Kathleen Treseder

"Nitrogen (N) enrichment is an element of that could influence the growth and abundance of many s. In this , I synthesized responses of microbial to N additions in 82 published field studies. I hypothesized that the biomass of , bacteria or the microbial community as a whole would be altered under N additions. I also predicted that changes in biomass would parallel changes in soil CO2 emissions. Microbial biomass declined 15% on average under , but fungi and bacteria were not significantly altered in studies that examined each group separately. Moreover, declines in abundance of microbes and fungi were more evident in studies of longer durations and with higher total amounts of N added. In addition, responses of microbial biomass to N fertilization were significantly correlated with responses of soil CO2 emissions. There were no significant effects of biomes, fertilizer types, ambient N deposition rates or methods of measuring biomass. Altogether, these results suggest that N enrichment could reduce microbial biomass in many ecosystems, with corresponding declines in soil CO2 emissions."

"In this commentary, I advocate for more detailed incorporation of in , to improve our projections of . Current Earth system models display relatively low predictability of stocks, which limit our ability to estimate future climate conditions. A more explicit incorporation of microbial mechanisms can increase the accuracy of ecosystem-scale models that inform the larger-scale Earth system models. Of the numerous microbial groups that can influence soil C dynamics, AM fungi are particularly tractable for integration in models. Arbuscular mycorrhizal fungi are globally abundant and perform critical roles in , such as augmentation of net and soil C storage. Moreover, AM communities exhibit relatively low diversity within ecosystems, compared to other microbial groups. In addition, global datasets of AM ecology are available for use in model development. Thus, AM communities can be readily simulated in next-generation trait-based models that link microbial diversity to ecosystem function. Altogether, we are well-poised to incorporate the dynamics of individual AM taxa in ecosystem models, which can then be coupled to Earth system models. Hopefully, these efforts would advance our ability to predict and plan for future climate change."

"When trees build wood, is incorporated. It takes a long time to decompose ... It’s a smaller scale in . Some of the material they make can be almost woody. The is tough to decompose. The cell walls stay in the soil, microscopically. ... It adds up to a lot ... twice as much carbon in the soil as in the , and much of that is in [fungi]."

"I asked whether —applies to microbes. I conducted a synthesis of empirical studies that tested relationships among microbial traits presumed to define the competitive, stress tolerance and ruderal, and other ecological strategies. There was broad support for Grime's triangle. However, the ecological strategies were inconsistently linked to shifts in under environmental changes like nitrogen and phosphorus addition, warming, , etc. We may be missing important ecological strategies that more closely influence microbial community composition under shifting environmental conditions. We may need to start by documenting changes in microbial communities in response to environmental conditions at fine spatiotemporal scales relevant for microbes. We can then develop empirically based ecological strategies, rather than modifying those based on . Synthesis. Microbes appear to sort into similar ecological strategies as plants. However, these microbial ecological strategies do not consistently predict how community composition will shift under environmental change. By starting ‘from the ground up’, we may be able to delineate ecological strategies more relevant for microbes."