Semi-natural Calcareous Grasslands Research Articles

Soil community composition in dynamic stages of semi-natural calcareous grassland.

European dry thin-soil calcareous grasslands (alvars) are species-rich semi-natural habitats. Cessation of traditional management, such as mowing and grazing, leads to shrub and tree encroachment and the local extinction of characteristic alvar species. While soil microbes are known to play a critical role in driving vegetation and ecosystem dynamics, more information is needed about their composition and function in grasslands of different dynamic stages. Here we assess the composition of soil fungal, prokaryotic, and plant communities using soil environmental DNA from restored alvar grasslands in Estonia. The study areas included grasslands that had experienced different degrees of woody encroachment prior to restoration (woody plant removal and grazing), as well as unmanaged open grasslands. We found that, in general, different taxonomic groups exhibited correlated patterns of between-community variation. Previous forest sites, which had prior to restoration experienced a high degree of woody encroachment by ectomycorrhizal Scots pine, were compositionally most distinct from managed open grasslands, which had little woody vegetation even prior to restoration. The functional structure of plant and fungal communities varied in ways that were consistent with the representation of mycorrhizal types in the ecosystems prior to restoration. Compositional differences between managed and unmanaged open grasslands reflecting the implementation of grazing without further management interventions were clearer among fungal, and to an extent prokaryotic, communities than among plant communities. While previous studies have shown that during woody encroachment of alvar grassland, plant communities change first and fungal communities follow, our DNA-based results suggest that microbial communities reacted faster than plant communities during the restoration of grazing management in alvar grassland. We conclude that while the plant community responds faster to cessation of management, the fungal community responds faster to restoration of management. This may indicate hysteresis, where the eventual pathway back to the original state (grazed ecosystem) differs from the pathway taken towards the alternative state (abandoned semi-natural grassland ecosystem).

Grazing conserves threatened carabid beetles in semi-natural calcareous grasslands better than mowing, especially at low intensities

Grazing conserves threatened carabid beetles in semi-natural calcareous grasslands better than mowing, especially at low intensities

Increasing connectivity enhances habitat specialists but simplifies plant\u2013insect food webs

Strong declines of grassland species diversity in small and isolated grassland patches have been observed at local and landscape scales. Here, we study how plant–herbivore interaction webs and habitat specialisation of leafhopper communities change with the size of calcareous grassland fragments and landscape connectivity. We surveyed leafhoppers and plants on 14 small (0.1–0.6 ha) and 14 large (1.2–8.8 ha) semi-natural calcareous grassland fragments in Central Germany, differing in isolation from other calcareous grasslands and in the percentage of arable land in the surrounding landscape (from simple to complex landscapes). We quantified weighted trophic links between plants and their phytophagous leafhoppers for each grassland fragment. We found that large and well-connected grassland fragments harboured a high portion of specialist leafhopper species, which in turn yielded low interaction diversity and simple plant-leafhopper food webs. In contrast, small and well-connected fragments exhibited high levels of generalism, leading to higher interaction diversity. In conclusion, food web complexity appeared to be a poor indicator for the management of insect diversity, as it is driven by specialist species, which require high connectivity of large fragments in complex landscapes. We conclude that habitat specialists should be prioritized since generalist species associated with small fragments are also widespread in the surrounding landscape matrix.

Successful restoration of moth abundance and species-richness in grassland created under agri-environment schemes

