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Lecomte X, Bugalho MN, Catry FX, Fernandes PM, Cera A, Caldeira MC. Ungulates mitigate the effects of drought and shrub encroachment on the fire hazard of Mediterranean oak woodlands. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2024; 34:e2971. [PMID: 38581136 DOI: 10.1002/eap.2971] [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: 02/18/2022] [Revised: 12/16/2023] [Accepted: 01/31/2024] [Indexed: 04/08/2024]
Abstract
Climate change is increasing the frequency of droughts and the risk of severe wildfires, which can interact with shrub encroachment and browsing by wild ungulates. Wild ungulate populations are expanding due, among other factors, to favorable habitat changes resulting from land abandonment or land-use changes. Understanding how ungulate browsing interacts with drought to affect woody plant mortality, plant flammability, and fire hazard is especially relevant in the context of climate change and increasing frequency of wildfires. The aim of this study is to explore the combined effects of cumulative drought, shrub encroachment, and ungulate browsing on the fire hazard of Mediterranean oak woodlands in Portugal. In a long-term (18 years) ungulate fencing exclusion experiment that simulated land abandonment and management neglect, we investigated the population dynamics of the native shrub Cistus ladanifer, which naturally dominates the understory of woodlands and is browsed by ungulates, comparing areas with (no fencing) and without (fencing) wild ungulate browsing. We also modeled fire behavior in browsed and unbrowsed plots considering drought and nondrought scenarios. Specifically, we estimated C. ladanifer population density, biomass, and fuel load characteristics, which were used to model fire behavior in drought and nondrought scenarios. Overall, drought increased the proportion of dead C. ladanifer shrub individuals, which was higher in the browsed plots. Drought decreased the ratio of live to dead shrub plant material, increased total fuel loading, shrub stand flammability, and the modeled fire parameters, that is, rate of surface fire spread, fireline intensity, and flame length. However, total fuel load and fire hazard were lower in browsed than unbrowsed plots, both in drought and nondrought scenarios. Browsing also decreased the population density of living shrubs, halting shrub encroachment. Our study provides long-term experimental evidence showing the role of wild ungulates in mitigating drought effects on fire hazard in shrub-encroached Mediterranean oak woodlands. Our results also emphasize that the long-term effects of land abandonment can interact with climate change drivers, affecting wildfire hazard. This is particularly relevant given the increasing incidence of land abandonment.
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Affiliation(s)
- Xavier Lecomte
- Forest Research Center, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, Lisbon, Portugal
- Center for Applied Ecology "Prof. Baeta Neves" (CEABN-InBIO), School of Agriculture, University of Lisbon, Lisbon, Portugal
| | - Miguel N Bugalho
- Center for Applied Ecology "Prof. Baeta Neves" (CEABN-InBIO), School of Agriculture, University of Lisbon, Lisbon, Portugal
| | - Filipe X Catry
- Center for Applied Ecology "Prof. Baeta Neves" (CEABN-InBIO), School of Agriculture, University of Lisbon, Lisbon, Portugal
| | - Paulo M Fernandes
- Center for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Trás-os-Montes and Alto Douro (UTAD), Vila Real, Portugal
- ForestWISE-Collaborative Laboratory for Integrated Forest and Fire Management, Vila Real, Portugal
| | - Andreu Cera
- Center for Applied Ecology "Prof. Baeta Neves" (CEABN-InBIO), School of Agriculture, University of Lisbon, Lisbon, Portugal
| | - Maria C Caldeira
- Forest Research Center, Associate Laboratory TERRA, School of Agriculture, University of Lisbon, Lisbon, Portugal
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2
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Van Passel J, Bernardino PN, Lhermitte S, Rius BF, Hirota M, Conradi T, de Keersmaecker W, Van Meerbeek K, Somers B. Critical slowing down of the Amazon forest after increased drought occurrence. Proc Natl Acad Sci U S A 2024; 121:e2316924121. [PMID: 38768350 PMCID: PMC11145287 DOI: 10.1073/pnas.2316924121] [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: 10/05/2023] [Accepted: 04/05/2024] [Indexed: 05/22/2024] Open
Abstract
Dynamic ecosystems, such as the Amazon forest, are expected to show critical slowing down behavior, or slower recovery from recurrent small perturbations, as they approach an ecological threshold to a different ecosystem state. Drought occurrences are becoming more prevalent across the Amazon, with known negative effects on forest health and functioning, but their actual role in the critical slowing down patterns still remains elusive. In this study, we evaluate the effect of trends in extreme drought occurrences on temporal autocorrelation (TAC) patterns of satellite-derived indices of vegetation activity, an indicator of slowing down, between 2001 and 2019. Differentiating between extreme drought frequency, intensity, and duration, we investigate their respective effects on the slowing down response. Our results indicate that the intensity of extreme droughts is a more important driver of slowing down than their duration, although their impacts vary across the different Amazon regions. In addition, areas with more variable precipitation are already less ecologically stable and need fewer droughts to induce slowing down. We present findings indicating that most of the Amazon region does not show an increasing trend in TAC. However, the predicted increase in extreme drought intensity and frequency could potentially transition significant portions of this ecosystem into a state with altered functionality.
