Leaf to Landscape: Understanding and Mapping the Vulnerability of Forests to Hotter Droughts

Forests across the southwestern U.S. are crucial components of recreation and play an important role in state and local economies. Healthy forests also provide needed habitat for many wildlife species and contribute many other important services to our planet. “Hotter droughts” (otherwise normal droughts whose effects on ecosystems are exacerbated by higher temperatures) are an emerging climate change threat to forests with some of their earliest and strongest appearances happening in the Southwest. The Leaf to Landscape project uses California’s unusually hot drought as a potential preview of the future, allowing us to collect information that will help guide forest management in the face of a warming climate.
 
This project seeks to understand the effects of the hotter drought on Sierra Nevada forests across three different spatial scales (from leaves to landscapes): (1) water stress and the physiology of individual trees; (2) measurements of foliage dieback and tree mortality in tree populations; and (3) large landscape mapping of the vulnerability of forests to drought using airborne sensors. Linking the findings across these scales will help us better understand the thresholds of forest stress and dieback – including for the iconic giant sequoias – and how and why these thresholds vary across landscapes. Important products will include maps of forest vulnerability to hotter droughts of the future. Our results will help forest managers target forest treatments – such as prescribed fire – that are aimed at increasing the likelihood that forests will persist in the face of future climatic changes.