1
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Aguirre NM, Ochoa ME, Holmlund HI, Palmeri GN, Lancaster ER, Gilderman GS, Taylor SR, Sauer KE, Borges AJ, Lamb AND, Jacques SB, Ewers FW, Davis SD. How megadrought causes extensive mortality in a deep-rooted shrub species normally resistant to drought-induced dieback: The role of a biotic mortality agent. PLANT, CELL & ENVIRONMENT 2024; 47:1053-1069. [PMID: 38017668 DOI: 10.1111/pce.14768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 10/21/2023] [Accepted: 11/03/2023] [Indexed: 11/30/2023]
Abstract
Southern California experienced unprecedented megadrought between 2012 and 2018. During this time, Malosma laurina, a chaparral species normally resilient to single-year intense drought, developed extensive mortality exceeding 60% throughout low-elevation coastal populations of the Santa Monica Mountains. We assessed the physiological mechanisms by which the advent of megadrought predisposed M. laurina to extensive shoot dieback and whole-plant death. We found that hydraulic conductance of stem xylem (Ks, native ) was reduced seven to 11-fold in dieback adult and resprout branches, respectively. Staining of stem xylem vessels revealed that dieback plants experienced 68% solid-blockage, explaining the reduction in water transport. Following Koch's postulates, persistent isolation of a microorganism in stem xylem of dieback plants but not healthy controls indicated that the causative agent of xylem blockage was an opportunistic endophytic fungus, Botryosphaeria dothidea. We inoculated healthy M. laurina saplings with fungal isolates and compared hyphal elongation rates under well-watered, water-deficit, and carbon-deficit treatments. Relative to controls, we found that both water deficit and carbon-deficit increased hyphal extension rates and the incidence of shoot dieback.
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Affiliation(s)
- Natalie M Aguirre
- Ecology and Evolutionary Biology Program, Texas A&M University, College Station, Texas, USA
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Marissa E Ochoa
- Natural Science Division, Pepperdine University, Malibu, California, USA
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA
| | - Helen I Holmlund
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | | | - Emily R Lancaster
- Natural Science Division, Pepperdine University, Malibu, California, USA
- School of Marine Sciences, University of Maine, Orono, Maine, USA
| | - Gina S Gilderman
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Shaquetta R Taylor
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Kaitlyn E Sauer
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Adriana J Borges
- Natural Science Division, Pepperdine University, Malibu, California, USA
| | - Avery N D Lamb
- Natural Science Division, Pepperdine University, Malibu, California, USA
- Nicholas School of the Environment, The Divinity School, Duke University, Durham, North Carolina, USA
| | - Sarah B Jacques
- Natural Science Division, Pepperdine University, Malibu, California, USA
- Department of Surgery, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | - Frank W Ewers
- Department of Biological Sciences, California State Polytechnic University, Pomona, California, USA
| | - Stephen D Davis
- Natural Science Division, Pepperdine University, Malibu, California, USA
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2
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Ma Q, Su Y, Niu C, Ma Q, Hu T, Luo X, Tai X, Qiu T, Zhang Y, Bales RC, Liu L, Kelly M, Guo Q. Tree mortality during long-term droughts is lower in structurally complex forest stands. Nat Commun 2023; 14:7467. [PMID: 37978191 PMCID: PMC10656564 DOI: 10.1038/s41467-023-43083-8] [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: 04/20/2023] [Accepted: 10/31/2023] [Indexed: 11/19/2023] Open
Abstract
Increasing drought frequency and severity in a warming climate threaten forest ecosystems with widespread tree deaths. Canopy structure is important in regulating tree mortality during drought, but how it functions remains controversial. Here, we show that the interplay between tree size and forest structure explains drought-induced tree mortality during the 2012-2016 California drought. Through an analysis of over one million trees, we find that tree mortality rate follows a "negative-positive-negative" piecewise relationship with tree height, and maintains a consistent negative relationship with neighborhood canopy structure (a measure of tree competition). Trees overshadowed by tall neighboring trees experienced lower mortality, likely due to reduced exposure to solar radiation load and lower water demand from evapotranspiration. Our findings demonstrate the significance of neighborhood canopy structure in influencing tree mortality and suggest that re-establishing heterogeneity in canopy structure could improve drought resiliency. Our study also indicates the potential of advances in remote-sensing technologies for silvicultural design, supporting the transition to multi-benefit forest management.
