Mapping the vulnerability of giant sequoias after extreme drought in California using remote sensing
Baeza A, Martin RE, Stephenson NL, Das AJ, Hardwick P, Nydick K, Mallory J, Slaton M, Evans K, Asner GP. 2021. Mapping the vulnerability of giant sequoias after extreme drought in California using remote sensing. Ecological Applications. 31(7)
Between 2012 and 2016, California suffered one of the most severe droughts onrecord. During this period Sequoiadendron giganteum (giant sequoias) in the Sequoia andKings Canyon National Parks (SEKI), California, USA experienced canopy water content(CWC) loss, unprecedented foliage senescence, and, in a few cases, death. We present an assess-ment of the vulnerability of giant sequoia populations to droughts that is currently lacking andneeded for management. We used a temporal trend of remotely sensed CWC obtained between2015 and 2017, and recently georeferenced giant sequoia crowns to quantify the vulnerabilityof 7,408 individuals in 10 groves in the northern portion of SEKI. CWC is sensitive to changesin liquid water in tree canopies; therefore, it is a useful metric for quantifying the response ofsequoia trees to drought. Temporal trends indicated that 9% of giant sequoias had a significantdecline or consistently low CWC, suggesting these trees were likely operating at low photosyn-thetic capacity and potentially at high risk to drought stress. We also found that 20% of thegiant sequoias had an increase or consistently high level of CWC, indicating these trees were atlow risk to drought stress. These vulnerability categories were used in a random forest modelwith a combination of topographic, fire-related, and climate variables to generate high-resolution vulnerability risk maps. These maps show that higher risk is associated with lowerelevation and higher climate water deficit. We also found that sequoias at higher elevations butlocated near meadows had higher vulnerability risk. These results and the vulnerability mapscan identify vulnerable sequoias that may be difficult to save or locations of refugia to be pro-tected, and thus may aid forest managers in preparation for future droughts.
- Type
- Journal Article
- Authors
- Baeza, Andres; Martin, Roberta; Stephenson, Nathan; Das, Adrian; Hardwick, Paul; Nydick, Koren; Mallory, Jeff; Slaton, Michele; Evans, Kirk; Asner, Gregory
- Units
- SEKI
- Keywords
- canopy water content, CWC, remote sensing, vulnerability risk maps