Assessment of Forest Vulnerability to Climate Change from Imaging Spectroscopy

Abstract:

Global forests are undergoing increasing temperatures and major changes in precipitation, including drought and flooding. Current satellite technology is not designed to assess forest vulnerability and response to climate change, so new approaches are needed from space. Two key indicators of forest vulnerability and response to climate change are canopy water and non-structural carbohydrate (NSC) content. However, measurement of canopy water and NSC content is prohibitively labor intensive in the field, especially in forests where foliage is difficult to access, and where canopy properties vary enormously by species and across environments. Imaging spectroscopy may allow quantitative mapping the combination of canopy water and NSC, but this possibility remains largely unproven. We analyzed foliar water and NSC at leaf, canopy and stand levels using visible-to-shortwave infrared (VSWIR) spectroscopy. Leaf-level analyses demonstrated high precision and accuracy of water and NSC estimates in more than 10,000 live samples taken from thousands of forest canopy species worldwide. Airborne imaging spectroscopy from the Carnegie Airborne Observatory VSWIR spectrometer also provided high-accuracy canopy water and NSC estimates at the stand level. Spectral analyses indicated strong contributions of the shortwave-IR (1300-2500 nm) region to water and NSC determination at all scales. We conclude that canopy water and NSC can be remotely sensed, opening doors to monitor forest canopy physiological responses to environmental stress and climate change.