Assessing human impact on fen biodiversity: effects of different management regimes on butterfly, grasshopper, and carabid beetle assemblages

Fens and concomitantly the associated species assemblages have undergone dramatic declines in recent decades. Given that many remaining or restored fens are currently lying fallow, an important question is which management regime, if any, is most effective in preserving fen biodiversity. Against this background we here investigate the effects of five management regimes (intensive grassland, moist meadows, summer harvested sites, winter harvested sites, fallows) on three insect taxa (butterflies, grasshoppers, carabid beetles) in riverine fens in north-eastern Germany. Butterflies and grasshoppers showed highest species numbers, diversity and numbers of threatened species on moist meadows and were detrimentally affected by high vegetation. In contrast, ground dwelling carabid beetles were less strongly affected by different management regimes, but responded very sensitive to drainage. Winter harvested sites and fallows seemed to be particularly beneficial to carabid beetles. Overall, drained, intensive grassland was not suitable for preserving fen-specific communities, while extensively managed moist meadows harboured overall the highest numbers of threatened species. We conclude that in terms of management maintaining high water tables is most important. Furthermore, some management seems necessary to maintain stands with lower vegetation turf for associated species. However, care is needed to also maintain fallows and to consider the specific demands of some highly endangered, management-sensitive species.     

Missing the target? A critical view on butterfly conservation efforts on calcareous grasslands in south-western Germany

Butterflies are strongly declining on grassland habitats of Central Europe. Therefore, the success of conservation measures on high quality grassland habitats is controversially discussed. We compared the changes in butterfly diversity and community structure on six managed calcareous grasslands with eight unmanaged vineyard fallows. We obtained strong losses of species diversity and remarkable shifts of community compositions on both habitat types. However, the changes on vineyard fallows were only slightly more severe but more stochastic than on the calcareous grasslands. The shifts in community composition with respect to functional species traits were rather similar between the two different grassland types so that complex butterfly communities evolved into generalist-dominated ones. Connectivity was higher among vineyard fallows than among calcareous grasslands. Consequently, conservation measures on calcareous grasslands only partly achieved their goal to maintain the high species diversity and functional complexity still observed in the 1970s. The negative impacts of eutrophication and monotonisation of the landscape as well as climate change are affecting all habitats, independently from management concepts. Therefore, management on conservation sites can buffer against these effects, but is not sufficient for a full compensation.     

Seed bank diversity in mesic grasslands in relation to vegetation type,management and site conditions

Questions: 1. Do different management types (i.e. hay meadow, silage meadow, meadow‐pasture, pasture) have different impact on the size and composition of the seed bank of mesic grassland (Arrhenatheretalia)? 2. How strong is the effect of management on the seed bank in relation to above‐ground vegetation, edaphic factors and land‐use history? 3. Are there differences in C‐S‐R plant strategy types and seed longevity under different management regimes? Location: Lahn‐Dill Highlands in central‐western Germany. Methods: Above‐ground vegetation and the soil seed bank of 63 plots (at 21 sites) in mesic grasslands were studied. Differences between management types in quantitative seed bank traits and functional characteristics were tested by ANOVA. The impact of management, above‐ground vegetation, site conditions and land‐use history on seed bank composition were analysed by partial CCA. Results: Management had no significant impact on species richness and density of the seed bank but significantly influenced their floristic composition and functional characteristics. CCA revealed that even after adjustment for soil chemical parameters and above‐ground vegetation management still had significant impact on seed bank composition. ANOVA revealed that silage meadows contained higher proportions of R‐strategy compared to hay meadows. In contrast, in hay meadows and meadow‐pastures proportions of S‐strategy were higher than in silage meadows. Conclusions: The type of grassland management has little impact on quantitative seed bank traits. Management types with a high degree of disturbance lead to an increase of species following a ruderal strategy in the seed bank. Irrespective of management type only a limited proportion of characteristic grassland species is likely to re‐establish from the seed bank after disappearance from above‐ground vegetation.     

