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Title: Temperature response surfaces for mortality risk of tree species with future drought

Widespread, high levels of tree mortality, termed forest die-off, associated with drought and rising temperatures, are disrupting forests worldwide. Drought will likely become more frequent with climate change, but even without more frequent drought, higher temperatures can exacerbate tree water stress. The temperature sensitivity of drought-induced mortality of tree species has been evaluated experimentally for only single-step changes in temperature (ambient compared to ambient + increase) rather than as a response surface (multiple levels of temperature increase), which constrains our ability to relate changes in the driver with the biological response. Here we show that time-to-mortality during drought for seedlings of two western United States tree species, Pinus edulis (Engelm.) and Pinus ponderosa (Douglas ex C. Lawson), declined in continuous proportion with increasing temperature spanning a 7.7 °C increase. Although P. edulis outlived P. ponderosa at all temperatures, both species had similar relative declines in time-to-mortality as temperature increased (5.2% per °C for P. edulis; 5.8% per °C for P. ponderosa). When combined with the non-linear frequency distribution of drought duration—many more short droughts than long droughts—these findings point to a progressive increase in mortality events with global change due to warming alone and independent of additional changes in futuremore » drought frequency distributions. As such, dire future forest recruitment patterns are projected assuming the calculated 7–9 seedling mortality events per species by 2100 under business-as-usual warming occur, congruent with additional vulnerability predicted for adult trees from stressors like pathogens and pests. Our progressive projection for increased mortality events was driven primarily by the non-linear shape of the drought duration frequency distribution, a common climate feature of drought-affected regions. These results illustrate profound benefits for reducing emissions of carbon to the atmosphere from anthropogenic sources and slowing warming as rapidly as possible to maximize forest persistence.« less
ORCiD logo [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8]
  1. Oklahoma State Univ., Stillwater, OK (United States). Dept. of Plant Biology, Ecology, and Evolution
  2. Univ. of Arizona, Tucson, AZ (United States). School of Geography and Development. B2 Earthscience. Biosphere 2
  3. Center for Research in Food and Development (CIAD), Guaymas (Mexico)
  4. Sonoma State Univ., Rohnert Park, CA (United States). Dept. of Biology
  5. Univ. of Arizona, Tucson, AZ (United States). School of Natural Resources and the Environment
  6. Univ. of Arizona, Tucson, AZ (United States). School of Natural Resources and the Environment. Dept. of Ecology and Evolutionary Biology
  7. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  8. Univ. of California, Irvine, CA (United States). Ecology and Evolutionary Biology. Center for Environmental Biology
Publication Date:
Report Number(s):
Journal ID: ISSN 1748-9326
Grant/Contract Number:
AC05-76RL01830; EF-1340624; EF-1550756; EAR-1331408; FP-91717801-0
Accepted Manuscript
Journal Name:
Environmental Research Letters
Additional Journal Information:
Journal Volume: 12; Journal Issue: 11; Journal ID: ISSN 1748-9326
IOP Publishing
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of Arizona, Tucson, AZ (United States); Oklahoma State Univ., Stillwater, OK (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); LANL Laboratory Directed Research and Development (LDRD) Program; PNNL Laboratory Directed Research and Development (LDRD) Program; National Science Foundation (NSF); USEPA
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; drought; tree mortality; Pinus edulis; Pinus ponderosa; temperature; tree die-off; climate change ecology
OSTI Identifier: