1
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Devanand A, Falster GM, Gillett ZE, Hobeichi S, Holgate CM, Jin C, Mu M, Parker T, Rifai SW, Rome KS, Stojanovic M, Vogel E, Abram NJ, Abramowitz G, Coats S, Evans JP, Gallant AJE, Pitman AJ, Power SB, Rauniyar SP, Taschetto AS, Ukkola AM. Australia's Tinderbox Drought: An extreme natural event likely worsened by human-caused climate change. SCIENCE ADVANCES 2024; 10:eadj3460. [PMID: 38446893 PMCID: PMC10917352 DOI: 10.1126/sciadv.adj3460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 01/29/2024] [Indexed: 03/08/2024]
Abstract
We examine the characteristics and causes of southeast Australia's Tinderbox Drought (2017 to 2019) that preceded the Black Summer fire disaster. The Tinderbox Drought was characterized by cool season rainfall deficits of around -50% in three consecutive years, which was exceptionally unlikely in the context of natural variability alone. The precipitation deficits were initiated and sustained by an anomalous atmospheric circulation that diverted oceanic moisture away from the region, despite traditional indicators of drought risk in southeast Australia generally being in neutral states. Moisture deficits were intensified by unusually high temperatures, high vapor pressure deficits, and sustained reductions in terrestrial water availability. Anthropogenic forcing intensified the rainfall deficits of the Tinderbox Drought by around 18% with an interquartile range of 34.9 to -13.3% highlighting the considerable uncertainty in attributing droughts of this kind to human activity. Skillful predictability of this drought was possible by incorporating multiple remote and local predictors through machine learning, providing prospects for improving forecasting of droughts.
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Affiliation(s)
- Anjana Devanand
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Georgina M. Falster
- ARC Centre of Excellence for Climate Extremes, The Australian National University, Canberra, ACT, Australia
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia
| | - Zoe E. Gillett
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Sanaa Hobeichi
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Chiara M. Holgate
- ARC Centre of Excellence for Climate Extremes, The Australian National University, Canberra, ACT, Australia
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia
| | - Chenhui Jin
- ARC Centre of Excellence for Climate Extremes, Monash University, Melbourne, VIC, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC, Australia
| | - Mengyuan Mu
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Tess Parker
- ARC Centre of Excellence for Climate Extremes, Monash University, Melbourne, VIC, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC, Australia
| | - Sami W. Rifai
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
- School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Kathleen S. Rome
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Milica Stojanovic
- Centro de Investigación Mariña, Universidade de Vigo, Environmental Physics Laboratory (EPhysLab), Campus As Lagoas s/n, Ourense 32004, Spain
| | - Elisabeth Vogel
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Water Research Centre, School of Civil Engineering, University of New South Wales, Sydney, NSW, Australia
- Melbourne Climate Futures, The University of Melbourne, Parkville, VIC, Australia
| | - Nerilie J. Abram
- ARC Centre of Excellence for Climate Extremes, The Australian National University, Canberra, ACT, Australia
- Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia
| | - Gab Abramowitz
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Sloan Coats
- Department of Earth Sciences, University of Hawaiʻi at Mānoa, Honolulu, HI, USA
| | - Jason P. Evans
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Ailie J. E. Gallant
- ARC Centre of Excellence for Climate Extremes, Monash University, Melbourne, VIC, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC, Australia
| | - Andy J. Pitman
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Scott B. Power
- ARC Centre of Excellence for Climate Extremes, Monash University, Melbourne, VIC, Australia
- School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC, Australia
- Centre for Applied Climate Sciences, University of Southern Queensland, Toowoomba, QLD, Australia
- Climate Services International, Oakleigh, Melbourne, VIC, Australia
| | | | - Andréa S. Taschetto
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Anna M. Ukkola
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
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2
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Torres-Ruiz JM, Cochard H, Delzon S, Boivin T, Burlett R, Cailleret M, Corso D, Delmas CEL, De Caceres M, Diaz-Espejo A, Fernández-Conradi P, Guillemot J, Lamarque LJ, Limousin JM, Mantova M, Mencuccini M, Morin X, Pimont F, De Dios VR, Ruffault J, Trueba S, Martin-StPaul NK. Plant hydraulics at the heart of plant, crops and ecosystem functions in the face of climate change. THE NEW PHYTOLOGIST 2024; 241:984-999. [PMID: 38098153 DOI: 10.1111/nph.19463] [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: 07/04/2023] [Accepted: 11/05/2023] [Indexed: 01/12/2024]
Abstract
Plant hydraulics is crucial for assessing the plants' capacity to extract and transport water from the soil up to their aerial organs. Along with their capacity to exchange water between plant compartments and regulate evaporation, hydraulic properties determine plant water relations, water status and susceptibility to pathogen attacks. Consequently, any variation in the hydraulic characteristics of plants is likely to significantly impact various mechanisms and processes related to plant growth, survival and production, as well as the risk of biotic attacks and forest fire behaviour. However, the integration of hydraulic traits into disciplines such as plant pathology, entomology, fire ecology or agriculture can be significantly improved. This review examines how plant hydraulics can provide new insights into our understanding of these processes, including modelling processes of vegetation dynamics, illuminating numerous perspectives for assessing the consequences of climate change on forest and agronomic systems, and addressing unanswered questions across multiple areas of knowledge.
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Affiliation(s)
- José M Torres-Ruiz
- Université Clermont-Auvergne, INRAE, PIAF, 63000, Clermont-Ferrand, France
| | - Hervé Cochard
- Université Clermont-Auvergne, INRAE, PIAF, 63000, Clermont-Ferrand, France
| | - Sylvain Delzon
- University of Bordeaux, INRAE, UMR BIOGECO, Pessac, 33615, France
| | | | - Regis Burlett
- University of Bordeaux, INRAE, UMR BIOGECO, Pessac, 33615, France
| | - Maxime Cailleret
- INRAE, Aix-Marseille Université, UMR RECOVER, Aix-en-Provence, 13100, France
| | - Déborah Corso
- University of Bordeaux, INRAE, UMR BIOGECO, Pessac, 33615, France
| | - Chloé E L Delmas
- INRAE, Bordeaux Sciences Agro, ISVV, SAVE, F-33140, Villenave d'Ornon, France
| | | | - Antonio Diaz-Espejo
- Instituto de Recursos Naturales y Agrobiología (IRNAS), Consejo Superior de Investigaciones Científicas (CSIC), Seville, 41012, Spain
| | | | - Joannes Guillemot
- CIRAD, UMR Eco&Sols, Montpellier, 34394, France
- Eco&Sols, Univ. Montpellier, CIRAD, INRAe, Institut Agro, IRD, Montpellier, 34394, France
- Department of Forest Sciences, ESALQ, University of São Paulo, Piracicaba, 05508-060, São Paulo, Brazil
| | - Laurent J Lamarque
- Département des sciences de l'environnement, Université du Québec à Trois-Rivières, Trois-Rivières, G9A 5H7, Québec, Canada
| | | | - Marylou Mantova
- Agronomy Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Maurizio Mencuccini
- CREAF, Bellaterra (Cerdanyola del Vallès), Catalonia, E08193, Spain
- ICREA, Barcelona, 08010, Spain
| | - Xavier Morin
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, 34394, France
| | | | - Victor Resco De Dios
- Department of Forest and Agricultural Science and Engineering, University of Lleida, Lleida, 25198, Spain
- JRU CTFC-AGROTECNIO-CERCA Center, Lleida, 25198, Spain
| | | | - Santiago Trueba
- University of Bordeaux, INRAE, UMR BIOGECO, Pessac, 33615, France
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3
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Paschalis A, De Kauwe MG, Sabot M, Fatichi S. When do plant hydraulics matter in terrestrial biosphere modelling? GLOBAL CHANGE BIOLOGY 2024; 30:e17022. [PMID: 37962234 PMCID: PMC10952296 DOI: 10.1111/gcb.17022] [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: 07/05/2023] [Accepted: 10/23/2023] [Indexed: 11/15/2023]
Abstract
The ascent of water from the soil to the leaves of vascular plants, described by the study of plant hydraulics, regulates ecosystem responses to environmental forcing and recovery from stress periods. Several approaches to model plant hydraulics have been proposed. In this study, we introduce four different versions of plant hydraulics representations in the terrestrial biosphere model T&C to understand the significance of plant hydraulics to ecosystem functioning. We tested representations of plant hydraulics, investigating plant water capacitance, and long-term xylem damages following drought. The four models we tested were a combination of representations including or neglecting capacitance and including or neglecting xylem damage legacies. Using the models at six case studies spanning semiarid to tropical ecosystems, we quantify how plant xylem flow, plant water storage and long-term xylem damage can modulate overall water and carbon dynamics across multiple time scales. We show that as drought develops, models with plant hydraulics predict a slower onset of plant water stress, and a diurnal variability of water and carbon fluxes closer to observations. Plant water storage was found to be particularly important for the diurnal dynamics of water and carbon fluxes, with models that include plant water capacitance yielding better results. Models including permanent damage to conducting plant tissues show an additional significant drought legacy effect, limiting plant productivity during the recovery phase following major droughts. However, when considering ecosystem responses to the observed climate variability, plant hydraulic modules alone cannot significantly improve the overall model performance, even though they reproduce more realistic water and carbon dynamics. This opens new avenues for model development, explicitly linking plant hydraulics with additional ecosystem processes, such as plant phenology and improved carbon allocation algorithms.
