HMC Assistant Professor Jessica Guo Co-Authors New Study on Climate Extremes and Dryland Ecosystems

Jessica Guo, assistant professor of climate and biology at Harvey Mudd College, co-authored a new publication in New Phytologist examining how atmospheric drought shapes dryland plant productivity responses under variable precipitation regimes. The study complements her recent papers on how extreme heatwaves impact tree health under modest water limitation, published in Proceedings of the National Academy of Sciences (PNAS) in 2024 and a meta-analysis on vegetation responses to precipitation pulses, published in Global Change Biology in 2025.

Guo, a plant ecophysiologist and data scientist, investigates how plants interact with their environment under extreme stress, focusing on dryland systems vulnerable to lethal combinations of heat and drought. Her work is motivated by the visible impacts of climate change, even on drought-tolerant desert species.

The paper explores how plant communities, subjected to experimental conditions mimicking precipitation regimes of different frequency, respond in years with high vs. low atmospheric drought. Because warmer air can hold more water vapor, atmospheric drought intensifies exponentially as temperatures rise. This causes plant stomata to close to prevent excess water loss, which also reduces the amount of carbon dioxide they can fix through photosynthesis. Using a multi-year rainfall manipulation experiment, the researchers found that even under the same irrigation treatments, years with drier atmospheric conditions yielded 39% less productivity.

These findings highlight the risks posed by climate-driven changes to atmospheric dryness and rainfall patterns, underscoring the importance of understanding plant strategies for survival in water-limited environments.Guo serves as co-principal investigator of a National Science Foundation-funded Research Coordination Network, PSInet, that works to establish a comprehensive database of plant water potential. The initiative seeks to harmonize data on plant water stress measured, making them available to disciplines such as remote sensing and ecosystem modeling and enabling researchers to better predict and manage ecological responses to climate extremes.