for results of

the GLM analysis

88 Hydrobiologia (2012) 692:83–97

123

and abandoned treatments in the lower shore grass-

land (Fig. 3). There were no significant differences

before 2005. The extent of bare ground increased in

both treatment plots throughout the experiment, and

was significantly greater in cut plots from 2005,

achieving maximum mean cover of 24% in 2007.

Litter cover decreased substantially in cut plots in

2007, and was significantly less (mean 1.4%) than in

the abandoned plots (mean 10.9%). The cover of A.

stolonifera generally increased during the experiment

(Fig. 3) and especially in the abandoned plots where

it achieved a mean value of 25.9% in 2007, which

was significantly greater than in the cut plots (mean

15.3%). F. rubra declined in both treatments from

25

20

15

10

5

0

Mea

n %

cov

er

2003Bare

2004 2005 2006 2007 2003Litter

2004 2005 2006 2007

25

35

30

20

15

10

5

0

Mea

n %

cov

er

2003

Festuca rubra2004 2005 2006 2007

25

20

15

10

5

0

Mea

n %

cov

er

25

30

20

15

10

5

0

Mea

n %

cov

er

2003

Agrostis stolonifera2004 2005 2006 2007

10

12

8

6

4

2

0

Mea

n %

cov

er

2.5

3.54.04.5

3.0

2.01.5

1.00.50.0

Mea

n %

cov

er

2003

Potentilla anserina2004 2005 2006 2007 2003

Triglochin maritima2004 2005 2006 2007

2003

Eleocharis palustris

2004 2005 2006 2007

2.5

3.0

2.0

1.5

1.0

0.5

0.0

Mea

n %

cov

er

**

**

**

**

*

***

**

Fig. 3 Mean (n = 8, ±SE) abundance of species and vari-

ables with significant differences (GLM, LSD post hoc,

P value \ 0.05) between the abandoned (filled square) and

the cut (open square) plots for 2003–2007 in lower shore

grassland. *P \ 0.05 and **P \ 0.01. Note the different axis

scales

Hydrobiologia (2012) 692:83–97 89

123

approximately 15% mean cover before 2005 to \5%

thereafter, with significantly less in cut compared to

abandoned plots in 2007. Other species showing

significant differences had low levels of abundance

(Fig. 3); Potentilla anserina declined under both

treatments but was significantly more abundant in

abandoned plots in 2007, while the cover of T.

maritima and Eleocharis palustris was significantly

greater in abandoned compared to cut plots in 2005.

Diversity changes

The cut lower shore plots showed a significant (GLM,

LSD, P \ 0.05) decrease in all the diversity mea-

surements between 2004 and 2005, when J. gerardii

dominated with 60% mean cover, followed by

recovery in 2006 and then another significant

decrease in diversity in 2007. Abandoned plots did

not show such significant temporal changes, although

evenness was significantly reduced in 2005 when J.

gerardii reached 50% mean cover, but evenness

recovered in 2006. Species richness in the lower

shore grassland generally declined during the exper-

iment, as mean values fell from approximately 10 to

7.5 in cut and abandoned plots (Fig. 4a). Galium

palustre and Blysmus rufus were lost from the

abandoned plots, while cut plots also lost Odontites

vernus and Leontodon autumnalis. Abandoned plots

were significantly richer than cut plots in 2005 and

2007. Shannon–Wiener and Simpson’s Diversity

Index scores reflected and accentuated richness

patterns as values generally decreased over 5 years

and abandoned plot mean values were often higher

than those for the cut treatment, especially in 2005

12(a) *10

8

6

4

2

02003

2.4

2.32.22.12.01.9

1.81.7

1.61.5

Shan

non-

Wie

ner

Div

ersi

ty I

ndex

(H')

Shan

non-

Wie

ner

Eve

nnes

s In

dex

(J)

Sim

pson

Eve

nnes

s In

dex

(ED

)Si

mps

on D

iver

sity

Ind

ex (

D')

2004 2005 2006 2007

Spec

ies

rich

ness

2003 2004 2005 2006 2007

0.900.880.860.840.820.800.780.760.740.720.70

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

2003 2004 2005 2006 2007

20030.75

0.80

0.85

0.90

0.95

1.00

2004 2005 2006 2007 2003 2004 2005 2006 2007

*

(b)

(d) (e)

(c)

Fig. 4 Mean (n = 8, ± SE) species diversity values and

significant differences (GLM, LSD post-hoc test, P \ 0.05)

between the abandoned (filled square) and cut (open square)

plots in lower shore grassland for 2003–2007. *P \ 0.05.