Restoring intensive agricultural fields to species-rich semi-natural grassland could have profound effects on biodiversity and ecosystem services. However, only a minority of European agri-environment scheme funding is currently devoted to such measures (<1% in the UK) and too few studies compare biodiversity on restored habitats with that on appropriate control and reference sites. As a result, there is a lack of advice for land managers on how to implement habitat restoration to maximise conservation outcomes, especially for insects. We present a landscape-scale field study in which we tested whether the abundance and species-occurrence of moths (Lepidoptera) differed between arable fields, fields restored to species-rich grassland, and semi-natural calcareous grassland (CG). We also tested whether moths were affected by the frequency of CG indicator wildflowers, age of restoration and habitat connectivity of restored grassland. We found that the abundance of CG-associated moths on restored grassland was almost eight times that on arable fields, and abundance and species-occurrence did not differ significantly from that on semi-natural CG. The only group of moths that was more abundant on CG than restored grassland was associated with late successional stage habitats (e.g. woodland), which shows that trees and shrubs are key features maintaining insect biodiversity on CG. CG moths were more abundant on restored grassland sites where CG indicator wildflowers had established, suggesting that active enhancement of the plant community can increase the abundance of target insect groups. Restoring arable fields to species-rich grassland benefits moths over short timescales (as little as 3years) and at great distances from semi-natural CG (up to 7km). It should play a pivotal role in future agri-environment schemes aiming to increase insect biodiversity.

Local-scale spatial structure and community composition of orchid mycorrhizal fungi in semi-natural grasslands.

Orchid mycorrhizal (OrM) fungi play a crucial role in the ontogeny of orchids, yet little is known about how the structure of OrM fungal communities varies with space and environmental factors. Previous studies suggest that within orchid patches, the distance to adult orchids may affect the abundance of OrM fungi. Many orchid species grow in species-rich temperate semi-natural grasslands, the persistence of which depends on moderate physical disturbances, such as grazing and mowing. The aim of this study was to test whether the diversity, structure and composition of OrM fungal community are influenced by the orchid patches and management intensity in semi-natural grasslands. We detected putative OrM fungi from 0 to 32m away from the patches of host orchid species (Orchis militaris and Platanthera chlorantha) in 21 semi-natural calcareous grasslands using pyrosequencing. In addition, we assessed different ecological conditions in semi-natural grasslands but primarily focused on the effect of grazing intensity on OrM fungal communities in soil. We found that investigated orchid species were mostly associated with Ceratobasidiaceae and Tulasnellaceae and, to a lesser extent, with Sebacinales. Of all the examined factors, the intensity of grazing explained the largest proportion of variation in OrM fungal as well as total fungal community composition in soil. Spatial analyses showed limited evidence for spatial clustering of OrM fungi and their dependence on host orchids. Our results indicate that habitat management can shape OrM fungal communities, and the spatial distribution of these fungi appears to be weakly structured outside the orchid patches.

Spillover from adjacent crop and forest habitats shapes carabid beetle assemblages in fragmented semi-natural grasslands.

Semi-natural grasslands in Europe are insect biodiversity hotspots and important source habitats delivering ecosystem services to adjacent agricultural land by species spillover. However, this spillover might also occur in the opposite direction, affecting the diversity of semi-natural grasslands. This opposite spillover has got little attention in scientific literature even though generalist species penetrating into the grasslands can affect local biotic interactions, community composition and the conservation value of grassland habitats. In this study, we examined spillover effects from two different adjacent habitat types on carabid beetle assemblages in 20 semi-natural calcareous grasslands. The grasslands were either adjacent to a cereal crop field or to a coniferous forest. We found distinct differences in carabid beetle assemblages in calcareous grasslands depending on adjacent habitat type. Species richness and activity density were higher, but the evenness was lower in calcareous grasslands adjacent to crop fields compared with calcareous grasslands adjacent to coniferous forests. Further, we found a strong spillover of carabid beetles from adjacent crop fields after crop harvest, which may result in transiently increased predation pressure and resource competition in calcareous grasslands. Our results highlight that species composition, diversity and presumably ecosystem functions within semi-natural habitats are affected by the type and management of surrounding habitats. This needs to be considered by nature conservation measures, which aim to protect the unique insect communities of semi-natural European grasslands.