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Affiliation(s)
- Athanasios Paschalis
- Department of Civil and Environmental EngineeringImperial College LondonLondonUK
| | | | - Manon Sabot
- ARC Centre of Excellence for Climate Extremes and Climate Change Research CentreUniversity of New South WalesSydneyNew South WalesAustralia
| | - Simone Fatichi
- Department of Civil and Environmental EngineeringNational University of SingaporeSingaporeSingapore
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4
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Chen L, Li M, Li C, Zheng W, Liu R. Different Physiological Responses to Continuous Drought between Seedlings and Younger Individuals of Haloxylon ammodendron. PLANTS (BASEL, SWITZERLAND) 2023; 12:3683. [PMID: 37960040 PMCID: PMC10647405 DOI: 10.3390/plants12213683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/18/2023] [Accepted: 10/18/2023] [Indexed: 11/15/2023]
Abstract
Drought is an important environmental factor that influences physiological processes in plants; however, few studies have examined the physiological mechanisms underlying plants' responses to continuous drought. In this study, the seedlings and younger individuals of Haloxylon ammodendron were experimentally planted in the southern part of the Gurbantunggut Desert. We measured their photosynthetic traits, functional traits and non-structural carbohydrate contents (NSCs) in order to assess the effects of continuous drought (at 15-day and 30-day drought points) on the plants' physiological responses. The results showed that at the 15-day (15 d) drought point, the leaf light-saturated net photosynthetic rate (An) values of both the seedlings and the younger individuals were decreased (by -68.9% and -45.2%, respectively). The intrinsic water use efficiency (iWUE) of the seedlings was significantly lower than that of the control group (-52.2%), but there was no diffenrence of iWUE observed in younger individuals. At the 30-day (30 d) drought point, a decrease in the An (-129.8%) of the seedlings was induced via biochemical inhibition, with a lower potential maximum photochemical rate (Fv/Fm, 0.42) compared with the control group, while a decrease in the An (-52.3%) of the younger individuals was induced due to lower stomatal conductance (gs, -50.5%). Our results indicated that prolonged drought induced a greater risk of seedling mortality as the relatively limited ability of stomatal regulation may increase the possibility of massive embolism, resulting in hydraulic failure.
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Affiliation(s)
- Lidan Chen
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; (L.C.); (M.L.)
- University of Chinese Academy of Sciences, Beijing 100049, China
- Fukang National Station of Observation and Research for Desert Ecosystem, Fukang 831505, China
| | - Minqing Li
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; (L.C.); (M.L.)
- University of Chinese Academy of Sciences, Beijing 100049, China
- Fukang National Station of Observation and Research for Desert Ecosystem, Fukang 831505, China
| | - Congjuan Li
- National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;
| | - Weihua Zheng
- Institute of Agricultural Quality Standards and Testing Technology, Xinjiang Academy of Agricultural Sciecnes, Urumuqi 830091, China;
| | - Ran Liu
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China; (L.C.); (M.L.)
- University of Chinese Academy of Sciences, Beijing 100049, China
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5
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Blackman CJ, Billon LM, Cartailler J, Torres-Ruiz JM, Cochard H. Key hydraulic traits control the dynamics of plant dehydration in four contrasting tree species during drought. TREE PHYSIOLOGY 2023; 43:1772-1783. [PMID: 37318310 PMCID: PMC10652334 DOI: 10.1093/treephys/tpad075] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 06/07/2023] [Accepted: 06/08/2023] [Indexed: 06/16/2023]
Abstract
Trees are at risk of mortality during extreme drought, yet our understanding of the traits that govern the timing of drought-induced hydraulic failure remains limited. To address this, we tested SurEau, a trait-based soil-plant-atmosphere model designed to predict the dynamics of plant dehydration as represented by the changes in water potential against those observed in potted trees of four contrasting species (Pinus halepensis Mill., Populus nigra L., Quercus ilex L. and Cedrus atlantica (Endl.) Manetti ex Carriére) exposed to drought. SurEau was parameterized with a range of plant hydraulic and allometric traits, soil and climatic variables. We found a close correspondence between the predicted and observed plant water potential (in MPa) dynamics during the early phase drought, leading to stomatal closure, as well as during the latter phase of drought, leading to hydraulic failure in all four species. A global model's sensitivity analysis revealed that, for a common plant size (leaf area) and soil volume, dehydration time from full hydration to stomatal closure (Tclose) was most strongly controlled by the leaf osmotic potential (Pi0) and its influence on stomatal closure, in all four species, while the maximum stomatal conductance (gsmax) also contributed to Tclose in Q. ilex and C. atlantica. Dehydration times from stomatal closure to hydraulic failure (Tcav) was most strongly controlled by Pi0, the branch residual conductance (gres) and Q10a sensitivity of gres in the three evergreen species, while xylem embolism resistance (P50) was most influential in the deciduous species P. nigra. Our findings point to SurEau as a highly useful model for predicting changes in plant water status during drought and suggest that adjustments made in key hydraulic traits are potentially beneficial to delaying the onset of drought-induced hydraulic failure in trees.
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Affiliation(s)
- Chris J Blackman
- ARC Centre of Excellence for Plant Success in Nature and Agriculture, School of Natural Sciences, University of Tasmania, Hobart 7001, Australia
- Université Clermont-Auvergne, INRAE, PIAF, Clermont-Ferrand 63100, France
| | - Lise-Marie Billon
- Université Clermont-Auvergne, INRAE, PIAF, Clermont-Ferrand 63100, France
| | - Julien Cartailler
- Université Clermont-Auvergne, INRAE, PIAF, Clermont-Ferrand 63100, France
| | - José M Torres-Ruiz
- Université Clermont-Auvergne, INRAE, PIAF, Clermont-Ferrand 63100, France
| | - Hervé Cochard
- Université Clermont-Auvergne, INRAE, PIAF, Clermont-Ferrand 63100, France
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6
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Sanchez-Martinez P, Mencuccini M, García-Valdés R, Hammond WM, Serra-Diaz JM, Guo WY, Segovia RA, Dexter KG, Svenning JC, Allen C, Martínez-Vilalta J. Increased hydraulic risk in assemblages of woody plant species predicts spatial patterns of drought-induced mortality. Nat Ecol Evol 2023; 7:1620-1632. [PMID: 37640766 PMCID: PMC10555820 DOI: 10.1038/s41559-023-02180-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 07/26/2023] [Indexed: 08/31/2023]
Abstract
Predicting drought-induced mortality (DIM) of woody plants remains a key research challenge under climate change. Here, we integrate information on the edaphoclimatic niches, phylogeny and hydraulic traits of species to model the hydraulic risk of woody plants globally. We combine these models with species distribution records to estimate the hydraulic risk faced by local woody plant species assemblages. Thus, we produce global maps of hydraulic risk and test for its relationship with observed DIM. Our results show that local assemblages modelled as having higher hydraulic risk present a higher probability of DIM. Metrics characterizing this hydraulic risk improve DIM predictions globally, relative to models accounting only for edaphoclimatic predictors or broad functional groupings. The methodology we present here allows mapping of functional trait distributions and elucidation of global macro-evolutionary and biogeographical patterns, improving our ability to predict potential global change impacts on vegetation.
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Affiliation(s)
- Pablo Sanchez-Martinez
- Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain.
- CREAF, Cerdanyola del Valles, Barcelona, Spain.
