Why subsurface features matter for managing forests, water and fire in the face of increasing drought frequency and severity

Abstract:

Droughts can have both subtle and dramatic impacts on forest structure, species composition and function and consequently on water and nutrients exported from these systems. Many of these impacts depend not only on the magnitude and severity of climatic drivers of drought such as temperature and precipitation extremes but also on local forest geophysical features that determine the access of forest to water and how that water is routed to streams. We uses a combination of coupled ecohydrologic modeling, remote sensing and field based observations to show how subsurface properties can be a critical control on how forests respond to drought, using case studies from semi-arid mountain systems. We use this framework to show how changes in forest structure and function can in turn influence the response of streamflow to drought, even after precipitation and temperature regimes return to normal conditions., We also show how the effectiveness of forest management practices designed to mitigate extreme event impacts, including drought and fire, may depend strongly on subsurface hydrologic features. We conclude by presenting an approach for rapid assessment of location specific drought vulnerability and evaluation of forest management strategies that accounts for multi-year drought impacts of eco-hydrology and the potential for subsurface features to influence these responses.