Diversity is measured by a species richness, b Shannon–

Wiener (H0) diversity index, c Simpson’s (D0) diversity index,

d Shannon–Wiener (J) evenness index and e Simpson’s (ED)

evenness index

90 Hydrobiologia (2012) 692:83–97

123

and 2007 when cut plots had low scores (Fig. 4b, c).

However, there were no significant treatment differ-

ences for the diversity indices, or for the evenness

scores, which gave similar results for cut and

abandoned plots (Fig. 4d, e).

Tall grassland

Community changes

The DCA performed for tall grassland samples

explained 39% of the total variation within the plant

community with axes 1 and 2 representing 28 and

11%, respectively. CCA and correlation analysis

showed not only that axis 1 was most significantly

related to time (r = 0.646, P = 0.001) and axis 2

negatively to treatment (r = -0.542, P = 0.000), but

also that there was significant interaction between

them. All point scores showed large deviation around

the mean along axis 1 of the DCA (Fig. 5), indicating

considerable internal community variation each year

irrespective of treatment. The effects of cutting are

unclear but appear small, since treatment points are

closely aligned along axis 1 each year and cut values

only diverge slightly from abandoned scores along

axis 2 (Fig. 5).

Species changes

Community changes over time were prompted by

increased bare ground and decreased Elytrigia re-

pens, as well as decreasing litter, and increasing

Festuca rubra, in cut plots (Table 3). Although

annual cover changes were generally small, there

was a shift in both treatments between 2004 and

2005, illustrated by the scores along axis 2 in the

DCA (Fig. 5). This was characterised by significant

increases in bare ground and the cover of Phragmites

australis, while litter and E. repens were significantly

reduced (Table 3).

Six species, and the cover of litter, showed

significant differences between cut and abandoned

treatments in the tall grassland during the experiment

(Fig. 6). Cutting favoured Festuca arundinacea, F.

rubra and Peucedanum palustre, with an increasing

trend and significantly more cover in cut than the

abandoned plots in 2004, 2007 and 2005, respec-

tively. For example, F. rubra increased from a mean

of 10.9% cover in the cut plots in 2003 to 22.9% in

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.2 0.3 0.4 0.5 0.6 0.7 0.8

Axis 1 Eigen value 0.075

Axi

s 2

Eig

en v

alue

0.0

2

Abandoned Cut

Ct 04

A 07

A 03

Ct 03

A 06Ct 06

A 05

Ct 07

Ct 05

A 04

s.d

s.d

Fig. 5 Detrended Correspondence Analysis of plant commu-

nity cover in tall grassland between 2003 and 2007. Mean

values ± 1 SE (n = 8) are shown, with each point labelled

according to the treatment (Ct cut and A abandoned) and year

of survey (03 = 2003, 04 = 2004, 05 = 2005, 06 = 2006 and

07 = 2007)

Table 3 Summary of significant (GLM, LSD post hoc, P value \ 0.05) temporal changes in abundance in the tall grassland for

abandoned and cut treatments

Variable 2003–2004 2004–2005 2005–2006 2006–2007

Ab. Cut Ab. Cut Ab. Cut Ab. Cut

Bare ground 0.017 (-) 0.347 0.020 (?) 0.004 (?) 0.615 0.432 0.229 0.598

Litter 0.106 0.165 0.000 (-) 0.000 (-) 0.000 (?) 0.003 (?) 0.552 0.015 (-)

Elytrigia repens 0.434 0.039 (-) 0.045 (-) 0.012 (-) 0.744 0.064 0.410 0.605

Festuca rubra 0.252 0.988 0.183 0.004 (?) 0.068 0.006 (-) 0.815 0.000 (?)

Phragmites australis 0.522 0.006 (-) 0.040 (?) 0.010 (?) 0.584 0.006 (?) 0.460 0.349

Variables with greater than 5% mean cover and results from the post hoc pairwise comparisons are shown. Significant P values are in

bold with (?) = significant increase and (-) = significant decrease. See Appendix—Electronic supplementary material for results of

the GLM analysis

Hydrobiologia (2012) 692:83–97 91

123

2007, whereas in the abandoned plots, this grass

began the experiment with a mean cover of 9.1% and

finished with 11% (Fig. 6). There was a greater cover

of E. repens, P. australis and Valeriana officinalis in

abandoned compared to cut plots (Fig. 6), including

significant differences in 2005 for E. repens and 2007

for V. officinalis. The cover of P. australis remained

relatively stable during the experiment in the aban-

doned plots at 15–18%, but was disadvantaged by

cutting, especially in 2004 and 2005 when it was

significantly affected. The cover of litter fluctuated

over time, including a marked decrease in 2005, and

tended to diverge between treatments, such that there

was significantly more litter in the abandoned plots in

2005 and 2007.

