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

Ashley Lyons,Ian Powell,Anne Oxbrough,Paul A Ashton

doi:10.1007/s10531-017-1488-4

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https://doi.org/10.1007/s10531-017-1488-4

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Journal: Biodiversity & Conservation	Publication Date: Dec 16, 2017
Citations: 9	License type: open-access

Affiliation: Edge Hill University

Abstract

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.

Highlights

Calcareous grassland, considered among the most species rich and diverse habitats for many species groups in Europe, underwent wide scale loss and degradation following post 1950s agricultural intensification and as such has become the focus of conservation efforts (Willems 2001; Fischer and Stocklin 1997; Poschlod et al 2005; Poschlod and Wallis de Vries 2002; Roesch et al 2013; Wallis De Vries et al 2002)
The habitats were defined as: calcareous grassland which had a species rich sward with a mean sward height of 8.09 cm over the sampling period, limestone heath which occurred in patches exceeding 20 m2 and was dominated by mature stage Calluna vulgaris, and acid grassland which was dominated by N. stricta, and again occurred in patches exceeding 20 m2
This study found distinct spider species assemblages between heath and both grassland habitat types, the latter not differing from each other

Summary

Introduction

Calcareous grassland, considered among the most species rich and diverse habitats for many species groups in Europe, underwent wide scale loss and degradation following post 1950s agricultural intensification and as such has become the focus of conservation efforts (Willems 2001; Fischer and Stocklin 1997; Poschlod et al 2005; Poschlod and Wallis de Vries 2002; Roesch et al 2013; Wallis De Vries et al 2002). Afforded protection under Annex I of the EU habitats directive, an estimated 595, 973 ha is protected in the Natura 2000 network across EU member states (Calaciura and Spinelli 2008) Their management typically aims to maintain particular plant communities through prevention of succession and domination by one or few species (Willems 2001; Wallis de Vries et al 2002). 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 grazing management (Rodwell 1992; Rodwell et al 2007). Under reduced intensity sheep grazing, these patches are either maintained as acid grassland (dominated by Nardus stricta) or develop into the climax community of limestone heath [EC Habitats Directive Annex 1 (Joint Nature Conservation Committee 2013)]. At low stocking densities sheep restrict grazing to vegetation patches containing preferred plant species resulting in effectively ungrazed patches of less preferred vegetation (Hester and Baillie 1998)

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