Białystok Univeristy. Bosch, J.M. and Hewlett, J.D., 1982. ...... De belangrijkste vragen zijn: hoe en in welke mate kunnen we systemen van laagveen en natte ...
Restoration of severely degraded fens: ecological feasibility, opportunities and constraints
UNIVERSITEIT ANTWERPEN Faculteit Wetenschappen Departement Biologie
Restoration of severely degraded fens: ecological feasibility, opportunities and constraints Herstel van sterk gedegradeerde laagveensystemen: ecologische haalbaarheid, kansen en beperkingen
Proefschrift voorgelegd tot het behalen van de graad van Doctor in de Wetenschappen aan de Universiteit Antwerpen te verdedigen door
Agata Klimkowska
Promotor:
Prof. Dr. R. Van Diggelen
Co-promotors:
Prof. Dr. W. Dembek (Institute for Land Reclamation
and Grassland Farming, Poland)
Prof. Dr. P. Meire
Commission members: Prof. Dr. K. Prach (University of South Bohemia,
Czech Republic)
Prof. Dr. A.P. Grootjans (Radboud University
Nijmegen, the Netherlands)
Prof. Dr. I. Nijs
Prof. Dr. S. Temmerman Antwerpen 2008
The research reported in this thesis was carried out at the Community and Conservation Ecology Group, University of Groningen, The Netherlands and at the Department of Nature Protection in Rural Areas, the Institute for Land Reclamation and Grassland Farming, Poland.
© 2008 A. Klimkowska; all rights reserved. Klimkowska, A. 2008. Restoration of severely degraded fens: ecological feasibility, opportunities and constraints. PhD thesis, University of Antwerp.
Layout: Gertjan Jobse Figures layout: Dick Visser Photographs: Ab Grootjans (p. 142 top), Agata Klimkowska & Gertjan Jobse Printed by: Print Partners Ipskamp, Enschede
contents Chapter 1
General introduction
Chapter 2
Wet meadow restoration in Western Europe: A quantitative assessment of the effectiveness of several techniques
19
Species trait shifts in vegetation and soil seed bank during fen degradation
39
Chapter 3 Supplement
Degradation of species-rich meadows on agriculturally used peatlands
69
Chapter 4
Seed production in fens and fen meadows
77
Chapter 5
Vegetation re-development after fen meadow restoration by topsoil removal and hay transfer
95
Chapter 5 Supplement
The soil seed bank and the soil abiotic conditions after topsoil removal
113
Chapter 6
Eco-hydrological analysis and prospects for restoration of a degraded fen – the Całowanie Fen in Central Poland
123
Chapter 6 Supplement A
Costs of restoration with topsoil removal Całowanie Fen case study, Poland
143
Chapter 6 Supplement B
Environmental costs of degrading fens – groundwater pollution and carbon losses
151
Chapter 7
Fen meadow restoration on severely degraded fens: a synthesis
159
References Summary - Samenvatting - Streszczenie Acknowledgements Curriculum Vitae & Publications
177 201 219 223
Chapter 3
7
Eriophorum angustifolium
chapter
1
General introduction
chapter 1
Motivation for this thesis Fens are geogenous mires, influenced by moving water, which has been in contact with the mineral bedrock and that is often groundwater seepage (Joosten and Clarke 2002; Van Diggelen et al. 2006). Fens were previously common in temperate Europe (Wheeler and Shaw 1995; Joosten and Clarke 2002) and occupied diverse habitats: the lower parts of the landscape, river valleys and seepage areas, all over the continent (Wassen et al. 1996; Godwin et al. 2002; Grootjans et al. 2006). Fens provide multiple goods and ecosystem services (Pfadenhauer and Grootjans 1999; Zedler 2000). They host a relatively high biodiversity, including many rare and endangered species (Wheeler 1988; Wheeler and Shaw 1991). They facilitate water purification, retain water and decrease the risk of floods and droughts (Mitsch and Gosselink 2000; Zedler and Kercher 2005). Peatlands, including fens (Joosten and Clarke 2002), serve as carbon sinks, actively sequestrating (Armentano and Menges 1986; Gorham 1991; Belyea and Malmer 2004) or storing carbon (Chapman et al. 2003; Mitra et al. 2005). Peat deposits also contain paleoecological information on vegetation and climate (Barber 1993). Nevertheless, the majority of fens in Europe have been transformed for agricultural purposes and have disappeared or became degraded with increasing land use intensity (Joosten and Clarke 2002; Bragg and Lindsay 2003; Vasander et al. 2003; Dembek et al. 2004a; Montanarella et al. 2006). Under low intensity use, moderate drainage, annual hay mowing and/or low intensity grazing, diverse ecosystems of fen meadows with rich fauna and flora have evolved (Wheeler 1980; Van Diggelen et al. 1996; Bakker and Berendse 1999). The term ‘fen meadows’ is not clearly defined. This term is used for different vegetation communities, vegetation resulting from developments of different systems and communities with a different nutrient status (Hájek et al. 2006). For this thesis, my working definition of fen meadows is: semi-natural meadows that developed from fens after low-intensity use, and which contain a diverse flora, including some of the species typical for fens (Van Diggelen et al. 2006; Middleton et al. 2006a). These ecosystems developed under moderate use by man and management is therefore necessary for their maintenance (Middleton et al. 2006b). These systems are vanishing across Europe, because of the human-caused transformation of habitats and ceasing of the traditional management (Kucharski 1999, 2000; Andrzejewski and Weigle 2003; Mountford et al. 2006). Socioeconomic changes over the past fifty years led to intensification in agriculture and changes in land use and landscapes (Barendregt et al. 1995; Van Diggelen et al. 2005; Wassen et al. 2006). Traditional management on fens has often stopped, with negative consequences for biodiversity.
General introduction
Not only were most of the fens transformed for agriculture, but many of them became severely degraded. Degradation of fen systems results in the loss of ecosystem functions and services (Millennium Ecosystem Assessment 2005). Under intensive drainage, the peat soils rapidly decompose (Okruszko 1995a; Zeitz and Velty 2002) and subside up to 0.8-1 cm yr-1 (Egglesmann 1986; Egglesmann et al. 1993). A temporary increase of the nutrient availability and productivity (O’Toole 1970; Succow 1988; Kajak and Okruszko 1990) is followed by a reduction of the biodiversity (Hodgson et al. 2005) and an increased nutrient leaching to groundwater (Van Beek et al. 2004; Tiemeyer et al. 2007). After decades of intensive drainage, a decrease in the productivity may occur (Succow 1988; Van Duren et al. 1997). Carbon losses from drained peat soils are large (up to 670 g CO2 m-2 yr-1) (Hogg et al. 1992; Zeitz and Velty 2002) and may increase even more under intensive grassland management (Armentano and Verhoeven 1990). Severely degraded fens are considered to be a source of environmental problems. The available data on the degree of fen transformation across Europe are inconsistent, thus it is impossible to assess what percentage of fens is severely degraded. However, data from Poland suggest that more than half of the reclaimed fens underwent severe changes, which points to the large scale of the problem. In the present thesis, I consider the possibilities for restoring degraded fens to a less degraded state, to improve the ecosystem functions with benefit for both biodiversity and local farmers.
