Soil microbial communities play an essential role in terrestrial biogeochemical cycling. As our planet’s climate changes, it is vital to understand how shifts in microbial communities are linked to large-scale ecosystem effects. The terrestrial nitrogen cycle is an important ecosystem process that is largely driven by specific taxonomic groups of bacteria and archaea, which are sensitive to environmental changes. While many studies have examined the effects of climate change on microbial (mostly bacterial and fungal) communities and on rates of nitrogen cycling separately, fewer studies have examined both responses. Here, I review past studies that have examined the effects of climate change on microbial community structure and the rates of nitrogen cycling separately and concurrently. I also provide examples of ongoing and future experiments that would allow us to better understand the connection between soil microbial community composition and nitrogen cycling rates in the context of climate change.
Many climate change studies have found changes in bacterial community composition, in fungi-to-bacteria ratios, and in net nitrogen mineralization rates, nitrification potential and other processes associated with nitrogen cycling. Currently, soil microbial communities are assumed to be functionally redundant; in other words, a change in their community composition is expected to have minimal effects on the rates of terrestrial ecosystem processes because many microorganisms perform the same function at similar rates. However, more recent studies are finding correlations between shifts in microbial community composition and rates of ecosystem processes such as net nitrogen mineralization and nitrification, and some have found that this correlation persists after controlling for environmental factors. This suggests that microbial community composition can affect terrestrial ecosystem process rates independent of environmental conditions. If this is the case, then shifts in microbial communities due to climate change may have a significant impact on terrestrial ecosystems. Long-term, multi-factor climate change studies that examine microbial community structure and nitrogen cycling rates, such as the Boston Area Climate Experiment (BACE), can provide more insight into the relationship between microbial community structure and ecosystem process rates and may allow us to better predict terrestrial ecosystem responses to climate change.