With the increased prevalence and severity of hot droughts, the ability to anticipate mortality within forests is more important than ever. We conducted multi-year surveys using high-fidelity imaging spectroscopy coupled with light detection and ranging (LiDAR) with the Carnegie Airborne Observatory (CAO) to assess the impact of sustained canopy water loss on mortality. We assessed both gross canopy mortality in 2016, as well as the change in mortality between 2015 and 2016 in millions of sample points within conifers throughout the Sierra Nevada Mountains in California to address two primary questions: (1) can we use sustained water stress to predict gross tree mortality over the course of a drought, and (2) in the midst of a drought, can changes in CWC between years be used to predict future mortality?
Our findings indicate that, on average, there exists a strong correlation between sustained drought and gross mortality, as well as between year-to-year canopy water loss within a drought and subsequent mortality. While the correlations were found to be habitat-specific, when controlled sampling was performed to normalize for both geospatial location and habitat, the relationships held. Consequently, we present a set of robust, remotely-sensed indications of mortality both within and throughout the duration of a severe, hot drought.