Biology ETDs

Publication Date

Fall 10-28-2022


Dryland ecosystems are facing unprecedented climate extremes as a result of global climate change. Water is the most limiting factor in dryland ecosystems, therefore plants in drylands have developed crucial water-use strategies for drought survival. It is important to understand plant physiological responses to water stress as drylands are projected to experience more frequent, severe droughts in the coming decades. To test how plants respond to drought in a semiarid grassland, we measured δ13C, δ15N, and C/N ratio of common C3 and C4 plants (Bouteloua gracilis, B. eriopoda, Pleuraphis jamesii, Salsola tragus, Machaeranthera pinnatifida, Plantago patagonica) collected from drought and control plots using three drought experiments at the Sevilleta Long-Term Ecological Research (LTER) site located at the Sevilleta National Wildlife Refuge (SNWR) in central New Mexico, USA and spanning two ecosystem types: Chihuahuan Desert grassland and Plains grassland. C3 plants demonstrated water use efficient (WUE) strategies by exhibiting enriched δ13C values in response to drought, while C4 plants did not. Mean plant δ15N was depleted by 68% overall, suggesting an association with nitrogen-fixers under drought conditions. C3 plant C/N was unchanged by drought, indicating that C3 plants in drylands employ WUE strategies at the cost of losing nitrogen use efficiency (NUE). Variations in drought duration and severity did not impact plant trait values. However, plant trait values significantly varied among experiment locations, and plant trait values were generally most extreme at severe, long-term drought experiments in Great Plains grasslands. These results indicate that site effects were often greater than drought effects on plant δ13C, δ15N, and C/N ratio. Our results show that plants demonstrate a physiological response to drought. These findings provide important information on dryland species as we seek to understand the survival strategies used by plants in response to variable climate conditions.




drought, grassland, stable isotopes, Sevilleta, aridity, plants

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Scott Collins

Second Committee Member

Jennifer Rudgers

Third Committee Member

William Pockman

Included in

Biology Commons