Forest Drought Resistance at Large Geographic Scales

Forest conservation and carbon sequestration efforts are on the rise, yet the long-term stability of these efforts under a changing climate remains unknown. We generate nearly three decades of remotely sensed canopy water content throughout California, which we use to determine patterns of drought stress. Linking these patterns of drought stress with meteorological variables enables us to quantify spatially explicit biophysical drought resistance in terms of magnitude and duration. These maps reveal significant spatial heterogeneity in drought resistance and demonstrate that almost all forests have less resistance to severe, persistent droughts. By identifying the spatial patterning of biophysical drought resistance, we quantify an important component of long-term ecosystem stability that can be used for forest conservation, management, and policy decisions. Plain Language Summary As hot droughts become more frequent and more severe, it is important for long-term forest management to understand which forests are at risk and which have the capacity to withstand these events. To address this challenge, we generated and analyzed maps of canopy water content through time and compared them to maps of meteorology. This analysis revealed that some locations were able to endure significantly more drought before succumbing to significant canopy water loss, which indicates drought resistance. Our findings also highlighted that the effects of a recent, severe drought have persisted multiple years after the drought subsided. These findings are an important first step toward assessing spatially explicit forest stability in the face of a changing climate.