Interactive effect of depth profile, land history, and precipitation gradients across Kansas determines microbial community and function

Soumyadev Sarkar, Kaitlyn Ward, Qinghong Ran and Sonny T.M. Lee, Biology, Kansas State University, Manhattan, KS, Paige M. Hansen, Willow Kessler, Ligia F. T. de Souza, Terry D. Loecke, Sharon A. Billings and Benjamin A. Sikes, Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS

Background/Question/Methods:
Soil microbiomes play important roles in terrestrial ecosystem functioning by transporting and transforming resources. Gradual climatic changes often result in altered precipitation levels, and land-use can change the soil characteristics. Soil structure and function may also vary across soil-depth. These combined factors would impact plants and grassland productivity. Studying the interactive effects of such complex soil microbiome profiles across depth, land use, and precipitation levels are necessary to anticipate future climatic impacts. We collected soil from different locations with diverse land histories across Kansas and conducted a monolith experiment. We regulated the amount of water each monolith received to elucidate the structure and function of the soil microbiomes in the depth profiles. We used a combination of 16S rRNA amplicon and shotgun metagenomes to gain insights into the impact of land history, precipitation, and soil-depth on microbial community composition and function.
Results/Conclusions:
Soil-depth and land use had the most impact on the soil microbial structure and function. Our results showed the highest microbial diversity in the top 5 cm of the soil, and the least diversity in the deepest soils sampled. Microbial community structures and functions from native, agricultural, and post-agricultural soils were distinct. We also observed interactive effects of soil-depth, land history, and precipitation gradients on the microbial community. Post-hoc SIMPER analyses showed that Propionibacteriales and Rubrobacterales contributed to the highest dissimilarity between soil from different precipitation gradients. Bradyrhizobiaceae was most abundant in the top 5 cm of the soil, as well as in native and post-agricultural soil. On the other hand, Streptomycetales was the most dominant in the agricultural soil and was highly prevalent in the middle and bottom layer of the monolith. Our study also showed that soil-depth, land history, and precipitation had a significant impact on the carbon and nitrogen cycling functions. Our results provide insights into the implications of land history and precipitation alteration impacts on grassland restoration.