Diversity changes

Tall grassland species richness showed first a gradual

increase, then partial decline during the experiment in

25

20

15

10

5

02003

Litter2004 2005 2006 2007

Mea

n %

cov

er

25

35

30

20

15

10

5

0

Mea

n %

cov

er

2003Elymus repens

2004 2005 2006 2007

2003Festuca rubra

2004 2005 2006 20072003Festuca arundinacea

2004 2005 2006 2007

2003

Phragmites australis2004 2005 2006 2007 2003

Peucedanum palustre2004 2005 2006 2007

2003

Valeriana officinalis2004 2005 2006 2007

**

**

***

*

*

***

**

25

30

20

15

10

5

0

Mea

n %

cov

er

109876543210

Mea

n %

cov

er

25

30

20

15

10

5

0

Mea

n %

cov

er

25

35

30

20

15

10

5

0

Mea

n %

cov

er4

1

2

3

0

Mea

n %

cov

er

Fig. 6 Mean (n = 8, ±SE) abundance of species and vari-

ables with significant differences (GLM, LSD post hoc,

P value \ 0.05) between the abandoned (filled square) and

the cut (open square) plots for 2003–2007 in tall grassland.

*P \ 0.05, **P \ 0.01 and ***P \ 0.001. Note the different

axis scales

92 Hydrobiologia (2012) 692:83–97

123

both treatments (Fig. 7a), recording a significant

increase during 2004–2005 for both treatments

(GLM, LSD, P \ 0.05). The cut plots also showed

a significant increase during 2003–2004 and decline

during 2006–2007. Shannon–Wiener and Simpson’s

diversity indices reflect the richness results closely

(Fig. 7b, c), with no significant annual changes, but

the two evenness indices show more pronounced

fluctuations for both treatments (Fig. 7d, e), high-

lighted by significant annual variations for both in

2005–2007. Cut plots were consistently more species

rich than abandoned plots (Fig. 7a), exemplified by

mean values ranging from 15 to 18.9 species for cut

plots, and 13.1 to 17.3 species for abandoned plots,

although there were no significant differences. Mean

evenness values were higher in abandoned plots than

cut plots until 2005, after which treatment scores

were similar, and there were no significant differ-

ences between treatments at any time. Evenness

values may have been subdued by the abundance of

F. arundinacea and F. rubra in the cut plots, which

together achieved 50% mean cover by 2007, and by

F. arundinacea and P. australis in the abandoned

plots, which by 2007 represented 42% mean cover.

Discussion

Grassland dynamics

The lower shore community showed considerable

temporal changes, probably related to its hydrology,

2003 2004 2005 2006 2007

2003 2004 2005 2006 2007 2003 2004 2005 2006 2007

2003 2004 2005 2006 2007 2003 2004 2005 2006 2007

25

20

15

10

5

0

Spec

ies

rich

ness

2.4

2.6

2.8

3

2.2

2

1.8

1.6

Shan

non-

Wie

ner

Div

ersi

ty I

ndex

(H')

Shan

non-

Wie

ner

Eve

nnes

s In

dex

(J)

0.92

0.91

0.9

0.93

0.94

0.95

0.96

0.97

Sim

pson

Div

ersi

ty I

ndex

(D

') 0.94

0.92

0.9

0.88

0.86

0.84

0.82

0.8

Sim

pson

Eve

nnes

s In

dex 0.85

0.8

0.75

0.7

0.65

0.6

(E

D)

(a)

(b)

(d) (e)

(c)

Fig. 7 Mean (n = 8, ±SE) species diversity values and

significant differences (GLM, LSD post-hoc test, P \ 0.05)

between the abandoned (filled square) and cut (open square)