Effects of fen management and habitat parameters on staphylinid beetle (Coleoptera: Staphylinidae) assemblages in north-eastern Germany

Because fens have undergone dramatic declines in recent decades, an important question is which management regimes and habitat parameters are most effective in preserving fen biodiversity. The aim of the present study was to assess the effects of five different management regimes (intensive grassland, moist meadows, summer harvested sites, winter harvested sites, fallows) on staphylinid beetle assemblages. During the study period 5,989 individuals from 92 staphylinid beetle species were recorded. Species richness and abundance were highest on intensive grassland and fallows, and water level and vegetation height had significant impacts on the abundance of staphylinids. On winter-harvested sites species richness and abundance were lowest. In general, staphylinid beetles did not show pronounced variation among management regimes, while the environmental factors water level, vegetation height and top soil mineralisation seemed to have a larger structuring impact. The number of threatened species and the conservation index were highest on summer-harvested sites and fallows, representing fairly well-preserved fens. We conclude that summer harvest of reed beds or no management at all appears to be most beneficial for the conservation of staphylinid beetles.     

Environmental and historical effects on lichen diversity in managed and unmanaged wooded meadows

Question: Which environmental and historical variables affect epiphytic lichen diversity in managed and unmanaged wooded meadows? Location: The island of Gotland located in the Baltic Sea east of the Swedish mainland. Methods: We examined total epiphytic lichen diversity (crustose, foliose and fruticose species) on 1148 trees in eight grazed, eight traditionally managed (mowing, hay gathering and pollarding) and seven unmanaged wooded meadows. In addition to management, data on site location, habitat structure, history and adjacent habitat were analysed. Results: Lichen species richness increased with wooded meadow area and was greater within managed sites than in unmanaged meadows. Historic crown cover (ca. 1930) also influenced present‐day lichen richness. Geographic location, distance to sea, wooded meadow area and average tree circumference were important determinants of lichen species composition. Tree circumference was the strongest overall predictor of the number of species on individual trees. However, tree circumference interacted with management regime, whereby cessation of management appeared to reduce species richness most on large trees. Traditionally managed sites, on average, supported the greatest richness of red‐listed species. Conclusions: Management regime, wooded meadow area and canopy cover were the main drivers of lichen species richness, while geographic location, wooded meadow area, distance to sea and average tree circumference were important determinants of species composition.     

Rotational fallows as overwintering habitat for grassland arthropods: the case of spiders in fen meadows

Regular mowing of grassland is often necessary for plant conservation, but uncut vegetation is needed by many arthropods for overwintering. This may lead to conflicting management strategies for plant and arthropod conservation. Rotational fallows are a possible solution. They provide a spatio-temporal mosaic of mown and unmown areas that may combine benefits to both plants and arthropods. We tested if rotational fallows enhance spider overwintering in fen meadows. Rotational fallows consisted of three adjoining strips 10 m wide and 35–50 m long. Each year, one of these strips was left unmown (fallow) in an alternating manner so that each strip was mown two out of three years. Spiders were sampled during spring with emergence traps in nine pairs of currently unmown fallow strips and completely mown reference plots. Fallows significantly enhanced orb-weavers (Araneidae), sac spiders (Clubionidae) and ground spiders (Gnaphosidae). However, only 4.7% of the total variation in community composition was attributable to fallows. Community variation was larger between landscapes (34.5%) and sites (38.2%). Also β diversity was much higher between landscapes (45 species) and sites (22 species) than between fallows and mown reference plots (10 species). We conclude that the first priority for spider conservation is to preserve as many fen meadows in different landscapes as possible. Locally, rotational fallows enhance overwintering of the above-mentioned spider families, which are sensitive to mowing in other grassland types as well. Thus, rotational fallows would probably foster spider conservation in a wide range of situations. However, stronger effects can be expected from larger and/or older fallow areas.     

Floristic composition,site conditions and diversity of poet’s daffodil (Narcissus radiiflorus Salisb.) hay meadows in the Venetian Pre-Alps and outer Dolomites (N-Italy): implications for conservation and restoration

Abstract

Hay meadows are an important component of the alpine landscape, which evolved over millennia of human activities. When traditionally managed, hay meadows support a rich flora and are recognized for high species diversity. However, both intensification and abandonment can lead to a loss of biodiversity in this vegetation. In this paper, the focus was on the hay meadows where Narcissus radiiflorus Salisb. forms white mosaic carpets during the blooming period. This vegetation was studied through 26 phytosociological relevés, taken in the Venetian Pre-Alps and outer Dolomites (Northern Italy). Relevés were numerically classified and analysed in their relationships with site conditions. Moreover, diversity metrics were calculated for detecting the conservation status of hay meadows subjected to different types of disturbance. The results showed that poet’s daffodils’ dominance brings together hay meadows showing a substantial range of floristic and ecologic variation and that part of the stands dominated by Narcissus radiiflorus could be referred to a habitat type regarded as prioritary for nature conservation. Moreover, management-related variations in functional diversity suggested that the best practice recommended for conservation and restoration of this habitat is the continuation of traditional late mowing. This practice will allow preserving both biodiversity and ecosystem functions and services.     