Managing towards extinction: Diverging developments of plant and ground beetle assemblages following restoration of calcareous grasslands

Central European calcareous grasslands are particularly rich in species, harbouring an endangered flora and fauna. In this study, we analyse how invertebrates, like ground beetles, react on vegetation changes in these habitats. We ask if and how species of both groups may react on local environmental changes associated with conservation management regimes. For this reason, vascular plant and ground beetle communities were assessed at six semi-natural calcareous grasslands in Luxembourg before (1988–1992) and after (2008–2010) restoration had started. All studied grassland sites are protected as nature reserves and managed to preserve an open and diverse plant species composition. Our data indicate diverging trends for plant and ground beetle composition: Richness and abundance of species increased for plants and decreased for ground beetles, particularly for forest and Red List species. Functional diversity of plants and ground beetles remained stable, although the abundance of nitrogen-loving plant species increased. In ground beetles, we identified increased proportions of species with strong habitat associations. These findings underline that plant species, in particular typical calcareous grassland species, benefited from ongoing conservation management, while many ground beetle species, mostly the non-grassland specialists, suffered under the applied management regimes. These results highlight the general dilemma in nature conservation of how to prioritise management regimes in situ.

Exploring Life Forms for Linking Orthopteran Assemblage and Grassland Plant Community

Abstract Orthopterans are well known to represent the majority of insect biomass in many grassland ecosystems. However, the verification of a relationship between the traditional descriptors of orthopteran assemblage structure and plant community patterns is not straightforward. We explore the usefulness of the concept of life forms to provide insights on such ecosystem level relationship. For this purpose, thirty sample sites in semi-natural calcareous grasslands were classified according to the relative proportion of dominant herbaceous plant life forms. Orthopteran species were grouped in four categories, based on the Bei-Bienko’s life form categorization. The association among plant communities, orthopteran assemblages and environmental factors was tested by means of canonical correspondence analysis. Orthoptera groups were found to be associated with distinct plant communities, also indicating the effect of vegetation change on orthopteran assemblages. In particular, geobionta species were associated with all the most disturbed plant communities, while chortobionta and thamnobionta seemed to be dependent on better preserved grassland types. Therefore, the use of life forms could help informing on the relationships of orthopteran assemblages with grassland conservation state. Information on such community relationships at the local scale could also assist managers in the interpretation of habitat change maps in terms of biodiversity changes.

Local and landscape management drive trait-mediated biodiversity of nine taxa on small grassland fragments

Aim Biodiversity across the globe is heavily eroded by intensified management at local and landscape scales. Species communities of calcareous grasslands, which are among Europe's most diverse habitats, are severely threatened by the cessation of appropriate traditional management, loss of habitat connectivity and simplification of the surrounding landscape. However, our understanding of these often interrelated factors remains limited, in particular for trait-mediated responses across taxa. Here, we test the independent effects of local management (grazing, mowing and abandonment), habitat connectivity (measured by a connectivity index) and landscape complexity (indicated by the percentage of arable land) on nine taxa: plants, butterflies, bees, grasshoppers, hoverflies, spiders, true bugs, rove beetles and leafhoppers on small semi-natural calcareous grassland remnants (< 1 ha). Location Central Germany. Methods We use a joint analysis across taxa to identify general and trait-mediated responses (body size and Red List status) in species richness, abundance and community composition. Results We identified three key drivers of local diversity patterns: First, an increasing proportion of arable land from 10% to 80% led to a 29% loss of overall species richness. Second, despite differences between taxa, increasing habitat connectivity generally enhanced species richness. Connectivity effects were more accentuated in the large species per taxon, which can be expected to be good dispersers. Finally, grazing reduced species richness and abundance much more than annual mowing or short-term abandonment (5–15 years), in particular for red-listed species. We attribute this to plant resource removal through overgrazing and trampling. Main conclusions For the conservation management of small calcareous grasslands, we advocate an alternating strategy of mowing or lenient grazing and short-term abandonment, prioritizing connected fragments surrounded by diverse landscapes. Despite taxon-specific responses, our study across nine taxa demonstrates universal, trait-mediated effects of management, landscape complexity and connectivity on local biodiversity in fragmented communities.

Is the positive relationship between species richness and shoot morphological plasticity mediated by ramet density or is there a direct link?