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Affiliation(s)
- Qin Ma
- School of Geography, Nanjing Normal University, Nanjing, 210023, China
- Key Laboratory of Virtual Geographic Environment (Nanjing Normal University), Ministry of Education, Nanjing, 210023, China
- Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, 210023, China
| | - Yanjun Su
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China.
- China National Botanical Garden, 100093, Beijing, China.
- University of Chinese Academy of Sciences, 100049, Beijing, China.
| | - Chunyue Niu
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China
- China National Botanical Garden, 100093, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Qin Ma
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China
- China National Botanical Garden, 100093, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Tianyu Hu
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China
- China National Botanical Garden, 100093, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Xiangzhong Luo
- Department of Geography, National University of Singapore, Singapore, 117570, Singapore
| | - Xiaonan Tai
- Department of Biological Sciences, New Jersey Institute of Technology, Newark, NJ, 07102, USA
| | - Tong Qiu
- Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA, 16802, USA
| | - Yao Zhang
- Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, 100871, Beijing, China
| | - Roger C Bales
- Sierra Nevada Research Institute and School of Engineering, University of California, Merced, CA, 95343, USA
| | - Lingli Liu
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China
- China National Botanical Garden, 100093, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Maggi Kelly
- Department of Environmental Sciences, Policy and Management, University of California, Berkeley, CA, 94720, USA
- Division of Agriculture and Natural Resources, University of California, Berkeley, CA, 94720, USA
| | - Qinghua Guo
- Institute of Remote Sensing and Geographical Information Systems, School of Earth and Space Sciences, Peking University, Beijing, 100871, China
- Institute of Ecology, College of Urban and Environmental Science, Peking University, 100871, Beijing, China
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3
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López-Ballesteros A, Rodríguez-Caballero E, Moreno G, Escribano P, Hereş AM, Yuste JC. Topography modulates climate sensitivity of multidecadal trends of holm oak decline. GLOBAL CHANGE BIOLOGY 2023; 29:6336-6349. [PMID: 37688536 DOI: 10.1111/gcb.16927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 08/14/2023] [Accepted: 08/15/2023] [Indexed: 09/11/2023]
Abstract
Forest decline events have increased worldwide over the last decades being holm oak (Quercus ilex L.) one of the tree species with the most worrying trends across Europe. Since this is one of the tree species with the southernmost distribution within the European continent, its vulnerability to climate change is a phenomenon of enormous ecological importance. Previous research identified drought and soil pathogens as the main causes behind holm oak decline. However, despite tree health loss is a multifactorial phenomenon where abiotic and biotic factors interact in time and space, there are some abiotic factors whose influence has been commonly overlooked. Here, we evaluate how land use (forests versus savannas), topography, and climate extremes jointly determine the spatiotemporal patterns of holm oak defoliation trends over almost three decades (1987-2014) in Spain, where holm oak represents the 25% of the national forested area. We found an increasing defoliation trend in 119 out of the total 134 holm oak plots evaluated, being this defoliation trend significantly higher in forests compared with savannas. Moreover, we have detected that the interaction between topography (which covariates with the land use) and summer precipitation anomalies explains trends of holm oak decline across the Mediterranean region. While a higher occurrence of dry summers increases defoliation trends in steeper terrains where forests dominate, an inverse relationship was found in flatter terrains where savannas are mainly located. These opposite relationships suggest different causal mechanisms behind decline. Whereas hydric stress is likely to occur in steeper terrains where soil water holding capacity is limited, soil waterlogging usually occurs in flatter terrains what increases tree vulnerability to soil pathogens. Our results contribute to the growing evidence of the influence of local topography on forest resilience and could assist in the identification of potential tree decline hotspots and its main causes over the Mediterranean region.