Decline of rare and specialist species across multiple taxonomic groups after grassland intensification and abandonment

Traditionally managed mountain grasslands are declining as a result of abandonment or intensification of management. Based on a common chronosequence approach we investigated species compositions of 16 taxonomic groups on traditionally managed dry pastures, fertilized and irrigated hay meadows, and abandoned grasslands (larch forests). We included faunal above- and below-ground biodiversity as well as species traits (mainly rarity and habitat specificity) in our analyses. The larch forests showed the highest species number (345 species), with slightly less species in pastures (290 species) and much less in hay meadows (163 species). The proportion of rare species was highest in the pastures and lowest in hay meadows. Similar patterns were found for specialist species, i.e. species with a high habitat specificity. After abandonment, larch forests harbor a higher number of pasture species than hay meadows. These overall trends were mainly supported by spiders and vascular plants. Lichens, bryophytes and carabid beetles showed partly contrasting trends. These findings stress the importance to include a wide range of taxonomic groups in conservation studies. All in all, both abandonment and intensification had similar negative impacts on biodiversity in our study, underlining the high conservation value of Inner-Alpine dry pastures.     

Influence of abandonment on syrphid assemblages in mountainous meadows

Grasslands are often managed with different intensities in the European Alps. Studies have shown that a medium management can benefit plant and animal biodiversity in these ecosystems. However, in recent decades abandonment of extensively managed meadows is an ongoing global challenge. Syrphids (hoverflies) have been recognized as a threatened group due to environmental drivers, and these managed grasslands provide preferred habitats for them. Yet, at what extent syrphids respond to grassland management strategies is little known. We investigated whether abandonment of managed mountain meadows (mown once a year, no fertilizer use) affects syrphid abundance, richness and species assemblages. Moreover, the influence of plant richness, flower frequency and surrounding landscape on syrphids were assessed. Four managed meadows were compared with four abandoned meadows in a mountainous region in Austria. Adult syrphids were sampled over two consecutive years (June and August 2015–2016) by sweep netting using line transects and observation plots. Syrphid abundance was significantly higher in managed than abandoned meadows and increased with increasing plant richness and flower frequency across management types. Management and sampling time also significantly affected syrphid species assemblages. Syrphid richness and abundance were not influenced by surrounding landscape. We conclude that both abandoned and managed meadows provide important habitat types for syrphids. Therefore, efforts should be made to maintain both managed and abandoned meadows in order to protect syrphid species within mountainous landscapes.     

Biodiversity in agricultural landscapes: different non-crop habitats increase diversity of ground-dwelling beetles (Coleoptera) but support different communities

Agricultural intensification poses a major threat to the conservation of biodiversity and associated ecosystem services. Since non-crop habitats are regarded as important refuges for farmland biodiversity, various greening measures have been proposed to halt biodiversity loss. However, the effectiveness of these measures for biodiversity conservation is still under debate. Therefore, we here compared ground-dwelling beetle (Coleoptera) assemblages of different non-crop habitats (field margins, set-aside fields sown with wildflowers, and permanent grassland fallows) and wheat fields within an intensively used agricultural landscape in western Germany. Taxonomic diversity of Carabidae, Staphylinidae and other coleopteran families and their conservation value were higher in all non-crop habitats than on wheat fields. Surprisingly, though, different types of non-crop habitats did not differ in species richness or the number of threatened species. Thus, field margins and sown wildflower fields were as effective in promoting beetle diversity as grassland fallows. However, different non-crop habitats supported different species assemblages, and several species, in particular especially large ones, were restricted to grassland fallows. These results suggest that different greening measures are effective in promoting the biodiversity of beetles, and that permanent grassland fallows are essential for nature conservation. The fact that habitat types harbored different assemblages stresses the need to combine a variety of greening measures to yield the highest benefit for biodiversity.