- School of GeoSciences, University of Edinburgh, Edinburgh, UK.
| | | | - Raúl García-Valdés
- CREAF, Cerdanyola del Valles, Barcelona, Spain
- Department of Biology and Geology, Physics and Inorganic Chemistry, Rey Juan Carlos University, Móstoles, Madrid, Spain
| | | | - Josep M Serra-Diaz
- Université de Lorraine, AgroParisTech, INRAE, Nancy, France
- Eversource Energy Center, University of Connecticut, Storrs, CT, USA
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA
| | - Wen-Yong Guo
- Research Center for Global Change and Complex Ecosystems & Zhejiang Tiantong Forest Ecosystem National Observation and Research Station, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, P. R. China
- Department of Biology, Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) & Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Aarhus University, Aarhus C, Denmark
| | - Ricardo A Segovia
- Institute of Ecology and Biodiversity (IEB), Santiago, Chile
- Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile
| | - Kyle G Dexter
- School of GeoSciences, University of Edinburgh, Edinburgh, UK
- Royal Botanic Garden Edinburgh, Edinburgh, UK
| | - Jens-Christian Svenning
- Department of Biology, Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) & Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Aarhus University, Aarhus C, Denmark
| | - Craig Allen
- Department of Geography and Environmental Studies, University of New Mexico, Albuquerque, NM, USA
| | - Jordi Martínez-Vilalta
- Universitat Autònoma de Barcelona, Cerdanyola del Valles, Barcelona, Spain
- CREAF, Cerdanyola del Valles, Barcelona, Spain
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7
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Keppel G, Sarnow U, Biffin E, Peters S, Fitzgerald D, Boutsalis E, Waycott M, Guerin GR. Population decline in a Pleistocene refugium: Stepwise, drought-related dieback of a South Australian eucalypt. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 876:162697. [PMID: 36898535 DOI: 10.1016/j.scitotenv.2023.162697] [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: 11/22/2022] [Revised: 03/03/2023] [Accepted: 03/03/2023] [Indexed: 06/18/2023]
Abstract
Refugia can facilitate the persistence of species under long-term environmental change, but it is not clear if Pleistocene refugia will remain functional as anthropogenic climate change progresses. Dieback in populations restricted to refugia therefore raises concerns about their long-term persistence. Using repeat field surveys, we investigate dieback in an isolated population of Eucalyptus macrorhyncha during two droughts and discuss prospects for its continued persistence in a Pleistocene refugium. We first confirm that the Clare Valley in South Australia has constituted a long-term refugium for the species, with the population being genetically highly distinct from other conspecific populations. However, the population lost >40 % of individuals and biomass through the droughts, with mortality being just below 20 % after the Millennium Drought (2000-2009) and almost 25 % after the Big Dry (2017-2019). The best predictors of mortality differed after each drought. While north-facing aspect of a sampling location was significant positive predictor after both droughts, biomass density and slope were significant negative predictors only after the Millennium Drought, and distance to the north-west corner of the population, which intercepts hot, dry winds, was a significant positive predictor after the Big Dry only. This suggests that more marginal sites with low biomass and sites located on flat plateaus were more vulnerable initially, but that heat-stress was an important driver of dieback during the Big Dry. Therefore, the causative drivers of dieback may change during population decline. Regeneration occurred predominantly on southern and eastern aspects, which would receive the least solar radiation. While this refugial population is experiencing severe decline, some gullies with lower solar radiation appear to support relatively healthy, regenerating stands of red stringybark, providing hope for persistence in small pockets. Monitoring and managing these pockets during future droughts will be essential to ensure the persistence of this isolated and genetically unique population.
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Affiliation(s)
- Gunnar Keppel
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia; AMAP, Université de Montpellier, CIRAD, CNRS, INRAE, IRD, Montpellier, France.
| | - Udo Sarnow
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia
| | - Ed Biffin
- State Herbarium of South Australia, Botanic Gardens and State Herbarium, Department for Environment and Water, Adelaide, Australia.
| | - Stefan Peters
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia.
| | - Donna Fitzgerald
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia.
| | - Evan Boutsalis
- UniSA STEM and Future Industries Institute, University of South Australia, GPO Box 2471, SA 5001 Adelaide, Australia.
| | - Michelle Waycott
- State Herbarium of South Australia, Botanic Gardens and State Herbarium, Department for Environment and Water, Adelaide, Australia.
| | - Greg R Guerin
- School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia.
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8
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Potkay A, Feng X. Do stomata optimize turgor-driven growth? A new framework for integrating stomata response with whole-plant hydraulics and carbon balance. THE NEW PHYTOLOGIST 2023; 238:506-528. [PMID: 36377138 DOI: 10.1111/nph.18620] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 11/11/2022] [Indexed: 06/16/2023]
Abstract
Every existing optimal stomatal model uses photosynthetic carbon assimilation as a proxy for plant evolutionary fitness. However, assimilation and growth are often decoupled, making assimilation less ideal for representing fitness when optimizing stomatal conductance to water vapor and carbon dioxide. Instead, growth should be considered a closer proxy for fitness. We hypothesize stomata have evolved to maximize turgor-driven growth, instead of assimilation, over entire plants' lifetimes, improving their abilities to compete and reproduce. We develop a stomata model that dynamically maximizes whole-stem growth following principles from turgor-driven growth models. Stomata open to assimilate carbohydrates that supply growth and osmotically generate turgor, while stomata close to prevent losses of turgor and growth due to negative water potentials. In steady state, the growth optimization model captures realistic stomatal, growth, and carbohydrate responses to environmental cues, reconciles conflicting interpretations within existing stomatal optimization theories, and explains patterns of carbohydrate storage and xylem conductance observed during and after drought. Our growth optimization hypothesis introduces a new paradigm for stomatal optimization models, elevates the role of whole-plant carbon use and carbon storage in stomatal functioning, and has the potential to simultaneously predict gross productivity, net productivity, and plant mortality through a single, consistent modeling framework.
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Affiliation(s)
- Aaron Potkay
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA
- Saint Anthony Falls Laboratory, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA
| | - Xue Feng
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA
- Saint Anthony Falls Laboratory, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA
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9
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Ruffault J, Limousin JM, Pimont F, Dupuy JL, De Càceres M, Cochard H, Mouillot F, Blackman CJ, Torres-Ruiz JM, Parsons RA, Moreno M, Delzon S, Jansen S, Olioso A, Choat B, Martin-StPaul N. Plant hydraulic modelling of leaf and canopy fuel moisture content reveals increasing vulnerability of a Mediterranean forest to wildfires under extreme drought. THE NEW PHYTOLOGIST 2023; 237:1256-1269. [PMID: 36366950 DOI: 10.1111/nph.18614] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Accepted: 11/03/2022] [Indexed: 06/16/2023]
Abstract
Fuel moisture content (FMC) is a crucial driver of forest fires in many regions world-wide. Yet, the dynamics of FMC in forest canopies as well as their physiological and environmental determinants remain poorly understood, especially under extreme drought. We embedded a FMC module in the trait-based, plant-hydraulic SurEau-Ecos model to provide innovative process-based predictions of leaf live fuel moisture content (LFMC) and canopy fuel moisture content (CFMC) based on leaf water potential ( ψ Leaf ). SurEau-Ecos-FMC relies on pressure-volume (p-v) curves to simulate LFMC and vulnerability curves to cavitation to simulate foliage mortality. SurEau-Ecos-FMC accurately reproduced ψ Leaf and LFMC dynamics as well as the occurrence of foliage mortality in a Mediterranean Quercus ilex forest. Several traits related to water use (leaf area index, available soil water, and transpiration regulation), vulnerability to cavitation, and p-v curves (full turgor osmotic potential) had the greatest influence on LFMC and CFMC dynamics. As the climate gets drier, our results showed that drought-induced foliage mortality is expected to increase, thereby significantly decreasing CFMC. Our results represent an important advance in our capacity to understand and predict the sensitivity of forests to wildfires.
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Affiliation(s)
| | | | | | | | | | - Hervé Cochard
- Université Clermont-Auvergne, INRAE, PIAF, 63000, Clermont-Ferrand, France
| | - Florent Mouillot
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, 34000, Montpellier, France
| | - Chris J Blackman
- School of Biological Sciences, University of Tasmania, Hobart, Tas., 7001, Australia
| | - José M Torres-Ruiz
- Université Clermont-Auvergne, INRAE, PIAF, 63000, Clermont-Ferrand, France
| | - Russell A Parsons
- Fire Sciences Laboratory, Rocky Mountain Research Station, USDA Forest Service, Missoula, MT, 59808, USA
| | | | | | - Steven Jansen
- Institute of Systematic Botany and Ecology, Ulm University, D-89081, Ulm, Germany
| | | | - Brendan Choat
- Western Sydney University, Penrith, NSW, 2751, Australia
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10
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Losso A, Challis A, Gauthey A, Nolan RH, Hislop S, Roff A, Boer MM, Jiang M, Medlyn BE, Choat B. Canopy dieback and recovery in Australian native forests following extreme drought. Sci Rep 2022; 12:21608. [PMID: 36517498 PMCID: PMC9751299 DOI: 10.1038/s41598-022-24833-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 11/21/2022] [Indexed: 12/15/2022] Open
Abstract
In 2019, south-eastern Australia experienced its driest and hottest year on record, resulting in massive canopy dieback events in eucalypt dominated forests. A subsequent period of high precipitation in 2020 provided a rare opportunity to quantify the impacts of extreme drought and consequent recovery. We quantified canopy health and hydraulic impairment (native percent loss of hydraulic conductivity, PLC) of 18 native tree species growing at 15 sites that were heavily impacted by the drought both during and 8-10 months after the drought. Most species exhibited high PLC during drought (PLC:65.1 ± 3.3%), with no clear patterns across sites or species. Heavily impaired trees (PLC > 70%) showed extensive canopy browning. In the post-drought period, most surviving trees exhibited hydraulic recovery (PLC:26.1 ± 5.1%), although PLC remained high in some trees (50-70%). Regained hydraulic function (PLC < 50%) corresponded to decreased canopy browning indicating improved tree health. Similar drought (37.1 ± 4.2%) and post-drought (35.1 ± 4.4%) percentages of basal area with dead canopy suggested that trees with severely compromised canopies immediately after drought were not able to recover. This dataset provides insights into the impacts of severe natural drought on the health of mature trees, where hydraulic failure is a major contributor in canopy dieback and tree mortality during extreme drought events.