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Affiliation(s)
- Ana López-Ballesteros
- Department of Agricultural and Forest Systems, and the Environment, Agrifood Research and Technology Centre of Aragon (CITA), Zaragoza, Spain
| | - Emilio Rodríguez-Caballero
- Department of Agronomy and Centro de Investigación de Colecciones Científicas (CECOUAL), Universidad de Almería, Almeria, Spain
| | - Gerardo Moreno
- Forestry School, Institute for Dehesa Research (INDEHESA), Universidad de Extremadura, Plasencia, Spain
| | | | - Ana-Maria Hereş
- Faculty of Silviculture and Forest Engineering, Transilvania University of Braşov, Braşov, Romania
- BC3-Basque Centre for Climate Change, Scientific Campus of the University of the Basque Country, Leioa, Spain
| | - Jorge Curiel Yuste
- BC3-Basque Centre for Climate Change, Scientific Campus of the University of the Basque Country, Leioa, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
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4
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Paz-Kagan T, Alexandroff V, Ungar ED. Detection of goat herding impact on vegetation cover change using multi-season, multi-herd tracking and satellite imagery. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 895:164830. [PMID: 37356756 DOI: 10.1016/j.scitotenv.2023.164830] [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: 09/19/2022] [Revised: 06/06/2023] [Accepted: 06/10/2023] [Indexed: 06/27/2023]
Abstract
The frequency and severity of Mediterranean forest fires are expected to worsen as climate change progresses, heightening the need to evaluate understory fuel management strategies as rigorously as possible. Prescribed small-ruminant foraging is considered a sustainable, cost-effective strategy, but demonstrating a link between animal presence and vegetation change is challenging. This study tested whether the effect of small-ruminant herd presence in Mediterranean woodlands can be detected by integrating remote sensing and herd tracking at the landscape scale. The daily foraging routes of seven shepherded goat herds that exploited a 100-km2 forested area of the Judean Hills, Israel, were tracked over six years using GPS (Global Positioning System) collars. Herd locations were converted to stocking rates, with units of animal-presence-days per unit area per defined time period, and mapped at a spatial resolution of 10 m. We estimated pixel-level vegetation cover change based on a time series of 63 monthly Landsat-8 images expressed as the normalized soil-adjusted vegetation index (SAVI). Spatiotemporal trend analysis assessed the magnitude and direction of change, and a random forest machine-learning algorithm estimated the relative impact on vegetation cover change of environmental factors as well as the herd-related factors of stocking rate that accrued over six years and distance to the closest corral. The last two factors were among the most influential factors determining vegetation cover change in the regional and individual-herd analyses. In some respects, the permanent herds differed in their spatial pattern of stocking rate from the mobile herds that periodically relocated their night corral throughout the year, but stocking rate scaled logarithmically for all herds individually and combined. The combination of multi-season GPS tracking, remote sensing, and machine-learning techniques, applied at a regional scale, detected herd impacts on vegetation cover trends, consistent with livestock foraging being an effective tool for fuel reduction in Mediterranean woodlands.
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Affiliation(s)
- Tarin Paz-Kagan
- French Associates Institute for Agriculture and Biotechnology of Dryland, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 8499000, Israel.
| | - Vladimir Alexandroff
- French Associates Institute for Agriculture and Biotechnology of Dryland, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 8499000, Israel.
| | - Eugene David Ungar
- Department of Natural Resources, Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, 68 HaMaccabim Road, P.O.B 15159, Rishon LeZion 7505101, Israel.
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5
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Young DJN, Estes BL, Gross S, Wuenschel A, Restaino C, Meyer MD. Effectiveness of forest density reduction treatments for increasing drought resistance of ponderosa pine growth. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2023; 33:e2854. [PMID: 37032063 DOI: 10.1002/eap.2854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 03/10/2023] [Indexed: 06/02/2023]
Abstract
As the climate changes, it is increasingly important to understand how forests will respond to drought and how forest management can influence those outcomes. In many forests that have become unnaturally dense, "restoration treatments," which decrease stand density using fire and/or mechanical thinning, are generally associated with reduced mortality during drought. However, the effects of such treatments on tree growth during drought are less clear. Previous studies have yielded apparently contradictory results, which may stem from differences in underlying aridity or drought intensity across studies. To address this uncertainty, we studied the growth of ponderosa pine (Pinus ponderosa) in paired treated and untreated areas before and during the extreme California drought of 2012-2016. Our study spanned gradients in climate and tree size and found that density reduction treatments could completely ameliorate drought-driven declines in growth under some contexts, specifically in more mesic areas and in medium-sized trees (i.e., normal annual precipitation > ca. 1100 mm and tree diameter at breast height < ca. 65 cm). Treatments were much less effective in ameliorating drought-associated growth declines in the most water-limited sites and largest trees, consistent with underlying ecophysiology. In medium-sized trees and wetter sites, growth of trees in untreated stands decreased by more than 15% during drought, while treatment-associated increases in growth of 25% or more persisted during the drought. Trees that ultimately died due to drought showed greater growth reductions during drought relative to trees that survived. Our results suggest that density reduction treatments can increase tree resistance to water stress, and they highlight an important pathway for treatments to influence carbon sequestration and other ecosystem services beyond mitigating tree mortality.
