How Can Soil Biotic Interactions Influence Biogeochemically Relevant Microbial Trait Emergence Under Agricultural Management?.

Soil microorganisms are a controlling force on biogeochemical cycles, mediating the fate of soil carbon (C) and nutrient inputs with direct effects on agroecosystem health. Because agroecosystems are highly managed systems and microbes are often sensitive to environmental change, we may have the opportunity to positively influence microbial communities through environmental alterations (e.g. irrigation, tillage). However, community assembly is also structured by biotic interactions which has only recently been explored in soils, largely at the theoretical level. Recently, enthusiasm has emerged for more trait-based classifications of microbial communities to better predict community assembly and facilitate linking microbial assemblages to ecosystem functions. Microbial traits (such as stress-tolerance, growth rate and nutrient and C use efficiency) can emerge at the community-level from the interplay of both environmental (e.g. pH gradients) and biotic (e.g. competition and commensalism) filtering that effect ecosystem outcomes. Microbial C use efficiency (CUE) is an essential trait influencing soil C cycling, where microbes with a high CUE will convert more C into microbial biomass relative to C returned to the atmosphere through catabolic respiration. Research on CUE has largely been focused on environmental controls, such as resource quality and soil temperature. Yet, how microbes interact with each other, potential trait trade-offs, and community diversity can influence how CUE is manifested under different environments. In an effort to orient research goals towards improving our understanding of biological effects on key biogeochemical traits such as CUE, I discuss how microbial community competition, commensalism, diversity and resiliency might impact CUE. I consider some agricultural management strategies such as tillage regimes, fertility practices, and crop rotational diversity as ways that we might harness the interplay of both environmental and biotic filtering to influence CUE.