Calcareous Grassland Habitat Research Articles

Presence-absence of plant habitat specialists in 15 patches of dry calcareous grassland.

Dry grasslands on calcareous bedrock in warm climates around the Oslo Fjord are naturally fragmented biodiversity hotspots. This habitat geographically coincides with the most densely populated area of Norway. Many habitat specialists, along with the habitat itself, are red-listed because of land-use change, forest encroachment, and invasive species that cause habitat loss and greater isolation of remaining patches. To ensure effective conservation, data on species presences and absences are necessary to quantify states, changes, and extinction risks in specific populations and habitat patches. We present presence-absence data of 49 vascular plant species in 15 patches of dry calcareous grassland habitat, surveyed in 2009, 2019, and in 2020. The species are considered to be habitat specialists and, thus, unlikely to occur between the patches.

Soil Seed Bank Persistence Across Time and Burial Depth in Calcareous Grassland Habitats.

Seed persistence in the soil is crucial for population dynamics. Interspecific differences in soil seed mortality could be a mechanism that may stimulate species coexistence in herbaceous plant communities. Therefore, understanding the levels and causes of seed persistence is vital for understanding community composition and population dynamics. In this study, we evaluated the burial depth as a significant predictor of the temporal dynamics of soil seed persistence. We suppose that species differ in this temporal dynamics of soil seed persistence according to burial depth. Furthermore, we expected that burial depth would affect soil seed persistence differently concerning the species-specific type of dormancy, light, and fluctuating temperature requirements for germination. Seeds of 28 herbaceous species of calcareous grasslands were buried in the field into depths of 1, 5, and 10 cm under the soil surface. Seed viability was tested by germination and tetrazolium tests several times for three years. Species-specific seed traits—a type of dormancy, light requirements and alternating temperature requirements for germination, and longevity index—were used for disentangling the links behind species-specific differences in soil seed persistence. Our study showed differences in soil seed persistence according to the burial depth at the interspecific level. Generally, the deeper the buried seeds, the longer they stayed viable, but huge differences were found between individual species. Species-specific seed traits seem to be an essential determinant of seed persistence in the soil. Seeds of dormant species survived less and only dormant seeds stayed viable in the soil. Similarly, seeds of species without light or alternating temperature requirements for germination generally remained viable in the soil in smaller numbers. Moreover, seeds of species that require light for germination stayed viable longer in the deeper soil layers. Our results help understand the ecosystem dynamics caused by seed reproduction and highlight the importance of a detailed long-term investigation of soil seed persistence. That is essential for understanding the fundamental ecological processes and could help restore valuable calcareous grassland habitats.

Identifying plant and environmental indicators of ancient and recent calcareous grasslands

Dry calcareous grasslands are among the most species-rich habitats in Central Europe, harbouring numerous threatened species. Because of their strong decline, they are being protected under the European Habitats Directive. However, apart from this general decline, new grasslands developed after the abandonment of arable fields on marginal land over the course of the last few centuries or even decades. The main question of this study was which species may indicate the age of a dry calcareous grassland habitat in the Franconian Jurassic mountains near Kallmünz. We compared the diversity parameters and nature conservation value of both grassland types. Additionally, we searched for differences in habitat and soil parameters. Furthermore, we asked if there is a general pattern of indicator species among available studies on ancient (i.e. those continuously used as pastures at least since 1830) and recent (i.e. those temporarily farmed as arable fields after 1830) calcareous grasslands. We compiled a list of indicator species of both ancient and recent grasslands in the study region. Comparison with other studies leads to the conclusion that there are not many species that clearly indicate grassland age across different regions (the best indicators are Carex caryophyllea, Cirsium acaule and Hippocrepis comosa for ancient grasslands, and Agrimonia eupatoria and Astragalus glyciplyllos for recent grasslands). Ancient grasslands harbour a somewhat greater number of threatened species than recent grasslands. Many species of the ancient grasslands under study can be considered relict species of steppic grasslands or open pine forests (e.g. Hippocrepis comosa, Pulsatilla vulgaris, Teucrium chamaedrys, Teucrium montanum and Thymus praecox). Recent grasslands also harbour rare and endangered species, especially disturbance-tolerant relicts of former arable use (e.g. Melampyrum arvense) and may therefore be of high conservation value, too. The average number of species per plot is greater in ancient grasslands. However, the most species-rich plot (46 species of vascular plants within a 4-m2 quadrat) was found in a 60 years old grassland. Arable cultivation in the past has altered the physical and chemical properties of the soil of recent grasslands. In general, ancient grasslands occur on nutrient-poorer and less calcium-rich soils with high water holding capacity. High water holding capacity is connected with high humus content, which increases the importance of ancient grasslands for carbon storage. The challenges and benefits of differentiating grasslands of different age in the management of protected areas and landscape planning (e.g. the identification of High Nature Value farmland) are discussed.

