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Drivers and mechanisms of tree mortality in moist tropical forests.

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posted on 2019-03-04, 10:25 authored by N McDowell, CD Allen, K Anderson-Teixeira, P Brando, R Brienen, J Chambers, B Christoffersen, S Davies, C Doughty, A Duque, F Espirito-Santo, R Fisher, CG Fontes, D Galbraith, D Goodsman, C Grossiord, H Hartmann, J Holm, DJ Johnson, AR Kassim, M Keller, C Koven, L Kueppers, T Kumagai, Y Malhi, SM McMahon, M Mencuccini, P Meir, P Moorcroft, HC Muller-Landau, OL Phillips, T Powell, CA Sierra, J Sperry, J Warren, C Xu, X Xu
Tree mortality rates appear to be increasing in moist tropical forests (MTFs) with significant carbon cycle consequences. Here, we review the state of knowledge regarding MTF tree mortality, create a conceptual framework with testable hypotheses regarding the drivers, mechanisms and interactions that may underlie increasing MTF mortality rates, and identify the next steps for improved understanding and reduced prediction. Increasing mortality rates are associated with rising temperature and vapor pressure deficit, liana abundance, drought, wind events, fire and, possibly, CO2 fertilization-induced increases in stand thinning or acceleration of trees reaching larger, more vulnerable heights. The majority of these mortality drivers may kill trees in part through carbon starvation and hydraulic failure. The relative importance of each driver is unknown. High species diversity may buffer MTFs against large-scale mortality events, but recent and expected trends in mortality drivers give reason for concern regarding increasing mortality within MTFs. Models of tropical tree mortality are advancing the representation of hydraulics, carbon and demography, but require more empirical knowledge regarding the most common drivers and their subsequent mechanisms. We outline critical datasets and model developments required to test hypotheses regarding the underlying causes of increasing MTF mortality rates, and improve prediction of future mortality under climate change.


This article is the product of the workshop ‘Tropical forest mortality’ held in Santa Fe, NM, USA, in 2015. The workshop and writing of the article were supported by the Next Generation Ecosystem Experiment‐Tropics project, Department of Energy, Office of Science.



New Phytologist, 2018, 219 (3), pp. 851-869

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/School of Geography, Geology and the Environment


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Additional Supporting Information may be found online in the Supporting Information tab for this article :Fig. S1 Comparison of two approaches for calculating mortality rates from inventory data reveals only negligible impacts on the final estimates.Fig. S2 Representation of Fig. 2 from the main text using different metrics, such as biomass mortality. Fig. S3 Representation of Fig. 3 from the main text using different metrics, such as basal area. Fig. S4 Projected changes in atmospheric relative humidity from CMIP5 models under RC8.5. Fig. S5 Projected changes in precipitation from CMIP5 models under RCP8.5. Fig. S6 Projected changes in atmospheric wind speeds from CMIP5 models under RCP 8.5.Methods S1A review of how inventory data are converted into mortality rate estimates and the implications of differing calculations and statistics (in relation to Fig. 2 within the main text). Methods S2 Description of methods used for Fig. 3 from the maintext. Notes S1 On the role of nutrients in moist tropical forest (MTF) mortality. Notes S2A potential approach to Earth system model (ESM) modeling of hydraulics.



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