Key concepts Abiotic conditions in fens and fen meadows In this thesis, I focus on systems of groundwater-fed fens, called soligenous fens. Groundwater that supplies such fens is usually rich in Ca, Fe, Mg; poor in N, P, Cl, SO42- and has a relatively high pH (Wassen et al. 1996; Wheeler and Proctor 2000). This result in low nutrient availability for plants and, in such conditions many stress-tolerant, poor-competitive species can co-exist (Verhoeven 1986; Olde Venterink et al. 2001, 2003). High water levels result in water saturation in the catotelm (permanent) and acrotelm (temporary), low oxygen availability, low redox potential, low microbial activities and low decomposition rates (De Mars et al. 1997; De Mars and Wassen 1999). Additionally, these fens are also supplied with rainwater and can be flooded by rivers, both modifying nutrient cycling processes (Grootjans et al. 1988; Wassen et al. 1990; Koerselman et al. 1993; Wassen and Joosten 1996). Nutrient cycling affects the productivity and the vegetation development. This also results in a gradient from low-productive, nutrient-poor fens (sedge-moss fens), to productive, nutrient-rich fens (for example tall sedge fens).
chapter 1
Low intensity use on semi-natural fen meadows only slightly interrupts the hydrological regimes, but suppresses highly competitive species and slows down the vegetation succession (Wheeler and Shaw 1994; Kotowski and Van Diggelen 2004). Centuries of biomass removal with no fertilization resulted in nutrient impoverishment (P, K) and limitations of vegetation productivity (Olde Venterink et al. 2001). This resulted in co-existence of many plant species, including lowcompetitive ones.
Environmental degradation Deterioration of resources such as water and soil and the destruction of ecosystems lead to environmental degradation. This process accelerated over the past fifty years, causing irreversible changes in ecosystems (Millennium Ecosystem Assessment 2005). For example, about 60 % of world ecosystem services has been degraded. Species extinction rates are 100-1000 times above the background rate. Human use of the available fresh water worldwide increased to 40 % (Millennium Ecosystem Assessment 2005). The regional and global scale factors that contribute to fen degradation are: changes in hydrological systems, subsequent desiccation and degradation of peat soils, climate change, habitat deterioration (eutrophication, acidification), habitat fragmentation and isolation (high extinction risk and lower re-colonisation chances) and the consequent loss of species richness (Saunders et al. 1991; Hannah et al. 2002; Chapman et al. 2003; Dembek et al. 2004a; Krauss et al. 2004; Van Belle et al. 2006; Picó and Van Groenendael 2007).
Ecological restoration Ecological restoration is the process of assisting in the recovery of an ecosystem that has been degraded, damaged or destroyed. It is an intentional activity that initiates or accelerates an ecological pathway or trajectory through time, towards a reference state (Society for Ecological Restoration 2006). Defining realistic goals and evaluating success is crucial in restoration (Hobbs and Norton 1996). The concept of a reference vegetation or reference system is useful in setting restoration goals. There are several ways to define references: historical, geographical, functional, etc. In the case of historical references, actions aim at restoration of a system back to its former state. Historical references require reliable data and often rely on a set of species, but may overlook unmeasured factors (White and Walker 1997). Using historical references may intend to bring back the situation from the recent past, which in the present conditions might be impossible, because
10
General introduction
of changed landscape settings and human-induced processes (e.g. acidification, nitrogen deposition). Well-preserved ecosystems near-by, or natural sites in a distant location might be also used as a reference. This provides contemporary data on such systems and may guide restoration of certain processes and functions. Such references are an approximation or an analogy to what a restored system could become. However, because of a high degree of ecological variation in plant communities and site-specific processes (White and Walker 1997), they may not be exact matches. Also, on-going changes of the ‘reference’ might mean that it is already at some stage of degradation. Different concepts of nature result in different goals for restoration. They vary with respect to the focus (e.g. target species vs. functions), the spatial and temporal scale (e.g. species vs. landscape; time-scope of years vs. centuries), and the level of ambition (e.g. restoring of the original system vs. improving conditions) (Ehrenfeld 2000; Van Diggelen et al. 2001; Hobbs and Harris 2001). Common goals of ecological restoration are target species or vegetation types, entire systems or functions.
Target species or vegetation types The common approach driving most restoration actions is protection, revival or re-establishment of rare and/or endangered species. These species might or might not be a key species for a given ecosystem, but they are often the most sensitive to habitat change, hence they disappear first (Grime 2002). Focusing on rare species, without considering the broader site situation, is insufficient (Grootjans et al. 2002; Roberge and Angelstam 2004). Stochastic or genetic processes might influence small and isolated populations and lead to their extinction (Schemske et al. 1994; Hanski 1998). Therefore, putting all effort into maintaining or re-introducing a few species without considering their chances for long-term survival is usually unsuccessful. Nevertheless, the concept of target species is useful. Such species could indicate the presence of suitable habitats and a “healthy” system (Launer and Murphy 1994; Bakker and Berentse 1999; Caro and O’Doherty 1999). This is a clear and measurable tool for evaluating the restoration success (Miller and Hobbs 2007) and can be easily communicated to the public (e.g. flagship species). Such ‘focal species’ are an issue for policy-makers and funding institutions. However, one should realize that the outcomes of restoration depend strongly on pre-defined target species, because references and optimal conditions for different species can be contrasting (Harris and Van Diggelen 2005). Target species are often associated with certain vegetation types, which can then be defined as target communities (Bakker and Berentse 1999; Bakker et al. 2000). This broader definition of the goal allows for more space for natural developments
11
chapter 1
of plant communities, with a variety of species interactions. If a target vegetation continues to develop for a long period of time, it is an indicator that restoration was successful. This goal overlaps with the restoration of biological diversity, mostly in the sense of species richness (α diversity) (Whittaker 1972). Restoration of biodiversity (Bakker et al. 2000) incorporates concepts of species interactions, thus stable and co-existing populations of various organisms are the anticipated outcome of restoration. Biodiversity also provides a link to ecosystem characteristics and ecosystem restoration (Naeem et al. 1994; Tilman et al. 1996).
Recovery of a system For durable restoration of target species and vegetation, we need to consider a larger scale than just protected islands of nature reserves. Landscape ecology (Naveh 1994) and eco-hydrology (Grootjans et al. 1996; Wassen and Grootjans 1996) contributed to the system restoration approach, which is relevant to fen and wetland restoration (Grootjans et al. 2006). The existence and quality of fens or fen meadows depend on the landscape settings, the functioning of the hydrological systems and bio-chemical processes, including those taking places in the surrounding areas (Grootjans et al. 2002; Lamers et al. 2002). Hence, one should consider a fen system - a section of the landscape that keeps the fen in a stable condition (Grootjans and Van Diggelen 1995) - as a goal for restoration. System recovery considers ecosystem components (abiotic habitat and biota) together with the processes that support them, while restoration of a function may focus on a selected process, with or without the presence of biotic and abiotic components.
Re-installing selected functions The functions or services of fen ecosystems (Costanza et al. 1998), such as water storage, water purification or carbon sequestration can also be subjects of restoration (Zedler 2000, 2003). Restoring a selected function of an ecosystem or restoring a set of functions within a different ecosystem type are feasible from an ecological point of view and probably more suitable for changing conditions. The ecosystem services can be expressed in monetary values and compared with other economic activities. This makes restoration more attractive from a socioeconomic perspective, as it helps to convince general public that ecosystem restoration is necessary. Although ‘restoration of a function’ approach seems easier to implement than restoring a set of target species, actions aimed at multiple services of an ecosystem require a firm knowledge of species, communities and processes as well as the ability to project this into the future (Hobbs and Harris 2001; Kremen 2005).