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Affiliation(s)
- Derek J N Young
- Department of Plant Sciences, University of California, Davis, Davis, California, USA
| | - Becky L Estes
- USDA Forest Service, Pacific Southwest Region, Vallejo, California, USA
| | - Shana Gross
- USDA Forest Service, Pacific Southwest Region, Vallejo, California, USA
| | - Amarina Wuenschel
- USDA Forest Service, Pacific Southwest Region, Vallejo, California, USA
| | | | - Marc D Meyer
- USDA Forest Service, Pacific Southwest Region, Vallejo, California, USA
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6
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Hartmann H, Bastos A, Das AJ, Esquivel-Muelbert A, Hammond WM, Martínez-Vilalta J, McDowell NG, Powers JS, Pugh TAM, Ruthrof KX, Allen CD. Climate Change Risks to Global Forest Health: Emergence of Unexpected Events of Elevated Tree Mortality Worldwide. ANNUAL REVIEW OF PLANT BIOLOGY 2022; 73:673-702. [PMID: 35231182 DOI: 10.1146/annurev-arplant-102820-012804] [Citation(s) in RCA: 50] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Recent observations of elevated tree mortality following climate extremes, like heat and drought, raise concerns about climate change risks to global forest health. We currently lack both sufficient data and understanding to identify whether these observations represent a global trend toward increasing tree mortality. Here, we document events of sudden and unexpected elevated tree mortality following heat and drought events in ecosystems that previously were considered tolerant or not at risk of exposure. These events underscore the fact that climate change may affect forests with unexpected force in the future. We use the events as examples to highlight current difficulties and challenges for realistically predicting such tree mortality events and the uncertainties about future forest condition. Advances in remote sensing technology and greater availably of high-resolution data, from both field assessments and satellites, are needed to improve both understanding and prediction of forest responses to future climate change.
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Affiliation(s)
- Henrik Hartmann
- Max Planck Institute for Biogeochemistry, Department of Biogeochemical Processes, Jena, Germany;
| | - Ana Bastos
- Max Planck Institute for Biogeochemistry, Department of Biogeochemical Integration, Jena, Germany
| | - Adrian J Das
- US Geological Survey, Western Ecological Research Center, Three Rivers, Sequoia and Kings Canyon Field Station, California, USA
| | - Adriane Esquivel-Muelbert
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- Birmingham Institute of Forest Research, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - William M Hammond
- Agronomy Department, University of Florida, Gainesville, Florida, USA
| | - Jordi Martínez-Vilalta
- CREAF, Bellaterra (Cerdanyola del Vallès), Catalonia, Spain
- Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Catalonia, Spain
| | - 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
| | - Jennifer S Powers
- Departments of Ecology, Evolution and Behavior and Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Thomas A M Pugh
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- Birmingham Institute of Forest Research, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden
| | - Katinka X Ruthrof
- Department of Biodiversity, Conservation and Attractions, Kensington, Western Australia, Australia
- Murdoch University, Murdoch, Western Australia, Australia
| | - Craig D Allen
- Department of Geography and Environmental Studies, University of New Mexico, Albuquerque, New Mexico, USA
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7
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Preisler Y, Hölttä T, Grünzweig JM, Oz I, Tatarinov F, Ruehr NK, Rotenberg E, Yakir D. The importance of tree internal water storage under drought conditions. TREE PHYSIOLOGY 2022; 42:771-783. [PMID: 34726242 DOI: 10.1093/treephys/tpab144] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 10/22/2021] [Indexed: 06/13/2023]
Abstract
Global warming and drying trends, as well as the increase in frequency and intensity of droughts, may have unprecedented impacts on various forest ecosystems. We assessed the role of internal water storage (WS) in drought resistance of mature pine trees in the semi-arid Yatir Forest. Transpiration (T), soil moisture and sap flow (SF) were measured continuously, accompanied by periodical measurements of leaf and branch water potential (Ψleaf) and water content (WC). The data were used to parameterize a tree hydraulics model to examine the impact of WS capacitance on the tree water relations. The results of the continuous measurements showed a 5-h time lag between T and SF in the dry season, which peaked in the early morning and early afternoon, respectively. A good fit between model results and observations was only obtained when the empirically estimated WS capacitance was included in the model. Without WS during the dry season, Ψleaf would drop below a threshold known to cause hydraulic failure and cessation of gas exchange in the studied tree species. Our results indicate that tree WS capacitance is a key drought resistance trait that could enhance tree survival in a drying climate, contributing up to 45% of the total daily transpiration during the dry season.
