Tipping the scales: alternative stable states and the role of soil microbes in ecosystem resilience

Michaels, Theo K

Publication

Tipping the scales: alternative stable states and the role of soil microbes in ecosystem resilience

Michaels, Theo K

Abstract

Abrupt and persistent ecosystem state shifts often give rise to non-linear recovery behavior, which challenges ecosystem recovery and the societies that depend on them. The challenges of non-linear ecosystem behavior and our ability to address it, may be a mismatch of scale. Traditional approaches to the study of non-linear ecosystem behavior often assumes well-mixed systems where abrupt changes are driven by ecosystem-scale processes, and as such the role of local scale dynamics is not well understood. In this dissertation, I examine the role of local scale interactions mediated by soil microbes, and how these interactions drive changes between ecosystem states. In chapter 1, I highlight how transitions between alternative stable states are impeded by a mismatch of scale and developed a conceptual framework that draws from nucleation theory to incorporate spatial dynamics into the alternative stable states model. As part of this framework, I discussed the potential for autocatalytic nucleation dynamics within a variety of ecosystems, draw implications for ecosystem resilience and transitions between alternate states, and show how nucleation principles can be applied to ecosystem management. Applying this framework, in chapter 2 I test the conditions of, and potential for, nucleation leveraging tallgrass prairie and post-agricultural lands as a model system of alternative stable states. I found that introducing patches of late successional tallgrass prairie into post-agricultural lands, can generate the net local positive feedback dynamics necessary for patch expansion as predicted by autocatalytic nucleation. To understand the contribution of soil microbes in the maintenance or erosion of ecosystem resilience, in chapter 3, I examine the attributes of microbial fronts, with a specific focus on soil fungi, and their role in advancing or maintaining soil functional boundaries of adjacent ecosystems. Using experimentally created edges consisting of tallgrass prairie and post-agricultural fields, I found that land use history affected the pace, direction, and lag times of microbial front propagation. These findings point to ways of thinking about how we may want to encourage or prevent microbial front advancement to facilitate land management needs. While these three studies focus on local scale interactions from an ecological perspective, in chapter 4 I provide an account of a place-based social interaction based on my work at Anderson County Prairie Preserve. This account highlights the importance of building local scale relationships and asks how these interactions might scale to influence land management goals across private and institutional boundaries. Together these studies highlight how both social and ecological local scale interactions have the potential to manifest themselves in landscape scale change. By tipping the scales and considering the role of local scale interactions in ecosystem resilience, this dissertation fosters a deeper understanding of ecosystem state shifts, and offers up new perspectives to help guide restoration and land management techniques in order to meet the needs of the lands we steward in a time of unprecedented change.