Abstract: Microbial communities drive many important ecosystem processes, yet we lack a predictive understanding of how microbial functions shift across environmental conditions. Since the responses of microbial communities to environmental conditions are likely governed by physiological trade-offs, identifying and validating key microbial traits and trade-offs is important for better understanding how microbes respond to their environmental and alter ecosystem function. We characterized three microbial community traits (efficient growth, resource acquisition, and stress tolerance: Y-A-S framework) and their trade-offs across manipulations of drought stress and carbon resource availability.
We leveraged a large-scale rainout shelter experiment at the Kellogg Biological Station LTER to explore variation in soil microbial traits. In three field types (convention wheat, conventional no-till wheat, and early successional field), we applied two rainfall treatments (drought and irrigated control) and applied two carbon treatments (sorghum addition and control). To measure soil microbial traits, we used metagenomic sequencing and the following functional assays: PCA of five carbon degrading enzyme activities (resource acquisition trait), carbon use efficiency (growth efficiency trait), and trehalose assay (stress tolerance trait).
We found that carbon degrading enzyme activity increased in response to carbon addition (F=265, p< 0.001) across all field types while drought did not alter enzyme activity. Similarly, carbon use efficiency increased in carbon addition treatments (F=10, p=0.002) across all field types, but in contrast, carbon use efficiency increased in drought although only in no-till wheat fields (F=9, p=0.002). Trehalose amount increased with drought (F=6.9, p=0.01). Lastly, we found no evidence of trade-offs between the functional assays of efficient growth, resource acquisition, and stress tolerance. Overall, we found mixed evidence regarding the Y-A-S framework.
