Soil Microbial Assembly and Function in Agroecosystems Under Various Management and Disturbance Regimes
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Date
2022-10-26
Authors
Shek, Katherine
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Publisher
University of Oregon
Abstract
Soil microbes are key to the functioning of terrestrial ecosystems through their roles in nutrient cycling, carbon sequestration, and interactions with plants along a mutualistic to parasitic continuum. Management practices in agricultural systems impose significant disturbances to ecosystems, which can influence soil microbial assembly patterns in the rhizosphere of crop plants with implications for functional outcomes of agroecosystem productivity and stability under different management regimes. Plant-soil interactions and community composition can vary under changing environmental contexts, making it difficult to predict agroecosystem functional responses to subsequent disturbances such as climate change pressures or pathogen invasion. Drawing general conclusions regarding soil microbial responses to agricultural management across environmental and ecological contexts thus requires cross-scale investigations of soil microbial communities in agroecosystems under different management, in different regions, and under cultivation of different crop species. My dissertation aims to unveil generalizable patterns in soil microbial assembly and function in agroecosystems under different management regimes, varying in disturbance intensity and environmental context. In Chapter II, I determine how soil microbial assembly patterns vary depending on the season and spatial scale at which microbial composition is examined in Oregon vineyard agroecosystems under different management. In Chapter III, I investigate soil fungal composition and emergent function in Mexican coffee agriculture under various disturbance regimes, drawing connections between specific functional groups of fungi and their roles governing nutrient cycling functions. My final chapter elucidates bipartite assembly patterns in plant-mycorrhizal fungal communities, and how plant community diversity relates to mycorrhizal fungal nutritive function in a prairie-pasture grass ecosystem; this ecosystem is an essential component of food systems, and together with cropland makes up more than half of global land under management. Understanding how specific practices affect plant-associated bacterial and fungal communities in agricultural soils will enhance our ability to predict agroecosystem stability under climate change, identifying vulnerable regions and cropping systems pertinent to food security and sustainability goals.
This dissertation includes previously submitted and co-authored material.
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Keywords
agroecosystems, biodiversity, fungal ecology, microbial ecology, mycology, soil ecology