Available at: https://digitalcommons.calpoly.edu/theses/3422
Date of Award
8-2026
Degree Name
MS in Environmental Sciences and Management
Department/Program
Natural Resources Management
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Seeta Sistla
Advisor Department
Natural Resources Management
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
Renewable energy sources such as utility-scale solar energy (USSE) are rapidly expanding globally. USSE can help mitigate the consequences of using fossil fuels by reducing greenhouse gas emissions from energy generation, but their expansion coincides with concerns about how the presence of USSE arrays affect ecosystem properties and functions. Shading created by the panels can reduce plant water stress and increase plant productivity in arid and semiarid regions relative to the native landscape; however, the effect of this novel shading on soil microbial decomposers (who are key regulators of terrestrial carbon storage) is less clear. USSE arrays will likely impact the storage and cycling of soil carbon—the largest terrestrial pool of carbon in many ecosystems—both through increased plant inputs and altered microbial decomposer activity. However, the influence of solar arrays on soil carbon pools—which depends on interconnected plant and soil microbial responses to shading— remains poorly understood.
To assess the impacts of USSE placement on fallowed farmland that is managed by grazing on ecosystem carbon storage, a suite of environmental monitoring, soil biogeochemical, and plant assessments were completed at two USSE farms in San Luis Obispo County, CA from August 2024 – May 2026. Our field soil respiration data suggests microbially driven respiration pulses following rain events—pulses that are typical in dryland systems because decomposers are stimulated by rainfall— are suppressed within the array footprint relative to an unshaded reference area. Our field observations showed that the soils within the arrays generally respired less carbon, contained less SOC, and less C in the ecosystem pools than the soils and ecosystem in the reference area following rain events in our semi-arid study region. With growing global demands for solar energy production, there are pressures from many different sectors to rapidly construct USSE arrays. This research will help to identify synergies and trade-offs between USSE energy generation and terrestrial conservation goals.