Future vulnerability mapping based on response to extreme climate events: Dieback thresholds in an endemic California oak |
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| Authors: | Blair C McLaughlin Rachel V Blakey Naia Morueta‐Holme |
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| Institution: | 1. Department of Natural Resources and Society, University of Idaho, Moscow, Idaho;2. Department of Ecology and Evolutionary Biology, University of California at Santa Cruz, Santa Cruz, CaliforniaBrittni Brown and Blair McLaughlin should be considered joint first authors.;3. Missouri Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife Sciences, University of Missouri, Columbia, Missouri;4. The Institute for Bird Populations, Point Reyes Station, California;5. Department of Integrative Biology, University of California at Berkeley, Berkeley, California;6. Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark |
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| Abstract: | Aim This study presents a bioclimate modelling approach, using responses to extreme climate events, rather than historical distributional associations, to project future species vulnerability and refugia. We aim to illustrate the compounding effects of groundwater loss and climate on species vulnerability. Location California, USA. Methods As a case study, we used the 2012–2015 California drought and resulting extensive dieback of blue oak (Quercus douglasii). We used aerial dieback surveys, downscaled climate data and subsurface water change data to develop boosted regression tree models identifying key thresholds associated with dieback throughout the blue oak distribution. We (1) combined observed dieback–climatic threshold relationships with climate futures to anticipate future areas of vulnerability and (2) used satellite‐derived measurements of subsurface water loss in drought/dieback modelling to capture the mediating effect of groundwater on species response to climatic drought. Results A model including climate, climate anomalies and subsurface water change explained 46% of the variability in dieback. Precipitation in 2015 and subsurface water change accounted for 62.6% of the modelled probability of dieback. We found an interaction between precipitation and subsurface water in which dieback probability increased with low precipitation and subsurface water loss. The relationship between precipitation and dieback was nonlinear, with 99% of dieback occurring in areas that received <363 mm precipitation. Based on a MIROC_rcp85 future climate scenario, relative to historical conditions, 13% of the blue oak distribution is predicted to experience more frequent years below this precipitation threshold by mid‐century and 81% by end of century. Main conclusions As ongoing climate change and extreme events impact ecological processes, the identification of thresholds associated with observed dieback may be combined with climate futures to help identify vulnerable populations and refugia and prioritize climate change‐related conservation efforts. |
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| Keywords: | climate change drought forest dieback groundwater
Quercus douglasii
refugia vulnerability mapping |
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