Arachnologische Mitteilungen 35

Arachnol. Mitt. 35: 51-60 Nürnberg, Juli 2008 Spider fauna of semi-dry grasslands on a military training base in Northwest Germany (Münster) Sascha Buchholz & Volker Hartmann Abstract: The spider fauna of semi-dry grasslands on the military training area of Dorbaum near Münster (North Rhine-Westphalia) was investigated. From 2002 to 2003 a total of 11,194 mature spiders from 141 species and 20 families was caught by pitfall trapping and hand sampling. Among them are 18 species listed in the Red Data Book of North Rhine-Westphalia, four species are rare or previously rarely recorded. Most of the spiders are habitat generalists that extend their occurrence into all types of habitats, while the number of species which are stenotopic to sand habitats is noticeably low (n = 13). The spider data were analysed with Principal Component Analysis (PCA). It is possible to distinguish spider communities of neighbouring forested habitats from species groups of open habitats, but there is no uniform spider community which is characteristic for semi-dry grassland. Keywords: Araneae, inland dunes, sand habitat, spider community,Westphalian Bay In northwestern Germany sand habitats are rare and restricted to small areas (V ERBÜCHELN & J ÖBGES 2000, P ARDEY 2004). Many habitats like dry grassland, heathland and inland dunes are en- dangered (V ERBÜCHELN et al. 1999) and contain a large number of specialised and rare animal species (B ELLMANN 1997, S TEVEN 2004). Spiders play an important role in ecological surveys – they are abundant, occupy a wide array of spatial and tem- poral niches, have high within-habitat taxonomic diversity, respond immediately to habitat change and are useful indicators of the overall species richness and ecological status of biotic communities (K IECHLE 1992, K REMEN et al. 1993,W ISE 1993, S CHULTZ & F INCH 1996, N ORRIS 1999). Never- theless, information about the ecology of spiders in sand habitats of Northwest Germany is still very poor (Lower Saxony: R ABELER 1951, L ADEMANN 1995, F INCH 1997,M ERKENS 2002; North Rhine- Westphalia: J ÄGER 1996, G RIGO 1997). Further work seems imperative for successful conservation and habitat management. This study about the epigeic spiders of the semi-dry grasslands on the military training area of Dorbaum near Münster is part of a detailed investigation of the ecology of spiders in sand habitats of the Westphalian Bay. Study area The study was carried out at a military training area which is located northeast of Münster near the districts Handorf and Dorbaum at an elevation of 50 m a.s.l. covering about 400 ha (Abb. 1). In the north the Ems river forms the boundary of the area. The study area is glacially formed and the ice-age top layers are fluviatile and aeolic sands with dry soil conditions. The climate is sub-Atlantic with a mean annual temperature of 9.5 to 10 °C and mean annual precipitation of 700 to 750 mm (M EYNEN & S CHMITHÜSEN 1959, M URL NRW 1989). Ac- cording to M EYNEN & S CHMITHÜSEN (1959) the potential natural vegetation is the Fago-Quercetum typicum. S TARKMANN et al. (1993) and G ROSSE (1995) describe the actual vegetation which consists of several endangered plant species. Beyond pine ( Pinus sylvestris ) and oak forests ( Quercus robur ), mainly at the edge of the area, small patches of dry grasslands with dry soil conditions and a sparse her- bal layer (Thero-Airion: Airo-Festucetum ovinae, Filagini-Vulpietum), dominated by Vulpia myuros and Aira caryophyllea , are distributed in parts of the training area. Furthermore the Airetum praecocis and the Spergulo-Corynephoretum are also present. All over the study area former dry grassland sites are overgrown by semi-dry grassland ( Agrostis capillaris - grassland, Holcus lanatus -grassland) (Beulting pers. comm.). For a further detailed description of the grassland vegetation types see G ROSSE (1995).The military training area was established in the second Sascha BUCHHOLZ & Volker HARTMANN, University of Münster, Institute of Landscape Ecology, Department of Community Ecology,Robert-Koch-Str.26,D-48149 Münster,Germany.E-mail: sbuchhol@uni-muenster.de, voha@uni-muenster.de eingereicht: 19.12.2007, akzeptiert: 21.5.2008