Tree mortality in blue oak woodland during extreme drought in Sequoia National Park, California
Blue oak woodlands in California have been a focus of conservation concern for many years. Numerous studies have found that existing seedling and sapling numbers are inadequate to sustain current populations, and recent work has suggested that blue oak woodlands might be particularly vulnerable to a warming climate. California has recently experienced a drought of historically unprecedented severity, resulting in the mortality of tens of millions of trees, including an apparent spike in mortality in oak communities. Here we present the results of a survey of tree mortality and composition in blue oak woodlands in Sequoia National Park. We found that 18% (95% CI = 14–24,) of all standing trees and 23% (95% CI = 17–30) of standing Quercus douglasii Hook. & Arn. (blue oak) were dead, substantially higher than proportions of dead trees recorded in pre-drought datasets, which showed 4% (95% CI = 2–9) standing dead for all trees and 5% (95% CI = 4–7) dead or 8% (95% CI = 4–16) standing dead for blue oak. Furthermore, much of this mortality appeared to be recent. Based on foliage or fine twig retention, 19% (95% CI = 14–26) of blue oak and 23% (95% CI = 16–31) of Quercus wislizeni A. DC. (interior live oak) appear to have died recently. In contrast, only 5% (95% CI = 3–8) of Aesculus californica (Spach) Nutt. (California buckeye) and 5% (95% CI = 2–11) of Fraxinus dipetala Hook. & Arn. (California ash) appear to have died recently. Even after such high mortality, with blue oak basal area dropping by 26% (from 9.5 m2/ha [95% CI = 7.4–11.6] to 7.0 m2/ha [95% CI = 5.3–8.7]), blue oak remains the dominant species in these ecosystems. However, given the lack of recruitment and the apparent vulnerability to extreme drought, blue oak populations may be at risk for severe decline if such mortality events become more frequent.
Citation Information
| Publication Year | 2020 |
|---|---|
| Title | Tree mortality in blue oak woodland during extreme drought in Sequoia National Park, California |
| DOI | 10.3120/0024-9637-66.4.164 |
| Authors | Adrian J. Das, Nicholas J. Ampersee, Anne Hopkins Pfaff, Nathan L. Stephenson, Tedmund J Swiecki, Elizabeth A Bernhardt, Patricia Haggerty, Koren R. Nydick |
| Publication Type | Article |
| Publication Subtype | Journal Article |
| Series Title | Madroño |
| Index ID | 70208838 |
| Record Source | USGS Publications Warehouse |
| USGS Organization | Western Ecological Research Center |
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Tree mortality in blue oak woodlands in Sequoia National Park during the extreme drought
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- Data
Tree mortality in blue oak woodlands in Sequoia National Park during the extreme drought
These data were collected to quantify oak mortality during the 2014-2017 drought. 30 tenth hectare drought plots were established throughout the blue oak woodland of Sequoia National Park. Information on species, size, and mortality were collected for all standing trees in each plot. In addition, two long-term 2.25 ha plots were established, in which the same data were collected. - Connect