12
General introduction
Methods of ecological restoration Preserving hydrological regimes and mowing or grazing are adequate methods to prevent degradation of existing fen meadows, but are not sufficient for the restoration of severely degraded fens (Kotowski 2002; Grootjans et al. 2002). Improvement of environmental conditions in severely degraded fens is obviously necessary. This entails increasing wetness (by raising water levels) (Wassen et al. 1990; Jansen et al. 2000) and decreasing nutrient availability (Verhoeven et al. 1996; Van Duren et al. 1997). Various restoration methods were tested on moderately transformed fen meadows, but there is hardly any knowledge on how these methods work on severely degraded areas. Three selected methods: rewetting, topsoil removal and seed transfer are described below. Wetlands can be restored only under suitable climatic and hydrogeological conditions (Bedford 1999). Rewetting is a frequently proposed and widely used method (Pfadenhauer and Klötzli 1996; Pfadenhauer and Grootjans 1999). Existing examples suggest that rewetting alone might not be sufficient to restore severely degraded fens, especially when nutrient- or sulphur-polluted water is used (Lamers et al. 2002). Lowering the availability of nitrogen and phosphorus has been indicated as a necessary step in fen restoration (Van Duren et al. 1997; Olde Venterink et al. 2002). Topsoil removal has been proposed as a radical method to address these issues. This method was proven to be effective in nutrient impoverishment on mineral soils or soils with a shallow organic layer (Verhagen et al. 2001; Tallowin and Smith 2001). Yet, it has rarely been applied to peat soils (Ramseier 2000; Patzelt et al. 2001) and no such experience exists on severely degraded peatlands. Improving abiotic conditions alone may not be sufficient to restore fens or fen meadows. The target species have been eliminated from intensively used areas and they are lacking in local and regional species pools (Zobel et al. 1998). The lack of propagules and/or micro-sites for establishment is the bottleneck for successful restoration of species-rich fen meadows (Bakker et al. 1996; Bakker and Berendse 1999; Coulson et al. 2001; Grootjans et al. 2002; Isselstein et al. 2002). Likely, the soil seed banks cannot facilitate re-establishment of species-rich fen meadows (McDonald et al. 1996; Matus et al. 2003). Next to that, the dispersal capacity of target species is, in general, low (Poschlod and Bonn 1998; Soons et al. 2005; Van den Broek et al. 2005). To overcome the seed availability limitation, some seed transfer methods have been introduced. Often, seeds are transferred from species-rich, local provenance donor meadows with hay. Direct sowing with seed mixtures, transfer of soil, planting seedlings or sods transplanting are also sometimes used (Bruelheide and Flintrop 2000; Bank et al. 2002; Vécrin and Muller 2003; Walker et al. 2004), but hay transfer remains the most popular technique. Some studies demonstrated that
13
chapter 1
hay transfer combined with topsoil removal can be very successful (Patzelt et al. 2001; Hölzel and Otte 2003; Kiehl et al. 2006). However, this combination of methods has not been tested on severely degraded fens yet. Various other processes may determine the establishment of the target species, including the availability of micro-sites (Grubb 1977; Grace 1999), seedling competition (Ramseier 2000; Donath et al. 2006), the abilities for vegetative growth (Tallowin and Smith 2001) or successful reproduction (Vergeer et al. 2003; Hooftman et al. 2004; Kwak and Bekker 2006). Vegetation development in newly restored sites is often unpredictable and may follow an undesired trajectory (Klötzli and Grootjans 2001; Walker et al. 2004). Hence, it is valuable to study the vegetation re-establishment on degraded fens after restoration, in order to improve our understanding of the effects of different methods on the processes in the vegetation.
Outline of the thesis The central issue of this thesis is: how and to what extent we can restore fen systems on severely degraded peatlands and what the major constraints limiting successful restoration are. In this thesis, I focus on the processes related to vegetation development in restored meadow communities. I also focus on the effects of a novel restoration method: topsoil removal and propagule transfer. I combine research on different aspects of vegetation development and eco-hydrological studies. The applied dimension includes an assessment of the ecological effectiveness of selected restoration methods on severely degraded fens in Poland and some socioeconomic aspects of such restoration. I use Całowanie Fen (Bagno Całowanie) in Central Poland, as a model system of a severely degraded fen. Several other sites in Poland, Germany and the Netherlands were used to represent fens and fen meadows in different stages of transformation (Fig. 1.1). A pilot restoration project in the model system was carried out with the aim to improve the habitat conditions and restore the species-rich, mesotrophic fen meadows and/or the moderately eutrophic fen meadows (Caricion nigrae and/or Calthion palustris alliances, after Matuszkiewicz 2001).
14
General introduction
In this thesis, I discuss the following key-topics: 1. Possibilities to restore species-rich fen meadows on severely degraded fens with methods of topsoil removal, hay transfer and rewetting (chapter 2, 5). 2. Presence of biotic constraints, related to past vegetation development, the soil seed bank and seed production, affecting the restoration process (chapter 3, 4, 5). 3. The restorability of the fen meadow on severely degraded fens, depending on the processes in the vegetation and the possibility to secure stable hydrological regimes in the surrounding landscape (chapter 3, 6). In chapter 1, I introduce the key concepts and background of this research. In chapter 2, I evaluate the quantitative effects of restoration on the plant community composition in semi-natural wet meadows in Western Europe. I focus on the effects of three methods: rewetting, topsoil removal and seed transfer. I investigate the effects of the selected methods on the overall restoration success and whether the topsoil removal depth and the type of seed transfer material affect the degree of success. In chapter 3, I analyse shifts in life strategies, trait combinations and seed bank types in plant communities during fen degradation. Ecological processes, such as fen degradation, work on the level of plant traits, rather than on species’ identities (Diaz et al. 2002; Pywell et al. 2003). As a result, shifts in trait combinations may occur in the vegetation and in the soil seed bank. These may have consequences for the restoration possibilities. Hypothetically, the soil seed bank can provide propagules for re-development of the target vegetation (Maas and Schopp-Guth 1995), but it can also be a source of persistent seeds of unwanted species (see e.g. Bossuyt and Hermy 2003). The soil seed bank of severely degraded meadows is poorly studied. I investigate the soil seed bank density and longevity during the degradation process. In chapter 4, I estimate the size and composition of the seed production in plant communities of fens, fen meadows and degraded meadows. The seed production in these plant communities is hardly known, although even rough estimates would be relevant for nature management and restoration. In restoration practice, the seed availability limitation can be overcome by hay transfer. A base-line assumption is that a community similar to a donor meadow will develop after hay transfer. However, when the similarity between the vegetation composition and the seed composition is low (Rasran et al. 2006), the restored vegetation may be different from the desired one. Seed production may have important consequences for the invasibility of a community (Davis et al. 2005). Therefore, it will also affect the chance to develop species-rich fen meadows. I expect a positive relationship between the number of
15
chapter 1
4
3
2 1
Figure 1.1 Location of the study sites: 1 – Całowanie Fen (Poland); 2 – Lipsk Fen (Poland); 3 – Gützkow Wiesen (Germany); 4 – Kappersbult, Drentse Aa (the Netherlands).
seeds produced and the drainage intensity. I also expect a higher similarity between vegetation composition and seed composition in degraded meadows than in undrained fens. In order to better understand the processes in the vegetation development after topsoil removal combined with hay transfer, I carry out a field experiment, described in chapter 5. In the field experiment, I manipulate the depth of the topsoil removal, the availability of seeds and the access of large animals. I assess the effects of the seed transfer with hay and the local soil seed bank on the species abundance in the vegetation. I investigate the development of vegetation over time in different treatments and compare it to the reference and the degraded vegetation. In chapter 6, I present an eco-hydrological study of the model system Całowanie Fen. The restoration prospects of a degraded fen depend on the hydrological conditions and the landscape settings of the peatland and its surroundings (Grootjans and Van Diggelen 1995; Grootjans et al. 1996). In this chapter, I take a system restoration approach. I examine the functioning and transformations of the system and how changing land use may affect the restoration prospects. These analyses help to identify the limitations that arise from conditions outside the area, define feasible restoration targets and propose appropriate actions.
16
General introduction
Finally, in chapter 7, I combine and discuss the findings of previous chapters. I elaborate on the success factors and constraints of restoration. I assess the ecological prospects of fen meadow restoration and possible scenarios for severely degraded peatlands. I also shortly present other considerations for restoration on severely degraded fens and challenges for future research. I provide additional information and identify some knowledge gaps in several supplements to the chapters. The supplements are relevant to the main thesis questions and to the general discussion. The supplements, however, do not comprise work that could be published in a peer-reviewed journal. In the supplement to Chapter 3, I discuss the degradation of species-rich meadows on agriculturally used peatlands and some socioeconomic aspects of it. In the supplement to Chapter 5, I describe the soil seed bank and the abiotic conditions after topsoil removal. In the supplements to Chapter 6, I discuss the environmental and economical costs and benefits, associated with restoring the degraded fens. This thesis has been prepared according to the western European standards and follows a model of several peer-reviewed publications, combined in a comprehensive work. I am the first author of all the chapters and I accomplished most of the field and laboratory work, data analysis and preparation of the publications. The coauthors contributed by advising, supervising the work, and providing part of the unprocessed data.
