Abstract ID: 3.12629 | Accepted as Talk | Talk | TBA | TBA

Climate change is leading to increased frequency and intensity of drought events. It is crucial to understand how they impact mountain ecosystems, which are disproportionally affected by global warming. Here, we sampled soil cores at the end of a long-term experiment with recurring summer drought (8 years) to investigate the soil microbial communities in a subalpine forest (2000 m a.s.l.) in the Austrian Central Alps, which is dominated by spruce and larch. We investigated ectomycorrhizal (ECM) communities by morphotyping of colonized root tips and molecular identification by Sanger sequencing. Additionally, fungal and bacterial soil communities were investigated by amplicon sequencing and relevant soil parameters were measured to obtain a comprehensive, and inclusive, understanding of cumulative effects of drought on soil microbial communities. We hypothesized a decrease in species richness and diversity for drought plots compared to control, as well as changes in the community structure due to the establishment of a more drought tolerant community. Interestingly, for none of the three communities (ECM, bacteria and fungi) declines in richness or diversity were detected. We found significant differences in beta-diversity for bacterial and fungal communities between control and drought plots, however, little variance between communities was explained by the factor drought. For example, random variation in pH across the plots had a larger influence on communities and for ECM no significant effect of drought on beta-diversity at all was detected. The drought also led to significant changes in soil parameters, mainly decreases in nitrogen availability, which indirectly influenced the decline of certain bacterial taxa. Overall, these findings suggest, that soil microbial communities at the site are largely resilient to recurring drought, likely a result of the site being at the upper distribution limit of these forest types and due to buffering effects of mixed forest stands.