Heatwave induced tree mortality: Can multispectral imaging detect heat stress?

Authors: Maggie E Ng*, Hampshire College, School of Natural Science, Amherst MA (United States), Darin Law, University of Arizona, School of Natural Resources and the Environment, Tucson AZ (United States), David D Breshears, University of Arizona, School of Natural Resources and the Environment, Tucson AZ (United States), Greg A Barron-Gafford, University of Arizona, School of Geography and Development, Tucson AZ (United States), Jason P Field, University of Arizona, School of Natural Resources and the Environment, Tucson AZ (United States), Mallory L Barnes, University of Arizona, School of Natural Resources and the Environment, Tucson AZ (United States), Angelina Martinez-Yrizar, Universidad Nacional Autónoma de Mexico, Hermosillo (Mexico)
Topics: Remote Sensing, Arid Regions
Keywords: Remote sensing, tree die-off, arid regions, southwest, NDVI, drought, water stress
Session Type: Poster
Day: 4/13/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded


Large-scale tree die-off in response to drought is a global warming phenomenon of increasing concern. Recent research suggests that heatwaves may be a trigger of mortality for trees during relatively hotter droughts. Consequently, experiments are needed to examine if heatwaves induce or exacerbate mortality in tree species suffering from drought and heat stress. We are experimentally investigating relationships between tree mortality and heat stress using seedlings of piñon pine (Pinus edulis), a tree species which has experienced recent widespread die-off and has been a focus of hotter-drought-related mortality. We are testing a ground-based, non-destructive multispectral imaging method to determine changes in tree morphology caused by heat and water stress in seedlings over time. We used multispectral imaging to calculate the Normalized Difference Vegetation Index (NDVI), an estimate of live green vegetation, for tree seedlings in various stages of heat and drought stress. We simultaneously used RGB imaging to calculate percent brown foliage. With the use of a leaf porometer and RGB imaging we were also able to calculate whole seedling stomatal conductance. Preliminary results suggest that as piñon pine seedlings experience decreasing available soil water, mean NDVI decreases, percent brown increases, and plant water loss increases. NDVI may be useful to detect a particular color threshold, caused by foliar water loss, when mortality becomes inevitable. These results may be useful in detecting morphological and physiological changes in trees suffering from drought stress, as well as accurately detecting if drought and heat stress predispose trees to mortality following a heatwave event.

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