2011 Annual Report 1a.Objectives (from AD-416) a) Assimilation of remote sensing information into hydrologic modeling; b) Interpretation of remote sensing products in the context of ecohydrologic feedbacks. 1b.Approach (from AD-416) The experimental design is built on remote sensing, measurements and modeling to better understand the ecohydrologic impacts of climate change and woody plant encroachment. Experiments are planned for ARS watershed locations in Arizona, Oklahoma and Georgia. 3.Progress Report In 2011, we determined the impact of Lehmann lovegrass invasion on ecosystem water use by comparing post-storm water loss before, during and after a natural grassland transition. Results indicate that, compared to an ecosystem dominated by native grasses, dominance of Lehmann lovegrass is associated with an increase in water loss through evaporation after storms in the summer growing season. This cumulative effect contributed to observed increases in post-invasion evaporation over the growing season. These results offer an insight into the impact of invasive species on water cycle in semiarid rangelands in the western United States. Greater evaporation from soil could lead to a “drying” of the ecosystem, which could have implications for the persistence of Lehmann lovegrass and the resilience of native species. The project was managed through close interaction and regular in person meetings between the primary UA faculty member, ARS scientists, and graduate students.