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Penha D, Brum M, Alves LF, Domingues TF, Meneses A, Branches R, Restrepo-Coupe N, Oliveira RS, Moura JMS, Pequeno PACLA, Prohaska N, Saleska SR. Preserving isohydricity: vertical environmental variability explains Amazon forest water-use strategies. TREE PHYSIOLOGY 2024; 44:tpae088. [PMID: 39041710 DOI: 10.1093/treephys/tpae088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 07/07/2024] [Accepted: 07/18/2024] [Indexed: 07/24/2024]
Abstract
Increases in hydrological extremes, including drought, are expected for Amazon forests. A fundamental challenge for predicting forest responses lies in identifying ecological strategies which underlie such responses. Characterization of species-specific hydraulic strategies for regulating water-use, thought to be arrayed along an 'isohydric-anisohydric' spectrum, is a widely used approach. However, recent studies have questioned the usefulness of this classification scheme, because its metrics are strongly influenced by environments, and hence can lead to divergent classifications even within the same species. Here, we propose an alternative approach positing that individual hydraulic regulation strategies emerge from the interaction of environments with traits. Specifically, we hypothesize that the vertical forest profile represents a key gradient in drought-related environments (atmospheric vapor pressure deficit, soil water availability) that drives divergent tree water-use strategies for coordinated regulation of stomatal conductance (gs) and leaf water potentials (ΨL) with tree rooting depth, a proxy for water availability. Testing this hypothesis in a seasonal eastern Amazon forest in Brazil, we found that hydraulic strategies indeed depend on height-associated environments. Upper canopy trees, experiencing high vapor pressure deficit (VPD), but stable soil water access through deep rooting, exhibited isohydric strategies, defined by little seasonal change in the diurnal pattern of gs and steady seasonal minimum ΨL. In contrast, understory trees, exposed to less variable VPD but highly variable soil water availability, exhibited anisohydric strategies, with fluctuations in diurnal gs that increased in the dry season along with increasing variation in ΨL. Our finding that canopy height structures the coordination between drought-related environmental stressors and hydraulic traits provides a basis for preserving the applicability of the isohydric-to-anisohydric spectrum, which we show here may consistently emerge from environmental context. Our work highlights the importance of understanding how environmental heterogeneity structures forest responses to climate change, providing a mechanistic basis for improving models of tropical ecosystems.
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Affiliation(s)
- Deliane Penha
- Instituto de Biodiversidade e Florestas, Programa de Pós-Graduação Sociedade, Natureza e Desenvolvimento, Universidade Federal do Oeste do Pará, Vera Paz, s/n, Salé, Santarém, Pará, 68040-255, Brazil
- Instituto de Engenharia e Geociências, Programa de Pós-Graduação em Recursos Naturais da Amazônia, Universidade Federal do Oeste do Pará, Vera Paz, s/n, Salé, Santarém, Pará, 68040-255, Brazil
| | - Mauro Brum
- Department of Ecology and Evolutionary Biology, University of Arizona, 1200 E University Blvd, Tucson, AZ 85721, United States
- Departamento de Biologia Vegetal, Instituto de Biologia, CP 6109, Universidade Estadual de Campinas (UNICAMP), Barão Geraldo, Campinas SP 13083-970, Brazil
| | - Luciana F Alves
- Center for Tropical Research, Institute of the Environment and Sustainability, University of California, Los Angeles, 619 Charles E. Young Drive East, La Kretz Hall, Suite 300, Box 951496, Los Angeles, CA 90095-1496, United States
| | - Tomas F Domingues
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Av. Bandeirantes, 3900, Monte Alegre, Ribeirão Preto, SP 14040-901, Brazil
| | - Anderson Meneses
- Instituto de Biodiversidade e Florestas, Programa de Pós-Graduação Sociedade, Natureza e Desenvolvimento, Universidade Federal do Oeste do Pará, Vera Paz, s/n, Salé, Santarém, Pará, 68040-255, Brazil
