Linking Basin-Scale, Stand-Level, and Individual Tree Water Stress Indicators for Groundwater-Dependent Riparian Forests in Multiple-Use River Basins

Suny College Of Environmental Science And Forestry, Syracuse NY

Investigators

Abstract

This research project will develop a suite of water-stress indicators at several scales to assess the health of riparian ecosystems in response to sustained groundwater decline. This project will address a topic of scientific and societal importance, namely how to evaluate and help prevent negative impacts of drought and human-induced water shortages on vulnerable, high-value riparian ecosystems. It will integrate advanced methods in two rapidly emerging fields, hyperspectral remote sensing and isotope dendroecology, to develop a more holistic understanding of water stress at multiple scales of resolution. The project will compare water stress indicators that vary in their timing, strength, and rates of change, and it will facilitate the evaluation of warning signs and time lags among physiological water stress, reduced growth, and dieback in individual trees as well as synoptic forest decline evident throughout a river corridor. This project has the potential to influence groundwater management practices throughout California and in water-limited, multiple-use basins elsewhere. In partnership with The Nature Conservancy and other project collaborators, the investigators will integrate project findings with statewide guidelines for protecting groundwater-dependent riparian ecosystems mandated under California's recently implemented Groundwater Sustainability Management Act. The investigators will interact with groundwater conservation and management efforts in river basins through workshops for managers and stakeholders. They will mentor early-career environmental scientists, including women in STEM fields, and they will conduct outreach activities for elementary and secondary school students to increase regional environmental awareness in the study region. Riparian forests and woodlands are hotspots of biodiversity, and they support key functions and habitats within river corridors, but they are particularly sensitive to large changes in water supply. This project will take place in the Santa Clara River in southern California, where sustained groundwater pumping for irrigation during a severe drought has had negative impacts and allows for study of riparian woodland response to changing environmental conditions over both short and longer terms. The investigators will assess the signals and thresholds of water stress over the last decade using high-resolution aerial imagery and tree-rings to develop predictors of long-term impairment and collapse. They will capitalize on extensive groundwater well records to link water-table dynamics with changes in plant water status detected at two different scales through the use of basin-wide, high-resolution aerial imagery taken seasonally during the drought and annual growth and carbon isotope data from tree rings covering the same period.