Drought and in particular high-temperature droughts are increasingly a concern in semi-arid climates through the globe. Within these regions both forest health and water resources are highly sensitive to the severity and frequency of drought. Drought conditions reduce streamflow, but also water availability and in the case of high temperature drought, water demand for terrestrial ecosystems. Hydrologic and ecosystem responses are coupled since changes in water use by terrestrial ecosystems can in turn influence the impact of drought on downslope streamflow. Further the impact of drought on forest structure, via declines in productivity, increases in fire and mortality and ultimately species change can have longer-term impacts on streamflow, even after precipitation and temperature regimes return to more normal conditions. We argue that accounting for multi-year and coupled ecohydrologic post-drought impacts is an important component of assessing ecosystem health and water resource impacts of droughts in a changing climate. A multi-year, coupled perspective is also important for the strategic allocation of forest management practices, including fuel treatments that may be targeted for reducing the impact of droughts. We utilize a coupled eco-hydrologic model, combined with field measurements from the Sierra Critical Zone Observatory and elsewhere to show how forest structural changes can be a dominant control on streamflow responses, particularly in years following drought and show how forest management practices can interact with drought vulnerability in sometimes surprising ways. We conclude by presenting an approach for rapid assessment of location specific drought vulnerability and management impacts that takes these interactions into account.
Hall S.J; Tague, C.; Moritz, M. (2016): Managing forests, water resources and their interaction in the face of increasing drought frequency and severity in semi-arid regions. Fall Meeting, American Geophysical Union, December 2016. Abstract H24B-01..