2024 Abstracts

Assessing Rangeland Function Under Altered Precipitation Regimes: Can a Deluge Rescue Forage Production Following Catastrophic Loss of the Dominant Species?


J. Alexander Siggers* (alex.siggers@colostate.edu), Melinda D. Smith


Colorado State University, Fort Collins, CO


The frequency of co-occurring droughts and deluges (i.e., large rainfall events) are projected to increase due to atmospheric warming. The potential ecosystem-scale impacts of these compound extremes are largely unquantified, yet they could be largely responsible for intra- and interannual variation in biogeochemical cycling. Ecosystem functionality is particularly vulnerable to altered precipitation regimes in water-limited systems such as the semi-arid shortgrass steppe of the western Great Plains. Key determinants of ecosystem stability are dominant species which, by definition, play a vital role in driving functionality (e.g., carbon storage via biomass production). Evidence has shown that climatic extremes can push dominant species to their physiological limits, leading to their loss from the system. This project seeks to understand how semi-arid grasslands will respond to compound drought-deluge in the presence and absence of the dominant species.

The proposed study will be initialized in the shortgrass steppe of northeastern Colorado by installing rainout shelters and simulating compound drought-deluge via water addition. Emphasis will be placed on the role of the dominant grass species, Bouteloua gracilis and Bouteloua dactyloides, in driving responses by superimposing a removal treatment that mimics the realistic loss of dominants. Researchers anticipate the addition of a late-growing season deluge to stimulate plant growth, microbial activity, and nutrient cycling, but they do not expect it to fully compensate for the loss of dominants. Aboveground (e.g., productivity and plant community composition) and belowground (e.g., microbial community structure and soil moisture) variables will be measured throughout the study. Investigating multiple trophic levels may lend insight to potential asynchronous responses to climate extremes.