Ground-Dwelling Arthropods and Ski-Pistes

Research on the impact of ski-runs on ground-dwelling arthropods has so far been largely neglected, despite the fact that such invertebrates may provide goods and services that are fundamental for mountain ecosystem functioning, and may be usefully employed as bio-indicators of human-induced environmental disturbance. In this chapter we present the results of previous research carried out in the north-western Italian Alps by pitfall trapping on ski-pistes, in adjacent habitats (i.e. forests or alpine prairies) and at the habitat edge. Research focused mainly on ground beetle and spider assemblages, but several results on other groups of arthropods (harvestmen, grasshoppers) were also provided. Below the tree line, all parameters of diversity (i.e. mean abundance, species richness and Shannon index) of brachypterous carabids (reduced wings or wingless) significantly decreased from forest interior to open habitats (i.e. ski-piste or pasture), whereas those of spiders and macropterous carabids (full-sized wings) increased from forest interior to open habitat. Ski-pistes showed lower values than pastures in all community parameters. Indicator Species Analysis showed that there were fewer species significantly preferring forest ski-pistes compared to those preferring pastures, and that there were very few species which were exclusive to ski-pistes (mainly generalist/eurieciouos species). Above the tree line, mean abundance and species richness of brachypterous carabids, spiders and grasshoppers decreased significantly from natural grasslands to ski-pistes. This was not true for the guild of macropterous beetles, which was composed of species with contrasting ecological requirements. Most of the species (some of them endemic to restricted areas in the western Italian Alps) had clear preferences for natural grassland and only two species of ground beetles (one being a generalist) had preference for ski-pistes. Both below and above the tree line, generalized linear models showed that the poor grass cover of skipistes is a serious hindrance to colonization by ground-dwelling arthropods. The potential impact of ski-pistes on the functioning of high altitude ecosystems and on the conservation of endemic species is discussed.