17
Topsoil removal in Bargerveen, the Netherlands
chapter
2
Wet meadow restoration in Western Europe: A quantitative assessment of the effectiveness of several techniques Agata Klimkowska, Rudy Van Diggelen, Jan P. Bakker and Ab P. Grootjans
Biological Conservation 140 (2007) 318-328
chapter 2
Abstract Techniques such as rewetting, topsoil removal, diaspore transfer or combinations of these are increasingly applied in fen meadow and flood meadow restoration in Western Europe. In this paper, we present a quantitative assessment of the effectiveness of the commonly used meadow restoration methods. We use the change in ‘saturation index’ to evaluate the degree of success. The index reflects the completeness of restored communities in comparison to regional target communities. Meadow restoration has limited success in most cases, with an average increase in species richness below 10 % of the regional species pool. Restoration success was partly determinated by the starting situation. The more species-rich the starting situation, the higher the saturation index after restoration but, at the same time, the smaller the increase in the number of target species due to restoration. Topsoil removal and diaspore transfer were found to contribute most to restoration success. A combination of topsoil removal and diaspore transfer and a combination of all three techniques appeared to be the most effective measure and resulted in an increase in the saturation index of up to 16 %. Rewetting alone had no measurable effect on restoration success.
Key words restoration success; rewetting; topsoil removal; diaspore transfer; Saturation Index
20
Effectiveness of wet meadow restoration
INTRODUCTION Between 50 to 90 % of wetland ecosystems on organic soils have been lost in Europe (Joosten and Clarke 2002). Particularly fens were transformed into meadows, pastures or arable land. Recently there is increasing concern to conserve and restore fens and fen meadows for their high biodiversity and characteristic plant species (Tallowin and Smith 2001). Much knowledge in the field of semi-natural meadow restoration already exists in Western Europe, but a quantitative assessment of the project outcomes is often missing. The main causes of fen degradation are drainage and associated peat degradation (Wild 1997; Chapman et al. 2003; Rupp et al. 2004), acidification (Grootjans et al. 2002) and eutrophication (Wassen et al. 1998; Lamers et al. 2002). Rewetting, therefore, is considered as a conditio sine qua non for fen meadow restoration (Grootjans and Van Diggelen 1995; Pfadenhauer and Klötzli 1996). A second essential condition for fen meadow restoration is a reduction in trophic status. A radical technique to lower nutrient availability is to remove the entire topsoil. This measure proved to be quite successful on mineral soils (Verhagen et al. 2001; Tallowin and Smith 2001; Hölzel and Otte 2003), but little experience exists for organic soils (but see Patzelt et al. 2001; Beltman et al. 2001). However, only restoring environmental conditions may not be enough. A sufficient number of viable propagules of target species and appropriate conditions for germination and establishment should be present (Verhagen et al. 2001; Hölzel 2005). Many authors showed that the soil seed bank is often an insufficient source for re-colonisation (Maas and Schopp-Guth 1995; McDonald et al. 1996; Jensen 1998). Seed dispersal is often too limited to compensate for this deficiency (Poschlod and Bonn 1998; Vécrin et al. 2002; Middleton et al. 2006c). Seed dispersal of fen or flooded meadow plants, measured in the field was proven to be very limited (Van Dorp et al. 1996; Bischoff 2002), despite adaptations such as high buoyancy (Van den Broek et al. 2005). Therefore, addition of diaspores has been introduced as a technique in meadow restoration (Hölzel and Otte 2003; Kiehl and Wagner 2006). Successful restoration was also achieved by other variants of species addition: seeding, transplanting or transferring soil from donor areas (Klötzli 1987; Bruelheide and Flintrop 2000; Bank et al. 2002; Vécrin and Muller 2003). The present paper aims at a quantitative assessment of restoration efforts in seminatural wet meadows. We focus on the effects of three, afore mentioned, restoration techniques: rewetting, topsoil removal and diaspore transfer. These techniques are compared with respect to the effect they have on the plant community composition. A systematic, in-depth meta-analysis is not possible due to lack of sufficient goodquality data.
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chapter 2
Research questions We started the analysis by measuring the degree of resemblance in species composition between restored meadow communities and regional reference vegetation types (a). Next, we investigated the relation between degree of change in plant richness and the initial plant community composition (b). Then we analysed the relative effect of the the three restoration techniques on the overall restoration success (c). In a limited number of cases we had more detailed information on the depth of topsoil removal and type of diaspore material used for transfer. In these cases, we analysed whether removal depth and type of transfer material affect the degree of success (d).
MATERIALS AND METHODS Selection of systems We focus on three semi-natural meadow types. Mesotrophic fen meadows (MFM, 1) of the Junco-Molinion (or Molinion) communities occur in nutrient-poor sites, often after long-term hay making without fertilization. Eutrophic fen meadows (EFM, 2) (Calthion palustris) occur often on deep peat soils, along fen margins and brooks or after moderate drainage and fertilization of fens. Flood meadows (FM, 3) of the Lolio-Potentillion anserinae, Alopecurion pratensis or Cnidion alliances develop in regularly flooded sites. All three meadow types occur on peat soil (O), on mixed organic-mineral or mineral soils. The latter two soil types were combined into one category (M/O).
Data compilation Unfortunately, there are no electronic databases available with records of wet meadows restoration and we, therefore, had to obtain the data through professional networks and experts (e.g. Society for Ecological Restoration). We used peer-reviewed, published sources and records of conservation agencies of projects performed in Western Europe, located on organic or mixed mineral-organic soils. Data on plant species composition from before and after the intervention came from permanent plots or relevés taken for monitoring purposes. No independent reviewer check on data quality could be performed. We obtained information on project location, meadow type (MFM, EFM, FM), soil type, techniques applied, land use before restoration (meadow or arable field) and
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Effectiveness of wet meadow restoration
species composition of the vegetation. Whenever possible, we included information on the period since restoration (age), approximate surface area, topsoil removal depth and type of diaspore material in the analysis. Concerning rewetting, the specifications of the adopted technique, such as sources of water, extent of water-level rise or fluctuation patterns are known to affect the outcomes of restoration (e.g. Lucassen et al. 2005a). Unfortunately, these details were often missing. As we aimed at a general evaluation, we defined ‘rewetting’ as any type of activity leading to an increase in wetness of a site. Similarly, the factor ‘diaspore transfer’ comprises various activities, all aiming at bringing new species to a site.
Comparison method Various studies differed in their objectives and methodologies, and data differed in quality. Some studies were set up as scientific experiments, whereas others were poorly documented projects. We quantified the effect of the restoration by comparing the local vegetation composition with the regional species pool (Zobel et al. 1998) for a particular meadow type and expressed it as a saturation index (SI). This saturation index concept (Wolters et al. 2005) enables to quantify and compare the success of restoration experiments in different countries and on different sites. SI expresses the proportion of the regional species pool that is actually recorded at a given site and consists of a value between zero and one. The saturation index estimates the ‘completeness’ of the community, but does not give an idea about the ‘nature conservation interest’ of the vegetation. It shows the similarity of the recovering community to the typical community of a particular meadow type for a given region. We used presence-absence data to calculate this index. We selected three geographical regions (the Netherlands, Germany and the United Kingdom), differing in the number and type of species, and three meadow types. The regional species pools of the three types of wet meadows were derived from frequency tables in the literature. For the Netherlands we used Schaminée et al. (1996), for Germany Oberdorfer (1977) and for the United Kingdom Rodwell (1992) (Table 2.1). Species were included in the species pool if they occurred with a frequency exceeding 20 % in the description of a particular vegetation type. We refer to these species as ‘target species’. We used changes in saturation index before and after restoration (ΔSI) as an indicator of restoration success: ΔSI = SI after restoration – SI start situation, expressed as absolute value. We used data from before the restoration or data from control plots to calculate ΔSI. When we could not obtain data on the initial community
23
chapter 2
composition, we made the following assumptions. If the restoration was conducted on former arable land we assumed that the starting situation SI = 0. If the restoration was conducted on agriculturally improved grassland, we estimated the starting SI on the basis of species lists of agricultural grasslands in the region. One study from three sites in the Netherlands (Kolham, Dannemeer, Woudbloem), showed that there were no significant changes in the total number of species (t=1.32, p=0.2; n=12) in the starting situation and after 3 years in the control plots (no treatment applied). The overlap in species composition was above 60 %. The appearance of one or two species per sample from the regional species pool in the control treatment contributed little to the saturation index. We, therefore, assumed that changes in the community composition are also in other areas the result of the applied restoration measures, especially when we consider a short period of time.