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Affiliation(s)
- Johanna Van Passel
- Division Forest, Nature and Landscape, KU Leuven, Leuven3001, Belgium
- KU Leuven Plant Institute, KU Leuven, Leuven3001, Belgium
| | - Paulo N. Bernardino
- Division Forest, Nature and Landscape, KU Leuven, Leuven3001, Belgium
- Department of Plant Biology, University of Campinas, Campinas-SP13083-970, Brazil
| | - Stef Lhermitte
- Division Forest, Nature and Landscape, KU Leuven, Leuven3001, Belgium
- Department Geoscience & Remote Sensing, Delft University of Technology, Delft2600, The Netherlands
| | - Bianca F. Rius
- Center for Meteorological and Climatic Research Applied to Agriculture, University of Campinas, Campinas-SP13083-970, Brazil
- Interdisciplinary Environmental Studies Laboratory, Department of Physics, Federal University of Santa Catarina, Florianópolis, SC88040-900, Brazil
| | - Marina Hirota
- Department of Plant Biology, University of Campinas, Campinas-SP13083-970, Brazil
- Interdisciplinary Environmental Studies Laboratory, Department of Physics, Federal University of Santa Catarina, Florianópolis, SC88040-900, Brazil
| | - Timo Conradi
- Plant Ecology, University of Bayreuth, Bayreuth95447, Germany
| | | | - Koenraad Van Meerbeek
- Division Forest, Nature and Landscape, KU Leuven, Leuven3001, Belgium
- KU Leuven Plant Institute, KU Leuven, Leuven3001, Belgium
| | - Ben Somers
- Division Forest, Nature and Landscape, KU Leuven, Leuven3001, Belgium
- KU Leuven Plant Institute, KU Leuven, Leuven3001, Belgium
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3
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He P, Sardans J, Wang X, Ma C, Man L, Peñuelas J, Han X, Jiang Y, Li MH. Nutritional changes in trees during drought-induced mortality: A comprehensive meta-analysis and a field study. GLOBAL CHANGE BIOLOGY 2024; 30:e17133. [PMID: 38273504 DOI: 10.1111/gcb.17133] [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: 08/17/2023] [Revised: 12/13/2023] [Accepted: 12/15/2023] [Indexed: 01/27/2024]
Abstract
Both macronutrients and micronutrients are essential for tree growth and development through participating in various ecophysiological processes. However, the impact of the nutritional status of trees on their ability to withstand drought-induced mortality remains inconclusive. We thus conducted a comprehensive meta-analysis, compiling data on 11 essential nutrients from 44 publications (493 independent observations). Additionally, a field study was conducted on Pinus sylvestris L. trees with varying drought-induced vitality loss in the "Visp" forest in southern Switzerland. No consistent decline in tree nutritional status was observed during tree mortality. The meta-analysis revealed significantly lower leaf potassium (K), iron (Fe), and copper (Cu) concentrations with tree mortality. However, the field study showed no causal relationships between nutritional levels and the vitality status of trees. This discrepancy is mainly attributed to the intrinsic differences in the two types of experimental designs and the ontogenetic stages of target trees. Nutrient reductions preceding tree mortality were predominantly observed in non-field conditions, where the study was conducted on seedlings and saplings with underdeveloped root systems. It limits the nutrient uptake capacity of these young trees during drought. Furthermore, tree nutritional responses are also influenced by many variables. Specifically, (a) leaf nutrients are more susceptible to drought stress than other organs; (b) reduced tree nutrient concentrations are more prevalent in evergreen species during drought-induced mortality; (c) of all biomes, Mediterranean forests are most vulnerable to drought-induced nutrient deficiencies; (d) soil types affect the direction and extent of tree nutritional responses. We identified factors that influence the relationship between tree nutritional status and drought survival, and proposed potential early-warning indicators of impending tree mortality, for example, decreased K concentrations with declining vitality. These findings contribute to our understanding of tree responses to drought and provide practical implications for forest management strategies in the context of global change.
