Evidence of a trait-specific response to burning in springtails (Hexapoda: Collembola) in the boreal forests of European Russia

The reaction of soil fauna to forest fires is highly variable in space across large ecoregions, the reasons for which are still not completely documented. We tested regional differences in the response of springtail (Hexapoda: Collembola) taxonomic richness, total abundance and collembolan abundance, which share combinations of the two traits (reproduction mode and vertical distribution), in a pilot study within boreal forests of European Russia. We selected four stands burned five years ago and four respective controls in each of the three boreal forest subregions: northern, middle and southern taiga. Plots were located along a 1500 km-long north-south transect covering most of the existing climatic and edaphic gradient within this ecoregion. The General Linear Model (GLM) results showed that fire had a significant effect on the abundance of collembolans that shared certain trait combinations (sexually reproducing epiedaphic species), while the total collembolan abundance depended on the forest subregion, but not burning. The abundance of sexually reproducing epiedaphic springtails decreased in burned plots by 40%, on average, in comparison with the respective controls. This reduction was positively correlated with the degree of fire severity and negatively correlated with litter thickness and soil water holding capacity. We conclude that fires induce a consistent shift in the composition of the springtail functional trait community, which is driven more by the forest stand level of litter thickness and moisture than by subregional forest differences. Our study revealed the potential of the functional trait composition to be a sensitive and informative tool for tracing the effects of fire in boreal forests, which is relatively independent from regional differences.