Data analysis Prior to analysis, the indices (SI after restoration and ΔSI) were transformed with the function: SItransf. = ln (SI + 1) to improve the normality of the distribution. If for a given location and restoration technique plots were replicated, we averaged individual SI’s and used one value. The number of observations with different restoration techniques applied was in some cases somewhat unbalanced (Table 2.2). Most of the data originated from the Netherlands, while studies from other countries were under-represented. In our data, some combination of techniques might be more often used than others, thus we checked for strong inter-correlation between techniques, using variance inflation factors. We assumed that the data originating from scientific studies with replicates and registered start situations or controls are of better quality than other data. Due to strong dichotomies in the results of the analysis of both sub-sets (revealed in sensitivity analysis, not presented here), we used only the sub-sets of better quality data for further analysis. We used a Student t-test to investigate the questions (a) and (d). For question (b) we used regression analysis. We performed a main-effect ANOVA, to determine the factors influencing restoration success (c). Prior to the analysis, we tested whether the criteria of normality and of homogeneity of variance were met. Due to the limited number of data, we could not test for any interaction effects between the different restoration techniques and with meadow type. Our main intention in the analysis was to evaluate the effectiveness of different restoration techniques, including their
24
Effectiveness of wet meadow restoration
Table 2.1 Reference vegetation types per meadow type and geographic region (Schaminée et al. 1996; Rodwell 1992; Oberdorfer 1977). The number of species included in the regional species pool is given in bold.
Meadow type
Mespotrophic fen meadow
The Netherlands (used also for Eastern France)
Junco-Molinion alliance 47
Germany (used also for Switzerland)
UK (used also for West Norway)
Juncion acutiflori, Molinion alliances 81
Juncus subnodulosusCirsium palustre M22, Juncus effusus/acutiflorusGalium palustre M23, Molinia caerulea - Cirsium dissectum M24, Molinia caerulea - Potentilla erecta M25 71
Eutrophic fen meadow
Calthion alliance 41
Calthion palustris alliance 47
Cynosurus cristatus-Caltha palustris MG8, Holcus lanatus-Deschampsia cespitosa MG9, Holco-Juncetum effusi MG10, Filipendula ulmariaAngelica sylvestris M27, Iris pseudacorus-Filipendula ulmaria M28 80
Flood meadow
Lolio-Potentillion anserinae Alopecurion pratensis alliances 50
Cnidion alliance 36 Agropyro-Rumicion alliance 15
Alopecurus pratensisSanguisorba officinalis MG4, Festuca rubra-Agrostis stoloniferaPotentilla anserina MG11, Agrostis stolonifera-Alopecurus geniculatus MG13 56
Table 2.2 Number of observations per restoration technique. Rewetting
Topsoil removal
No diaspore transfer
Diaspore transfer
Total
No rewetting
No
(92)
6
6
No rewetting
Yes
10
13
23
10
19
29
Total Rewetting
No
16
7
23
Rewetting
yes
23
17
40
Total
39
24
63
Total
49
43
92
25
chapter 2
combinations. Therefore, we re-arranged the data, grouped them according to the restoration techniques applied and tested the effect of combined restoration measures with the Kruskal-Wallis non-parametric test. For preliminary data exploration we used histograms. All analyses were performed with the Statistica 7 package for Windows.
RESULTS Data overview Data from 36 sites were collected, resulting in 119 individual observations (Appendix 2.1). Due to the lack of reliable records on the initial situation in some observations, we could only use 92 observations for further analyses. The majority of the observations came from the Netherlands, usually 3-5 yr after restoration and from small-scale (< 1ha) projects. Preliminary data exploration showed no relation between the restoration success (ΔSI) and country, soil type, age or size. The variance inflation factors (meadow type 1.010; rewetting 1.103; soil removal 1.055; transfer 1.048) showed that inter-correlation between the predictors is minimal. The saturation index after restoration increased significantly from 0.16 to 0.23 (t =-3.18, p 1000 = 4
Seed mass
Value seed weight [mg]
Continuous
average mass [g]
Flowering period
Flowering period (end - start)
Ordinal
1 = one month, 2 = two months, etc.
Strategy CRS Persistence Canopy height
Clonal growth
Regeneration
60
0.21
0.36
0.29
0.36
0.26
0.25
0.20
0.42
0.37
n.d.
0.21
0.37
0.26
Carex elata
Carex panicea
Galium uliginosum
Carex flava + C. lepicocarpa
Carex acutiformis
Carex lasiocarpa
Cirsium palustre
Lychnis flos-cuculi
Agrostis stolonifera
Carex diandra
Myosotis palustris
Poa pratensis
Epilobium palustre
V
0.1
0.3
0.2
0.1
0
0.5
1
0.8
0
1
0.9
0.9
0
0.5 1651.9 (178)
1147.1 (105)
57.6 (6)
70.2 (7)
82.7 (8)
85.4 (8)
95.3 (9)
122.4 (11)
261.3 (24)
262.7 (25)
322.7 (31)
550.0 (53)
616.3 (59)
9.5 (1)
0.0
0.0
0.0
194.9 (21)
35.2 (4)
0.0
336.6 (38)
244.9 (30)
1517.4 (219)
204.9 (23)
252.7 (28)
17119.7 (1922)
Seed density 0-5 cm 829.0 (80)
Seed density 5 - 10 cm
8585.3 (815)
Seed density 10 - 15 cm 18.9 (2)
0.0
0.0
0.0
27.9 (3)
0.0
0.0
286.2 (30)
193.2 (20)
579.9 (109)
0.0
154.5 (16)
375.6 (39)
5563.6 (585)
L class sp
t
t
t
lp
sp
sp
lp
lp
lp
sp
sp
lp
lp
0
0.6
0
0
0
0.4
0.3
0.2
0
0
1
0
0.1
0.7
V
Seed density 0-5 cm 8.0 (1)
1717.2 (216)
190.8 (24)
55.7 (7)
0.0
0.0
0.0
0.0
Symbols: LI = Longevity Index, V – frequency in the aboveground vegetation, L class – the longevity classification (t - transient; sp - short-term persistent; lp – long-term persistent).
0.91
LI
Juncus articulatus
0.0
174.9 (22)
8.0 (1)
0.0
0.0
0.0
0.0
0.0
Seed density 5 - 10 cm
L class sp
sp
sp
t
t
t
t
t
0
0.6
0
0
0
0.5
0.2
0
0
0
0.8
0
0
0
degraded meadow
47.8 (6)
167.2 (21)
0.0
0.0
2260.6 (284)
Seed density 0-5 cm
fen meadow
24.6 (3)
458.4 (58)
0.0
15.3 (2)
3256.3 (428)
Seed density 5 - 10 cm
fen
V
Appendix 3.2 Species composition and abundance in the aboveground vegetation and in the soil seed bank of a fen (Lipsk Fen), fen meadow (Gützkower Wisen) and degraded meadow (Całowanie Fen). In the table seed density (number of seeds m-2) is given together with number of seedlings counts (in brackets).
