Biology ETDs

Publication Date

Summer 7-28-2026

Abstract

Drylands are major drivers of interannual variability in the global terrestrial carbon sink, and their influence is expected to increase as climate change promotes the expansion of hotter and drier regions. Predicting the consequences of these shifts remains challenging because ecosystem models are largely developed for mesic systems, which differ from drylands in water and nutrient availability, decomposition rates, respiration dynamics, and microbial communities. Improving our understanding of carbon cycling in drylands is therefore critical. This research focuses on soil CO₂ efflux, a major pathway of terrestrial carbon release driven by plant root respiration and microbial decomposition. I investigated the environmental controls on soil respiration in the Chihuahuan Desert grassland at the Sevilleta National Wildlife Refuge. I hypothesized that biological complexity influences how soil respiration responds to environmental drivers, leading to differences in respiration magnitude, environmental sensitivity, and variability among cover types that scale to ecosystem-level carbon fluxes. Hourly soil CO₂ fluxes were measured from May through September 2024 in three treatments: bare ground (trenched), bare ground with litter addition (trenched), and Bouteloua eriopoda with litter addition. Chamber measurements were paired with meteorological data from an eddy covariance tower. Using these data, I developed a generalized additive model (GAM) relating soil respiration to temperature, soil moisture, and gross primary productivity. The model was then applied to historical tower data to reconstruct soil respiration from 2007–2024. Results showed that, when scaled by percent cover, respiration was generally greatest in the B. eriopoda treatment, while all treatments exhibited substantial variability. These findings suggest that ecosystem structure influences the relative contributions of vegetation, litter, and bare ground to total soil respiration in this dryland ecosystem.

Project Sponsors

Sevilleta LTER

Language

English

Keywords

soil respiration, carbon flux, ecosystem respiration, autotrophic, heterotrophic, CO2 flux, soil, CO2, variability, dryland, arid, desert grassland, LI8100

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

Marcy Litvak

Second Committee Member

Megan Rae DeVan

Third Committee Member

Jennifer Rudgers

Fourth Committee Member

Eric Griffin

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