- Instituto de Engenharia e Geociências, Programa de Pós-Graduação em Recursos Naturais da Amazônia, Universidade Federal do Oeste do Pará, Vera Paz, s/n, Salé, Santarém, Pará, 68040-255, Brazil
- Instituto de Engenharia e Geociências, Laboratório de Inteligência Computacional, Universidade Federal do Oeste do Pará, Vera Paz, s/n, Salé, Santarém, Pará, 68040-255, Brazil
| | - Rardiles Branches
- Programa de Pós-Graduação em Meteorologia, Instituto Nacional de Pesquisas Espaciais, Rodovia Presidente Dutra, km 40, Cachoeira Paulista, São Paulo 12630-000, Brazil
| | - Natalia Restrepo-Coupe
- Department of Ecology and Evolutionary Biology, University of Arizona, 1200 E University Blvd, Tucson, AZ 85721, United States
| | - Rafael S Oliveira
- Departamento de Biologia Vegetal, Instituto de Biologia, CP 6109, Universidade Estadual de Campinas (UNICAMP), Barão Geraldo, Campinas SP 13083-970, Brazil
| | - José Mauro S Moura
- Instituto de Engenharia e Geociências, Programa de Pós-Graduação em Recursos Naturais da Amazônia, Universidade Federal do Oeste do Pará, Vera Paz, s/n, Salé, Santarém, Pará, 68040-255, Brazil
- Interdisciplinary and Intercultural Training Institute, Federal University of Western Para, Vera Paz, s/n, Salé, Santarém, Pará, 68040-255, Brazil
| | - Pedro A C L Aurélio Pequeno
- Programa de Pós-graduação em Recursos Naturais (PRONAT), Universidade Federal de Roraima, Av. Cap. Ene Garcez, 2413, Aeroporto, Roraima, Boa Vista, 69310-000, Brazil
| | - Neill Prohaska
- Department of Ecology and Evolutionary Biology, University of Arizona, 1200 E University Blvd, Tucson, AZ 85721, United States
| | - Scott R Saleska
- Department of Ecology and Evolutionary Biology, University of Arizona, 1200 E University Blvd, Tucson, AZ 85721, United States
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Anfodillo T, Olson ME. Stretched sapwood, ultra-widening permeability and ditching da Vinci: revising models of plant form and function. ANNALS OF BOTANY 2024; 134:19-42. [PMID: 38634673 PMCID: PMC11161570 DOI: 10.1093/aob/mcae054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Accepted: 04/14/2024] [Indexed: 04/19/2024]
Abstract
BACKGROUND The mechanisms leading to dieback and death of trees under drought remain unclear. To gain an understanding of these mechanisms, addressing major empirical gaps regarding tree structure-function relations remains essential. SCOPE We give reasons to think that a central factor shaping plant form and function is selection simultaneously favouring constant leaf-specific conductance with height growth and isometric (1:1) scaling between leaf area and the volume of metabolically active sink tissues ('sapwood'). Sapwood volume-leaf area isometry implies that per-leaf area sapwood volumes become transversely narrower with height growth; we call this 'stretching'. Stretching means that selection must favour increases in permeability above and beyond that afforded by tip-to-base conduit widening ("ultra-widening permeability"), via fewer and wider vessels or tracheids with larger pits or larger margo openings. Leaf area-metabolically active sink tissue isometry would mean that it is unlikely that larger trees die during drought because of carbon starvation due to greater sink-source relationships as compared to shorter plants. Instead, an increase in permeability is most plausibly associated with greater risk of embolism, and this seems a more probable explanation of the preferential vulnerability of larger trees to climate change-induced drought. Other implications of selection favouring constant per-leaf area sapwood construction and maintenance costs are departure from the da Vinci rule expectation of similar sapwood areas across branching orders, and that extensive conduit furcation in the stem seems unlikely. CONCLUSIONS Because all these considerations impact the likelihood of vulnerability to hydraulic failure versus carbon starvation, both implicated as key suspects in forest mortality, we suggest that these predictions represent essential priorities for empirical testing.