L class sp
lp
t
lp
lp
Species trait shifts during fen degradation
61
0.07
0.20
0.64
0.38
0.37
0.37
0.48
0.53
0.44
0.69
0.11
0.04
0.28
0.20
0.07
0.00
0.14
0.11
0.48
0.05
0.00
0.00
0.00
0.17
Lycopus europeus
Epilobium hirsutum
Potentilla erecta
Lythrum salicaria
Sagina nodosa
Conyza canadensis
Betula pubescens
Linum catharticum
Typha latifolia
Carex rostrata
Potentilla palustris
Carex chordorriza
Galium palustre
Parnassia palustris
Menyanthes trifoliata
Festuca rubra
Caltha palustris
Cardamine pratensis
Crepis paludosa
Salix cinerea
Carex appropinquata
Valeriana officinale
Calamagrostis stricta
LI
Eriophorum angustifolium
V
0.5
0.5
0.6
0.6
0.6
0.8
0.8
0.9
1
0.6
0.4
0.1
0.4
0.8
0
0.3
0.4
0
0
0.1
0.1
0
0.4
0.5
Seed density 0-5 cm 0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
9.3 (1)
9.6 (1)
11.2 (1)
30.5 (3)
31.7 (3)
31.7 (3)
33.6 (3)
33.8 (3)
35.0 (3)
44.2 (4)
Seed density 5 - 10 cm 0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
8.6 (1)
17.5 (2)
26.1 (3)
26.5 (3)
270.7 (25)
9.5 (1)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
19.3 (2)
0.0
Seed density 10 - 15 cm 0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
117.2 (12)
0.0
164.1 (17)
9.7 (1)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
L class t
t
t
t
t
t
t
t
t
lp
lp
lp
lp
lp
lp
t
t
sp
sp
t
t
sp
sp
t
V 0
0.6
0
0
0.5
0.1
1
1
0
0
0.6
0
0
0
0
0
0
0
0
0.1
0
0.2
0
0.1
Seed density 0-5 cm 0.0
0.0
198.8 (25)
985.8 (124)
63.6 (8)
437.3 (55)
71.6 (9)
0.0
31.8 (4)
8.0 (1)
63.6 (8)
437.3 (55)
0.0
0.0
8.0 (1)
0.0
182.9 (23)
0.0
31.8 (4)
15.9 (2)
0.0
0.0
8.0 (1)
0.0
127.2 (16)
0.0
Seed density 5 - 10 cm
fen meadow
L class t
lp
t
sp
t
sp
sp
sp
lp
sp
sp
t
V 0
0.8
0
0.3
0
0
0
1
0
0
0.1
0
0
0
0
0
0
0
0.1
0.5
0
0.2
0
0
degraded meadow
0.0
0.0
0.0
0.0
15.9 (2)
111.4 (14)
222.9 (28)
294.5 (37)
Seed density 0-5 cm
62 0.0
0.0
0.0
0.0
37.2 (5)
0.0
160.7 (20)
356.6 (45)
Seed density 5 - 10 cm
fen
L class t
t
t
t
lp
t
sp
lp
chapter 3
n.d.
0.00
0.50
0.23
0.18
0.20
0.00
0.12
n.d.
n.d.
n.d.
0.14
0.42
0.12
n.d.
0.02
0.00
n.d.
0.26
0.53
n.d.
Salix rosmarinifolia
Peucedanum palustre
Eupatorium canabinum
Carex nigra
Ranunculus acris
Andromenda polifolia
Frangula alnus
Salix pentandra
Betula humilis
Baeothryon alpinum
Carex limosa
Padus avium
Pedicularis palustris
Poa palustris
Sonchus sp.
Sorbus aucuparia
Viburnum opulus
Juncus sp.
Deschampsia caespitosa
Ranunculus repens
Carex sp.
0.51
0.80
Holcus lanatus
Ranunculus sceleratus
0.30
n.d.
Epilobium sp.
Cerastrium holosteoides
0.15
Stellaria palustris
0
0
0
0
0
0
0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.3
0.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
0.1
1
0.3
1
1
1
0.6
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0.6
0
0
0
159.0 (20) 580.4 (73)
3084.6 (388) 906.3 (114)
302.1 (38)
429.3 (54)
715.5 (90)
31.8 (4)
39.8 (5)
612.2 (77)
12298.7 (1547)
437.3 (55)
9126.6 (1148)
8.0 (1)
0.0
0.0
0.0
0.0
23055.0 (2900)
15.9 (2)
0.0
0.0
23.9 (3)
55.7 (7)
lp
sp
sp
sp
sp
sp
sp
sp
t
t
sp
t
0
0.9
0.8
0
1
0.9
0
0
0
0
0
0
0
0
0
0
0
0
0
0.7
0
0.8
0
0
0
0
79.6 (10)
55.7 (7)
1998.0 (251)
95.5 (12)
71.6 (9)
0.0
15.9 (2)
0.0
86.7 (12)
58.0 (8)
1314.7 (178)
255.9 (34)
113.0 (14)
0.0
0.0
7.0 (1)
lp
lp
sp
lp
lp
t
sp
lp
Species trait shifts during fen degradation
63
0
0.24
n.d.
0.92
0.21
0.63
0.08
0.75
0.08
0.65
n.d.
0.04
0.04
1.00
0.40
0.23
0.02
0.17
0.49
0.08
0.04
0.58
0.00
0.00
Agrostis sp.
Juncus effusus
Lotus pedunculatus
Rorippa palustris
Lemna minor
Veronica beccabunga
Filipendula ulmaria
Juncus inflexus
Rumex hydralaphatum
Lathyrus pratensis
Festuca arundinacea
Cyperus fuscus
Primula farinosa
Eleocharis palustris
Geum rivale
Carex disticha
Mentha aquatica
Alopecurus pratensis
Polygonum bistorta
Poa trivialis
Cirsium oleraceum
Triglochin palustris
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
LI
0.57
V
Epilobium ciliatum + E. montanum + E. parviflorum Plantago lanceolata
V 0.6
0.7
0.7
0.8
0.9
1
1
1
0.1
0
0
0.1
0.4
0
0
0.2
0
0
0
0.9
0.1
0.1
0.3
0.6
Seed density 0-5 cm 0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
8.0 (1)
8.0 (1)
8.0 (1)
8.0 (1)
8.0 (1)
8.0 (1)
8.0 (1)
8.0 (1)
15.9 (2)
15.9 (2)
79.5 (10)
111.3 (14)
111.3 (14)
119.3 (15)
198.8(25)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
39.8 (5)
0.0
0.0
0.0
0.0
8.0 (1)
8.0 (1)
8.0 (1)
15.9 (2)
0.0
39.8 (5)
0.0
0.0
0.0
0.0
8.0 (1)
Seed density 5 - 10 cm
Seed density 5 - 10 cm
fen meadow
L class t
t
t
t
t
t
t
t
lp
sp
sp
t
t
lp
lp
lp
lp
sp
lp
t
t
t
t
sp
V 0
0
0.8
0.1
0.1
0
0
0.4
0
0
0
0
0
0
0
0
0
0
0
0.2
0
0
0.9
0.5
degraded meadow
748.2 (94)
0.0
0.0
0.0
214.9 (27)
159.2 (20)
79.6 (10)
87.6 (11)
589.0 (74)
Seed density 0-5 cm
64 432.5 (58)
0.0
0.0
0.0
134.2 (15)
179.9 (24)
107.7 (14)
162.5 (23)
536.1 (70)
Seed density 5 - 10 cm
fen
L class sp
t
t
t
sp
lp
t
lp
lp
sp
chapter 3
L class
Seed density 10 - 15 cm
Seed density 0-5 cm
0.06
0.02
0.00
0.06
0.36
n.d.
0.30
0.00
0.02
0.14
0.20
0.04
0.10
0.27
0.20
0.27
0.17
Festuca pratensis
Achillea ptarmica
Juncus subnodulosus
Arrhenaterum elatius
Carex paniculata
Elymus sp.