     

Diversification of mowing regime increases arthropods diversity in species-poor cultural hay meadows

Agricultural intensification reduces the biodiversity of European farmlands. Hay meadows represent an important farmland habitat, traditionally used to produce hay. With decreased demand for hay, the continuation of hay harvest is supported by Agri-environmental schemes across European Union. Modern hay harvest techniques differ from traditional manual harvest by removing the grass instantaneously over large land areas. To minimize adverse effects on meadow invertebrates, diversifying harvest operations is time and space is often recommended, but effects of such diversification are little studied. We compared the impact of uniform hay harvests with harvests executed in patchy manners, using four arthropod groups (butterflies, ground beetles, orthopterans and spiders) at productive, species-poor meadows in the Czech Republic. Butterflies, observed along transects, avoided uniformly cut units, preferring those cut as strips or blocks. In the three remaining groups, recorded using pitfall traps, a majority of species prevailed in traps located in uncut conditions. Synchronous mowing of large areas suppresses population sizes and diminishes the diversity of common arthropods. Besides of direct mortality and depletion of such resources as nectar or shelter, it synchronises sward regrowth, threatening also species requiring short-sward patches. Uniformly executed mowing contradicts the biodiversity conservation goal of Agri-environmental schemes. Diversifying the mowing operations via temporary fallows, or sequential mowing of land units, will improve the situation for common cultural meadows.     

Evaluating alternative mowing regimes for conservation management of Central European mesic hay meadows: A field experiment

Conservation status of hay meadows highly depends on their management. The main goal of this study was to assess the efficiency of different mowing regimes in maintenance of plant species richness and diversity of mesic hay meadows. The field experiment was carried out on a species rich, mesic hay meadow in Western Hungary. We evaluated the effects of four alternative types of management on the plant community after 7 years of continuous treatment: (1) mowing twice a year, typical traditional management, (2) mowing once a year in May, most practised currently by local farmers, (3) mowing once a year in September, often proposed for conservation management and (4) abandonment of mowing. Traditional mowing resulted in significantly higher number and higher diversity of vascular plant species than other mowing regimes. Mowing twice a year was the only efficient way to control the spread of the invasive Solidago gigantea, and mowing in September was more successful in it than mowing in May. We conclude that the traditional mowing regime is the most suitable to maintain botanical diversity of mesic hay meadows; however, other regimes should also be considered if certain priority species are targeted by conservation.     

Habitat management by aboriginals promotes high spider diversity on an Asian tropical island

Orchid Island, 92  km off the southeast coast of Taiwan, has the northernmost tropical forests in East Asia. We assessed effects of habitat management by Orchid Island inhabitants, the Yami people, on spider diversity by comparing assemblages collected from the ground to canopy among four habitats (natural forest, cultivated woodland, second growth forest and grasslands) that receive different degrees of disturbance. Species and guild composition did not differ among replicates of habitat but differed significantly among habitats. Variation in spider diversity was inversely correlated with vegetation density. Cultivated woodland subjected to an intermediate level of disturbances had a lower understory vegetation density than natural forest, but higher spider diversity. Neither insect abundance nor biomass varied significantly among habitats suggesting little room for effects of prey availability on spider diversity. It appears that the Yami people maintain high spider diversity on Orchid Island by generating novel habitat types with different vegetation structures and disturbance regimes.     

Reinforced Traditional Management is Needed to Save a Declining Meadow Species. A Demographic Analysis

The changes in agricultural practices during the last century have led to a drastic decrease in the number of traditionally managed hay meadows. Also, traditional management practices are often applied more cursorily in the remaining meadows. In combination with an increase in aerial anthropogenic nitrogen deposition, this has led to a loss of biodiversity. To investigate whether the current management is sufficient for maintaining viable populations of a typical meadow plant, Succisa pratensis, we experimentally reinforced the raking and mowing parts of the traditional management over four years in a two-by-two factorial experiment in three traditionally managed wooded hay meadows on the Baltic island of Gotland, Sweden. We found decreased litter and hay production in two of the three studied meadows as a result of our treatments. Plant sizes and asymptotic population growth rates (??) of S. pratensis increased, particularly in plots receiving the combined raking and mowing treatment. Stochastic long-term population growth rates (?? _s ) increased under the reinforced management: projected population sizes 50?years into the future showed a three-fold increase in raked plots and a 17-fold increase in plots that were both raked and mown. Because we found positive responses even in these seemingly well-managed meadows we conclude that it is essential that management is carried out more thoroughly to ensure viable population sizes. Our conclusion applies to most semi-natural grasslands receiving anthropogenic nitrogen, or where traditional management practices are less rigorously applied. We also suggest using biomass estimation instead of vegetation height as a measure of management strength.     