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Affiliation(s)
- Tommaso Anfodillo
- Department Territorio e Sistemi Agro-Forestali, University of Padova, Legnaro (PD) 35020, Italy
| | - Mark E Olson
- Instituto de Biología, Universidad Nacional Autónoma de México, Tercer Circuito sn de Ciudad Universitaria, Ciudad de México 04510, Mexico
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Brum M, Vadeboncoeur M, Asbjornsen H, Puma Vilca BL, Galiano D, Horwath AB, Metcalfe DB. Ecophysiological controls on water use of tropical cloud forest trees in response to experimental drought. TREE PHYSIOLOGY 2023; 43:1514-1532. [PMID: 37209136 DOI: 10.1093/treephys/tpad070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 05/03/2023] [Accepted: 05/17/2023] [Indexed: 05/22/2023]
Abstract
Tropical montane cloud forests (TMCFs) are expected to experience more frequent and prolonged droughts over the coming century, yet understanding of TCMF tree responses to moisture stress remains weak compared with the lowland tropics. We simulated a severe drought in a throughfall reduction experiment (TFR) for 2 years in a Peruvian TCMF and evaluated the physiological responses of several dominant species (Clusia flaviflora Engl., Weinmannia bangii (Rusby) Engl., Weinmannia crassifolia Ruiz & Pav. and Prunus integrifolia (C. Presl) Walp). Measurements were taken of (i) sap flow; (ii) diurnal cycles of stem shrinkage, stem moisture variation and water-use; and (iii) intrinsic water-use efficiency (iWUE) estimated from foliar δ13C. In W. bangii, we used dendrometers and volumetric water content (VWC) sensors to quantify daily cycles of stem water storage. In 2 years of sap flow (Js) data, we found a threshold response of water use to vapor pressure deficit vapor pressure deficit (VPD) > 1.07 kPa independent of treatment, though control trees used more soil water than the treatment trees. The daily decline in water use in the TFR trees was associated with a strong reduction in both morning and afternoon Js rates at a given VPD. Soil moisture also affected the hysteresis strength between Js and VPD. Reduced hysteresis under moisture stress implies that TMCFs are strongly dependent on shallow soil water. Additionally, we suggest that hysteresis can serve as a sensitive indicator of environmental constraints on plant function. Finally, 6 months into the experiment, the TFR treatment significantly increased iWUE in all study species. Our results highlight the conservative behavior of TMCF tree water use under severe soil drought and elucidate physiological thresholds related to VPD and its interaction with soil moisture. The observed strongly isohydric response likely incurs a cost to the carbon balance of the tree and reduces overall ecosystem carbon uptake.
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Affiliation(s)
- Mauro Brum
- Department of Natural Resources & the Environment, University of New Hampshire, 56 College Rd, Durham, NH 03824, USA
| | - Matthew Vadeboncoeur
- Earth Systems Research Center, University of New Hampshire, 8 College Rd, Durham, NH 03824, USA
| | - Heidi Asbjornsen
- Department of Natural Resources & the Environment, University of New Hampshire, 56 College Rd, Durham, NH 03824, USA
- Earth Systems Research Center, University of New Hampshire, 8 College Rd, Durham, NH 03824, USA
| | - Beisit L Puma Vilca
- Facultad de Ciencias Biológicas, Universidad Nacional de San Antonio Abad del Cusco, Av. de La Cultura 773, Cusco, Cusco Province 08000, Peru
- Asociación Civil Sin Fines De Lucro Para La Biodiversidad, Investigación Y Desarrollo Ambiental En Ecosistemas Tropicales (ABIDA), Urbanización Ucchullo Grande, Avenida Argentina F-9, Cusco, Perú
| | - Darcy Galiano
- Facultad de Ciencias Biológicas, Universidad Nacional de San Antonio Abad del Cusco, Av. de La Cultura 773, Cusco, Cusco Province 08000, Peru
- Asociación Civil Sin Fines De Lucro Para La Biodiversidad, Investigación Y Desarrollo Ambiental En Ecosistemas Tropicales (ABIDA), Urbanización Ucchullo Grande, Avenida Argentina F-9, Cusco, Perú
| | - Aline B Horwath
- Asociación Civil Sin Fines De Lucro Para La Biodiversidad, Investigación Y Desarrollo Ambiental En Ecosistemas Tropicales (ABIDA), Urbanización Ucchullo Grande, Avenida Argentina F-9, Cusco, Perú
| | - Daniel B Metcalfe
- Department of Ecology & Environmental Science, Umeå University, KBC-huset, Linnaeus väg 6, Umeå 901 87, Sweden
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Feeley KJ, Bernal-Escobar M, Fortier R, Kullberg AT. Tropical Trees Will Need to Acclimate to Rising Temperatures-But Can They? PLANTS (BASEL, SWITZERLAND) 2023; 12:3142. [PMID: 37687387 PMCID: PMC10490527 DOI: 10.3390/plants12173142] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 08/29/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023]
Abstract
For tropical forests to survive anthropogenic global warming, trees will need to avoid rising temperatures through range shifts and "species migrations" or tolerate the newly emerging conditions through adaptation and/or acclimation. In this literature review, we synthesize the available knowledge to show that although many tropical tree species are shifting their distributions to higher, cooler elevations, the rates of these migrations are too slow to offset ongoing changes in temperatures, especially in lowland tropical rainforests where thermal gradients are shallow or nonexistent. We also show that the rapidity and severity of global warming make it unlikely that tropical tree species can adapt (with some possible exceptions). We argue that the best hope for tropical tree species to avoid becoming "committed to extinction" is individual-level acclimation. Although several new methods are being used to test for acclimation, we unfortunately still do not know if tropical tree species can acclimate, how acclimation abilities vary between species, or what factors may prevent or facilitate acclimation. Until all of these questions are answered, our ability to predict the fate of tropical species and tropical forests-and the many services that they provide to humanity-remains critically impaired.
