Management intensification and temporal dynamics shape microbial communities in a Southern Plains agroecosystem

Abstract

Land use intensification has resulted in the conversion of complex natural systems into simpler, managed environments which has a considerable impact on physical and chemical soil properties as well as above and belowground diversity for crop production. The productivity of agricultural systems greatly depends on a number of ecosystems services provided by the soil biota which are directly and indirectly affected by land use. Important ecosystem services provided by soil microbial communities include biogeochemical cycling, plant nutrient availability, and organic matter decomposition, all of which contribute to the overall functioning of the soil environment. Soil microbial communities and soil properties are not only influenced by land use, but a combination of temporal dynamics including seasonal management, climatic variations, and their interactions. While detecting differences in the microbial DNA pools over shorter periods is challenging, microbial communities changes have been clearly documented over months, seasons, and years raising the question if sampling at a single time point is enough to describe microbial community differences especially concerning environmental changes and management practices. Therefore, understanding the consequences of such interactions on soil microbial composition, diversity, and function is essential for maintaining the productivity and stability of valuable soil ecosystems. Thus, this dissertation aimed to explore the interaction between land use and temporal variation on soil microbial communities under varying levels of management disturbance in a U.S. Southern Plains agroecosystem with the goal of better understanding the impact on microbial community diversity, function, and interactions in order to provide information to better inform future management decisions to sustain soil health. Overall, the work in this dissertation provided valuable evidence on the microbial community response to land use and land management disturbance as well as the interaction with time in a U.S. Southern Plains agroecosystem. Intensive management disturbance greatly impacted the soil bacterial and viral communities reducing abundance and diversity in addition to diminishing many soil properties generally associated with healthy soils. A more in-depth look at the microbial community interactions also revealed that long-term cropland use impacts network complexity, stability, and their interaction generating microbial communities that likely can quickly adapt to repeated management disturbance. Many of these findings support the idea that land use conversion and management disturbance has a negative impact on soil microbial communities and soil properties, while also providing new insight into other vital parts of soil communities (i.e. viruses) and looking beyond changes in microbial diversity to better understand how agriculture affects soil microbial communities.