Impacts of Microbial Diversity on Soil Carbon and Ecosystem Function

Abstract

Climate change induced biodiversity loss threatens to diminish the ability of diverse microbial communities to promote the stability and productivity of soils. These communities not only sequester carbon by producing microbial necromass, but also serve as the underpinning for the critical functions that drive terrestrial carbon cycling. Understanding how ecosystems and soil carbon stocks respond to shifts in microbial community composition and diversity will influence the role of soils as a carbon sink or source on a warming planet. Using both laboratory incubations and observational field samples from the Harvard Forest Long-Term Ecological Research (LTER) site, I investigated how microbial diversity affected the persistence of microbially-derived soil organic matter and ecosystem function. Overall, taxonomic diversity appears to have little effect on either necromass persistence or ecosystem function. The diversity of the microbial community producing soil organic matter is not a driver of the carbon use efficiency of microbial necromass, suggesting that the microbially-transformed soil organic matter bears similar susceptibility to decomposition, regardless of the community composition that produces the necromass. Additionally, bacterial taxonomic diversity was not a driver of ecosystem function at the Harvard Forest LTER. However, bacterial functional diversity, in particular acquisition trait richness, had a negative relationship with ecosystem function in soils exposed to chronic warming. Altogether, these results indicate that the microbial taxonomic diversity has little impact on the persistence of microbial necromass in the short-term or on ecosystem function at the Harvard Forest LTER. However, microbial acquisition trait richness did have a negative relationship with ecosystem function in soils exposed to chronic warming. Together these results highlight that microbial functional diversity, not microbial taxonomic diversity, may be a better approach to understanding how microbial diversity drives ecosystem function in a changing climate.Doctor of Philosophy (Ph.D.)2026-02-0