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Affiliation(s)
- Kenneth J. Feeley
- Department of Biology, University of Miami, Coral Gables, FL 33146, USA; (M.B.-E.); (R.F.); (A.T.K.)
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Rowland L, Ramírez-Valiente JA, Hartley IP, Mencuccini M. How woody plants adjust above- and below-ground traits in response to sustained drought. THE NEW PHYTOLOGIST 2023. [PMID: 37306017 DOI: 10.1111/nph.19000] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 04/01/2023] [Indexed: 06/13/2023]
Abstract
Future increases in drought severity and frequency are predicted to have substantial impacts on plant function and survival. However, there is considerable uncertainty concerning what drought adjustment is and whether plants can adjust to sustained drought. This review focuses on woody plants and synthesises the evidence for drought adjustment in a selection of key above-ground and below-ground plant traits. We assess whether evaluating the drought adjustment of single traits, or selections of traits that operate on the same plant functional axis (e.g. photosynthetic traits) is sufficient, or whether a multi-trait approach, integrating across multiple axes, is required. We conclude that studies on drought adjustments in woody plants might overestimate the capacity for adjustment to drier environments if spatial studies along gradients are used, without complementary experimental approaches. We provide evidence that drought adjustment is common in above-ground and below-ground traits; however, whether this is adaptive and sufficient to respond to future droughts remains uncertain for most species. To address this uncertainty, we must move towards studying trait integration within and across multiple axes of plant function (e.g. above-ground and below-ground) to gain a holistic view of drought adjustments at the whole-plant scale and how these influence plant survival.
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Affiliation(s)
- Lucy Rowland
- Geography, Faculty of Environment, Science and Economy, University of Exeter, Exeter, EX4 4RJ, UK
| | | | - Iain P Hartley
- Geography, Faculty of Environment, Science and Economy, University of Exeter, Exeter, EX4 4RJ, UK
| | - Maurizio Mencuccini
- CREAF, Campus de Bellaterra (UAB), Cerdanyola del Vallés, Barcelona, 08193, Spain
- ICREA, Barcelona, 08010, Spain
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Vinod N, Slot M, McGregor IR, Ordway EM, Smith MN, Taylor TC, Sack L, Buckley TN, Anderson-Teixeira KJ. Thermal sensitivity across forest vertical profiles: patterns, mechanisms, and ecological implications. THE NEW PHYTOLOGIST 2023; 237:22-47. [PMID: 36239086 DOI: 10.1111/nph.18539] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 07/31/2022] [Indexed: 06/16/2023]
Abstract
Rising temperatures are influencing forests on many scales, with potentially strong variation vertically across forest strata. Using published research and new analyses, we evaluate how microclimate and leaf temperatures, traits, and gas exchange vary vertically in forests, shaping tree, and ecosystem ecology. In closed-canopy forests, upper canopy leaves are exposed to the highest solar radiation and evaporative demand, which can elevate leaf temperature (Tleaf ), particularly when transpirational cooling is curtailed by limited stomatal conductance. However, foliar traits also vary across height or light gradients, partially mitigating and protecting against the elevation of upper canopy Tleaf . Leaf metabolism generally increases with height across the vertical gradient, yet differences in thermal sensitivity across the gradient appear modest. Scaling from leaves to trees, canopy trees have higher absolute metabolic capacity and growth, yet are more vulnerable to drought and damaging Tleaf than their smaller counterparts, particularly under climate change. By contrast, understory trees experience fewer extreme high Tleaf 's but have fewer cooling mechanisms and thus may be strongly impacted by warming under some conditions, particularly when exposed to a harsher microenvironment through canopy disturbance. As the climate changes, integrating the patterns and mechanisms reviewed here into models will be critical to forecasting forest-climate feedback.
