The impact of grazing on spider communities in a mesophytic calcareous dune grassland |
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Authors: | Bonte D Maelfait J -P and Hoffmann M |
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Institution: | (1) Institute of Nature Conservation, Kliniekstraat 25, B-1070 Brussels, Belgium;(2) Lab, Botany, University of Ghent, K.L. Ledeganckstraat 25, B-9000 Ghent, Belgium;(3) Lab Animal Ecology, Department of Biology, University of Ghent, K.L. Ledeganckstraat 25, B-9000 Ghent, Belgium |
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Abstract: | During 1994–1995 and 1997–1998 spiders were sampled with pitfall traps in a botanically rich, mesophytic, calcareous dune
grassland in Belgium. As a consequence of intensive cattle grazing, vegetation variation in a large part of the area had diminished.
The study area was also patchily grazed by rabbits. Community analysis with TWINSPAN revealed five distinct spider communities.
Ecological differentiation was best explained by combination of the habitat variables: distance from grazed or non-grazed
vegetation,Rosa pimpinellifolia cover and grass cover in both summer and winter. Species diversity was highest in the border zone between the cattle-grazed
and non cattle-grazed sites.
Correlation of the most abundant spider species with the vegetation determinants explains the ecological differentiation between
the spider communities. Species were classified into seven major groups that reflect the species’ habitat preferences. The
group showing clear association with non cattle-grazed, tall vegetation consists of common species. Characteristic species
for the intensively cattle-grazed sites are common aeronauts and rare species such asWalckenaeria stylifrons, Mastigusa arietina, Ceratinopsis romana andPardosa monticola. The latter are shown to be dependent on ungrazed vegetation for juvenile development and overwintering. Intensive grazing
results in homogeneous short vegetation, which can only be colonized by ‘open ground’ species with a well-developed dispersal
capacity, or by species which are not dependent on litter-rich situations for juvenile development. An extensive cattle grazing
regime results in a patchy mosaic grassland where, in addition to the above mentioned groups of species, other species survive
by migrating between the buffered litter rich ungrazed vegetation and the short vegetation. Additionally, some typical and
rare species prefer the transition zone between the grazed and the ungrazed vegetation because they are associated with specific
habitat structures or inhabiting ant-species. |
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Keywords: | Araneae Dune management Hibernation habitat Non-metric multidimensional scaling |
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