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Affiliation(s)
- Adriano Losso
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
- Department of Botany, University of Innsbruck, Sternwartestraße 15, 6020, Innsbruck, Austria.
| | - Anthea Challis
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Alice Gauthey
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- Plant Ecology Research Laboratory PERL, Ecole Polytechnique Fédérale de Lausanne EPFL, 1015, Lausanne, Switzerland
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland
| | - Rachael H Nolan
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- NSW Bushfire Risk Management Research Hub, Wollongong, NSW, Australia
| | - Samuel Hislop
- Forest Science, NSW Department of Primary Industries, Parramatta, NSW, 2150, Australia
| | - Adam Roff
- Department of Planning, Industry and Environment, Remote Sensing and Landscape Science, 26 Honeysuckle Drive, Newcastle, NSW, 2302, Australia
| | - Matthias M Boer
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- NSW Bushfire Risk Management Research Hub, Wollongong, NSW, Australia
| | - Mingkai Jiang
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- College of Life Sciences, Zhejiang University, 866 Yuhangtang Rd, Hangzhou, Zhejiang, China
| | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
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11
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De Kauwe MG, Sabot MEB, Medlyn BE, Pitman AJ, Meir P, Cernusak LA, Gallagher RV, Ukkola AM, Rifai SW, Choat B. Towards species-level forecasts of drought-induced tree mortality risk. THE NEW PHYTOLOGIST 2022; 235:94-110. [PMID: 35363880 PMCID: PMC9321630 DOI: 10.1111/nph.18129] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/28/2022] [Indexed: 05/14/2023]
Abstract
Predicting species-level responses to drought at the landscape scale is critical to reducing uncertainty in future terrestrial carbon and water cycle projections. We embedded a stomatal optimisation model in the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model and parameterised the model for 15 canopy dominant eucalypt tree species across South-Eastern Australia (mean annual precipitation range: 344-1424 mm yr-1 ). We conducted three experiments: applying CABLE to the 2017-2019 drought; a 20% drier drought; and a 20% drier drought with a doubling of atmospheric carbon dioxide (CO2 ). The severity of the drought was highlighted as for at least 25% of their distribution ranges, 60% of species experienced leaf water potentials beyond the water potential at which 50% of hydraulic conductivity is lost due to embolism. We identified areas of severe hydraulic stress within-species' ranges, but we also pinpointed resilience in species found in predominantly semiarid areas. The importance of the role of CO2 in ameliorating drought stress was consistent across species. Our results represent an important advance in our capacity to forecast the resilience of individual tree species, providing an evidence base for decision-making around the resilience of restoration plantings or net-zero emission strategies.
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Affiliation(s)
| | - Manon E. B. Sabot
- ARC Centre of Excellence for Climate ExtremesSydneyNSW2052Australia
- Climate Change Research CentreUniversity of New South WalesSydneyNSW2052Australia
| | - Belinda E. Medlyn
- Hawkesbury Institute for the EnvironmentWestern Sydney UniversityLocked Bag 1797PenrithNSW2751Australia
| | - Andrew J. Pitman
- ARC Centre of Excellence for Climate ExtremesSydneyNSW2052Australia
- Climate Change Research CentreUniversity of New South WalesSydneyNSW2052Australia
| | - Patrick Meir
- School of GeosciencesThe University of EdinburghEdinburghEH9 3FFUK
| | - Lucas A. Cernusak
- College of Science and EngineeringJames Cook UniversityCairnsQld4878Australia
| | - Rachael V. Gallagher
- Hawkesbury Institute for the EnvironmentWestern Sydney UniversityLocked Bag 1797PenrithNSW2751Australia
| | - Anna M. Ukkola
- ARC Centre of Excellence for Climate ExtremesSydneyNSW2052Australia
- Climate Change Research CentreUniversity of New South WalesSydneyNSW2052Australia
| | - Sami W. Rifai
- ARC Centre of Excellence for Climate ExtremesSydneyNSW2052Australia
- Climate Change Research CentreUniversity of New South WalesSydneyNSW2052Australia
| | - Brendan Choat
- Hawkesbury Institute for the EnvironmentWestern Sydney UniversityLocked Bag 1797PenrithNSW2751Australia
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12
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Beringer J, Moore CE, Cleverly J, Campbell DI, Cleugh H, De Kauwe MG, Kirschbaum MUF, Griebel A, Grover S, Huete A, Hutley LB, Laubach J, Van Niel T, Arndt SK, Bennett AC, Cernusak LA, Eamus D, Ewenz CM, Goodrich JP, Jiang M, Hinko‐Najera N, Isaac P, Hobeichi S, Knauer J, Koerber GR, Liddell M, Ma X, Macfarlane C, McHugh ID, Medlyn BE, Meyer WS, Norton AJ, Owens J, Pitman A, Pendall E, Prober SM, Ray RL, Restrepo‐Coupe N, Rifai SW, Rowlings D, Schipper L, Silberstein RP, Teckentrup L, Thompson SE, Ukkola AM, Wall A, Wang Y, Wardlaw TJ, Woodgate W. Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network. GLOBAL CHANGE BIOLOGY 2022; 28:3489-3514. [PMID: 35315565 PMCID: PMC9314624 DOI: 10.1111/gcb.16141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 01/30/2022] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those 'next users' of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO2 sink to a net CO2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under-represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long-term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers.
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13
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Li X, Xi B, Wu X, Choat B, Feng J, Jiang M, Tissue D. Unlocking Drought-Induced Tree Mortality: Physiological Mechanisms to Modeling. FRONTIERS IN PLANT SCIENCE 2022; 13:835921. [PMID: 35444681 PMCID: PMC9015645 DOI: 10.3389/fpls.2022.835921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
Drought-related tree mortality has become a major concern worldwide due to its pronounced negative impacts on the functioning and sustainability of forest ecosystems. However, our ability to identify the species that are most vulnerable to drought, and to pinpoint the spatial and temporal patterns of mortality events, is still limited. Model is useful tools to capture the dynamics of vegetation at spatiotemporal scales, yet contemporary land surface models (LSMs) are often incapable of predicting the response of vegetation to environmental perturbations with sufficient accuracy, especially under stressful conditions such as drought. Significant progress has been made regarding the physiological mechanisms underpinning plant drought response in the past decade, and plant hydraulic dysfunction has emerged as a key determinant for tree death due to water shortage. The identification of pivotal physiological events and relevant plant traits may facilitate forecasting tree mortality through a mechanistic approach, with improved precision. In this review, we (1) summarize current understanding of physiological mechanisms leading to tree death, (2) describe the functionality of key hydraulic traits that are involved in the process of hydraulic dysfunction, and (3) outline their roles in improving the representation of hydraulic function in LSMs. We urge potential future research on detailed hydraulic processes under drought, pinpointing corresponding functional traits, as well as understanding traits variation across and within species, for a better representation of drought-induced tree mortality in models.
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Affiliation(s)
- Ximeng Li
- College of Life and Environmental Science, Minzu University of China, Beijing, China
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
| | - Benye Xi
- Ministry of Education Key Laboratory of Silviculture and Conservation, Beijing Forestry University, Beijing, China
| | - Xiuchen Wu
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, China
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
| | - Jinchao Feng
- College of Life and Environmental Science, Minzu University of China, Beijing, China
| | - Mingkai Jiang
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
- College of Life Sciences, Zhejiang University, Hangzhou, China
| | - David Tissue
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
- Global Centre for Land-based Innovation, Western Sydney University, Richmond, NSW, Australia
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14
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Trugman AT. Integrating plant physiology and community ecology across scales through trait-based models to predict drought mortality. THE NEW PHYTOLOGIST 2022; 234:21-27. [PMID: 34679225 DOI: 10.1111/nph.17821] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 10/02/2021] [Indexed: 06/13/2023]
Abstract
Forests are a critical carbon sink and widespread tree mortality resulting from climate-induced drought stress has the potential to alter forests from a carbon sink to a source, causing a positive feedback on climate change. Process-based vegetation models aim to represent the current understanding of the underlying mechanisms governing plant physiological and ecological responses to climate. Yet model accuracy varies across scales, and regional-scale model predictive skill is frequently poor when compared with observations of drought-driven mortality. I propose a framework that leverages differences in model predictive skill across spatial scales, mismatches between model predictions and observations, and differences in the mechanisms included and absent across models to advance the understanding of the physiological and ecological processes driving observed patterns drought-driven mortality.