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Affiliation(s)
- Nidhi Vinod
- Conservation Ecology Center, Smithsonian's National Zoo & Conservation Biology Institute, Front Royal, VA, 22630, USA
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA, 90039, USA
| | - Martijn Slot
- Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Panama City, Panama
| | - Ian R McGregor
- Center for Geospatial Analytics, North Carolina State University, Raleigh, NC, 27607, USA
| | - Elsa M Ordway
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA, 90039, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Marielle N Smith
- Department of Forestry, Michigan State University, East Lansing, MI, 48824, USA
- School of Natural Sciences, College of Environmental Sciences and Engineering, Bangor University, Bangor, LL57 2DG, UK
| | - Tyeen C Taylor
- Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA, 90039, USA
| | - Thomas N Buckley
- Department of Plant Sciences, University of California, Davis, CA, 95616, USA
| | - Kristina J Anderson-Teixeira
- Conservation Ecology Center, Smithsonian's National Zoo & Conservation Biology Institute, Front Royal, VA, 22630, USA
- Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Panama City, Panama
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Giles AL, Rowland L, Bittencourt PRL, Bartholomew DC, Coughlin I, Costa PB, Domingues T, Miatto RC, Barros FV, Ferreira LV, Groenendijk P, Oliveira AAR, da Costa ACL, Meir P, Mencuccini M, Oliveira RS. Small understorey trees have greater capacity than canopy trees to adjust hydraulic traits following prolonged experimental drought in a tropical forest. TREE PHYSIOLOGY 2022; 42:537-556. [PMID: 34508606 DOI: 10.1093/treephys/tpab121] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 09/08/2021] [Indexed: 06/13/2023]
Abstract
Future climate change predictions for tropical forests highlight increased frequency and intensity of extreme drought events. However, it remains unclear whether large and small trees have differential strategies to tolerate drought due to the different niches they occupy. The future of tropical forests is ultimately dependent on the capacity of small trees (<10 cm in diameter) to adjust their hydraulic system to tolerate drought. To address this question, we evaluated whether the drought tolerance of neotropical small trees can adjust to experimental water stress and was different from tall trees. We measured multiple drought resistance-related hydraulic traits across nine common neotropical genera at the world's longest-running tropical forest throughfall-exclusion experiment and compared their responses with surviving large canopy trees. Small understorey trees in both the control and the throughfall-exclusion treatment had lower minimum stomatal conductance and maximum hydraulic leaf-specific conductivity relative to large trees of the same genera, as well as a greater hydraulic safety margin (HSM), percentage loss of conductivity and embolism resistance, demonstrating that they occupy a distinct hydraulic niche. Surprisingly, in response to the drought treatment, small trees increased specific hydraulic conductivity by 56.3% and leaf:sapwood area ratio by 45.6%. The greater HSM of small understorey trees relative to large canopy trees likely enabled them to adjust other aspects of their hydraulic systems to increase hydraulic conductivity and take advantage of increases in light availability in the understorey resulting from the drought-induced mortality of canopy trees. Our results demonstrate that differences in hydraulic strategies between small understorey and large canopy trees drive hydraulic niche segregation. Small understorey trees can adjust their hydraulic systems in response to changes in water and light availability, indicating that natural regeneration of tropical forests following long-term drought may be possible.