Little is known about the consequences of phenotypic plasticity in co-existing species for plant community structure. However, it has been proposed that the potential of plants to exhibit plastic responses to light availability could be a key factor determining the capability of individuals to co-exist at small scales. Our previous research demonstrated that morphological plasticity to light was positively related to small-scale species richness in a temperate grassland. However, it remained unclear whether this relationship was solely due to a higher shoot density in plastic assemblages, or whether diversity was directly related to the morphological plasticity of the co-inhabitants. We used two data sets to clarify this relationship: experimentally acquired estimates of plasticity to light availability for 45 herbaceous plant species, and species richness and ramet density data from a 2-year permanent plot study in a semi-natural calcareous grassland. There was little ramet mortality observed in the permanent plot study indicating that the link between plasticity and richness does not operate through reduced mortality in more morphologically plastic assemblages. The local density of ramets explained most of variation in small-scale richness, but there was also a significant direct density-independent effect of mean shoot plasticity on richness, showing that plasticity to light directly enhances the small-scale co-existence of species.

The intimacy between sexual traits and Grime’s CSR strategies for orchids coexisting in semi-natural calcareous grassland at the Olive Lawn

The diversity of orchid species in semi-natural calcareous grassland is thought to depend on floral variability. However, differences in primary life-history strategy, or the overall suite of functional traits, could also affect coexistence. Both primary strategy (affecting day-to-day survival) and reproductive traits (representing periodic events) have been hypothesized to contribute to a general mechanism regulating the local persistence and relative abundance of species. We recorded species identity at 8,000 points at the centimetre scale along sixteen 5-m long transects at the Olive Lawn, a xeric sand calcareous grassland near Lecco, Italy. Transects allowed the relative abundance and spatial aggregation of Grime’s competitor, stress-tolerator, ruderal (CSR) strategies to be quantified. Orchid flowering and fruiting phenology was recorded alongside the phenology of graminoid growth. Seven orchid species were present and exhibited a spectrum of strategies spanning two extremes, (1) small early-flowering ruderals (R/CR-selected), and (2) larger-leaved competitors (C/CR) flowering later as dominant graminoids attained maximum height. These orchids, and other subordinate species in the community, exhibited random spatial distributions amongst dominant graminoids that exhibited a high degree of spatial aggregation and similar, but non-identical, stress-tolerator (S) strategies. The reproductive phenology of meadow orchids is an intimate component of their CSR strategies, and appears to promote coexistence by allowing segregation between temporal niches and the exploitation of opportunities between clumps of dominant species. Only for closely related species with identical CSR strategies, such as Ophrys benacensis and Ophrys sphegodes, could specific floral differences alone explain coexistence.

Assessing the impact of land abandonment, nitrogen enrichment and fairy-ring fungi on plant diversity of Mediterranean grasslands

Semi-natural calcareous grasslands are of great conservation interest because of their high species richness, but they are threatened by land abandonment and nitrogen eutrophication. These plant communities evolved as a result of a long history of human activity, which generated and maintained these habitats by extensive grazing and mowing. Calcareous grasslands are listed as a priority for conservation in the EC Habitats Directive. However, the effects of different management regimes, nitrogen enrichment, and soil-borne pathogens on plant species diversity are less clear for grasslands of the Mediterranean Basin, compared to meadows in Northern and Central Europe. In this study, we assessed the impact of land abandonment, nitrogen enrichment, and fairy-ring fungi on species diversity in semi-natural grasslands found in the Mediterranean Basin by comparing the available literature with findings from recent studies carried out in Central Italy. In a series of field experiments, the cutting of abandoned grassland consistently reduced the living biomass of the dominant perennial grasses, such as Brachypodium rupestre and Bromus erectus, and promoted a rapid increase in species richness and diversity by allowing the establishment of rare species. There was a similar, but less effective, restoration of species diversity and composition in mowed grassland after litter removal. We also show that nitrogen enrichment at levels comparable to atmospheric deposition depresses species diversity, which also hampers the positive effects of litter removal. Our findings are consistent with previous results achieved in Northern and Central Europe, which however, mainly focused on grasslands with intermediate to high primary productivity levels. The limited availability of data from low-productivity, drought-prone Mediterranean grasslands requires further studies to assess the impact of land abandonment and nitrogen eutrophication in such ecosystems. Finally, we discuss the role of fairy-ring fungi in the maintenance of plant diversity in species-rich grassland. We show that fairy-ring fungi (e.g. Agaricus campestris) critically affect the spatial distribution and diversity of coexisting plant species. By killing the dominant perennial herbs, these radially growing plant pathogens produce empty niches for rare, short-lived species, thus affecting the vegetation pattern. Overall, our results are of interest for environmental managers, as they provide guidelines for the restoration of abandoned areas and the conservation of these species-rich habitats.