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Affiliation(s)
- Anna T Trugman
- Department of Geography, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
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15
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Binks O, Cernusak LA, Liddell M, Bradford M, Coughlin I, Carle H, Bryant C, Dunn E, Oliveira R, Mencuccini M, Meir P. Forest system hydraulic conductance: partitioning tree and soil components. THE NEW PHYTOLOGIST 2022; 233:1667-1681. [PMID: 34861052 DOI: 10.1111/nph.17895] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 11/23/2021] [Indexed: 06/13/2023]
Abstract
Soil-leaf hydraulic conductance determines canopy-atmosphere coupling in vegetation models, but it is typically derived from ex-situ measurements of stem segments and soil samples. Using a novel approach, we derive robust in-situ estimates for whole-tree conductance (ktree ), 'functional' soil conductance (ksoil ), and 'system' conductance (ksystem , water table to canopy), at two climatically different tropical rainforest sites. Hydraulic 'functional rooting depth', determined for each tree using profiles of soil water potential (Ψsoil ) and sap flux data, enabled a robust determination of ktree and ksoil . ktree was compared across species, size classes, seasons, height above nearest drainage (HAND), two field sites, and to alternative representations of ktree ; ksoil was analysed with respect to variations in site, season and HAND. ktree was lower and changed seasonally at the site with higher vapour pressure deficit (VPD) and rainfall; ktree differed little across species but scaled with tree circumference; rsoil (1/ksoil ) ranged from 0 in the wet season to 10× less than rtree (1/ktree ) in the dry season. VPD and not rainfall may influence plot-level k; leaf water potentials and sap flux can be used to determine ktree , ksoil and ksystem ; Ψsoil profiles can provide mechanistic insights into ecosystem-level water fluxes.
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Affiliation(s)
- Oliver Binks
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Lucas A Cernusak
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Qld, 4878, Australia
| | - Michael Liddell
- Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Qld, 4878, Australia
| | - Matt Bradford
- CSIRO Land and Water, Atherton, Qld, 4883, Australia
| | - Ingrid Coughlin
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Hannah Carle
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Callum Bryant
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Elliot Dunn
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Rafael Oliveira
- Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, Sao Paulo, 13083-970, Brazil
| | | | - Patrick Meir
- Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
- School of Geosciences, University of Edinburgh, Edinburgh, EH9 3FF, UK
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16
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Cernusak LA, De Kauwe MG. Red light shines a path forward on leaf minimum conductance. THE NEW PHYTOLOGIST 2022; 233:5-7. [PMID: 34714941 DOI: 10.1111/nph.17794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Qld, 4878, Australia
| | - Martin G De Kauwe
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
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17
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Lemaire C, Blackman CJ, Cochard H, Menezes-Silva PE, Torres-Ruiz JM, Herbette S. Acclimation of hydraulic and morphological traits to water deficit delays hydraulic failure during simulated drought in poplar. TREE PHYSIOLOGY 2021; 41:2008-2021. [PMID: 34259313 DOI: 10.1093/treephys/tpab086] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 07/07/2021] [Indexed: 05/27/2023]
Abstract
The capacity of trees to tolerate and survive increasing drought conditions in situ will depend in part on their ability to acclimate (via phenotypic plasticity) key hydraulic and morphological traits that increase drought tolerance and delay the onset of drought-induced hydraulic failure. However, the effect of water-deficit acclimation in key traits that determine time to hydraulic failure (THF) during extreme drought remains largely untested. We measured key hydraulic and morphological traits in saplings of a hybrid poplar grown under well-watered and water-limited conditions. The time for plants to dry-down to critical levels of water stress (90% loss of stem hydraulic conductance), as well as the relative contribution of drought acclimation in each trait to THF, was simulated using a soil-plant hydraulic model (SurEau). Compared with controls, water-limited plants exhibited significantly lower stem hydraulic vulnerability (P50stem), stomatal conductance and total canopy leaf area (LA). Taken together, adjustments in these and other traits resulted in longer modelled THF in water-limited (~160 h) compared with well-watered plants (~50 h), representing an increase of more than 200%. Sensitivity analysis revealed that adjustment in P50stem and LA contributed the most to longer THF in water-limited plants. We observed a high degree of trait plasticity in poplar saplings in response to water-deficit growth conditions, with decreases in stem hydraulic vulnerability and leaf area playing a key role in delaying the onset of hydraulic failure during a simulated drought event. These findings suggest that understanding the capacity of plants to acclimate to antecedent growth conditions will enable better predictions of plant survivorship during future drought.
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Affiliation(s)
- Cédric Lemaire
- Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand F-63000, France
| | - Chris J Blackman
- Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand F-63000, France
| | - Hervé Cochard
- Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand F-63000, France
| | - Paulo Eduardo Menezes-Silva
- Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand F-63000, France
- Department of Biology, Goiano Federal Institute of Education, Science and Technology-IF Goiano, Rio Verde, Goiás, Brazil
| | - José M Torres-Ruiz
- Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand F-63000, France
| | - Stéphane Herbette
- Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand F-63000, France
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18
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Nolan RH, Collins L, Leigh A, Ooi MKJ, Curran TJ, Fairman TA, Resco de Dios V, Bradstock R. Limits to post-fire vegetation recovery under climate change. PLANT, CELL & ENVIRONMENT 2021; 44:3471-3489. [PMID: 34453442 DOI: 10.1111/pce.14176] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 08/09/2021] [Accepted: 08/13/2021] [Indexed: 06/13/2023]
Abstract
Record-breaking fire seasons in many regions across the globe raise important questions about plant community responses to shifting fire regimes (i.e., changing fire frequency, severity and seasonality). Here, we examine the impacts of climate-driven shifts in fire regimes on vegetation communities, and likely responses to fire coinciding with severe drought, heatwaves and/or insect outbreaks. We present scenario-based conceptual models on how overlapping disturbance events and shifting fire regimes interact differently to limit post-fire resprouting and recruitment capacity. We demonstrate that, although many communities will remain resilient to changing fire regimes in the short-term, longer-term changes to vegetation structure, demography and species composition are likely, with a range of subsequent effects on ecosystem function. Resprouting species are likely to be most resilient to changing fire regimes. However, even these species are susceptible if exposed to repeated short-interval fire in combination with other stressors. Post-fire recruitment is highly vulnerable to increased fire frequency, particularly as climatic limitations on propagule availability intensify. Prediction of community responses to fire under climate change will be greatly improved by addressing knowledge gaps on how overlapping disturbances and climate change-induced shifts in fire regime affect post-fire resprouting, recruitment, growth rates, and species-level adaptation capacity.
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Affiliation(s)
- Rachael H Nolan
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia
- NSW Bushfire Risk Management Research Hub, Wollongong, New South Wales, Australia
| | - Luke Collins
- School of Ecosystem and Forest Sciences, University of Melbourne, Creswick, Victoria, Australia
- Department of Ecology, Environment & Evolution, La Trobe University, Bundoora, Victoria, Australia
- Pacific Forestry Centre, Canadian Forest Service, Natural Resources Canada, Canada
| | - Andy Leigh
- School of Life Sciences, University of Technology Sydney, Broadway, New South Wales, Australia
| | - Mark K J Ooi
- NSW Bushfire Risk Management Research Hub, Wollongong, New South Wales, Australia
- School of Biological, Earth and Environmental Sciences, University of New South Wales UNSW, Sydney, New South Wales, Australia
| | - Timothy J Curran
- Department of Pest-management and Conservation, Lincoln University, Lincoln, New Zealand
| | - Thomas A Fairman
- School of Ecosystem and Forest Sciences, University of Melbourne, Creswick, Victoria, Australia
| | - Víctor Resco de Dios
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang, China
- Joint Research Unit CTFC-AGROTECNIO, University of Lleida, Lleida, Spain
- Department of Crop and Forest Sciences, University of Lleida, Lleida, Spain
| | - Ross Bradstock
- NSW Bushfire Risk Management Research Hub, Wollongong, New South Wales, Australia
- Centre for Environmental Risk Management of Bushfires, University of Wollongong, Wollongong, New South Wales, Australia
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19
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Slot M, Nardwattanawong T, Hernández GG, Bueno A, Riederer M, Winter K. Large differences in leaf cuticle conductance and its temperature response among 24 tropical tree species from across a rainfall gradient. THE NEW PHYTOLOGIST 2021; 232:1618-1631. [PMID: 34270792 PMCID: PMC9290923 DOI: 10.1111/nph.17626] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/12/2021] [Indexed: 05/09/2023]
Abstract
More frequent droughts and rising temperatures pose serious threats to tropical forests. When stomata are closed under dry and hot conditions, plants lose water through leaf cuticles, but little is known about cuticle conductance (gmin ) of tropical trees, how it varies among species and environments, and how it is affected by temperature. We determined gmin in relation to temperature for 24 tropical tree species across a steep rainfall gradient in Panama, by recording leaf drying curves at different temperatures in the laboratory. In contrast with our hypotheses, gmin did not differ systematically across the rainfall gradient; species differences did not reflect phylogenetic patterns; and in most species gmin did not significantly increase between 25 and 50°C. gmin was higher in deciduous than in evergreen species, in species with leaf trichomes than in species without, in sun leaves than in shade leaves, and tended to decrease with increasing leaf mass per area across species. There was no relationship between stomatal and cuticle conductance. Large species differences in gmin and its temperature response suggest that more frequent hot droughts may lead to differential survival among tropical tree species, regardless of species' position on the rainfall gradient.