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Affiliation(s)
- Peng He
- Tianjin Key Laboratory of Animal and Plant Resistance, College of Life Sciences, Tianjin Normal University, Tianjin, China
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Jordi Sardans
- CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Catalonia, Spain
- CREAF, Cerdanyola del Vallès, Catalonia, Spain
| | - Xiaoyu Wang
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
- Jiyang College, Zhejiang Provincial Key Laboratory of Germplasm Innovation and Utilization for Garden Plants, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Chengcang Ma
- Tianjin Key Laboratory of Animal and Plant Resistance, College of Life Sciences, Tianjin Normal University, Tianjin, China
| | - Liang Man
- Tianjin Key Laboratory of Animal and Plant Resistance, College of Life Sciences, Tianjin Normal University, Tianjin, China
| | - Josep Peñuelas
- CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Catalonia, Spain
- CREAF, Cerdanyola del Vallès, Catalonia, Spain
| | - Xingguo Han
- College of Life Sciences, Hebei University, Baoding, China
| | - Yong Jiang
- College of Life Sciences, Hebei University, Baoding, China
| | - Mai-He Li
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
- College of Life Sciences, Hebei University, Baoding, China
- Key Laboratory of Geographical Processes and Ecological Security in Changbai Mountains, Ministry of Education, School of Geographical Sciences, Northeast Normal University, Changchun, China
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4
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Blonder BW, Brodrick PG, Chadwick KD, Carroll E, Cruz-de Hoyos RM, Expósito-Alonso M, Hateley S, Moon M, Ray CA, Tran H, Walton JA. Climate lags and genetics determine phenology in quaking aspen (Populus tremuloides). THE NEW PHYTOLOGIST 2023; 238:2313-2328. [PMID: 36856334 DOI: 10.1111/nph.18850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 02/19/2023] [Indexed: 05/19/2023]
Abstract
Spatiotemporal patterns of phenology may be affected by mosaics of environmental and genetic variation. Environmental drivers may have temporally lagged impacts, but patterns and mechanisms remain poorly known. We combine multiple genomic, remotely sensed, and physically modeled datasets to determine the spatiotemporal patterns and drivers of canopy phenology in quaking aspen, a widespread clonal dioecious tree species with diploid and triploid cytotypes. We show that over 391 km2 of southwestern Colorado: greenup date, greendown date, and growing season length vary by weeks and differ across sexes, cytotypes, and genotypes; phenology has high phenotypic plasticity and heritabilities of 31-61% (interquartile range); and snowmelt date, soil moisture, and air temperature predict phenology, at temporal lags of up to 3 yr. Our study shows that lagged environmental effects are needed to explain phenological variation and that the effect of cytotype on phenology is obscured by its correlation with topography. Phenological patterns are consistent with responses to multiyear accumulation of carbon deficit or hydraulic damage.
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Affiliation(s)
- Benjamin W Blonder
- Department of Environmental Science, Policy, and Management, University of California - Berkeley, Berkeley, CA, 94720, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
| | - Philip G Brodrick
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - K Dana Chadwick
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Erin Carroll
- Department of Environmental Science, Policy, and Management, University of California - Berkeley, Berkeley, CA, 94720, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
| | - Roxanne M Cruz-de Hoyos
- Department of Environmental Science, Policy, and Management, University of California - Berkeley, Berkeley, CA, 94720, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
| | | | - Shannon Hateley
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Minkyu Moon
- Department of Earth & Environment, Boston University, Boston, MA, 02215, USA
| | - Courtenay A Ray
- Department of Environmental Science, Policy, and Management, University of California - Berkeley, Berkeley, CA, 94720, USA
- Rocky Mountain Biological Laboratory, Crested Butte, CO, 81224, USA
| | - Hoang Tran
- Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, 08540, USA
- Atmospheric Sciences & Global Change Division, Pacific Northwest National Laboratory, Richland, WA, 99354, USA
| | - James A Walton
- Molecular Ecology Laboratory, Department of Wildland Resources, Utah State University, Logan, UT, 84322, USA
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5
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The Interplay of the Tree and Stand-Level Processes Mediate Drought-Induced Forest Dieback: Evidence from Complementary Remote Sensing and Tree-Ring Approaches. Ecosystems 2022. [DOI: 10.1007/s10021-022-00793-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractDrought-induced forest dieback can lead to a tipping point in community dominance, but the coupled response at the tree and stand-level response has not been properly addressed. New spatially and temporally integrated monitoring approaches that target different biological organization levels are needed. Here, we compared the temporal responses of dendrochronological and spectral indices from 1984 to 2020 at both tree and stand levels, respectively, of a drought-prone Mediterranean Pinus pinea forest currently suffering strong dieback. We test the influence of climate on temporal patterns of tree radial growth, greenness and wetness spectral indices; and we address the influence of major drought episodes on resilience metrics. Tree-ring data and spectral indices followed different spatio-temporal patterns over the study period (1984–2020). Combined information from tree growth and spectral trajectories suggests that a reduction in tree density during the mid-1990s could have promoted tree growth and reduced dieback risk. Additionally, over the last decade, extreme and recurrent droughts have resulted in crown defoliation greater than 40% in most plots since 2019. We found that tree growth and the greenness spectral index were positively related to annual precipitation, while the wetness index was positively related to mean annual temperature. The response to drought, however, was stronger for tree growth than for spectral indices. Our study demonstrates the value of long-term retrospective multiscale analyses including tree and stand-level scales to disentangle mechanisms triggering and driving forest dieback.
