Measuring the effects of reduced snow cover on alpine arthropods: an Australian perspective

Snow is one of the most important factors in the ecology of alpine ecosystems. Already, snow seasonally covers just 0.15% of Australia and this area is forecast to decline considerably in the coming decades. Many small arthropods remain active throughout the winter, within the space beneath the snowpack where the insulating properties of snow create a thermally stable environment. Using field surveys and experimental manipulation of snow depth at two locations in the Australian alpine region, I explored the diversity of winter-active arthropods and tested their response to reduced snow. Using pitfall traps, individuals from up to 16 arthropod Orders were detected beneath the snow during each winter, with the Collembola, Araneae, Acari and Coleoptera accounting for 85-99% of the individuals collected. Removal of the snow layer increased daily temperature fluctuations, the number of days below freezing and, in contrast to previous studies, raised the mean surface temperatures. Community composition was altered by snow removal. This effect was driven by a strong reduction in the abundance of dominant species at one location, and by an increase in the numbers of individuals of dominant taxa at the other location. Subnivean arthropod communities in Australia thus appear sensitive to snow conditions at small spatial scales.