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Affiliation(s)
- Martijn Slot
- Smithsonian Tropical Research InstituteApartado 0843‐03092BalboaAncónRepublic of Panama
| | - Tantawat Nardwattanawong
- Smithsonian Tropical Research InstituteApartado 0843‐03092BalboaAncónRepublic of Panama
- University of East AngliaNorwichNR4 7TJUK
| | - Georgia G. Hernández
- Smithsonian Tropical Research InstituteApartado 0843‐03092BalboaAncónRepublic of Panama
| | - Amauri Bueno
- Julius‐von Sachs‐Institute for BiosciencesBotany IIUniversity of WürzburgJulius‐von‐Sachs‐Platz 3WürzburgD‐97082Germany
| | - Markus Riederer
- Julius‐von Sachs‐Institute for BiosciencesBotany IIUniversity of WürzburgJulius‐von‐Sachs‐Platz 3WürzburgD‐97082Germany
| | - Klaus Winter
- Smithsonian Tropical Research InstituteApartado 0843‐03092BalboaAncónRepublic of Panama
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20
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Jiao T, Williams CA, De Kauwe MG, Schwalm CR, Medlyn BE. Patterns of post-drought recovery are strongly influenced by drought duration, frequency, post-drought wetness, and bioclimatic setting. GLOBAL CHANGE BIOLOGY 2021; 27:4630-4643. [PMID: 34228866 DOI: 10.1111/gcb.15788] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 06/14/2021] [Accepted: 06/21/2021] [Indexed: 06/13/2023]
Abstract
Understanding vegetation recovery after drought is critical for projecting vegetation dynamics in future climates. From 1997 to 2009, Australia experienced a long-lasting drought known as the Millennium Drought (MD), which led to widespread reductions in vegetation productivity. However, vegetation recovery post-drought and its determinants remain unclear. This study leverages remote sensing products from different sources-fraction of absorbed photosynthetically active radiation (FPAR), based on optical data, and canopy density, derived from microwave data-and random forest algorithms to assess drought recovery over Australian natural vegetation during a 20-year period centered on the MD. Post-drought recovery was prevalent across the continent, with 6 out of 10 drought events seeing full recovery within about 6 months. Canopy density was slower to recover than leaf area seen in FPAR. The probability of full recovery was most strongly controlled by drought return interval, post-drought hydrological condition, and drought length. Full recovery was seldom observed when drought events occurred at intervals of 3 months or less, and moderately dry (standardized water balance anomaly [SWBA] within [-1, -0.76]) post-drought conditions resulted in less complete recovery than wet (SWBA > 0.3) post-drought conditions. Press droughts, which are long term but not extreme, delayed recovery more than pulse droughts (short term but extreme) and led to a higher frequency of persistent decline. Following press droughts, the frequency of persistent decline differed little among biome types but peaked in semi-arid regions across aridity levels. Forests and savanna required the longest recovery times for press drought, while grasslands were the slowest to recover for pulse drought. This study provides quantitative thresholds that could be used to improve the modeling of ecosystem dynamics post-drought.
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Affiliation(s)
- Tong Jiao
- Graduate School of Geography, Clark University, Worcester, MA, USA
| | | | - Martin G De Kauwe
- ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, NSW, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
- Evolution & Ecology Research Centre, University of New South Wales, Sydney, NSW, Australia
| | | | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
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21
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Nadal-Sala D, Grote R, Birami B, Knüver T, Rehschuh R, Schwarz S, Ruehr NK. Leaf Shedding and Non-Stomatal Limitations of Photosynthesis Mitigate Hydraulic Conductance Losses in Scots Pine Saplings During Severe Drought Stress. FRONTIERS IN PLANT SCIENCE 2021; 12:715127. [PMID: 34539705 PMCID: PMC8448192 DOI: 10.3389/fpls.2021.715127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/08/2021] [Indexed: 06/01/2023]
Abstract
During drought, trees reduce water loss and hydraulic failure by closing their stomata, which also limits photosynthesis. Under severe drought stress, other acclimation mechanisms are trigged to further reduce transpiration to prevent irreversible conductance loss. Here, we investigate two of them: the reversible impacts on the photosynthetic apparatus, lumped as non-stomatal limitations (NSL) of photosynthesis, and the irreversible effect of premature leaf shedding. We integrate NSL and leaf shedding with a state-of-the-art tree hydraulic simulation model (SOX+) and parameterize them with example field measurements to demonstrate the stress-mitigating impact of these processes. We measured xylem vulnerability, transpiration, and leaf litter fall dynamics in Pinus sylvestris (L.) saplings grown for 54 days under severe dry-down. The observations showed that, once transpiration stopped, the rate of leaf shedding strongly increased until about 30% of leaf area was lost on average. We trained the SOX+ model with the observations and simulated changes in root-to-canopy conductance with and without including NSL and leaf shedding. Accounting for NSL improved model representation of transpiration, while model projections about root-to-canopy conductance loss were reduced by an overall 6%. Together, NSL and observed leaf shedding reduced projected losses in conductance by about 13%. In summary, the results highlight the importance of other than purely stomatal conductance-driven adjustments of drought resistance in Scots pine. Accounting for acclimation responses to drought, such as morphological (leaf shedding) and physiological (NSL) adjustments, has the potential to improve tree hydraulic simulation models, particularly when applied in predicting drought-induced tree mortality.
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Affiliation(s)
- Daniel Nadal-Sala
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Rüdiger Grote
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Benjamin Birami
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
- University of Bayreuth, Chair of Plant Ecology, Bayreuth, Germany
| | - Timo Knüver
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
- Department of Botany, University of Innsbruck, Innsbruck, Austria
| | - Romy Rehschuh
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Selina Schwarz
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Nadine K. Ruehr
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
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22
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Liu Q, Peng C, Schneider R, Cyr D, Liu Z, Zhou X, Kneeshaw D. TRIPLEX-Mortality model for simulating drought-induced tree mortality in boreal forests: Model development and evaluation. Ecol Modell 2021. [DOI: 10.1016/j.ecolmodel.2021.109652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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23
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De Kauwe MG, Medlyn BE, Tissue DT. To what extent can rising [CO 2 ] ameliorate plant drought stress? THE NEW PHYTOLOGIST 2021; 231:2118-2124. [PMID: 34101183 DOI: 10.1111/nph.17540] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 06/01/2021] [Indexed: 06/12/2023]
Abstract
Plant responses to elevated atmospheric carbon dioxide (eCO2 ) have been hypothesized as a key mechanism that may ameliorate the impact of future drought. Yet, despite decades of experiments, the question of whether eCO2 reduces plant water use, yielding 'water savings' that can be used to maintain plant function during periods of water stress, remains unresolved. In this Viewpoint, we identify the experimental challenges and limitations to our understanding of plant responses to drought under eCO2 . In particular, we argue that future studies need to move beyond exploring whether eCO2 played 'a role' or 'no role' in responses to drought, but instead more carefully consider the timescales and conditions that would induce an influence. We also argue that considering emergent differences in soil water content may be an insufficient means of assessing the impact of eCO2 . We identify eCO2 impact during severe drought (e.g. to the point of mortality), interactions with future changes in vapour pressure deficit and uncertainty about changes in leaf area as key gaps in our current understanding. New insights into CO2 × drought interactions are essential to better constrain model theory that governs future climate model projections of land-atmosphere interactions during periods of water stress.
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Affiliation(s)
- Martin G De Kauwe
- ARC Centre of Excellence for Climate Extremes, Sydney, NSW, 2052, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - David T Tissue
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
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24
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Peters JMR, López R, Nolf M, Hutley LB, Wardlaw T, Cernusak LA, Choat B. Living on the edge: A continental-scale assessment of forest vulnerability to drought. GLOBAL CHANGE BIOLOGY 2021; 27:3620-3641. [PMID: 33852767 DOI: 10.1111/gcb.15641] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 03/12/2021] [Indexed: 06/12/2023]
Abstract
Globally, forests are facing an increasing risk of mass tree mortality events associated with extreme droughts and higher temperatures. Hydraulic dysfunction is considered a key mechanism of drought-triggered dieback. By leveraging the climate breadth of the Australian landscape and a national network of research sites (Terrestrial Ecosystem Research Network), we conducted a continental-scale study of physiological and hydraulic traits of 33 native tree species from contrasting environments to disentangle the complexities of plant response to drought across communities. We found strong relationships between key plant hydraulic traits and site aridity. Leaf turgor loss point and xylem embolism resistance were correlated with minimum water potential experienced by each species. Across the data set, there was a strong coordination between hydraulic traits, including those linked to hydraulic safety, stomatal regulation and the cost of carbon investment into woody tissue. These results illustrate that aridity has acted as a strong selective pressure, shaping hydraulic traits of tree species across the Australian landscape. Hydraulic safety margins were constrained across sites, with species from wetter sites tending to have smaller safety margin compared with species at drier sites, suggesting trees are operating close to their hydraulic thresholds and forest biomes across the spectrum may be susceptible to shifts in climate that result in the intensification of drought.