Rumex crispus
Selinum carvifolium
Briza media
Carex vesicaria
Phleum pratense
Valeriana dioica
Achemilla millefolium
Antoxantum odoratum
Carex hirta
Molinia caerulea
Trollius europaeus
0.81
0.63
0.64
0.33
0.19
Sagina procumbens
Capsella bursa pastoris
Urtica dioica
Veronica arvensis + V. dilenii
Potentilla anserina
0.50
0.23
Rumex acetosa
Cardaminopsis arenosa
0.00
Rhinanthus angustifolius
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.3
0.3
0.3
0.3
0.3
0.4
0.4
0.4
0.4
0.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
1
0.5
1
0.8
0.5
0.8
0
0
0.1
1
0.9
0
0
0
0
0
0
0
0
0
0
0
0.2
0.8
0
1385.5 (155) 332.6 (46)
1655.7 (208) 1098.5 (138)
294.5 (37)
440.9 (59)
440.4 (54)
6508.0 (864)
3860.6 (485)
477.6 (60)
6258.8 (860)
0.0
14.3 (2)
292.7 (37)
0.0
87.3 (12)
4672.5 (587)
0.0
0.0
71.6 (9)
0.0
8.0 (1)
lp
sp
sp
sp
lp
lp
t
lp
lp
t
lp
Species trait shifts during fen degradation
65
0.35
0.66
0.71
0.89
0.22
0.39
0.67
0.83
0.70
0.47
0.52
0.40
0.52
0.11
0.56
0.57
0.37
0.66
0.53
0.38
0.41
0.60
Plantago pauciflora
Stellaria media
Juncus buffonius
Linaria vulgaris
Mentha x verticiliata
Polygonum persicaria
Chenopodium alba
Veronica serpyllifolia
Hypericum tetrapterum
Viola arvense
Polygonum hydropiper
Sonchus asper
Leontodon autumnalis
Polygonum aviculare
Bidens frondosa + B. tripartita
Trifolium repens
Plantago major
Senecio vulgare
Luzula campestris
Veronica chamedrys
Fallopia convulvus
LI
Rorippa sylvestris
V
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
V 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Seed density 5 - 10 cm
Seed density 0-5 cm
Seed density 5 - 10 cm
fen meadow
V 0.5
0.7
0.1
0
0.1
0.6
0
0.1
0.3
0.3
0.7
0.4
0
0
0.2
0
0.2
0.4
0
0.3
0
0.1
degraded meadow
0.0
0.0
0.0
0.0
0.0
0.0
0.0
8.0 (1)
8.0 (1)
15.9 (2)
15.9 (2)
23.9 (3)
31.8 (4)
31.8 (4)
39.8 (5)
63.7 (8)
79.6 (10)
79.6 (10)
79.6 (10)
87.6 (11)
214.9 (27)
254.7 (32)
Seed density 0-5 cm
66 0.0
0.0
8.4 (1)
14.6 (2)
31.0 (4)
42.4 (6)
55.6 (8)
6.7 (1)
14.5 (2)
41.9 (6)
299.7 (42)
0.0
7.0 (1)
t
t
lp
lp
lp
lp
lp
lp
lp
lp
lp
t
sp
lp
lp 75.1 (9)
lp 963.5 (134)
lp
lp
lp
517.2 (63)
115.9 (14)
180.8 (23)
325.3 (43)
sp
lp 52.2 (7)
sp
2585.4 (286)
L class
169.4 (21)
Seed density 5 - 10 cm
fen
chapter 3
L class
L class
Seed density 10 - 15 cm
Seed density 0-5 cm
0.09
0.04
0.34
0.19
0.23
n.d.
Galeobdolon luteum
Galium verum
Medicago lupulina
Solidago canadensis
Trifolium pratense
Veronica sp.
0
0
0
0
0
0
0
0.10
0.04
Herlacleum sphondyllium
0
Sample represented approx. surface m2
0.53
Atriplex patula
0
4884.4
0.13
Galium aparine
0
Volume of analysed sample cm3
0.20
Cirsium arvense
0
0
SUM
0.75
Epilobium obscurum
13358.5 (1266)
0.34
Galeopsis tetrahit
0.11
5510.5
21945.8 (2501)
0.10
5230.1
7490.7 (833)
0
0
0
0
0
0
0
0
0
0
0
0
0.125
6280.0
45593.3 (5735)
0.125
6280.0
11956.8 (1504)
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.4
0.5
0.125
6280.0
20489.0 (2574)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.13
6566.35
28964.4 (3774)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
t
t
t
t
t
t
t
t
t
t
t
t
Species trait shifts during fen degradation
67
Degraded meadows in Całowanie Fen, Poland
chapter
3 supplement
Degradation of species-rich meadows on agriculturally used peatlands Agata Klimkowska
chapter 3 supplement
I present here a literature overview on the peat soil degradation and the vegetation changes on the drained fens. The example of the vegetation changes in Całowanie Fen is discussed. Some socioeconomic aspects of fen degradation and fen meadow restoration are considered as well.
Degradation of peat soils Fens have been systematically drained since the 17th century in Western Europe (Chapman et al. 2003) and since the 19th century in Central and Eastern Europe (CEE) (Meissner et al. 2003). The desiccation has resulted in peat decomposition (Okruszko 1995b) and in soil volume losses up to 53-70 %, due to peat shrinkage and oxidation (Heinz 2005; Zeitz and Velty 2002; Wild 1997). These resulted in the formation of moorsh soil and, in extreme situations, a hydrophobic layer of granular or powder substrate with no water storage capacity (Kajak and Okruszko 1990; Ilnicki and Zeitz 2003). The losses of nitrogen from organic soils in the CEE conditions can rise up to 300 kg N ha-1 yr-1 (Eschner 1989; Zeitz and Velty 2002; Jankowska-Huflejt 2006). The release of nutrients leads to eutrophication and speeds-up the succession on the abundant land (Schmidt et al. 2000). The enhanced phosphorus availability due to peat mineralization and fertilisation is likely to cause the decline of rare species (Janssens et al. 1998; Rupp et al. 2004; Wassen et al. 2005).
Degradation of the vegetation Changes in the abiotic conditions result in changes in the vegetation (Fig. 3.5). The mesotrophic, peat-forming communities, dominated by sedges and bryophytes (Magnocaricion, Scheuzerio-Caricetea fuscae) were replaced by non peatforming species-rich meadows (the alliance Calthion palustris: Cirsio-Polygonetum, Deschampsietum caespitosae, Epilobio-Juncetum effuse or Molinion caeruleae alliance) or less stable communities of the Arrhenatheretalia order (Pałczyński 1966; Jasnowski 1972; Jankowski 1991; Kotowska et al. 1996; Dąbkowski et al. 2000). An introduced grass species, ruderals, and other species of Ranunculaceae, Rosaceae, Umbelliferae, Scrophulariaceae, Labiatae and Composite families contribute to high species diversity on the reclaimed fens (Jasnowski 1972). Later, the species-rich semi-natural meadows gradually disappear and are replaced by species-poor meadows from the Alopecurion pratensis alliance (Deschampsia caespitose – Potentilla anserina or Poo-Festucetum rubrae or Holcus lanatus communites) (Jankowski 1991; Banaszuk et al. 1996; Fijałkowski 1996; Kucharski and Pisarek 1996; Kucharski 2000). Further intensive drainage leads to species-poor, low productivity meadows, dominated by Festuca rubra and Cardaminopsis arenosa, Deschampsia caespitose (e.g.