The conservation of ground layer lichen communities in alvar grasslands and the relevance of substitution habitats

Semi-natural calcareous grasslands (alvars) are biodiversity hotspots in Northern Europe, particularly for herb layer plants. In the last century, traditional management has ceased, and the area of grasslands has declined due to extensive encroachment. We were interested in the drivers of ground layer (alias terricolous or epigeic) lichen communities. Our survey consisted of 86 habitat fragments in western Estonia, covering four types of historic alvar grasslands and three types of alvar-like habitats. We found that the ground lichen communities were primarily soil-type-specific, but were also affected by historic disturbances and land use change. In contrast to knowledge about herb layer communities, for which shrub encroachment has been shown to be main driver, the increased density of the herb layer and the reduced diversity of microhabitats were major drivers for the ground layer lichen community. These drivers caused a decrease in species richness, but only within the species of conservation value, and also led to a shift in the composition of lichen growth form from the dominance of squamulose and crustose towards fruticose lichens. We conclude that the traditional practice of restoring alvars by cutting shrubs is insufficient to maintain ground layer lichen biodiversity. Alvar maintenance practices should include grazing, which creates various small-scale ground disturbances and increases microhabitat heterogeneity. Alvar-like habitats originating from large-scale historic disturbances appeared to be suitable for calcicolous epigeic lichens, and can therefore be considered to be temporary substitution habitats, i.e. refugia for the regional species pool.

Contrasting genetic and morphologic responses on recent population decline in two burnet moths (Lepidoptera, Zygaenidae)

Species often respond differently to identical environmental changes. Such different responses might be the consequence of varying ecological requirements and tolerances of specialists compared to generalists. We selected two closely related burnet moth species with contrasting ecological requirements: Zygaena carniolica is restricted to semi-natural calcareous grasslands and represents a stenotopic taxon, while Zygaena viciae occurs more widespread at extensively used meadows forming larger metapopulations. To examine different responses to recent habitat fragmentation, we analysed genetic and morphologic variation between populations of these two Zygaenid species in western Germany and adjoining areas in France and Luxembourg. Our data indicate contrasting genetic and morphologic patterns for both species: the genetic differentiation among populations is lower for Z. carniolica (FST: 0.049) compared to Z. viciae (FST: 0.058). The genetic diversity for Z. carniolica is rather low and homogeneously distributed over all populations, while Z. viciae has more alleles, which are unevenly distributed and often restricted to single populations, as shown by GENELAND models. The level of morphologic variance among and within (e.g. asymmetry) individuals is low for Z. carniolica, but much higher for Z. viciae. We conclude that these contrasting patterns mirror opposite responses on recent habitat degradation and associated loss of interconnectivity as a result of habitat destruction and land-use intensification. The data suggest that species like Z. viciae, with (historically) higher abundances suffer even stronger under the recent habitat loss. Morphologic asymmetry and genetic differentiation in the latter species rises, while diversity declines. More specialised taxa occurring in naturally isolated habitats (indicated by Species Distribution Models) feature an originally lower level of genetic diversity, and thus the impact of habitat decline on species’ persistence is less dramatic, as shown for Z. carniolica. Hence, we conclude that past and recent occurrence pattern has to be taken into account when interpreting data in the light of conservation measures.