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6
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Klipel J, Bergamin RS, Esquivel‐Muelbert A, de Lima RAF, de Oliveira AA, Prado PI, Müller SC. Climatic distribution of tree species in the Atlantic Forest. Biotropica 2022. [DOI: 10.1111/btp.13140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joice Klipel
- Laboratório de Ecologia Vegetal, Programa de Pós‐Graduação em Ecologia, Instituto de Biociências Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | - Rodrigo Scarton Bergamin
- Laboratório de Ecologia Vegetal, Programa de Pós‐Graduação em Ecologia, Instituto de Biociências Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
- Laboratório de Estudos em Vegetação Campestre, Programa de Pós‐Graduação em Botânica Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | - Adriane Esquivel‐Muelbert
- School of Geography, Earth and Environmental Sciences University of Birmingham Birmingham UK
- Birmingham Institute of Forest Research University of Birmingham Birmingham UK
| | - Renato A. F. de Lima
- Tropical Botany, Naturalis Biodiversity Center Leiden The Netherlands
- Departamento de Ecologia, Instituto de Biociências Universidade de São Paulo São Paulo Brazil
| | | | - Paulo Inácio Prado
- Departamento de Ecologia, Instituto de Biociências Universidade de São Paulo São Paulo Brazil
| | - Sandra Cristina Müller
- Laboratório de Ecologia Vegetal, Programa de Pós‐Graduação em Ecologia, Instituto de Biociências Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
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7
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Kerr KL, Anderegg LDL, Zenes N, Anderegg WRL. Quantifying within‐species trait variation in space and time reveals limits to trait‐mediated drought response. Funct Ecol 2022. [DOI: 10.1111/1365-2435.14112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Kelly L. Kerr
- School of Biological Sciences University of Utah Salt Lake City UT USA
| | - Leander D. L. Anderegg
- Department of Ecology, Evolution, and Marine Biology University of California Santa Barbara Santa Barbara CA USA
| | - Nicole Zenes
- School of Biological Sciences University of Utah Salt Lake City UT USA
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8
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Wu D, Vargas G G, Powers JS, McDowell NG, Becknell JM, Pérez-Aviles D, Medvigy D, Liu Y, Katul GG, Calvo-Alvarado JC, Calvo-Obando A, Sanchez-Azofeifa A, Xu X. Reduced ecosystem resilience quantifies fine-scale heterogeneity in tropical forest mortality responses to drought. GLOBAL CHANGE BIOLOGY 2022; 28:2081-2094. [PMID: 34921474 DOI: 10.1111/gcb.16046] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 12/07/2021] [Accepted: 12/07/2021] [Indexed: 06/14/2023]
Abstract
Sensitivity of forest mortality to drought in carbon-dense tropical forests remains fraught with uncertainty, while extreme droughts are predicted to be more frequent and intense. Here, the potential of temporal autocorrelation of high-frequency variability in Landsat Enhanced Vegetation Index (EVI), an indicator of ecosystem resilience, to predict spatial and temporal variations of forest biomass mortality is evaluated against in situ census observations for 64 site-year combinations in Costa Rican tropical dry forests during the 2015 ENSO drought. Temporal autocorrelation, within the optimal moving window of 24 months, demonstrated robust predictive power for in situ mortality (leave-one-out cross-validation R2 = 0.54), which allows for estimates of annual biomass mortality patterns at 30 m resolution. Subsequent spatial analysis showed substantial fine-scale heterogeneity of forest mortality patterns, largely driven by drought intensity and ecosystem properties related to plant water use such as forest deciduousness and topography. Highly deciduous forest patches demonstrated much lower mortality sensitivity to drought stress than less deciduous forest patches after elevation was controlled. Our results highlight the potential of high-resolution remote sensing to "fingerprint" forest mortality and the significant role of ecosystem heterogeneity in forest biomass resistance to drought.
