Simulating sagebrush-cheatgrass plant community Biomass production in the Great Basin using ALMANAC

Authors: Schantz, Merilynn; Kiniry, James; Williams, Amber; Thorp, Kelly; Hardegree, Stuart; Newingham, Beth; Williams, Christopher; Davies, Kirk; Sheley, Roger

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2024
Publication Date: 12/13/2024
Citation: Schantz, M.C., Kiniry, J.R., Williams, A.S., Thorp, K.R., Hardegree, S.P., Newingham, B.A., Williams, C.J., Davies, K.W., Sheley, R.L. 2024. Simulating sagebrush-cheatgrass plant community Biomass production in the Great Basin using ALMANAC. Ecosphere. https://doi.org/10.1002/csc2.21440.
DOI: https://doi.org/10.1002/csc2.21440

Interpretive Summary: Cheatgrass (Bromus tectorum L.) is a widespread species of concern throughout the western US. Assessing the production of cheatgrass and the plant community in which it is growing using simulation models can lead to better management of forage availability and plant interactions in invaded plant communities. The present study was designed to evaluate the accuracy of simulating sagebrush-cheatgrass plant community species yields using the ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria) model. The many significant correlations between measured and simulated production across plant community groupings and sites suggest that ALMANAC can be a useful tool for estimating total grass production and interactions across most sites in the western US, especially with further model development in these regions.

Technical Abstract: Cheatgrass (Bromus tectorum L.) is a widespread species of concern throughout the western US as it dominates many low elevation rangelands and continues to spread into surrounding plant communities. Cheatgrass is a winter annual that can produce high-quality forage during a short period in the spring. In most areas, this production comes at a critical time for livestock production systems in need of cheap protein feed. Assessing the production of cheatgrass and the plant community in which it is growing using simulation models can lead to better management of forage availability and plant interactions in invaded plant communities. The present study was designed to evaluate the accuracy of simulating sagebrush-cheatgrass plant community species yields (Mg·ha-1) using the ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria) model. ALMANAC is a process-oriented simulator of plant production that accounts for competing species interactions. For this study, data were used from the Sagebrush Steppe Treatment Evaluation Project (Sage-STEP) to simulate cheatgrass, perennial grass, forb, and sagebrush yields that were collected at six representative cheatgrass invaded sagebrush-steppe sites across the Great Basin from 2006-2018. Our results identified high correlation rates between ALMANAC simulations and measured data of total cheatgrass and perennial grass yields across a native sagebrush and perennial grass community, a cheatgrass-forb dominated community, and a community co-dominated by sagebrush, perennial grasses, cheatgrass, and forbs. Sagebrush and forb yields were, alternatively, poorly simulated across many of the sites and years. Model accuracy also varied by site largely depending on elevation and year. Moreover, the high annual variability in simulated cheatgrass yields suggests that further ALMANAC development is needed to accurately prescribe annual grazing management plans for cheatgrass dominated sites. Collectively, these findings suggest that ALMANAC may be a useful tool for estimating total grass production and interactions across most sites in the western US, especially with further model development in these regions.