Long-term experimental restoration in a calcareous grassland: Identifying the most effective restoration strategies

Calcareous grasslands are among the most diverse habitats, supporting species-rich vegetation. Propagule limitation and availability of microsites for germination represent major constraints to the successful restoration of these grasslands. To date, little information is available on the effectiveness of seed addition and soil disturbance on the restoration success of encroached semi-natural calcareous grasslands. Here, we conducted a 1year before –9year after control-impact (BACI) study aimed at testing the effect of the addition of seeds of native species and livestock grazing on calcareous grasslands. Each restoration measure and their combination differed in their impact on these communities and varied over time. Grazing had a significant, beneficial, impact on these communities, although the impact was species-specific. On average, grazed plots were characterized by a higher number of species and a lower vegetation cover. Nine years after treatment application, grazed site were dominated by Trifolium incarnatum subsp. molinerii, Xeranthemum cylindraceum, Orlaya grandiflora, Teucrium chamaedrys and Bromus erectus while ungrazed sites were dominated by B. erectus, X. cylindraceum, O. grandiflora and Prunus spinosa. Only 8 out of 34 species responded significantly to disturbance or/and disturbance and seed addition while 22 species were significantly affected by the sampling year and 18 by a blocking factor. The low recruitment from added seeds and the fact that seed addition is a time-and labor-consuming activity suggests that an adequate level of disturbance and natural regeneration represent the most cost-effective approach to the restoration of these calcareous grasslands.

Are butterflies and moths suitable ecological indicator systems for restoration measures of semi-natural calcareous grassland habitats?

The selection of suitable ecological indicator groups is of great importance for environmental assessments. To test and compare two such groups, we performed transect walks of butterflies and light traps of moths at eight sample localities in the Carinthian Alps. All of them were conducted with identical methods in the years 2002 and 2004 allowing the evaluation of the response on the conservation measures performed on five of the eight sites in late 2002. We recorded a total of 2346 butterflies (including Zygaenidae and Sesiidae) representing 83 species and 7025 moths of 534 species. 150 of these species were listed in the Red Data Book of Carinthia. In general, butterflies increased from 2002 to 2004 while moths declined. The highest increase rates of butterflies were obtained for the numbers of individuals of calcareous grassland specialists at the conservation sites, while their numbers were unchanged at the control sites. Similar trend differences between conservation and control sites were obtained for the Red Data Book butterfly species. On the contrary, the development of moth individuals was more positive at the control than the conservation sites for calcareous grassland specialists (only macro-moths) and species of the Red Data Book. However, change rates of species numbers were positively correlated between butterflies and moths. Principal Component Analysis revealed strong differences between the different sites, but mostly consistent results for butterflies and moths; however, stronger differences between years were only detected for some of the conservation sites for the butterfly communities. Our results show that butterflies as well as moths are suitable ecological indicator groups, but they do not yield identical results. Thus, butterflies are more suitable for the analysis of open habitats, whereas moths are suitable for open and forested habitats as well. Furthermore, butterflies might be a more sensitive indicator group than moths for the short-term detection of conservation measures, especially for the restoration of open habitat types.

Patch Size and Landscape Effects on Pollinators and Seed Set of the Horseshoe Vetch, Hippocrepis comosa, in an Agricultural Landscape of Central Europe