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Affiliation(s)
- Donghai Wu
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA
| | - German Vargas G
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Jennifer S Powers
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
- Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, USA
| | - Nate G McDowell
- Atmospheric Sciences and Global Change Division, Pacific Northwest National Lab, Richland, Washington, USA
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Justin M Becknell
- Environmental Studies Program, Colby College, Waterville, Maine, USA
| | - Daniel Pérez-Aviles
- Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, USA
| | - David Medvigy
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Yanlan Liu
- School of Earth Sciences, The Ohio State University, Columbus, Ohio, USA
| | - Gabriel G Katul
- Department of Civil and Environmental Engineering and the Nicholas School of the Environment, Duke University, Durham, North Carolina, USA
| | | | - Ana Calvo-Obando
- Escuela de Ing. Forestal, Instituto Tecnológico de Costa Rica, Barrio Los Ángeles, Cartago, Costa Rica
| | | | - Xiangtao Xu
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA
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9
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Das AJ, Slaton MR, Mallory J, Asner GP, Martin RE, Hardwick P. Empirically validated drought vulnerability mapping in the mixed conifer forests of the Sierra Nevada. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2022; 32:e2514. [PMID: 35094444 DOI: 10.1002/eap.2514] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/30/2021] [Accepted: 08/26/2021] [Indexed: 06/14/2023]
Abstract
Severe droughts are predicted to become more frequent in the future, and the consequences of such droughts on forests can be dramatic, resulting in massive tree mortality, rapid change in forest structure and composition, and substantially increased risk of catastrophic fire. Forest managers have tools at their disposal to try to mitigate these effects but are often faced with limited resources, forcing them to make choices about which parts of the landscape to target for treatment. Such planning can greatly benefit from landscape vulnerability assessments, but many existing vulnerability analyses are unvalidated and not grounded in robust empirical datasets. We combined robust sets of ground-based plot and remote sensing data, collected during the 2012-2016 California drought, to develop rigorously validated tools for assessing forest vulnerability to drought-related canopy tree mortality for the mixed conifer forests of the Sequoia and Kings Canyon national parks and potentially for mixed conifer forests in the Sierra Nevada as a whole. Validation was carried out using a large external dataset. The best models included normalized difference vegetation index (NDVI), elevation, and species identity. Models indicated that tree survival probability decreased with greenness (as measured by NDVI) and elevation, particularly if trees were growing slowly. Overall, models showed good calibration and validation, especially for Abies concolor, which comprise a large majority of the trees in many mixed conifer forests in the Sierra Nevada. Our models tended to overestimate mortality risk for Calocedrus decurrens and underestimate risk for pine species, in the latter case probably due to pine bark beetle outbreak dynamics. Validation results indicated dangers of overfitting, as well as showing that the inclusion of trees already under attack by bark beetles at the time of sampling can give false confidence in model strength, while also biasing predictions. These vulnerability tools should be useful to forest managers trying to assess which parts of their landscape were vulnerable during the 2012-2016 drought, and, with additional validation, may prove useful for ongoing assessments and predictions of future forest vulnerability.
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Affiliation(s)
- Adrian J Das
- U.S. Geological Survey, Western Ecological Research Center, Sequoia and Kings Canyon Field Station, Three Rivers, California, USA
| | - Michèle R Slaton
- USDA Forest Service, Pacific Southwest Region, Remote Sensing Laboratory, McClellan, California, USA
| | - Jeffrey Mallory
- USDA Forest Service, Pacific Southwest Region, Remote Sensing Laboratory, McClellan, California, USA
| | - Gregory P Asner
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona, USA
| | - Roberta E Martin
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona, USA
| | - Paul Hardwick
- Division of Resources Management and Science, Sequoia and Kings Canyon National Parks, Three Rivers, California, USA
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10
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Peltier DMP, Guo J, Nguyen P, Bangs M, Wilson M, Samuels-Crow K, Yocom LL, Liu Y, Fell MK, Shaw JD, Auty D, Schwalm C, Anderegg WRL, Koch GW, Litvak ME, Ogle K. Temperature memory and non-structural carbohydrates mediate legacies of a hot drought in trees across the southwestern USA. TREE PHYSIOLOGY 2022; 42:71-85. [PMID: 34302167 DOI: 10.1093/treephys/tpab091] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 07/16/2021] [Indexed: 06/13/2023]
Abstract
Trees are long-lived organisms that integrate climate conditions across years or decades to produce secondary growth. This integration process is sometimes referred to as 'climatic memory.' While widely perceived, the physiological processes underlying this temporal integration, such as the storage and remobilization of non-structural carbohydrates (NSC), are rarely explicitly studied. This is perhaps most apparent when considering drought legacies (perturbed post-drought growth responses to climate), and the physiological mechanisms underlying these lagged responses to climatic extremes. Yet, drought legacies are likely to become more common if warming climate brings more frequent drought. To quantify the linkages between drought legacies, climate memory and NSC, we measured tree growth (via tree ring widths) and NSC concentrations in three dominant species across the southwestern USA. We analyzed these data with a hierarchical mixed effects model to evaluate the time-scales of influence of past climate (memory) on tree growth. We then evaluated the role of climate memory and the degree to which variation in NSC concentrations were related to forward-predicted growth during the hot 2011-2012 drought and subsequent 4-year recovery period. Populus tremuloides exhibited longer climatic memory compared to either Pinus edulis or Juniperus osteosperma, but following the 2011-2012 drought, P. tremuloides trees with relatively longer memory of temperature conditions showed larger (more negative) drought legacies. Conversely, Pinus edulis trees with longer temperature memory had smaller (less negative) drought legacies. For both species, higher NSC concentrations followed more negative (larger) drought legacies, though the relevant NSC fraction differed between P. tremuloides and P. edulis. Our results suggest that differences in tree NSC are also imprinted upon tree growth responses to climate across long time scales, which also underlie tree resilience to increasingly frequent drought events under climate change.