Plant diversity in a water-meadow landscape: the role of irrigation ditches

Species-rich, extensively managed grasslands are among the most threatened ecosystems in Europe. The traditional technique of meadow irrigation, formerly practised in large parts of Europe, may be a viable management option that meets both ecological and economical objectives. While studies on plant diversity of the meadow matrix exist, the role of other landscape components for biodiversity conservation is unknown. We quantify the role of irrigation and drainage ditches compared with field paths, and analysed the local and landscape plant species composition and diversity in a water-meadow landscape. The meadows are located in the river Queich catchment (Upper Rhine valley, Germany). We recorded plant species cover on 18 meadows, adjacent ditches and field paths and analysed alpha, beta and gamma diversity within and among these landscape components. Irrigation and drainage ditches were more species rich than meadows and more heterogeneous in their species composition compared with meadows and paths. Ditches contributed one-third of the landscape’s plant species numbers, habitat for wetland species and refuges for high nature value grassland species. Fertilization of the adjacent meadow had no negative impact on the ditch diversity, while well-maintained ditches were more plant species rich than ditches filled with sediments. Traditional flood meadow irrigation should be taken into account when sustainable grassland management techniques are discussed that meet economical and ecological needs. A major contribution to landscape richness arises from the ditch structures as crucial part of the traditional irrigation technique.     

The impact of site conditions and seed dispersal on restoration success in alluvial meadows

Abstract. We studied the restoration success of flood plain meadows in the northern Upper Rhine valley, where between 1988 and 1992, 35 ha of arable land was converted into grassland and subsequently managed for nature conservation. Remnant populations of typical alluvial meadow species were found in old meadows and along drainage ditches that dissect the whole area. We analysed the site conditions and phytosociological relevés in old and new meadows. Small differences in site parameters between old and new meadows contrasted with a clear floristic differentiation between the two meadow types. The vegetation of old meadows was much more differentiated along prevailing environmental gradients than the vegetation of new meadows. Despite the favourable site conditions for the re‐establishment of species‐rich meadows on the former arable land, restoration success was limited to the vicinity of remnant stands. In contrast to old meadows, indicator species of new grassland were still typical species of regularly disturbed ruderal and arable habitats, often capable of building up a persistent seed bank. The precise mapping of 23 target species revealed that even wind dispersal predominantly leads to re‐establishment in the close circumference of parent plants. We found no indication that regular flooding, hay‐making and autumnal grazing had an impact on recolonization of newly created grassland. Even under favourable conditions for the re‐establishment of target species, restoration success in alluvial meadows proved to be strongly dispersal limited. We discuss the implications of our findings for future restoration management in grasslands.     

Environmental and spatial drivers of spider diversity at contrasting microhabitats

The relative importance of environmental and spatial drivers of animal diversity varies across scales, but identifying these scales can be difficult if a sampling design does not match the scale of the target organisms' interaction with their habitat. In this study, we quantify and compare the effects of environmental variation and spatial proximity on ground‐dwelling spider assemblages sampled from three distinct microhabitat types (open grassland, logs, trees) that recur across structurally heterogeneous grassy woodlands. We used model selection and multivariate procedures to compare the effects of different environmental attributes and spatial proximity on spider assemblages at each microhabitat type. We found that species richness and assemblage composition differed among microhabitat types. Bare ground cover had a negative effect on spider richness under trees, but a positive effect on spider richness in open grassland. Turnover in spider assemblages from open grassland was correlated with environmental distance, but not geographic distance. By contrast, turnover in spiders at logs and trees was correlated with geographic distance, but not environmental distance. Our study suggests that spider assemblages from widespread and connected open grassland habitat were more affected by environmental than spatial gradients, whereas spiders at log and tree habitats were more affected by spatial distance among these discrete but recurring microhabitats. Deliberate selection and sampling of small‐scale habitat features can provide robust information about the drivers of arthropod diversity and turnover in landscapes.     

