Remote Sensing of Urban Vegetation during Drought in Southern California
UCSB Geography PhD student and Tague Team Lab member David Miller’s Final Defense will be on Friday, December 4, 2020 at 12:00 PM (PST) via Zoom (contact us for connection information)
Advisor: Joe McFadden
Committee Members: Dar Roberts and Naomi Tague
Abstract: During 2012-2016, California experienced one of the most severe droughts in its modern history, with limited precipitation and exceptionally high temperatures over an extended time period. Urban vegetation, such as trees and turfgrass lawns, provides many benefits, or ecosystem services, for people living in cities. For example, urban plants can cool their surroundings through shading and latent heat loss from evapotranspiration. These benefits may be difficult to maintain through extreme drought, especially in water-limited cities, and different types of vegetation may have different responses to drought. In this dissertation, I used remote sensing time series to quantify how urban vegetation responded to drought in Santa Barbara and Los Angeles, California.
In Chapter 1, I examined drought response in turfgrass and across nineteen urban tree species in the city of Santa Barbara using data from repeat flights of the Airborne Visible Infrared Imaging Spectrometer (AVIRIS) and AVIRIS-Next Generation (AVIRIS-NG). I compared many spectral indicators that may be expected to change within plant canopies during drought.
In Chapter 2, I evaluated how drought manifests seasonally and interannually during 2010-2019 across dominant types of trees and grass in the Santa Barbara area using Landsat and AVIRIS imagery. I compared the condition of dominant types of trees and grasses as they changed throughout the year using the Normalized Difference Vegetation Index (NDVI), difference in vegetation land surface temperature from impervious surfaces (∆LST), and equivalent water thickness (EWT). I also assessed the correlations of NDVI and ∆LST with the Standardized Precipitation Evapotranspiration Index (SPEI) to test to the effects of drought length and severity on vegetation.
In Chapter 3, I assessed annual changes in fractional cover of trees, turfgrass, non-photosynthetic vegetation (NPV; e.g., senesced grass, plant litter), and non-vegetated urban surfaces across the Los Angeles metropolitan area during 2013-2018 using AVIRIS imagery. I also compared vegetation changes based on median household income and estimates of outdoor water use.