Biology ETDs

Publication Date

Spring 2026

Abstract

Climate change is increasing rainfall variability, altering nutrient availability, and causing warming in drylands, which comprise approximately ~36% of Earth's terrestrial surface. These expanding ecosystems contribute the most to interannual variability in the global carbon cycling. Biological soil crusts (biocrusts)—often called the "skin of the Earth"—are critical components of dryland surfaces, consisting of successional microbial communities dominated initially by Cyanobacteria and later by a more diverse composition with other bacteria, archaea, lichen, fungi, and algae. These communities play essential roles in soil aggregation, erosion prevention, and carbon and nitrogen cycling. However, our ability to predict biocrust responses to environmental change is limited by incomplete understanding of how multiple stressors interact and whether biocrusts retain legacy effects that could impair post-disturbance recovery.

Through long-term field experiments manipulating nutrients (nitrogen and phosphorus additions), inter- and intra-annual rainfall variability, and warming across the Chihuahuan and Sonoran Deserts, we investigated biocrust responses to multiple environmental changes. We found that nitrogen addition consistently reduces cyanobacterial biomass and diversity in biocrusts regardless of rainfall regime, soil nutrient status, warming treatment, or desert location. Additionally, Cyanobacteria and carbon-related measurements (including soil organic matter and microbial biomass carbon) exhibited drought legacy effects persisting three years after drought cessation, while nitrogen pools recovered rapidly. These findings reveal the vulnerability of these keystone microbial communities to nitrogen enrichment and their limited capacity for recovery from severe drought. Given the critical ecosystem functions biocrusts provide, their loss could accelerate desertification with cascading consequences for global dryland carbon cycling.

Keywords

biocrust, drought, nitrogen deposition, bacteria, soil ecology, microbial ecology

Document Type

Dissertation

Degree Name

Biology

Level of Degree

Doctoral

Department Name

UNM Biology Department

First Committee Member (Chair)

Scott Collins

Second Committee Member

Jennifer Rudgers

Third Committee Member

Donald Natvig

Fourth Committee Member

Vanessa Fernandes

Fifth Committee Member

Eva Stricker

Comments

Revised version

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