plots in tall grassland for 2003–2007. No significant

differences were detected. Diversity is measured by a species

richness, b Shannon–Wiener (H0) diversity index, c Simpson’s

(D0) diversity index, d Shannon–Wiener (J) evenness index and

e Simpson’s (ED) evenness index

Hydrobiologia (2012) 692:83–97 93

123

which was more variable than for the tall grassland

(see Berg, 2009). This is highlighted by the frequency

of its flood events, namely 4 in 27 months of

hydrological monitoring, compared to the tall grass

vegetation, which was not inundated. Moreover, the

lower shore grassland was regularly flooded for

several weeks, with mean depths up to 20 cm above

ground during the summer (Berg, 2009). The water

table was also characteristically higher in the lower

shore than the tall grassland, with water levels being

within 20 cm of the ground surface continuously for

the peak growing period of June to September in

2005 and 2006, whereas the rhizosphere was usually

drained in the tall grassland. Hydrological fluctua-

tions not only affect the distribution of adult plants

(Leyer, 2005) but also the emergence and establish-

ment of seedlings (Peterson & Baldwin, 2004), which

consequently modify community composition and

could explain temporal vegetation changes. Winter

storms and/or flooding in summer just before sam-

pling in 2005 provoked particularly pronounced

changes in the lower shore community. These were

greater than any annual cutting effect, with signifi-

cantly depleted Festuca rubra and Glaux maritima,

while evenness was significantly reduced as Juncus

gerardii dominated. This species is an important

forage resource for wildfowl (Rannap et al., 2004),

highlighting a potential value of flooding for nature

conservation.

The tall grass community showed considerable

inherent community variation, reflecting its more

diverse composition, but rather modest temporal

changes. Winter storms of 2004–2005, and/or high

water levels in summer 2005, however, prompted a

shift in community composition. Bare ground and

Phragmites australis significantly increased, and

litter and Elytrigia repens decreased significantly,

although there was some recovery in subsequent

years. It is likely that litter was scoured by storms,

leaving bare ground and an opportunity for the

robust, hydrophytic P. australis to expand.

Responses to cutting

A loss of bare ground and accumulation of litter is

commonly related to management cessation (Bakker,

1998; MacDonald et al., 2000; Pavlu et al., 2005),

such that the main ecological consequences of long-

term abandonment is a decrease in regeneration

niches (Grubb, 1977) and small-scale diversity (e.g.

Persson, 1984; Rosset et al., 2001; Bouchard et al.,

2003; Pavlu et al., 2005). Thus, management prac-

tices such as grazing and cutting are usually associ-

ated with the creation of gaps within the sward and

decreased litter through removal of above ground

biomass and associated disturbance, which often

leads to enhanced species diversity (Fossati &

Pautou, 1989; Gerard et al., 2008).

In this study, cutting lower shore grassland

produced significantly more bare ground and even-

tually less litter than in abandoned lower shore

vegetation, but species diversity was not enhanced.

However, positive impacts on species diversity in

other studies were only revealed after 5–10 years of

management (e.g. Bakker et al., 2002; Lindborg &

Eriksson, 2004), suggesting that the 5-year duration

of this study may have been insufficient to detect

significant cutting trends upon diversity. Indeed, bare

ground also increased slightly within the abandoned

lower shore plots, demonstrating that additional

environmental factors impinged on the plant com-

munity, such as prolonged flooding, which also

creates gaps within the sward. Thus, the pronounced

hydrological dynamics of the lower shore grassland

are likely to have contributed to the fluctuating

diversity of this community, irrespective of vegeta-

tion management. Agrostis stolonifera increased in

both the abandoned and cut lower shore, and was

significantly more abundant after 5 years in the

abandoned plots. This grass spreads laterally and

rapidly using its stolons, which may have given it a

competitive advantage over other species, such as F.

rubra, which is a less competitive grass of small

stature (Grime et al., 1988) and decreased during the

study.

In contrast to the lower shore, cut tall grassland

was generally more diverse than abandoned vegeta-

tion, although not significantly so. Cutting signifi-

cantly stimulated Festuca arundinacea abundance in

the short term. The removal of tall vegetation through

cutting at the start of the experiment may have

triggered the germination of short-lived transient

seeds (Grime et al., 1988) and the production of new

tillers (Gibson & Newman, 2001) of this species,

resulting in increased cover. The advantage was not

sustained, however, possibly because F. arundinacea

is sensitive to competition by other grasses (Gibson &

Newman, 2001) such as F. rubra, which was also

94 Hydrobiologia (2012) 692:83–97

123

favoured by cutting and was significantly more

abundant in cut compared to abandoned tall grassland

after 5 years. The colonisation of F. rubra is

relatively slow compared to fast-growing species

(Grime et al., 1988), but it may have benefitted over

time from the significantly reduced litter, Elytrigia

repens and P. australis in the cut plots compared to

the abandoned vegetation. Other species of relatively

small stature may also have been favoured by such

community changes following cutting, including the

forb Peucedanum palustre, which is of conservation

value as a food plant for butterflies but is sensitive to

competition (Meredith & Grubb, 1993).