Agricultural land use intensification has caused a considerable decline of once common semi-natural habitats leaving only small and isolated habitat remnants within a homogeneous landscape matrix. Populations of flowering plant species in these remaining habitat fragments are also declining and can not offer sufficient resources for potential pollinators. The loss of pollinators and consequential pollination limitation is especially severe for obligately out-crossing plant species. In this study, pollination and reproductive success of Hippocrepis comosa was examined. Hippocrepis comosa L is a self-incompatible, declining plant species occurring on fragmented remnants in semi-natural calcareous grassland habitats in an agricultural landscape in Southern Lower Saxony, Germany. Plant-pollinator interactions were analysed in small, medium, and large plant patches in 15 differently sized calcareous grassland fragments surrounded by landscape matrices of differing complexity. Flower visitors were observed during three 15-minute observations, pollen supplementation experiments were performed to test for pollination limitation, and fruits from the plant patches were collected to calculate seed set. Hippocrepis comosa showed evidence of pollination limitation because hand-pollinated flowers set more seeds per inflorescence than open-pollinated flowers and seed set was strongly reduced by decreased visitation rates. Pollinators were most abundant in large patches and in diverse landscapes. Visitation rate was not affected by patch size. Hence, in order to maintain plant-pollinator interactions in an agricultural landscape, conservation efforts should include the preservation of calcareous grasslands that can support sufficiently large patches of a plant species and offer ample rewards for pollinators and the establishment of a diverse agricultural landscape around the semi-natural habitats that will further enhance pollinator abundance.

Grassland diversity related to the Late Iron Age human population density

1 Species-rich semi-natural grasslands in Europe developed during prehistoric times and have endured due to human activity. At the same time, intensive grassland management or changes in land use may result in species extinction. As a consequence, plant diversity in semi-natural calcareous grasslands may be related to both historical and current human population density. 2 We hypothesize that current vascular plant diversity in semi-natural calcareous grasslands is positively correlated with the Late Iron Age (c. 800-1000 years ago) density of human settlements (indicated by Late Iron Age fortresses and villages) due to enhancement of grassland extent and species dispersal, and negatively correlated with current human population density due to habitat loss and deterioration. 3 We described the size of the community vascular plant species pool, species richness per 1 m(2) and the relative richness (richness divided by the size of the species pool) in 45 thin soil, calcareous (alvar) grasslands in Estonia. In addition to historical and current human population density we considered simultaneously the effects of grassland area, connectivity to other alvar grasslands, elevation above sea level (indicating grassland age), soil pH, soil N, soil P, soil depth, soil depth heterogeneity, geographical east-west gradient, precipitation and spatial autocorrelation. 4 Both the size of the community species pool and the species richness are significantly correlated with the Late Iron Age human population density. In addition, species richness was unimodally related to the current human population density. The relative richness (species 'packing density') was highest in the intermediate current human population densities, indicative of moderate land-use intensity. 5 Community species pool size decreased non-linearly with increasing soil N, and was highest at intermediate elevation. Small-scale richness was greater when sites were well connected and when the elevation was intermediate. Spatial autocorrelation was also significant for both species pool size and small-scale richness. 6 In summary, human land-use legacy from prehistoric times is an important aspect in plant ecology, which could be an important contributor to the current variation in biodiversity. (Less)

Multivariate analysis of the response of overgrown semi-natural calcareous grasslands to restorative shrub cutting