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.

Hybrid ecosystems can contribute to local biodiversity conservation

Calcareous grasslands have become severely threatened habitats in Europe. The aim of this study was to investigate the changes in plant species richness, and functional and phylogenetic diversity in northern Estonian calcareous (alvar) grasslands resampled after 90 years of land-use change. Functional traits characterizing species that have benefited most from decreased habitat area and altered environmental conditions, and additional species that can potentially inhabit the remaining grassland patches were identified. Also changes in the relative amount of habitat-specific species were studied to detect a possible decrease in habitat integrity. Although grasslands in the studied region had lost most of their original area (~90 %), species richness had substantially increased due to invasion by more competitive, nutrient-demanding native species. Functional diversity generally increased, whereas phylogenetic diversity showed no response to altered conditions. Overall, these grasslands have lost their integrity as calcareous grassland habitat type in the region, because the relative amount of habitat-specific characteristic species has declined significantly. However, although the grasslands have transformed to a ‘hybrid’ habitat type and restoration to their previous state is likely not reasonable, such degraded species-rich grassland fragments can still be recognized as important habitats to preserve high local biodiversity and several characteristic species of calcareous grasslands. As current landscapes consist of an increasing number of hybrid and novel communities, new tools to supplement traditional conservation or restoration practices are necessary to recognize and maintain regions and habitats of high local biodiversity.

Natural Establishment of Specialist Plant Species after Topsoil Removal and Soil Perturbation in Degraded Calcareous Sandy Grassland

AbstractSpecialist plant species in calcareous sandy grasslands are threatened by acidification and high nutrient levels in the topsoil. We investigated whether topsoil removal and soil perturbation in degraded sandy grasslands could lead to establishment of specialist species belonging to the threatened xeric sand calcareous grassland habitat. Restoration actions performed in 2006 resulted in increased soil pH and reduced nitrogen availability. We found early colonisztion of the perennial key species Koeleria glauca after both deep perturbation and topsoil removal, and high seedling establishment in topsoil removal plots 5 and 6 years following the restoration treatment (2011–2012). After topsoil removal, overall vegetation composition in 2012 had developed toward the undegraded community, with target species accounting for 20% of the community after topsoil removal, compared to 30% in the undegraded vegetation, and less than 1% in untreated controls. Deep perturbation led to 7% target species, while there were almost no effects of shallow perturbation 6 years following treatment. These results demonstrate that topsoil removal can promote colonization of target species of calcareous sandy grassland and highlights the importance of considering the regeneration niche for target species when implementing restoration measures.

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.

Spider Diversity of an Upland Calcareous Grassland Habitat in the Brecon Beacons National Park, UK

Spider Diversity of an Upland Calcareous Grassland Habitat in the Brecon Beacons National Park, UK

The effects of habitat fragmentation on niche requirements of the marsh fritillary, Euphydryas aurinia, (Rottemburg, 1775) on calcareous grasslands in southern UK

The marsh fritillary, Euphydryas aurinia, has declined greatly in distribution across its range within Europe, resulting in its designation as a protected species under Annex II of the 1979 Bern Convention and the EC Habitats and Species Directive. The decline has been linked to a marked reduction in the extent of suitable calcareous and wet grassland habitats, habitats which have been lost through conversion of land to agriculture or urban areas, or reduced in quality due to inappropriate management. The UK is now one of the major strongholds for this butterfly in Europe, although much of the remaining habitat is small, isolated and highly fragmented. E. aurinia populations fluctuate greatly due to the combined effects of biotic (e.g. parasitoids) and abiotic (e.g. climate change) factors. We quantified the habitat associations of larval webs of E. aurinia on fragmented versus extensive (unfragmented) calcareous grassland habitat in southern England to test the hypothesis that habitat requirements of E. aurinia are more constrained within fragmented landscapes. Within both fragmented and unfragmented landscapes the quality and quantity of its main host plant in the UK, Succisa pratensis, was positively related to numbers of E. aurinia larval webs found. The sward height was also important at predicting the distribution of larval webs in both landscapes, although the heights were greater within sites in the unfragmented (≈20 cm) compared to fragmented (≈15 cm) landscape. We also found significant effects of elevation and the cover of bare ground on numbers of larval webs. Elevation was strongly correlated with the availability of host plant, whilst bare ground was only significant on sites within the fragmented landscape, showing a negative relationship with number of larval webs. Our results further emphasise the importance of not only maintaining the habitat quality of extant calcareous grassland sites for E. aurinia in the UK, but also increasing the size and connectivity of these sites to increase the chances and rate of (re)colonisation of unoccupied but suitable habitat. In addition, we show that the habitat requirements of E. aurinia on sites in a large unfragmented landscape may be less specific and thus require less extensive management than that required to create optimal conditions necessary at smaller, more isolated sites in fragmented landscapes.