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Affiliation(s)
- Drew M P Peltier
- School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Jessica Guo
- Communications and Cyber Technologies, University of Arizona, Tucson, AZ 85721, USA
| | - Phiyen Nguyen
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Michael Bangs
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Michelle Wilson
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Kimberly Samuels-Crow
- School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Larissa L Yocom
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan, UT 84322, USA
| | - Yao Liu
- Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Michael K Fell
- School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - John D Shaw
- USDA Forest Service, Rocky Mountain Research Station, Ogden, UT 84401, USA
| | - David Auty
- School of Forestry, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Christopher Schwalm
- Woods Hole Research Center, Falmouth, MA 02540, USA
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - William R L Anderegg
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - George W Koch
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Marcy E Litvak
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Kiona Ogle
- School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA
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Moreno-Fernández D, Viana-Soto A, Camarero JJ, Zavala MA, Tijerín J, García M. Using spectral indices as early warning signals of forest dieback: The case of drought-prone Pinus pinaster forests. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 793:148578. [PMID: 34174606 DOI: 10.1016/j.scitotenv.2021.148578] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 06/14/2021] [Accepted: 06/16/2021] [Indexed: 06/13/2023]
Abstract
Forest dieback processes linked to drought are expected to increase due to climate warming. Remotely sensed data offer several advantages over common field monitoring methods such as the ability to observe large areas on a systematic basis and monitoring their changes, making them increasingly used to assess changes in forest health. Here we aim to use a combined approximation of fieldwork and remote sensing to explore possible links between forest dieback and land surface phenological and trend variables derived from long Landsat time series. Forest dieback was evaluated in the field over 31 plots in a Mediterranean, xeric Pinus pinaster forest. Landsat 31-year time series of three greenness (EVI, NDVI, SAVI) and two wetness spectral indices (NMDI and TCW) were derived covering the period 1990-2020. Spectral indices from time series were decomposed into trend and seasonality using a Bayesian estimator while the relationships of the phenological and trend variables among levels of damage were assessed using linear and additive mixed models. We have not found any statistical pieces of evidence of extension or shortening patterns for the length of the phenological season over the examined 31-year period. Our results indicate that the dieback process was mainly related to the trend component of the spectral indices series whereas the phenological metrics were not related to forest dieback. We also found that plots with more dying or damaged trees displayed lower spectral indices trends after a severe drought event in the middle of the 1990s, which confirms the Landsat-derived spectral indices as indicators of early-warning signals. Drops in trends occurred earlier for wetness indices rather than for greenness indices which suggests that the former could be more appropriate for dieback detection, i.e. they could be used as early warning signals of impending loss of tree vigor.
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Affiliation(s)
- Daniel Moreno-Fernández
- Universidad de Alcalá, Departamento de Ciencias de la Vida, Forest Ecology and Restoration Group, Edificio Ciencias, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain.
