Climate dynamically controls water availability to plants. Fluctuations in temperature and precipitation affect the relative volumes of water stored in different terrestrial storage reservoirs (e.g., saturated v. unsaturated zones). Critically, shifts in climate affect the relative availability of these water sources to vegetation with potentially irreversible consequences. In many ecosystems, plant-available water is becoming limited as soils dry out due to lower precipitation, as evaporation rises under warmer temperatures, and as water tables decline. For plant species adapted to the range of water availability for a climate regime, a long-term decrease may prove damaging or fatal, particularly to species that are vulnerable to water stress. Increases in the spatial footprint of climatically induced water stress could drive shifts in species composition and ecological functioning over large areas of the globe.

We are investigating the links between climate, water availability, and the ecohydrology of water-limited deciduous broadleaf forests, especially in riparian zones subject to Mediterranean climate regimes because these important biomes serve as ‘canaries in the coal mine’, providing a window into the responses we may expect to see across a wider range of forest ecosystems that are evolving toward hotter, drier climates. We continue to expand this research to address the expression of trends in water availability across climate gradients and to forecast the ecohydrological effects of a warming/drying climate over coming decades.

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Growing season variations in climate and water along the Rhone River, France

Projects on this research theme include:

Understanding and assessing riparian habitat vulnerability to drought-prone climate regimes on Department of Defense bases in the Southwestern USA. Funded by the US Department of Defense’s Strategic Environmental Research and Development Program (SERDP), M. Singer (PI), K. Caylor, J. Stella, 2018-2022

Impacts of dynamic, climate-driven water availability on tree water use and health in Mediterranean riparian forests. Funded by National Science Foundation Hydrologic Sciences, M. Singer (PI), J. Stella, K. Caylor, 2017-2020

Linking basin-scale, stand-level, and individual tree water stress indicators for groundwater-dependent riparian forests in multiple-use river basins. Funded by National Science Foundation Geography and Spatial Sciences, J. Stella, M. Singer (co-PI), D. Roberts, 2017-2020

Assessing riparian forest water sources in the Santa Clara River basin. Funded by The Nature Conservancy, M. Singer (PI), J. Stella, 2018-2020

Publications on this research theme include:

*Kibler, C., Schmidt, C., Roberts, D.A., Stella, J.C., Lambert, A., Kui, L., Singer, M.B., (In Review); A brown wave of riparian woodland mortality following groundwater declines during the 2012-2019 California drought

*Sargeant, C.I., Singer, M.B. (In Review); Local and non-local controls on seasonal variations in water availability and use by riparian trees along a hydroclimatic gradient

*Warter, M., Singer, M.B., Roberts, D., Cuthbert, M.O., *Sabathier, R., Stella, J., Caylor, K. (In Review); Onset and propagation of drought into soil moisture and vegetation responses during the 2012-2019 drought in Southern California

*Sabathier, R., Singer, M.B., Roberts, D.A., Caylor, K., Stella, J.C. (In Press); Vegetation responses to climatic and geologic controls on water availability in southeastern Arizona, USA, Environmental Research Letters

*Rohde, M., Stella, J., Roberts, D., Singer, M.B., (In Press); Groundwater dependence of riparian woodlands and the disrupting effect of anthropogenically altered streamflow, Proceedings of the National Academy of Sciences (PNAS)

*Sargeant, C.I., Singer, M.B., Vallet-Coulomb, C. (2019); Identification of Source-water Oxygen isotopes in trees Toolkit (ISO-Tool) for deciphering historical water use by forest trees, Water Resources Research, 55(12):10954-10975, doi: 10.1029/2018WR024519. pdf

*Evans, C., Dritschel, D., Singer, M.B. (2018); Modelling subsurface hydrology in floodplains, Water Resources Research, 54(3):1428-1459, doi: 10.1002/2017WR020827. pdf

*Sargeant, C.S., Singer, M.B. (2016); Sub-annual variability in historical water source use by Mediterranean riparian trees, Ecohydrology, 9(7):1328-1345, doi: 10.1002/eco.1730. pdf

Singer, M.B., *Sargeant, C., Piégay, H., Riquier, J., Wilson, R.J.S., *Evans, C.M. (2014); Floodplain ecohydrology: Climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees, Water Resources Research, 50(5):4490-4513, doi: 10.1002/2014WR015581. pdf

Singer, M.B., Stella, J.C., Dufour, S., Piegay, H., Wilson, R.J.S., *Johnstone, L. (2013); Contrasting water-uptake and growth responses to drought in co-occurring riparian tree species. Ecohydrology, 6(3):402-412, doi: 10.1002/eco.1283. pdf