Ground-dwelling invertebrates of the high alpine: Changes in diversity and community composition along elevation (1500–3000 m)

Abstract

Although the number of studies on soil and ground-dwelling fauna is constantly increasing, only few focus on high alpine areas. We conducted a comprehensive survey of ground-dwelling invertebrates in (high) alpine dry pastures along three elevational gradients (1500 to 3000 m a.s.l.) in the LT(S)ER area ‘Val Mazia/Matschertal’, South Tyrol, Italy. The objectives were (i) to assess the composition of mobile, surface-active invertebrate communities and their diversity patterns along the elevation, and (ii) to analyse the influence of selected environmental factors (soil parameters and vegetation composition) on their composition.On 12 plots (three at each elevation step), we installed three pitfall traps per sampling period covering most of the growing season from May to September: three times for two weeks on the lower (1500 and 2000 m) and twice for three weeks on the higher plots (2500 and 3000 m). Taxa were mostly identified to family level and changes in activity densities, diversity indices and beta diversity were evaluated.Overall, activity density decreased gradually but not significantly from about 21 individuals per day and trap at 1500 m to just over 9 individuals at 3000 m. This indicates a highly active ground-dwelling community along the entire mountain ridge throughout the growing season. Alpha diversity differed significantly but inconsistently between elevations, while beta diversity remained constant along the gradient (Sörensen index around 0.60). Community composition differed for each elevation and turnover rates (i.e. the exchange of taxa) increased with elevation from 70 to 87 %. Elevation as a proxy for climate warming, rather than soil and vegetation related factors, was found to be the main driver of differences in community composition. At the current rate of global warming and with different communities at each elevation, ecosystem services and processes could be strongly affected by the expected changes in invertebrate community compositions.