Authors: David Miller*, University of California Santa Barbara, Michael Alonzo, American University, Dar Roberts, University of California Santa Barbara, Christina Tague, University of California Santa Barbara, Joseph McFadden, University of California Santa Barbara
Topics: Remote Sensing, Environmental Science, Urban Geography
Keywords: Remote sensing, drought, urban, California, tree species, turfgrass
Session Type: Paper
Start / End Time: 10:15 AM / 11:30 AM
Room: Virtual Track 10
Presentation File: No File Uploaded
Drought can greatly affect vegetation physiological functioning, and in urban areas, this may limit the ability of vegetation to provide ecosystem services, including canopy shading and evaporative cooling. However, different tree species may have different responses to drought, and this variability is especially unclear in semi-arid cities that have many prominent exotic urban forest species. More broadly, it is important to assess how urban vegetation may respond to drought due to growing urban populations and the increasing potential for future droughts globally. In this study, we evaluated the effects of the severe 2012-2016 California drought on 19 common urban tree species and turfgrass in Santa Barbara, California using remote sensing imagery from repeat flights of NASA airborne imaging spectrometers. We assessed changes in spectral indicators related to canopy greenness, water content, and plant pigments. All vegetation types had significant changes (p < 0.05) in at least four spectral indicators at the height of the drought in 2014. While turfgrass showed recovery soon after the drought ended in 2017, there were a wide array of responses across the different tree species. Needleleaf trees overall were more affected than were broadleaf trees, and trees with higher pre-drought leaf area index generally showed greater changes in spectral indicators compared to their condition prior to the drought in 2011, although with great variability. These results suggest that denser, leafier canopies were more difficult for trees to maintain during the drought, and that many ostensibly drought-tolerant tree species were also impacted by the drought’s severity.