The historical dynamics of calcareous grasslands in the central and southern Franconian Jurassic mountains: a comparative pedoanthracological and pollen analytical study

We present a thematic set on pedoanthracological research. In this paper a comparative analysis of soil wood charcoal from calcareous grasslands and pollen from an alluvial sediment profile has been carried out to reconstruct the history of calcareous grassland habitats in the Franconian Jura. Seven tree and shrub species (groups) were recorded from soil charcoal. Charcoal from Pinus dominated all spectra, indicating open forests or even less intensively grazed grasslands, which is supported by findings of remains of Juniperus and Ligustrum. Charcoals from Fagus, Quercus and Abies, indicating more closed forests, were comparatively rare. AMS radiocarbon datings assigned the charcoals to the period of the Roman Empire, the late Middle Ages and the early Modern Times correlating with the peaks of microcharcoals in the sediment profile. Juniperus pollen was used as indicator of calcareous grasslands. Plantago lanceolata, Galium type, Apiaceae, Ranunculaceae and Ballota/ Galeopsis pollen-types were significantly correlated with the occurrence of Juniperus and identified as further indicators. Pinus was selected as an indicator for open forests. Pollen of all indicator species occurred throughout the pollen profile starting in the Iron Age. The main peak of grassland indicator species pollen types was in the high Middle Ages. Maxima of Pinus pollen have been recorded in the periods of the Roman Empire and the late Middle Ages. We suggest extension maxima of less intensively grazed calcareous grasslands during the Roman Empire period and during the late Middle Ages and of intensively grazed grasslands in the high Middle Ages in the latter case correlated to intensive mining activities north of the study region. Increase in Pinus and the conversion of open into woody grasslands in the late Middle Ages/beginning of Modern Times was triggered by the abandonment of arable farming due to the decline of human population caused by pest diseases.

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.

Landscape structure and management regime as indicators of calcareous grassland habitat condition and species diversity

This study investigates the importance of spatial landscape characteristics and habitat management on the condition of calcareous grassland in the North Down Natural Area, Kent UK. We used a digitised map of the study area containing shapefiles of all the habitats including 82 patches of calcareous grassland together with management information for each patch and data on the presence and abundance of a range of calcareous grassland indicator plant species. We defined habitat condition by presence of indicator species and used classification trees to generate models with rules for predicting habitat condition from the landscape spatial characteristics and management information. We also applied the same method to investigate the factors affecting presence or diversity of three ecological groups of positive indicator species and dominance of a negative indicator species. All the models except one showed good classification accuracy and high kappa statistic. Favourable habitat condition was predicted by presence of different types of grazing management, presence of woodland around patches of calcareous grassland and shape complexity. These results indicate that calcareous grassland in favourable condition is management-dependent but also located in less intensively managed landscapes. Unfavourable habitat condition was predicted by threat factors such as lack of management and high incidence of arable or improved grassland around patches of calcareous grassland, indicating nutrient enrichment and habitat degradation. Some of these factors also predicted high diversity of the different ecological species groups. The value of this method for predicting habitat condition and species diversity from baseline ecological data for conservation monitoring at the landscape level is emphasised.

Habitat suitability modelling for calcareous grassland restoration on the South Downs, United Kingdom

The South Downs Area of Outstanding Natural Beauty, UK, is an internationally and nationally important landscape, which contains a significant proportion (28%) of the southeast of England's calcareous grassland resource. The traditional calcareous grassland habitats characteristic of the downland landscape have suffered significant losses since the Second World War, and the remaining sites are small, fragmented and confined to the more marginal areas, often steeper slopes. The re-creation and restoration of these species rich grasslands has become a central aim of national and regional conservation organisations, however, the methods and mechanism by which restoration sites could be identified has not been clarified. The purpose of this work was to study the landscape characteristics of the calcareous grassland systems, and by use of GIS-based modelling approaches identify those sites on the downland most suited to the re-establishment and expansion of calcareous grasslands. Using a weighted scoring approach, a GIS-based Habitat Suitability Model is developed for use as a tool to support strategic landscape evaluation and to provide a method of identifying sites for targeted restoration. The approach models the relationship between specific grassland communities and topographic variables, and is applied to the South Downs landscape in order to predict the nature of grassland communities likely to result from restoration efforts at specific sites.