| | - Alba Viana-Soto
- Universidad de Alcalá, Departamento de Geología, Geografía y Medio Ambiente, Environmental Remote Sensing Research Group. Calle Colegios 2, 28801 Alcalá de Henares, Spain
| | - Julio Jesús Camarero
- Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Montañana 1005, E-50192 Zaragoza, Spain
| | - Miguel A Zavala
- Universidad de Alcalá, Departamento de Ciencias de la Vida, Forest Ecology and Restoration Group, Edificio Ciencias, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain
| | - Julián Tijerín
- Universidad de Alcalá, Departamento de Ciencias de la Vida, Forest Ecology and Restoration Group, Edificio Ciencias, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain
| | - Mariano García
- Universidad de Alcalá, Departamento de Geología, Geografía y Medio Ambiente, Environmental Remote Sensing Research Group. Calle Colegios 2, 28801 Alcalá de Henares, Spain
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12
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The Role of Remote Sensing for the Assessment and Monitoring of Forest Health: A Systematic Evidence Synthesis. FORESTS 2021. [DOI: 10.3390/f12081134] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Forests are increasingly subject to a number of disturbances that can adversely influence their health. Remote sensing offers an efficient alternative for assessing and monitoring forest health. A myriad of methods based upon remotely sensed data have been developed, tailored to the different definitions of forest health considered, and covering a broad range of spatial and temporal scales. The purpose of this review paper is to identify and analyse studies that addressed forest health issues applying remote sensing techniques, in addition to studying the methodological wealth present in these papers. For this matter, we applied the PRISMA protocol to seek and select studies of our interest and subsequently analyse the information contained within them. A final set of 107 journal papers published between 2015 and 2020 was selected for evaluation according to our filter criteria and 20 selected variables. Subsequently, we pair-wise exhaustively read the journal articles and extracted and analysed the information on the variables. We found that (1) the number of papers addressing this issue have consistently increased, (2) that most of the studies placed their study area in North America and Europe and (3) that satellite-borne multispectral sensors are the most commonly used technology, especially from Landsat mission. Finally, most of the studies focused on evaluating the impact of a specific stress or disturbance factor, whereas only a small number of studies approached forest health from an early warning perspective.
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13
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Brun P, Psomas A, Ginzler C, Thuiller W, Zappa M, Zimmermann NE. Large-scale early-wilting response of Central European forests to the 2018 extreme drought. GLOBAL CHANGE BIOLOGY 2020; 26:7021-7035. [PMID: 33091233 PMCID: PMC7756440 DOI: 10.1111/gcb.15360] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 08/31/2020] [Accepted: 09/11/2020] [Indexed: 05/23/2023]
Abstract
The combination of drought and heat affects forest ecosystems by deteriorating the health of trees, which can lead to large-scale die-offs with consequences on biodiversity, the carbon cycle, and wood production. It is thus crucial to understand how drought events affect tree health and which factors determine forest susceptibility and resilience. We analyze the response of Central European forests to the 2018 summer drought with 10 × 10 m satellite observations. By associating time-series statistics of the Normalized Difference Vegetation Index (NDVI) with visually classified observations of early wilting, we show that the drought led to early leaf-shedding across 21,500 ± 2,800 km2 , in particular in central and eastern Germany and in the Czech Republic. High temperatures and low precipitation, especially in August, mostly explained these large-scale patterns, with small- to medium-sized trees, steep slopes, and shallow soils being important regional risk factors. Early wilting revealed a lasting impact on forest productivity, with affected trees showing reduced greenness in the following spring. Our approach reliably detects early wilting at the resolution of large individual crowns and links it to key environmental drivers. It provides a sound basis to monitor and forecast early-wilting responses that may follow the droughts of the coming decades.
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Affiliation(s)
- Philipp Brun
- Swiss Federal Research Institute (WSL)BirmensdorfSwitzerland
| | | | | | - Wilfried Thuiller
- Univ. Grenoble Alpes, CNRS, Univ. Savoie Mont Blanc, LECA, Laboratoire d'Écologie AlpineGrenobleFrance
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14
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Pre-Emptive Detection of Mature Pine Drought Stress Using Multispectral Aerial Imagery. REMOTE SENSING 2020. [DOI: 10.3390/rs12142338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Drought, ozone (O3), and nitrogen deposition (N) alter foliar pigments and tree crown structure that may be remotely detectable. Remote sensing tools are needed that pre-emptively identify trees susceptible to environmental stresses could inform forest managers in advance of tree mortality risk. Jeffrey pine, a component of the economically important and widespread western yellow pine in North America was investigated in the southern Sierra Nevada. Transpiration of mature trees differed by 20% between microsites with adequate (mesic (M)) vs. limited (xeric (X)) water availability as described in a previous study. In this study, in-the-crown morphological traits (needle chlorosis, branchlet diameter, and frequency of needle defoliators and dwarf mistletoe) were significantly correlated with aerially detected, sub-crown spectral traits (upper crown NDVI, high resolution (R), near-infrared (NIR) Scalar (inverse of NDVI) and THERM Δ, and the difference between upper and mid crown temperature). A classification tree model sorted trees into X and M microsites with THERM Δ alone (20% error), which was partially validated at a second site with only mesic trees (2% error). Random forest separated M and X site trees with additional spectra (17% error). Imagery taken once, from an aerial platform with sub-crown resolution, under the challenge of drought stress, was effective in identifying droughted trees within the context of other environmental stresses.
