Evaluating theories of drought‐induced vegetation mortality using a multimodel–experiment framework
Nate G. McDowell,Rosie A. Fisher,Chonggang Xu,Jean-Christophe Domec,Jean-Christophe Domec,Teemu Hölttä,D. Scott Mackay,John S. Sperry,Amanda L. Boutz,Lee T. Dickman,Nathan Gehres,Jean-Marc Limousin,Alison K. Macalady,Jordi Martínez-Vilalta,Maurizio Mencuccini,Jennifer A. Plaut,Jérôme Ogée,Robert E. Pangle,Daniel P. Rasse,Michael G. Ryan,Michael G. Ryan,Sanna Sevanto,Richard H. Waring,A. Park Williams,Enrico A. Yepez,William T. Pockman +25 more
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TLDR
It is suggested that for some ecosystems, integration of mechanistic pathogen models into current vegetation models, and evaluation against observations, could result in a breakthrough capability to simulate vegetation dynamics.Abstract:
'Summary' 305
I. 'Background' 305
II. 'Model–experiment approach' 306
III. 'Simulations of hydraulic failure and carbon starvation' 310
IV. 'On thresholds vs duration of stress as drivers of mortality' 311
V. 'Interdependence of hydraulic failure and carbon starvation' 314
VI. 'Next-generation, traditional, and empirical models' 316
VII. 'A path forward' 317
VIII. 'Conclusions' 318
'Acknowledgements' 318
References 318
Summary
Model–data comparisons of plant physiological processes provide an understanding of mechanisms underlying vegetation responses to climate. We simulated the physiology of a pinon pine–juniper woodland (Pinus edulis–Juniperus monosperma) that experienced mortality during a 5 yr precipitation-reduction experiment, allowing a framework with which to examine our knowledge of drought-induced tree mortality. We used six models designed for scales ranging from individual plants to a global level, all containing state-of-the-art representations of the internal hydraulic and carbohydrate dynamics of woody plants. Despite the large range of model structures, tuning, and parameterization employed, all simulations predicted hydraulic failure and carbon starvation processes co-occurring in dying trees of both species, with the time spent with severe hydraulic failure and carbon starvation, rather than absolute thresholds per se, being a better predictor of impending mortality. Model and empirical data suggest that limited carbon and water exchanges at stomatal, phloem, and below-ground interfaces were associated with mortality of both species. The model–data comparison suggests that the introduction of a mechanistic process into physiology-based models provides equal or improved predictive power over traditional process-model or empirical thresholds. Both biophysical and empirical modeling approaches are useful in understanding processes, particularly when the models fail, because they reveal mechanisms that are likely to underlie mortality. We suggest that for some ecosystems, integration of mechanistic pathogen models into current vegetation models, and evaluation against observations, could result in a breakthrough capability to simulate vegetation dynamics.read more
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On underestimation of global vulnerability to tree mortality and forest die‐off from hotter drought in the Anthropocene
TL;DR: In this article, the authors identify ten contrasting perspectives that shape the vulnerability debate but have not been discussed collectively and present a set of global vulnerability drivers that are known with high confidence: (1) droughts eventually occur everywhere; (2) warming produces hotter Droughts; (3) atmospheric moisture demand increases nonlinearly with temperature during drought; (4) mortality can occur faster in hotter Drought, consistent with fundamental physiology; (5) shorter Drought can become lethal under warming, increasing the frequency of lethal Drought; and (6) mortality happens rapidly
Journal ArticleDOI
Triggers of tree mortality under drought
Brendan Choat,Timothy J. Brodribb,Craig R. Brodersen,Remko A. Duursma,Rosana López,Rosana López,Belinda E. Medlyn +6 more
TL;DR: This work focuses on the current understanding of tree hydraulic performance under drought, the identification of physiological thresholds that precipitate mortality and the mechanisms of recovery after drought, and the potential application of hydraulic thresholds to process-based models that predict mortality.
