Effects of wild boar ( Sus scrofa L.) rooting on the bacterial community structure in mixed-hardwood forest soils in Switzerland

Abstract

Soil disturbances are known to influence the soil bacterial community structure and therefore have the potential to affect forest ecosystem functioning and productivity. Whereas most studies have focused on how disturbances originating from forest management practices alter these communities, almost nothing is known about the effects of biotic natural disturbances, especially the ones caused by large animals. Our goal was to determine how European wild boars ( Sus scrofa L.) affect soil microbial biomass carbon and bacterial community structure by rooting (grubbing) in the soil when searching for food. We sampled microbial biomass carbon immediately and 24 months after the rooting event and determined bacterial community structure immediately, 11, 14 and 18 months after rooting on paired rooted and non-rooted study plots in four hardwood forest stands. In addition, we measured plant available total nitrogen, soil moisture and soil temperatures for each sampling interval. Wild boar rooting had no significant effect on microbial biomass carbon or soil bacterial community structure, diversity, richness and evenness. However, we found that the bacterial community structure varied significantly with the sampling date. Correlations between bacterial community structure and different environmental parameters, namely plant available total nitrogen, soil moisture, and soil temperature were found to be responsible for these seasonal differences. Thus, seasonal changes in bacterial community structure seem to override rooting effects of wild boars at our study sites.