Date of Award
2026-05-01
Degree Name
Doctor of Philosophy
Department
Ecology and Evolutionary Biology
Advisor(s)
Dr. Kelly S. Ramirez
Abstract
Drylands cover more than 40% of Earth's land surface and support over two billion people, yet they are among the ecosystems most vulnerable to crossing ecological tipping points under global change. In the northern Chihuahuan Desert, the transition from historic black grama grassland to mesquite-dominated shrubland has accelerated soil erosion, destabilized nutrient cycling and made grass reestablishment increasingly difficult. Despite decades of investment in dryland restoration, revegetation efforts continue to fail at high rates. Growing evidence suggests that a fundamental gap in restoration design is missing: the soil microbiome, bacteria, archaea and fungi, that mediate nutrient cycling, soil stability and plant-microbe interactions. To address this gap, I investigated how dryland soil microbial communities assemble, reorganize, and respond to intervention across three complementary studies. In Chapter 2, I determine how drought and nitrogen enrichment shape rhizosphere community assembly in different plant species during early developmental stages. In Chapter 3, I characterize how soil microbial communities reorganize across the ecological transition states found at the Jornada Basin LTER. In Chapter 4, I test whether species-specific rhizosphere inoculation and mesquite litter addition can improve native grass germination and early plant growth in degraded interspace soils. Together, these chapters show that dryland microbiomes are neither passive nor easily manipulated, but instead exhibit species-specific, state-dependent, and stress-sensitive dynamics that constrain when and how microbial tools can support restoration. This dissertation advances a foundation for incorporating belowground biodiversity into dryland restoration practice and underscores the urgent need to align soil microbiome science with the scale and pace of global dryland degradation.
Language
en
Provenance
Received from ProQuest
Copyright Date
2026-05
File Size
168 p.
File Format
application/pdf
Rights Holder
Parikrama Sapkota
Recommended Citation
Sapkota, Parikrama, "Dryland Microbiomes Under Pressure: Understanding Microbial Assembly And Reorganization To Restore Degraded Landscapes" (2026). Open Access Theses & Dissertations. 4794.
https://scholarworks.utep.edu/open_etd/4794