Monitoring and evaluation of restoration management often suffers from poor sampling design and a lack of statistical rigour, seldom considering the spatial and temporal variability of habitat. We tested the effectiveness of shrub cutting on the restoration of calcareous grasslands, using a 4-year Before–After/Reference-Control-Impact (BARCI) project design with replicated patches of habitat. Departure from the control sites and convergence with the reference sites were analysed using the Principal Response Curves (PRC) method. The structure of communities was compared 1 year before and 3 years after management on control scrubland, restored ex-arable land, restored and reference grassland. Results show that shrub cutting did not suffice to restore the community composition of the semi-natural calcareous grasslands. The restored ex-arable areas maintained a community structure extremely similar to the control scrubland. The restored grassland, on the other hand, deviated from the control and slightly converged to the reference grassland, though not significantly. The dominant scrub species that was cut, Prunus spinosa , showed higher cover values compared to the reference grassland in any of the treatments, even the first year after cutting. Species typical of xeric and/or calcareous grassland were more abundant in the reference than in the restored grassland, while arable and ruderal species were more frequent in the restored sites. This study has demonstrated that the BARCI approach is a powerful tool for the evaluation of restoration management, as it was possible to evaluate not only departure from the unmanaged control, but also convergence with the reference community. The PRC method provided a comprehensive overview of the response of the 153 species involved in the study. Our results also indicate that the second PRC should be considered, when significant, to not exclude important information from the assessment. Die Erfolgskontrolle von ökologischen Restaurationsmaßnahmen leidet häufig an ungenügendem Design und mangelnder statistischer Genauigkeit, denn selten werden die räumliche und zeitliche Habitatvariabilität berücksichtigt. Wir prüften die Effektivität der Entbuschung für die Restauration von Kalkgrasland in einem vierjährigen ‘Before-After/Reference-Control-Impact (BARCI) Untersuchungsdesign mit replizierten Probestellen. Abweichung von den Kontrollflächen und Annäherung an die Referenzflächen wurden mit Hauptreaktionskurven (PRC) analysiert. Die Struktur der Gemeinschaften wurde ein Jahr vor und drei Jahre nach der Entbuschung untersucht: die Probestellen lagen auf Gebüschflächen (Kontrolle), restaurierten ehemaligen Ackerflächen, in restauriertem Grasland und im Referenz-Grasland. Die Entbuschung genügte nicht, um die Gemeinschaft von halbnatürlichem Kalkgrasland wiederherzustellen. Die restaurierten ehemaligen Ackerflächen behielten eine Gemeinschaftsstruktur, die der der Gebüschflächen äußerst ähnlich war. Die restaurierten Grasländer wichen dagegen von den Kontrollen ab und näherten sich leicht, wenn auch nicht signifikant, dem Referenz-Grasland an. Die dominante Buschart, die entfernt wurde, Prunus spinosa , erreichte in jeder Behandlung höhere Bedeckungsgrade als im Referenz-Grasland, sogar im ersten Jahr nach der Entbuschung. Arten der trockenen und/oder Kalkgrasländer waren auf den Referenzflächen zahlreicher als auf den restaurierten Grasländern, während hier Acker- und Ruderalarten häufiger vorkamen. Diese Untersuchung zeigt, daß der BARCI-Ansatz ein effektives Mittel für die Evaluation von Restaurationsmaßnahmen ist, da nicht nur die Abweichung von der unbehandelten Kontrolle, sondern auch die Annäherung an die Referenzgemeinschaft ermittelt werden kann. Die PRC-Methode bietet einen umfassenden Überblick über die Reaktionen der 153 Arten, die mit dieser Untersuchung erfaßt wurden. Unsere Ergebnisse zeigen, daß auch die zweite PRC, soweit signifikant, ausgewertet werden sollte, um nicht für die Bewertung wichtige Informationen außer acht zu lassen.

Effects of long term CO2enrichment on microbial community structure in calcareous grassland

Elevated CO 2 generally increases plant productivity, and has been found to alter plant community composition in many ecosystems. Because soil microbes depend on plant-derived C and are often associated with specific plant species, elevated CO 2 has the potential to alter structure and functioning of soil microbial communities. We investigated soil microbial community structure of a species-rich semi-natural calcareous grassland that had been exposed to elevated CO 2 (600 μL L -1 ) for 6 growing seasons. We analysed microbial community structure using phospholipid fatty acid (PLFA) profiles and DNA fingerprints obtained by Denaturing Gradient Gel Electrophoresis (DGGE) of 16S rDNA fragments amplified by the Polymerase Chain Reaction (PCR). PLFA profiles were not affected by CO 2 enrichment and the ratio of fungal and bacterial PLFA did not change. Ordination analysis of DNA fingerprints revealed a significant relation between CO 2 enrichment and variation in DNA fingerprints in summer (P = 0.01), but not in spring. This variation was due to changes in low-intensity bands, while dominant bands did not differ between CO 2 treatments. Diversity of the bacterial community, as assessed by number of bands in DNA fingerprints and calculation of Shannon diversity indices, was not affected by elevated CO 2 . Overall, only minor effects on microbial community structure were detected, corroborating earlier findings that soil carbon inputs did probably change much less than suggested by plant photosynthetic responses.