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15
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Schuldt B, Buras A, Arend M, Vitasse Y, Beierkuhnlein C, Damm A, Gharun M, Grams TE, Hauck M, Hajek P, Hartmann H, Hiltbrunner E, Hoch G, Holloway-Phillips M, Körner C, Larysch E, Lübbe T, Nelson DB, Rammig A, Rigling A, Rose L, Ruehr NK, Schumann K, Weiser F, Werner C, Wohlgemuth T, Zang CS, Kahmen A. A first assessment of the impact of the extreme 2018 summer drought on Central European forests. Basic Appl Ecol 2020. [DOI: 10.1016/j.baae.2020.04.003] [Citation(s) in RCA: 172] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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16
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Kulmatiski A, Yu K, Mackay DS, Holdrege MC, Staver AC, Parolari AJ, Liu Y, Majumder S, Trugman AT. Forecasting semi-arid biome shifts in the Anthropocene. THE NEW PHYTOLOGIST 2020; 226:351-361. [PMID: 31853979 DOI: 10.1111/nph.16381] [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: 09/19/2019] [Accepted: 12/06/2019] [Indexed: 06/10/2023]
Abstract
Shrub encroachment, forest decline and wildfires have caused large-scale changes in semi-arid vegetation over the past 50 years. Climate is a primary determinant of plant growth in semi-arid ecosystems, yet it remains difficult to forecast large-scale vegetation shifts (i.e. biome shifts) in response to climate change. We highlight recent advances from four conceptual perspectives that are improving forecasts of semi-arid biome shifts. Moving from small to large scales, first, tree-level models that simulate the carbon costs of drought-induced plant hydraulic failure are improving predictions of delayed-mortality responses to drought. Second, tracer-informed water flow models are improving predictions of species coexistence as a function of climate. Third, new applications of ecohydrological models are beginning to simulate small-scale water movement processes at large scales. Fourth, remotely-sensed measurements of plant traits such as relative canopy moisture are providing early-warning signals that predict forest mortality more than a year in advance. We suggest that a community of researchers using modeling approaches (e.g. machine learning) that can integrate these perspectives will rapidly improve forecasts of semi-arid biome shifts. Better forecasts can be expected to help prevent catastrophic changes in vegetation states by identifying improved monitoring approaches and by prioritizing high-risk areas for management.
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Affiliation(s)
- Andrew Kulmatiski
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan, UT, 84322-5230, USA
| | - Kailiang Yu
- Department of Environmental Systems Science, ETH Zurich, Universitatstrasse 16, 8092, Zurich, Switzerland
- Laboratoire des Sciences du Climat et de l'Environnement, IPSL-LSCE CEA/CNRS/UVSQ, F-91191, Gif-sur-Yvette, France
| | - D Scott Mackay
- Department of Geography and Department of Environment and Sustainability, University at Buffalo, Buffalo, NY, 14261, USA
| | - Martin C Holdrege
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan, UT, 84322-5230, USA
| | - Ann Carla Staver
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06511, USA
| | - Anthony J Parolari
- Department of Civil, Construction, and Environmental Engineering, Marquette University, Milwaukee, WI, 53233, USA
| | - Yanlan Liu
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Sabiha Majumder
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India
- Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, 560012, India
| | - Anna T Trugman
- Department of Geography, University of California Santa Barbara, Santa Barbara, CA, 93117, USA
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Correlation of Field-Measured and Remotely Sensed Plant Water Status as a Tool to Monitor the Risk of Drought-Induced Forest Decline. FORESTS 2020. [DOI: 10.3390/f11010077] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Increased frequency of tree mortality and forest decline due to anomalous drought events calls for the adoption of effective monitoring of tree water status over large spatial and temporal scales. We correlated field-measured and remotely sensed plant water status parameters, to test the possibility of monitoring the risk of drought-induced dehydration and hydraulic failure using satellite images calibrated on reliable physiological indicators of tree hydraulics. The study was conducted during summer 2019 in the Karst plateau (NE Italy) in a woodland dominated by Fraxinus ornus L.; Sentinel-2 images were acquired on a seasonal scale on the same dates when absolute water content (AbWC), relative water content (RWC), and minimum water potential (Ψmin) were measured in the field. Plant water status parameters were correlated with normalized difference vegetation index (NDVI and NDVI 8A), normalized difference water index (NDWI), and soil-adjusted vegetation index (SAVI). Significant Pearson and Spearman linear correlations (α < 0.05) emerged between all tree-level measured variables and NDWI, while for NDVI, NDVI 8A, and SAVI no correlation was found. Our results suggest the possibility of using the NDWI as a proxy of tree water content and water potential.
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