CFAES Give Today

School of Environment and Natural Resources


Graduate Exit Seminar - Marcos Gimenez Diaz

Plan to join Marcos Gimenez Diaz's graduate exit seminar on July 11, 2023, at 10:00 am via Zoom. Marcos will present, "Spatial Patterns and Environmental Factors Influencing Invasive Cheatgrass Occurrence and Soil Properties in Sagebrush Steppe."

Abstract: Arid and semi-arid ecosystems in western Washington State (USA) are highly valuable as they contain a diverse native flora, harbor many endemic species of fauna, and provide economic benefits. However, spatial patterns and environmental factors can alter soil physical properties and influence the expansion of non-native species such as cheatgrass in turn reducing native plant species. Understanding these ecological concerns is imperative in order to determine specific areas that are urgent for restoration and conservation. To assess these critical unknowns, this research focuses on two main objectives: i) to evaluate the distribution of invasive cheatgrass in relation to environmental characteristics, landscape disturbance, restoration, and fire history; and ii) to evaluate changes in soil physical parameters, specifically soil hardness and water infiltration, as a function of soil type, historical vegetation community, and disturbance. Results from species distribution models indicated that cheatgrass is strongly influenced by the number of fires and site-specific herbicide applications. In addition, heat load index emerged as an important environmental variable in the model indicating that cheatgrass is more likely to be present in areas with high environmental stress. In relation to the second objective, the results indicated that sandy soils were more likely to have low soil hardness and faster infiltration rates. Hard soils and slow infiltration rates were evident in plots with big sagebrush, herbaceous and live shrub microsites sites, and with current grazing. Fire frequency, however, did not emerge as significant in the models for infiltration rates or soil hardness.

Advisor: Dr. Matt Davies