Functional redundancy in peat microbial community after 18-years of in situ experimental manipulations mimicking climate warming and increased nutrient deposition

Given the pressures from anthropogenic perturbations, it is important to understand ecosystem responses to multiple stressors over long time scales at in situ conditions. Such information can guide management strategies and help predict future characteristics and services of an ecosystem. Here, we investigated the combined effect of 18 years simulated deposition of nitrogen (N), sulfate (S) and warming on taxonomic diversity and genome-encoded traits in peat microbial communities using in situ manipulation of a boreal oligotrophic minerogenic mire. The three perturbations individually effected 16S rRNA based prokaryotic community composition, where N addition had the most pronounced effect, and combinations with the other treatments led to additive effects. Yet, responses in the functional gene repertoire, as characterized by shotgun metagenomics, were mostly insignificant, except in connection to combined perturbations. The strong responses in taxonomical composition in contrast to minor responses in genome-encoded traits and ecosystem scale functions (e.g. methane emissions) points to functional redundancy as a ‘biodiversity guard’ that maintains ecosystem functioning when challenged with multiple stressors, thus, buffering against future changes in green house gases and carbon exchange.