Overall, the implementation of cutting led to

greater changes in composition and species abun-

dance in the lower shore community compared to the

tall grassland. Eight variables were significantly

affected by cutting in lower shore grassland (includ-

ing bare ground, litter, species richness and five

species) from a total of 24 that were measured (33%)

compared to only seven in the tall grassland (includ-

ing litter and six species) from a total of 39 (18%).

The greater responsiveness of the lower shore

grassland may have been related to its dynamic

hydrological regime, as the community is adapted to

a fluctuating hydroperiod featuring episodic and

sometimes prolonged flooding. It is possible that

cutting increased the level of disturbance and/or

stress above a threshold that affected plant abundance

and diversity in the frequently flooded grassland, and

that the lower shore community is characterised by

species with some ruderal traits (Grime, 1979) that

respond rapidly to changes. These results partially

concur with a study of Belgian restored floodplains,

which found that both flood frequency and mowing

affect species composition, but they differ in that

annual cutting and frequent flooding increased spe-

cies richness in the floodplain grasslands (Gerard

et al., 2008). In contrast to the lower shore, the tall

grassland featured a more stable water regime and

competitive species that respond more slowly to

changes, such that the community showed compar-

atively few effects of cutting, including any signif-

icant diversity impacts. Thus, species sensitive to

high disturbance or stress levels (e.g. F. rubra) were

negatively affected by cutting in the dynamic lower

shore grassland but favoured in the more stable tall

grassland. While this study was not an explicit test of

the role of diversity in wet grassland stability, the

results are consistent with Tilman (1999) who

suggested that species-poor communities are less

stable when stressed or disturbed compared to

species-rich communities, as there is more likelihood

that some species in diverse communities are able to

compensate for the reduction of competitors caused

by disturbance. However, Grman et al. (2010) found

that disturbed annual-dominated grassland communi-

ties were more stable than undisturbed perennial

communities, and that stability was maintained

despite losses in species richness, possibly because

of increased compensatory dynamics and increased

dominance by stable dominant species.

Conclusion: implications for restoration

This study has demonstrated that wet grassland plant

communities are dynamic and show differential

responses to cutting for restoration management.

Dynamism is dependent upon environmental factors,

illustrated in this study, particularly by hydrological

regime, which control plant community composition

and may interact with cutting to produce synergistic

effects. A greater proportion of significant changes

were observed in a species-poor lower shore grass-

land with a variable hydroperiod compared to a more

diverse tall grassland, which manifested some resis-

tance to cutting management during the 5 years of

study. This may have been because disturbance

thresholds were exceeded by the combination of

flooding and cutting in the lower shore grassland but

not in the tall grassland, where inundation was less

frequent and prolonged.

The relatively few significant changes that could

be directly attributed to cutting indicate that restora-

tion of abandoned wet grasslands may be a slow

process, in particular in communities composed of

highly competitive species such as the tall grassland

in this study. Cutting reduced the dominance of

competitive species in tall grassland (e.g. Phragmites

australis and Elytrigia repens) in the short term, to

the advantage of wet grassland species such as

Festuca arundinacea, Festuca rubra and Peuceda-

num palustre. More substantial community changes,

however, may only be apparent after many years or

with an increased level of disturbance, perhaps

through flooding, intensive grazing, burning or by

rotovating the grassland surface. Thus, if the

Hydrobiologia (2012) 692:83–97 95

123

restoration or management target is to remove

encroaching species or further enhance grassland

with residual diversity, then this may take consider-

able time and effort to achieve. However, the

apparent resistance of more diverse grasslands to

change may prevent rapid degradation in adverse

conditions, such as abandonment, inappropriate man-

agement, or even climate change, as the variety of

species present may help buffer impacts.

The significant changes in vegetation composition

observed in the lower shore grassland suggests that

cutting may have a more immediate and pronounced

effect in species-poor communities already subject,

and adapted, to environmental change, such as that

imposed by frequent flooding. In such circumstances,

restored vegetation management may impose addi-

tional disturbance upon the community, yielding

rapid species responses. However, the study has also

highlighted the importance of the hydrological

regime, and especially flooding, for restoring wet

grassland communities. If the target, therefore, is to

restore ‘naturally’ functioning wet grassland irre-

spective of plant diversity, then a dynamic hydrope-

riod incorporating water levels in the rhizosphere and

flooding may suffice.

Acknowledgments The study was funded by the Darwin

Initiative (Project Reference Number 162/13/013) and the

Earthwatch Institute. The authors would particularly like to

thank Elle Puurmann and Silvia Lotman for their support and

assistance in Estonia.

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