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Affiliation(s)
- Jennifer M R Peters
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
| | - Rosana López
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
| | - Markus Nolf
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
| | - Lindsay B Hutley
- Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, Australia
| | - Tim Wardlaw
- ARC Centre for Forest Value, University of Tasmania, Hobart, Tas, Australia
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Qld, Australia
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia
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25
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Xu X, Konings AG, Longo M, Feldman A, Xu L, Saatchi S, Wu D, Wu J, Moorcroft P. Leaf surface water, not plant water stress, drives diurnal variation in tropical forest canopy water content. THE NEW PHYTOLOGIST 2021; 231:122-136. [PMID: 33539544 DOI: 10.1111/nph.17254] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 01/27/2021] [Indexed: 05/25/2023]
Abstract
Variation in canopy water content (CWC) that can be detected from microwave remote sensing of vegetation optical depth (VOD) has been proposed as an important measure of vegetation water stress. However, the contribution of leaf surface water (LWs ), arising from dew formation and rainfall interception, to CWC is largely unknown, particularly in tropical forests and other high-humidity ecosystems. We compared VOD data from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) and CWC predicted by a plant hydrodynamics model at four tropical sites in Brazil spanning a rainfall gradient. We assessed how LWs influenced the relationship between VOD and CWC. The analysis indicates that while CWC is strongly correlated with VOD (R2 = 0.62 across all sites), LWs accounts for 61-76% of the diurnal variation in CWC despite being < 10% of CWC. Ignoring LWs weakens the near-linear relationship between CWC and VOD and reduces the consistency in diurnal variation. The contribution of LWs to CWC variation, however, decreases at longer, seasonal to inter-annual, time scales. Our results demonstrate that diurnal patterns of dew formation and rainfall interception can be an important driver of diurnal variation in CWC and VOD over tropical ecosystems and therefore should be accounted for when inferring plant diurnal water stress from VOD measurements.
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Affiliation(s)
- Xiangtao Xu
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, 14850, USA
| | - Alexandra G Konings
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Marcos Longo
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Andrew Feldman
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Liang Xu
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Sassan Saatchi
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
- Institute of Environment and Sustainability, University of California, Los Angeles, CA, 90024, USA
| | - Donghai Wu
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, 14850, USA
| | - Jin Wu
- School of Biological Sciences, University of Hong Kong, Hong Kong, China
| | - Paul Moorcroft
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
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26
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Venturas MD, Todd HN, Trugman AT, Anderegg WRL. Understanding and predicting forest mortality in the western United States using long-term forest inventory data and modeled hydraulic damage. THE NEW PHYTOLOGIST 2021; 230:1896-1910. [PMID: 33112415 DOI: 10.1111/nph.17043] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 10/20/2020] [Indexed: 06/11/2023]
Abstract
Global warming is expected to exacerbate the duration and intensity of droughts in the western United States, which may lead to increased tree mortality. A prevailing proximal mechanism of drought-induced tree mortality is hydraulic damage, but predicting tree mortality from hydraulic theory and climate data still remains a major scientific challenge. We used forest inventory data and a plant hydraulic model (HM) to address three questions: can we capture regional patterns of drought-induced tree mortality with HM-predicted damage thresholds; do HM metrics improve predictions of mortality across broad spatial areas; and what are the dominant controls of forest mortality when considering stand characteristics, climate metrics, and simulated hydraulic stress? We found that the amount of variance explained by models predicting mortality was limited (R2 median = 0.10, R2 range: 0.00-0.52). HM outputs, including hydraulic damage and carbon assimilation diagnostics, moderately improve mortality prediction across the western US compared with models using stand and climate predictors alone. Among factors considered, metrics of stand density and tree size tended to be some of the most critical factors explaining mortality, probably highlighting the important roles of structural overshoot, stand development, and biotic agent host selection and outbreaks in mortality patterns.
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Affiliation(s)
- Martin D Venturas
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
| | - Henry N Todd
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
| | - Anna T Trugman
- Department of Geography, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
| | - William R L Anderegg
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
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27
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Nadal-Sala D, Grote R, Birami B, Lintunen A, Mammarella I, Preisler Y, Rotenberg E, Salmon Y, Tatarinov F, Yakir D, Ruehr NK. Assessing model performance via the most limiting environmental driver in two differently stressed pine stands. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2021; 31:e02312. [PMID: 33630380 DOI: 10.1002/eap.2312] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 11/06/2020] [Accepted: 12/06/2020] [Indexed: 06/12/2023]
Abstract
Climate change will impact forest productivity worldwide. Forecasting the magnitude of such impact, with multiple environmental stressors changing simultaneously, is only possible with the help of process-based models. In order to assess their performance, such models require careful evaluation against measurements. However, direct comparison of model outputs against observational data is often not reliable, as models may provide the right answers due to the wrong reasons. This would severely hinder forecasting abilities under unprecedented climate conditions. Here, we present a methodology for model assessment, which supplements the traditional output-to-observation model validation. It evaluates model performance through its ability to reproduce observed seasonal changes of the most limiting environmental driver (MLED) for a given process, here daily gross primary productivity (GPP). We analyzed seasonal changes of the MLED for GPP in two contrasting pine forests, the Mediterranean Pinus halepensis Mill. Yatir (Israel) and the boreal Pinus sylvestris L. Hyytiälä (Finland) from three years of eddy-covariance flux data. Then, we simulated the same period with a state-of-the-art process-based simulation model (LandscapeDNDC). Finally, we assessed if the model was able to reproduce both GPP observations and MLED seasonality. We found that the model reproduced the seasonality of GPP in both stands, but it was slightly overestimated without site-specific fine-tuning. Interestingly, although LandscapeDNDC properly captured the main MLED in Hyytiälä (temperature) and in Yatir (soil water availability), it failed to reproduce high-temperature and high-vapor pressure limitations of GPP in Yatir during spring and summer. We deduced that the most likely reason for this divergence is an incomplete description of stomatal behavior. In summary, this study validates the MLED approach as a model evaluation tool, and opens up new possibilities for model improvement.
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Affiliation(s)
- Daniel Nadal-Sala
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, 82467, Germany
| | - Rüdiger Grote
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, 82467, Germany
| | - Benjamin Birami
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, 82467, Germany
| | - Anna Lintunen
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Latokartanonkaari 7, P.O. Box 27, Helsinki,, 00014, Finland
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, P.O. Box 68, Gustaf Hällströmin katu 2b, Helsinki,, 00014, Finland
| | - Ivan Mammarella
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Latokartanonkaari 7, P.O. Box 27, Helsinki,, 00014, Finland
| | - Yakir Preisler
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
| | - Eyal Rotenberg
- Deptartment of Environmental Sciences and Energy Research, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Yann Salmon
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Latokartanonkaari 7, P.O. Box 27, Helsinki,, 00014, Finland
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, P.O. Box 68, Gustaf Hällströmin katu 2b, Helsinki,, 00014, Finland
| | - Fedor Tatarinov
- Deptartment of Environmental Sciences and Energy Research, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Dan Yakir
- Deptartment of Environmental Sciences and Energy Research, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Nadine K Ruehr
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, 82467, Germany
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28
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Rowland L, Martínez-Vilalta J, Mencuccini M. Hard times for high expectations from hydraulics: predicting drought-induced forest mortality at landscape scales remains a challenge. THE NEW PHYTOLOGIST 2021; 230:1685-1687. [PMID: 33797779 DOI: 10.1111/nph.17317] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Affiliation(s)
- Lucy Rowland
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QE, UK
| | - Jordi Martínez-Vilalta
- CREAF, Bellaterra (Cerdanyola del Vallès), 08193, Spain
- Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), 08193, Spain
| | - Maurizio Mencuccini
- CREAF, Bellaterra (Cerdanyola del Vallès), 08193, Spain
- ICREA, Pg. Lluís Companys 23, Barcelona, 08010, Spain
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29
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Nolan RH, Gauthey A, Losso A, Medlyn BE, Smith R, Chhajed SS, Fuller K, Song M, Li X, Beaumont LJ, Boer MM, Wright IJ, Choat B. Hydraulic failure and tree size linked with canopy die-back in eucalypt forest during extreme drought. THE NEW PHYTOLOGIST 2021; 230:1354-1365. [PMID: 33629360 DOI: 10.1111/nph.17298] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 02/17/2021] [Indexed: 06/12/2023]
Abstract
Eastern Australia was subject to its hottest and driest year on record in 2019. This extreme drought resulted in massive canopy die-back in eucalypt forests. The role of hydraulic failure and tree size on canopy die-back in three eucalypt tree species during this drought was examined. We measured pre-dawn and midday leaf water potential (Ψleaf ), per cent loss of stem hydraulic conductivity and quantified hydraulic vulnerability to drought-induced xylem embolism. Tree size and tree health was also surveyed. Trees with most, or all, of their foliage dead exhibited high rates of native embolism (78-100%). This is in contrast to trees with partial canopy die-back (30-70% canopy die-back: 72-78% native embolism), or relatively healthy trees (little evidence of canopy die-back: 25-31% native embolism). Midday Ψleaf was significantly more negative in trees exhibiting partial canopy die-back (-2.7 to -6.3 MPa), compared with relatively healthy trees (-2.1 to -4.5 MPa). In two of the species the majority of individuals showing complete canopy die-back were in the small size classes. Our results indicate that hydraulic failure is strongly associated with canopy die-back during drought in eucalypt forests. Our study provides valuable field data to help constrain models predicting mortality risk.
