A synthetic review leads to a new hypothesis framework that sheds light on how and why plants are dying more under a warming climate.
Increasing rates of woody-plant mortality, including trees and shrubs, presents a large scientific challenge because we do not yet understand what is causing the increasing loss of plants. This study reviewed the literature to identify the key mechanisms underlying warming-induced mortality, and presented a testable framework that yields insight into the drivers of plant death as well as how to better model these processes. Ultimately, mortality under drought, rising temperature, and rising carbon dioxide results from depletion of water and carbon stores, leading to irreversible dehydration and the inability to maintain metabolism. Warming exacerbates these storage declines, while elevated carbon dioxide has mixed impacts. The net result of the increasing rate and severity of warming and drought overwhelms the benefits of elevated carbon.
Plant mortality is rising globally, leading to negative impacts on ecosystem services of value to society including economic, aesthetic, and ecological consequences. Plant mortality reduces carbon uptake and increases carbon loss, promoting a decline in terrestrial carbon storage. Despite these consequences, our ability to predict plant mortality is limited by a lack of knowledge of the underlying mechanisms, their response to climate, and their integration into models. Here, scientists reviewed the literature to generate a synthetic hypothesis framework that pinpoints the key mechanisms driving mortality under a changing environment. The result is a roadmap for future research, including the provision of a set of testable hypotheses that will rapidly increase our knowledge, and identification of key mechanisms that should be included in process models to enable more accurate representation of the impacts of climate change on plant survival.
Plant mortality is rising in concert with increasing droughts, warming, and carbon dioxide, but the mechanisms driving the increased mortality are poorly known. This knowledge gap leads to large challenges for prediction of the future of terrestrial ecosystems, including their role in water, carbon, and nutrient cycling. Here we integrated the literature on plant mortality and subsequently generated a synthetic and testable hypothesis framework describing the mechanisms underlying plant death in a warming and drying world. The stores of carbon and water are depleted under changing climate, with some amelioration due to rising carbon dioxide. The decline in these stores leads to failure to maintain hydration and metabolism, and can promote death outright or through failure to defend against attacking biotic agents. Acclimation can promote survival to an extent. Determining the net impacts of rising carbon dioxide versus drought and warming remain a major science challenge.
Contact: Nate McDowell, Pacific Northwest National Laboratory, firstname.lastname@example.org
N. G. M. and C. X. were supported by the Department of Energy, Office of Science project Next Generation Ecosystem Experiment-Tropics (NGEE-Tropics). G. S. was supported by the NSFBII-Implementation (2021898). D. T. acknowledges support from the Australian Research Council (DP0879531, DP110105102, LP0989881, LP140100232). M. D. K acknowledges support from the Australian Research Council (ARC) Centre of Excellence for Climate Extremes (CE170100023), the ARC Discovery Grant (DP190101823) and the NSW Research Attraction and Acceleration Program. C. G. was supported by the Swiss National Science Foundation (PZ00P3_174068). M. M. and J.M.V were supported by the Spanish Ministry of Science and Innovation (MICINN, CGL2017‐89149‐C2‐1‐R). A.T.T. acknowledges funding from the NSF Grant 2003205, the USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Programme Grant No. 2018-67012-31496 and the University of California Laboratory Fees Research Program Award No. LFR-20-652467. W.M.H. was supported by the NSF GRFP (1-746055). A.M.T. and H.D.A. were supported by the NSF Division of Integrative Organismal Systems, Integrative Ecological Physiology Program (IOS-1755345, IOS-1755346). H.D.A. also received support from the USDA National Institute of Food and Agriculture (NIFA), McIntire Stennis Project WNP00009 and Agriculture and Food Research Initiative award 2021-67013-33716. D.D.B. was supported by NSF (DEB-1550756, DEB-1824796, DEB-1925837), USGS SW Climate Adaptation Science Center (G18AC00320), USDA NIFA McIntire Stennis ARZT 1390130-M12-222, and a Murdoch University Distinguished Visiting Scholar award. D.S.M. was supported by NSF (IOS-1444571, IOS- 1547796). R.S.O. acknowledges funding from NERC-FAPESP 19/07773-1. W.R.L.A. was supported by the David and Lucille Packard Foundation, NSF grants 1714972, 1802880 and 2003017, and USDA NIFA AFRI grant no. 2018‐67019‐27850. R.S.O. acknowledges funding from NERC-FAPESP 19/07773-1. B.E.M. is supported by an Australian Research Council Laureate Fellowship (FL190100003. A.S. was supported by a Bullard Fellowship (Harvard University) and the University of Montana.
McDowell NG, Sapes G, Pivovaroff A, Adams H, Allen CD, Anderegg WRL, Arend M, Breshears DD, Brodribb T, Choat B, Cochard H, Cáceres MD, De Kauwe M, Grossiord C, Hammond WH, Hartmann H, Hoch G, Kahmen A, Klein T, Mackay DS, Mantova M, Martínez-Vilalta J, Medlyn BE, Mencuccini M, Nardini A, Oliveira RS, Sala A, Tissue DT, Torres-Ruiz JM, Trowbridge A, Trugman AT, Wiley E, Xu C. (2022) Mechanisms of woody plant mortality under rising drought, CO2, and vapor pressure deficit. Nature Reviews Earth and Environment. https://doi.org/10.1038/s43017-022-00272-1.