Journal ArticleDOI
A multi-species synthesis of physiological mechanisms in drought-induced tree mortality
Henry D. Adams,Melanie J. B. Zeppel,Melanie J. B. Zeppel,William R. L. Anderegg,Henrik Hartmann,Simon M. Landhäusser,David T. Tissue,Travis E. Huxman,Patrick J. Hudson,Trenton E. Franz,Craig D. Allen,Leander D. L. Anderegg,Greg A. Barron-Gafford,David J. Beerling,David D. Breshears,Timothy J. Brodribb,Harald Bugmann,Richard Cobb,Adam D. Collins,L. Turin Dickman,Honglang Duan,Brent E. Ewers,Lucía Galiano,David A. Galvez,Núria Garcia-Forner,Monica L. Gaylord,Monica L. Gaylord,Matthew J. Germino,Arthur Gessler,Uwe G. Hacke,Rodrigo Hakamada,Andy Hector,Michael W. Jenkins,Jeffrey M. Kane,Thomas Kolb,Darin J. Law,James D. Lewis,Jean-Marc Limousin,David M. Love,Alison K. Macalady,Jordi Martínez-Vilalta,Maurizio Mencuccini,Patrick J. Mitchell,J. D. Muss,Michael O'Brien,Anthony P. O'Grady,Robert E. Pangle,Elizabeth A. Pinkard,Frida I. Piper,Jennifer A. Plaut,William T. Pockman,Joe Quirk,Keith Reinhardt,Francesco Ripullone,Michael G. Ryan,Michael G. Ryan,Anna Sala,Sanna Sevanto,John S. Sperry,Rodrigo Vargas,Michel Vennetier,Danielle A. Way,Danielle A. Way,Chonggang Xu,Enrico A. Yepez,Nate G. McDowell +65 more
TL;DR: It is shown that, across multiple tree species, loss of xylem conductivity above 60% is associated with mortality, while carbon starvation is not universal, indicating that evidence supporting carbon starvation was not universal.
Journal ArticleDOI
Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts
Dorothe A. Frank,Markus Reichstein,Michael Bahn,Kirsten Thonicke,David Frank,Miguel D. Mahecha,Pete Smith,Marijn van der Velde,Sara Vicca,Flurin Babst,Flurin Babst,Christian Beer,Christian Beer,Nina Buchmann,Josep G. Canadell,Philippe Ciais,Wolfgang Cramer,Andreas Ibrom,Franco Miglietta,Ben Poulter,Anja Rammig,Anja Rammig,Sonia I. Seneviratne,Ariane Walz,Martin Wattenbach,Miguel A. Zavala,Jakob Zscheischler +26 more
TL;DR: It is found that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle, and forests are expected to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks.
Journal ArticleDOI
Tree mortality from drought, insects, and their interactions in a changing climate
William R. L. Anderegg,Jeffrey A. Hicke,Rosie A. Fisher,Craig D. Allen,Juliann E. Aukema,Barbara J. Bentz,Sharon M. Hood,Jeremy W. Lichstein,Alison K. Macalady,Nate G. McDowell,Yude Pan,Kenneth F. Raffa,Anna Sala,John D. Shaw,Nathan L. Stephenson,Christina L. Tague,Melanie J. B. Zeppel +16 more
TL;DR: Using data sets from the western USA and associated studies, a framework is presented for determining the relative contribution of drought stress, insect attack, and their interactions, critical for modeling mortality in future climates.
References
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Journal ArticleDOI
A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests
Craig D. Allen,Alison K. Macalady,Haroun Chenchouni,Dominique Bachelet,Nate G. McDowell,Michel Vennetier,Thomas Kitzberger,Andreas Rigling,David D. Breshears,Edward H. Hogg,Patrick Gonzalez,Rod Fensham,Zhen Zhang,Jorge Castro,N.A. Demidova,Jong Hwan Lim,Gillian Allard,Steven W. Running,Akkin Semerci,Neil S. Cobb +19 more
TL;DR: In this paper, the authors present the first global assessment of recent tree mortality attributed to drought and heat stress and identify key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system.
Journal ArticleDOI
Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests
TL;DR: Interdisciplinary science that integrates knowledge of the many interacting climate services of forests with the impacts of global change is necessary to identify and understand as yet unexplored feedbacks in the Earth system and the potential of forests to mitigate climate change.
Journal ArticleDOI
The dilemma of plants: To grow or defend.
TL;DR: A conceptual model of the evolution of plant defense is concluded, in which plant physioligical trade-offs interact with the abiotic environment, competition and herbivory.
Journal ArticleDOI
Mechanisms of plant survival and mortality during drought: why do some plants survive while others succumb to drought?
Nate G. McDowell,William T. Pockman,Craig D. Allen,David D. Breshears,Neil S. Cobb,Thomas Kolb,Jennifer A. Plaut,John S. Sperry,Adam G. West,Adam G. West,David G. Williams,Enrico A. Yepez +11 more
TL;DR: A hydraulically based theory considering carbon balance and insect resistance that allowed development and examination of hypotheses regarding survival and mortality was developed, and incorporating this hydraulic framework may be effective for modeling plant survival andortality under future climate conditions.
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