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Affiliation(s)
- Rachael H Nolan
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- Bushfire Risk Management Research Hub, Wollongong, NSW, 2522, Australia
| | - Alice Gauthey
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Adriano Losso
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- Department of Botany, University of Innsbruck, Sternwartestraße 15, Innsbruck, 6020, Austria
| | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Rhiannon Smith
- Ecosystem Management, University of New England, Armidale, NSW, 2351, Australia
| | - Shubham S Chhajed
- Department of Biological Sciences, Macquarie University, Macquarie Park, NSW, 2109, Australia
| | - Kathryn Fuller
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- Bushfire Risk Management Research Hub, Wollongong, NSW, 2522, Australia
| | - Magnolia Song
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Xine Li
- Department of Biological Sciences, Macquarie University, Macquarie Park, NSW, 2109, Australia
- Department of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, 225009, China
| | - Linda J Beaumont
- Department of Biological Sciences, Macquarie University, Macquarie Park, NSW, 2109, Australia
| | - Matthias M Boer
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- Bushfire Risk Management Research Hub, Wollongong, NSW, 2522, Australia
| | - Ian J Wright
- Department of Biological Sciences, Macquarie University, Macquarie Park, NSW, 2109, Australia
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
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30
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Jiang M, Kelly JWG, Atwell BJ, Tissue DT, Medlyn BE. Drought by CO 2 interactions in trees: a test of the water savings mechanism. THE NEW PHYTOLOGIST 2021; 230:1421-1434. [PMID: 33496969 DOI: 10.1111/nph.17233] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 01/21/2021] [Indexed: 06/12/2023]
Abstract
Elevated atmospheric CO2 (eCa ) may benefit plants during drought by reducing stomatal conductance (gs ) but any 'water savings effect' could be neutralized by concurrent stimulation of leaf area. We investigated whether eCa enhanced water savings, thereby ameliorating the impact of drought on carbon and water relations in trees. We report leaf-level gas exchange and whole-plant and soil water relations during a short-term dry-down in two Eucalyptus species with contrasting drought tolerance. Plants had previously been established for 9 to 11 months in steady-state conditions of ambient atmospheric CO2 (aCa ) and eCa , with half of each treatment group exposed to sustained drought for 5 to 7 months. The lower stomatal conductance under eCa did not lead to soil moisture savings during the dry-down due to the counteractive effect of increased whole-plant leaf area. Nonetheless, eCa -grown plants maintained higher photosynthetic rates and leaf water potentials, making them less stressed during the dry-down, despite being larger. These effects were more pronounced in the xeric species than the mesic species, and in previously water-stressed plants. Our findings indicate that eCa may enhance plant performance during drought despite a lack of soil water savings, especially in species with more conservative growth and water-use strategies.
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Affiliation(s)
- Mingkai Jiang
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Jeff W G Kelly
- Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia
| | - Brian J Atwell
- Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia
| | - David T Tissue
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia
- Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia
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31
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Two Severe Prolonged Hydrological Droughts Analysis over Mainland Australia Using GRACE Satellite Data. REMOTE SENSING 2021. [DOI: 10.3390/rs13081432] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In recent years, many droughts have happened over mainland Australia, especially the two severe prolonged droughts, from 2006 to 2009 and 2018 to 2020, resulting in serious water scarcity. Therefore, using the Total Storage Deficit Index (TSDI) from the Gravity Recovery and Climate Experiment (GRACE), we analyzed the two severe prolonged droughts from the perspective of the affected area, spatial evolution, frequency, severity and drought driving factors. The results show that the affected area of Drought 2006–2009 ranged from 57% to 95%, and that of Drought 2018–2020 ranged from 45% to 95%. Drought 2006–2009 took its rise in southeastern Australia and gradually spread to the central part. Drought 2018–2020 originated in the southwest corner of the Northern Territory and northern New South Wales, and gradually expanded to Western Australia and the whole New South Wales respectively. During Drought 2006–2009, Victoria suffered drought all months, including 59% mild drought and 41% moderate drought, North Territory had the highest drought severity of 44.26 and Victoria ranked the second high with the severity of 35.51 (cm months). For Drought 2018–2020, Northern Territory was also dominated by drought all months, including 92% mild drought and 8% moderate drought, the drought severities were in North Territory and Western Australia with 52.19 and 31.44 (cm months), respectively. Finally, the correlation coefficients between the two droughts and Indo-Pacific climate variability including El Niño-Southern Oscillation and Indian Ocean Dipole (IOD) are computed. By comparing the correlation coefficients of Drought 2018–2020 with Drought 2006–2009, we find that the impact of the El Niño on the hydrological drought becomes weaker while IOD is stronger, and the role of Southern Oscillation on droughts is diverse with the quite different spatial patterns. The results from Fourier analysis confirm that the two hydrological droughts are all related to Indo-Pacific climate variability but with slightly different driving mechanisms.
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Comparative Evaluation of Microwave L-Band VOD and Optical NDVI for Agriculture Drought Detection over Central Europe. REMOTE SENSING 2021. [DOI: 10.3390/rs13071251] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Agricultural droughts impose many economic and social losses on various communities. Most of the effective tools developed for agricultural drought assessment are based on vegetation indices (VIs). The aim of this study is to compare the response of two commonly used VIs to meteorological droughts—Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) and Soil Moisture and Ocean Salinity (SMOS) vegetation optical depth (VOD). For this purpose, meteorological droughts are calculated by using a standardized precipitation index over more than 24,000 pixels at 0.25° × 0.25° spatial resolution located in central Europe. Then, to evaluate the capability of VIs in the detection of agricultural droughts, the average values of VIs anomalies during dry and wet periods obtained from meteorological droughts are statistically compared to each other. Additionally, to assess the response time of VIs to meteorological droughts, a time lag of one to six months is applied to the anomaly time series of VIs during their comparison. Results show that over 35% of the considered pixels NDVI, over 22% of VOD, and over 8% of both VIs anomalies have a significant response to drought events, while the significance level of these differences and the response time of VIs vary with different land use and climate conditions.
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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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Felton AJ, Knapp AK, Smith MD. Precipitation-productivity relationships and the duration of precipitation anomalies: An underappreciated dimension of climate change. GLOBAL CHANGE BIOLOGY 2021; 27:1127-1140. [PMID: 33295684 DOI: 10.1111/gcb.15480] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 11/27/2020] [Indexed: 06/12/2023]
Abstract
In terrestrial ecosystems, climate change forecasts of increased frequencies and magnitudes of wet and dry precipitation anomalies are expected to shift precipitation-net primary productivity (PPT-NPP) relationships from linear to nonlinear. Less understood, however, is how future changes in the duration of PPT anomalies will alter PPT-NPP relationships. A review of the literature shows strong potential for the duration of wet and dry PPT anomalies to impact NPP and to interact with the magnitude of anomalies. Within semi-arid and mesic grassland ecosystems, PPT gradient experiments indicate that short-duration (1 year) PPT anomalies are often insufficient to drive nonlinear aboveground NPP responses. But long-term studies, within desert to forest ecosystems, demonstrate how multi-year PPT anomalies may result in increasing impacts on NPP through time, and thus alter PPT-NPP relationships. We present a conceptual model detailing how NPP responses to PPT anomalies may amplify with the duration of an event, how responses may vary in xeric vs. mesic ecosystems, and how these differences are most likely due to demographic mechanisms. Experiments that can unravel the independent and interactive impacts of the magnitude and duration of wet and dry PPT anomalies are needed, with multi-site long-term PPT gradient experiments particularly well-suited for this task.
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Affiliation(s)
- Andrew J Felton
- Department of Wildland Resources and The Ecology Center, Utah State University, Logan, UT, USA
| | - Alan K Knapp
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
| | - Melinda D Smith
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
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