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Affiliation(s)
- A L Giles
- Instituto de Biologia, University of Campinas (UNICAMP), R. Monteiro Lobato, 255 - Barão Geraldo, Campinas SP 13083-970, Brazil
| | - L Rowland
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK
| | - P R L Bittencourt
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK
| | - D C Bartholomew
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK
| | - I Coughlin
- Departamento de Biologia, FFCLRP, Universidade de São Paulo, Av. Bandeirantes, 3900 - Vila Monte Alegre, Ribeirão Preto SP 14040-900, Brazil
- Research School of Biology, Australian National University, 134 Linnaeus Way, Canberra ACT 2601, Australia
| | - P B Costa
- Instituto de Biologia, University of Campinas (UNICAMP), R. Monteiro Lobato, 255 - Barão Geraldo, Campinas SP 13083-970, Brazil
- Biological Sciences, Stirling Highway, Perth, WA 6009, Australia
| | - T Domingues
- Departamento de Biologia, FFCLRP, Universidade de São Paulo, Av. Bandeirantes, 3900 - Vila Monte Alegre, Ribeirão Preto SP 14040-900, Brazil
| | - R C Miatto
- Departamento de Biologia, FFCLRP, Universidade de São Paulo, Av. Bandeirantes, 3900 - Vila Monte Alegre, Ribeirão Preto SP 14040-900, Brazil
| | - F V Barros
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK
| | - L V Ferreira
- Museu Paraense Emílio Goeldi, Av. Gov Magalhães Barata, 376 - São Brás, Belém PA 66040-170, Brazil
| | - P Groenendijk
- Instituto de Biologia, University of Campinas (UNICAMP), R. Monteiro Lobato, 255 - Barão Geraldo, Campinas SP 13083-970, Brazil
| | - A A R Oliveira
- Museu Paraense Emílio Goeldi, Av. Gov Magalhães Barata, 376 - São Brás, Belém PA 66040-170, Brazil
| | - A C L da Costa
- Museu Paraense Emílio Goeldi, Av. Gov Magalhães Barata, 376 - São Brás, Belém PA 66040-170, Brazil
- Biological Sciences, Stirling Highway, Perth, WA 6009, Australia
| | - P Meir
- Research School of Biology, Australian National University, 134 Linnaeus Way, Canberra ACT 2601, Australia
- School of GeoSciences, University of Edinburgh, Drummond St Edinburgh EH9 3FF, UK
| | - M Mencuccini
- CREAF, Campus UAB, Edifici C Campus de Bellaterra Cerdanyola del Vallés 08193, Spain
- ICREA, Passeig de Lluís Companys, 23, Barcelona 08010, Spain
| | - R S Oliveira
- Instituto de Biologia, University of Campinas (UNICAMP), R. Monteiro Lobato, 255 - Barão Geraldo, Campinas SP 13083-970, Brazil
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Gora EM, Esquivel-Muelbert A. Implications of size-dependent tree mortality for tropical forest carbon dynamics. NATURE PLANTS 2021; 7:384-391. [PMID: 33782580 DOI: 10.1038/s41477-021-00879-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 02/11/2021] [Indexed: 05/25/2023]
Abstract
Tropical forests are mitigating the ongoing climate crisis by absorbing more atmospheric carbon than they emit. However, widespread increases in tree mortality rates are decreasing the ability of tropical forests to assimilate and store carbon. A relatively small number of large trees dominate the contributions of these forests to the global carbon budget, yet we know remarkably little about how these large trees die. Here, we propose a cohesive and empirically informed framework for understanding and investigating size-dependent drivers of tree mortality. This theory-based framework enables us to posit that abiotic drivers of tree mortality-particularly drought, wind and lightning-regulate tropical forest carbon cycling via their disproportionate effects on large trees. As global change is predicted to increase the pressure from abiotic drivers, the associated deaths of large trees could rapidly and lastingly reduce tropical forest biomass stocks. Focused investigations of large tree death are needed to understand how shifting drivers of mortality are restructuring carbon cycling in tropical forests.
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Affiliation(s)
- Evan M Gora
- Smithsonian Tropical Research Institute, Balboa, Ancón, Panama.
| | - Adriane Esquivel-Muelbert
- School of Geography, University of Birmingham, Birmingham, UK.
- Birmingham Institute of Forest Research, Birmingham, UK.
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Why is Tree Drought Mortality so Hard to Predict? Trends Ecol Evol 2021; 36:520-532. [PMID: 33674131 DOI: 10.1016/j.tree.2021.02.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 01/29/2021] [Accepted: 02/02/2021] [Indexed: 01/18/2023]
Abstract
Widespread tree mortality following droughts has emerged as an environmentally and economically devastating 'ecological surprise'. It is well established that tree physiology is important in understanding drought-driven mortality; however, the accuracy of predictions based on physiology alone has been limited. We propose that complicating factors at two levels stymie predictions of drought-driven mortality: (i) organismal-level physiological and site factors that obscure understanding of drought exposure and vulnerability and (ii) community-level ecological interactions, particularly with biotic agents whose effects on tree mortality may reverse expectations based on stress physiology. We conclude with a path forward that emphasizes the need for an integrative approach to stress physiology and biotic agent dynamics when assessing forest risk to drought-driven morality in a changing climate.
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