Acta Zoologica 46. (2000)

2000 / 1. szám - MAGURA TIBOR - TÓTHMÉRÉSZ BÉLA - MOLNÁR TIVADAR: Spatial distribution of carabids along grass-forest transects

2 MAGÚRA. T.. TÓTHMÉRÉSZ. В. & T. MOLNÁR needed for the purposes of nature conservation and conservation biology, in order to identify potentially rare habitats and species, and to assess their vulnerability and needs of protection (NIEMELÄ & HALME 1992). Carabid beetles, like most organisms, are generally non-randomly dis­tributed on several spatial scales (LUFF 1986, BÁLDI & ÁDÁM 1991, NIEMELÄ & SPENCE 1994, NIEMELÄ et al. 1990). This non-random carabid occurrence is determined by the heterogeneous distribution of abiotic conditions and resources (NIEMELÄ et al. 1992a). However, there are several scales of environmental hete­rogeneity, and species responses may be determined by different factors at vari­ous levels of environmental pattern (NIEMELÄ et al. 1992b). For example, on the regional scale the distribution of a particular carabid species may be determined mainly by geographic, climatic and historical factors (HENGEVELD 1987, PENEV & TURIN 1994, PENEV 1996). But on a local scale, that is, in an area which is well within the dispersal radius of the species, variation in distribution across habitat types may be determined by environmental conditions and interspecific interactions (NIEMELÄ et al. 1985, 1996, LUFF et al. 1992, HALME & NIEMELÄ 1993, Eyre 1994, Eyre & Luff 1994). In this paper we present an analysis of ground-beetle distribution on a local scale, in grass-forest transects at the ecological scale of interacting populations (NIEMELÄ & SPENCE 1994). Our objectives were to assess the extent of variation in the distribution of carabid species, and to relate this to habitat characteristics and to spatial distribution of co-occurring carabid species. MATERIAL AND METHODS Study area and sampling Sampling area was located at the Northern Mountains in the Aggtelek National Park, near the Mogyorós Peak (Haragistya). In this region oak-hornbeam forests (Querco-Carpinetum) and a grass association (Polygalo majori-Brachypoclietum pinnati) are the most extensive. There are three habitat types on the research area: (1) Grass (Polygalo majori-Brachypodietum pinnati), with dense herbaceous vegetation dominated by Polygala major, Brachypodietum pinnatum, Filipendula vulgaris, Salvia pratensis, Inula hirta, Geranium sanguineum. The litter layer, the shrubs and the canopy layer are missing in this habitat. Its area was approx. 40 ha. (2) Forest edge, with dense herbaceous vegetation originating from the adjacent grass. The shrub layer is also dense in this habitat, consisting mainly of shrubs and saplings of the canopy trees (Carpinus betulus, Corylus avellana and Prunus spinosa). The litter layer is thick and the ca­nopy layer is less closed than in the forest interior. (3) Forest interior: oak-hornbeam forest, with thick litter layer, moderate herbaceous and shrub layer and with 85-95 % canopy cover. The size of the forest stand was greater than 100 ha. Beetles were collected using unbaited pitfall traps, consisting of plastic cups (diameter 100 mm, volume 500 ml) containing ethylene-glycol as a killing-preserving solution (Spence & Nieme- LÄ 1994). Three replicated parallel transects of pitfall traps were set across the three studied habi­tats, about 50-70 meters from each other. The transects were perpendicular to the forest edge. Acta zool. hung. 46, 2000

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