70
Degradation of species-rich meadows on peatlands discussed changes because of drainage changes because of drainage changes because of abandonment or spontaneous succession
MODERATE (2X)
(2a) fen meadow Calthion palustris
(3a) hay meadow species - poor Calthion palustris
(3b) hay meadow Alopecurion pratensis
LOW (1X)
land use intensity
(3c) hay meadow Arrhenatheretalia elatioris
(2b) fen meadow Caricion nigrae (2c) fen meadow Molinion caeruleae
NON
(1) fen mire small sedgemoss communities
LOW
(4a) sedge beds or reed beds Phragmitetea Magnocaricion
(5a) species poor meadow Deschampsia cespitosa Holcus lanatus
(4b) tall herbs and shrub vegetation Filipendulion ulmariae (4c) shrub communities Alnion glutinosae
MODERATE
(5b) degraded meadow Festuca rubra Cardaminopsis arenosa
HIGH
drainage degree
Figure 3.5 Hypothetical changes of vegetation during the degradation process. We focused on three stages: fen vegetation (1), moderately drained fen meadow Calthion (2a) and severely drained and degraded meadow (5b). Low land use intensity means here: mown annually and no fertilisation, moderate intensity means mown twice a year and limited fertilisation. Vegetation types after Matuszkiewicz (2001).
Wizna Fen, Noteć River valley) with fragmented meadow sward, patches of bare soil or carpets of disturbance-indicating mosses and lichens (e.g. Łęczyca – Błonie, Biebrza - Kuwasy, Modzelówka) (Kwinichidze 1957; Okruszko 1957; Falkowski 1959; Kotowska et al.1996; Okruszko et al. 1999). Desiccation, excessive fertilisation and nutrient (K) deficiency (Okruszko 1957; Falkowski 1959; Kajak and Okruszko 1990; Prach 1996) were indicated as causes of the rapid meadow degradation. Ruderals and plants resistant to large water fluctuations (e.g. Senecio jacobea, Taraxacum officinale, Cardaminopsis arenosa, Urtica dioica, Cirsium arvense, species of Sedo-Scleranthetea or Artemisietea class) often dominate such meadows (Banaszuk et al. 1996; Kucharski and Pisarek 1996; Prach 1996; Kucharski 2000). On moderately drained and abandoned peatlands, tall herb (Filipendulion ulmariae) and shrub communities (Salicetum pentandro-cinereae) develop (Jankowski 1991; Kucharski 2000; Schmidt et al. 2000). In the case of spontaneous rewetting,
71
chapter 3 supplement
an increase of species typical for eutrophic sedge beds or reed beds was observed (Phragmitetea class) (Ilnicki et al. 1996; Prach 1996; Kucharski 2000).
Vegetation changes in Całowanie Fen Data from literature and present records were combined for an overview of the vegetation developments on the Całowanie Fen (52°00’47”N, 21°20’24”E) in Central Poland. Data from the 1960’s (Podbielkowski 1960; Nowak 1964), from the 1980’s (Oświt and Dembek 1984) and from 2000 onwards were used. Data were reclassified and were analysed with the multivariate ordination technique (Detrended Correspondence Analysis). The spatial coordinates of the records were not available, thus I assumed that the data represents the most abundant types of herbaceous vegetation. We found that the species composition of open vegetation changed over time (Fig. 3.6). Fens deteriorated: the composition of fen communities in the 1960’s was different from what was recorded recently, and the area became occupied by fen meadows and degraded meadows instead. The alderwood communities remained relatively unchanged. Because records of the tall sedge vegetation were not present in the older data sets, no change could be deduced. Molinion-type meadows possibly developed from species-rich fens. These analyses give only a general indication of the vegetation changes.
Agriculture on peatlands: socioeconomic perspective and future prospects Over 99 % of mires in Western Europe and 84 % in Poland has been lost due to drainage, fertilisation, cultivation, forestry and excavation (Joosten and Clarke 2002; Kotowski and Piórkowski 2003). Peatland degradation depended on the degree of change in hydrological systems, land use intensity and historical factors (Dembek et al. 2004a). In CEE reclaimed peatlands deteriorated to a high degree and are susceptible to mineralization, because of climatic conditions: high evapotranspiration in summer, a low precipitation surplus, freezing and soil structure damage in winter. Other reasons came from socioeconomic conditions: un-sound management in the communistic system, lack of proper water management and large-scale overdrainage (Dembek 2002; Dembek et al. 2004a). This resulted in a severe desiccation of some reclaimed peatlands, which suffer from soil degradation, a decline in productivity and deterioration of nature values. In Poland, peatlands are mainly used as permanent grasslands. More than half of the meadows on organic soils were drained deeper than required for optimal farming conditions and were abandoned or became marginal for farming. In
72
Degradation of species-rich meadows on peatlands
4
2
1960 1984 2000-2007 fen fen meadow fen meadow (Molinion) alderwood degraded meadow tall sedge
0
0
2
4
6
Figure 3.6 DCA of the vegetation data. First ordination axis: λ = 0.63, gradient length 5.6, cumulative percentage of variance explained 4.8 %. Second ordination axis: λ = 0.41, gradient length 3.8, cumulative percentage of variance explained 8 %. Number of samples 266, with in total 339 species.
addition, most of the large fen complexes were reclaimed and subsequently degraded and relatively well-preserved remnants are small and isolated (Fig. 3.7). Well-developed fen meadows on peatlands cover c. 0.269 *106 ha, while degraded meadows on drained peatlands cover c. 1.077 *106 ha (32 % of the total grassland area of Poland) (Grzyb and Prończuk 1994; Jankowska-Huflejt 2006). Both, intensification and abandonment may result in a decline in the quality of the environment and biodiversity in peatlands (Bartoszuk et al. 2004; Dembek 2002; Dembek et al. 2004b). Current policies recommend upgrading the environmental quality, sustainable management of resources and a need to maintain biodiversity of the low intensity agricultural systems. The financial instruments, such as AgroEnvironmental Schemes enable a limited conservation of semi-natural meadows, but are not capable of reversing the negative changes that took place in the degraded areas (Kleijn et al. 2001, 2006; Brzezińska et al. 2007). The more the system has been transformed and devastated, the more difficult it is to restore it (Van Andel and Grootjans 2006). In practice, there is little choice of sites for nature restoration and the available areas are often strongly degraded (Manchester et al. 1999). A spontaneous re-development of species-rich fen meadows on degraded peatlands in the present environmental and landscape conditions is not likely (Manchester et al. 1999; Chapman et al. 2003) and interventions such as nutrient impoverishment or introduction of target species are necessary (Bakker and Berendse 1999; Hopkins et
73
chapter 3 supplement
Data source: Geographical Information System on Polish Wetlands, compiled by the Department of Nature Protection in Rural Areas of the Institute for Land Reclamation and Grassland Farming, commissioned by the Ministry of the Environment, financed by the National Fund for Environmental Protection and Water Management
N
100 km degraded or partly degraded peatlands natural (non-degraded) peatlands
Figure 3.7 Degraded and non-degraded peatlands of Poland. Only the peatlands larger than 100 ha and with open vegetation are presented.
al. 1999; Grootjans et al. 2002). Restoration of the nature values on degraded fens can be combined with managing the rural landscape and providing ecosystem services: stop soil degradation, create nutrient-sinks to prevent water pollution, re-install water storage to mitigate the droughts and floods (Okruszko 1996; Zedler 2003; Dembek et al. 2004a; Farber et al. 2005; Foley et al. 2005; Krauze and Wagner 2007). Generally, an increase in agricultural investments is associated with the decline in biodiversity. The relationship between species diversity and productivity can be expressed by a hump-backed curve (Grime 1979; Hodgson et al. 2005). A positive relationship between species diversity and productivity was found for the low and
74
Degradation of species-rich meadows on peatlands
n=
5
4
4
4
14
biomass (g m-2)
800
600
6 c
F = 5.08 p < 0.01 bc
400
a
200
0
ab
a
ab
degraded meadow
restored restored fen meadow meadow meadow no hay hay applied Molinion
fen meadow Calthion
tall sedge vegetation
Figure 3.8 Biomass on different types of meadows in Całowanie Fen. Measurements from random 50 x 50 cm plots). Data collected in 2005 (student course, University of Groningen). ‘Restored meadow’ indicates the vegetation that developed after topsoil removal with or without hay transfer application. Error bars indicate the standard deviation from mean. Number of samples was indicated above the columns. Differences tested with simple ANOVA (R2 = 0.45, p=0.002). Letters indicate groups significantly different (p