Community composition of butterflies and bumblebees in fallows: niche breadth and dispersal capacity modify responses to fallow type and landscape

Fallows (i.e. fields temporarily taken out of production) provide important habitat for flower-visiting insects in intensively cultivated agricultural landscapes. Cost-efficiency of fallowing schemes could be enhanced through improved understanding of key characteristics of fallows and surrounding landscape that determine community composition and provide support for species of conservation concern. Impacts of fallow characteristics and landscape structure on the species composition of butterflies and bumblebees were studied in two types of perennial fallows in boreal farmland. To understand species’ responses to environmental factors from a conservation perspective, community composition was examined with respect to two species traits—niche breadth and dispersal capacity. Whereas overall species composition of butterflies and bumblebees was strongly affected by forest cover in the surrounding landscape, the studied species traits were most related to fallow type and the cover of perennial grasslands. Habitat breadth of butterflies was narrowest in long-term grassland fallows in landscapes with high grassland cover. Dispersal capacity of butterflies was also lowest in grassland-rich landscapes. Diet breadth of bumblebees was narrower in long-term grassland fallows than in short-term fallows. The results confirm that the diversity of butterflies and bumblebees can be enhanced by establishing and managing fallows both in open and forested landscapes. For conservation of habitat specialists and less mobile species, retention of long-term fallows in grassland-rich landscapes is apparently the best option. The results provide no justification for exempting forested regions or farms with high grassland cover from the ecological focus area requirement under the European Union’s current agricultural policy.     

Habitat associations of epigeal spiders in upland calcareous grassland landscapes: the importance for conservation

Upland calcareous grassland landscapes are typically comprised of a matrix of calcareous grassland, acid grassland and limestone heath plant communities. This matrix of habitats is produced by a combination of underlying geology, climate and management. These landscapes are typically managed through grazing, with management targeted to maintain particular plant communities in the calcareous grassland habitat, whilst patches of acid grassland and limestone heath are not targeted by conservation management. The biodiversity value of acid grassland and limestone heath patches within the calcareous grassland matrix are unknown. This study provides the first assessment of their biodiversity value by examining aspects of epigeal spider diversity supported by these non-target habitat patches in comparison to calcareous grassland. Spiders were sampled in each habitat from April to August 2014 using pitfall traps across three upland regions in Great Britain. Spider species assemblages were distinct between limestone heath and both grassland types. Distinction in species assemblages are likely due to differences in vegetation structure and microclimate, e.g., humidity, degree of shade. Each habitat type supported several rare species (e.g., Jacksonella falconeri, Agyneta subtilis) revealing the contribution to spider fauna. The distinct spider species assemblage and presence of rare species in limestone heath patches demonstrate their importance in the upland calcareous grassland matrix. This study highlights the value of monitoring biodiversity in non-target habitats within a habitat matrix alongside those that are actively targeted by management.     

Disentangling the role of management,vegetation structure,and plant quality for Orthoptera in lowland meadows

Seminatural grasslands provide habitats for various species and are important for biodiversity conservation. The understanding of the diverse responses of species and traits to different grassland managenient methods is therefore urgently needed. We disentangled the role of grassland management (fertilization and irrigation), vegetation structure (biomass, sward height) and plant quality (protein and fiber content) for Orthoptera communities in lowland hay meadows in Germany. We found vegetation structure to be the most important environmental category in explaining community structure of Orthoptera (species richness, total individuals, fiinctional diversity and species composition). Intensively used meadows (fertilized, irrigated, high plant biomass) were characterized by assemblages with few species, low functional diversity, and low conservation value. Thereby, the relatively moderate fertilizer inputs in our study system of up to -75 kg N/ha/year reduced functional diversity of Orthoptera, while this negative effect of fertilization was not detectable when solely considering taxonomic aspects. We found strong support for a prominent role of plant quality in shaping Orthoptera communities and especially the trait composition. Our findings demonstrate the usefulness of considering both taxonomic and functional comp on ents (functio nal diversity) in biodiversity research and we suggest a stronger involvement of plant quality measures in Orthoptera studies.