Grassland plant-soil-microbial responses to climate extremes and land use change
Siggers, J. A. 2026.
Abstract
Atmospheric warming is intensifying the global hydrological cycle, leading to increased
occurrence of hydroclimatic extremes. Extreme droughts and deluges (persistent, torrential rain
events) are already impacting ecosystems globally, with each leaving legacy effects of altered
plant-soil interactions and ecosystem structure and function. The likelihood of co-occurring
hydroclimatic extremes, such as droughts and deluges, increases with each degree of warming,
yet little is known about how ecosystems will be affected when these events co-occur,
particularly through altered interactions between plants and soil microbiomes. Similarly, climate
solutions, such as renewable energy development, are altering abiotic determinants of ecosystem
functionality (e.g., light and water availability). Solar photovoltaic energy (PV) is currently the
cheapest, most scalable renewable energy option, though PV arrays occupy greater land area than
alternative energy forms and may have unintended consequences for their host ecosystems. Thus,
global change drivers are altering precipitation inputs and other abiotic factors in profound and
unique ways, yet experimental assessments of their ecological impacts are limited and highly
context dependent. Further, altered precipitation regimes and land use changes are likely to be
especially consequential in grasslands, where water is the predominant limiting resource and PV
deployment is most expansive. In this dissertation I investigated how these global change drivers
impacted grassland ecosystems through altered plant function and soil microbial communities
across the United States drought on soil microbial communities across representative grassland types of the US Great
Plains. The second chapter shifted focus to the shortgrass steppe of northeastern Colorado, where
I investigated the ecosystem impacts of compounded extreme drought and deluge. The final
chapter assessed plant-soil-microbial responses to a PV array in a C3 pasture in northeastern
Colorado. Altogether, this work suggests that global change drivers will have immense
contemporaneous and lasting impacts on grassland ecosystems, highlighting the pressing need to
understand our ecosystems before they are irreversibly altered. reat Plains. The first chapter examined the legacy effects of extreme