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Affiliation(s)
- Yakir Preisler
- Earth and Planetary Science, Weizmann Institute of Science, 234 Herzl St. Rehovot, Rehovot 7610001, Israel
- Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Herzl Street POB 12, Rehovot 7610001, Israel
| | - Teemu Hölttä
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, 3 Yliopistonkatu st, 0001 Helsinki, Finland
| | - José M Grünzweig
- Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Herzl Street POB 12, Rehovot 7610001, Israel
| | - Itay Oz
- Earth and Planetary Science, Weizmann Institute of Science, 234 Herzl St. Rehovot, Rehovot 7610001, Israel
- Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Herzl Street POB 12, Rehovot 7610001, Israel
| | - Fedor Tatarinov
- Earth and Planetary Science, Weizmann Institute of Science, 234 Herzl St. Rehovot, Rehovot 7610001, Israel
| | - Nadine K Ruehr
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen 82467, Germany
| | - Eyal Rotenberg
- Earth and Planetary Science, Weizmann Institute of Science, 234 Herzl St. Rehovot, Rehovot 7610001, Israel
| | - Dan Yakir
- Earth and Planetary Science, Weizmann Institute of Science, 234 Herzl St. Rehovot, Rehovot 7610001, Israel
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8
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Antonarakis AS, Bogan SA, Goulden ML, Moorcroft PR. Impacts of the 2012-2015 Californian drought on carbon, water and energy fluxes in the Californian Sierras: Results from an imaging spectrometry-constrained terrestrial biosphere model. GLOBAL CHANGE BIOLOGY 2022; 28:1823-1852. [PMID: 34779555 DOI: 10.1111/gcb.15995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 10/15/2021] [Accepted: 10/28/2021] [Indexed: 06/13/2023]
Abstract
Accurate descriptions of current ecosystem composition are essential for improving terrestrial biosphere model predictions of how ecosystems are responding to climate variability and change. This study investigates how imaging spectrometry-derived ecosystem composition can constrain and improve terrestrial biosphere model predictions of regional-scale carbon, water and energy fluxes. Incorporating imaging spectrometry-derived composition of five plant functional types (Grasses/Shrubs, Oaks/Western Hardwoods, Western Pines, Fir/Cedar and High-elevation Pines) into the Ecosystem Demography (ED2) terrestrial biosphere model improves predictions of net ecosystem productivity (NEP) and gross primary productivity (GPP) across four flux towers of the Southern Sierra Critical Zone Observatory (SSCZO) spanning a 2250 m elevational gradient in the western Sierra Nevada. NEP and GPP root-mean-square-errors were reduced by 23%-82% and 19%-89%, respectively, and water flux predictions improved at the mid-elevation pine (Soaproot), fir/cedar (P301) and high-elevation pine (Shorthair) flux tower sites, but not at the oak savanna (San Joaquin Experimental Range [SJER]) site. These improvements in carbon and water predictions are similar to those achieved with model initializations using ground-based inventory composition. The imaging spectrometry-constrained ED2 model was then used to predict carbon, water and energy fluxes and above-ground biomass (AGB) dynamics over a 737 km2 region to gain insight into the regional ecosystem impacts of the 2012-2015 Californian drought. The analysis indicates that the drought reduced regional NEP, GPP and transpiration by 83%, 40% and 33%, respectively, with the largest reductions occurring in the functionally diverse, high basal area mid-elevation forests. This was accompanied by a 54% decline in AGB growth in 2012, followed by a marked increase (823%) in AGB mortality in 2014, reflecting an approximately 10-fold increase in per capita tree mortality from ~55 trees km-2 year-1 in 2010-2011, to ~535 trees km-2 year-1 in 2014. These findings illustrate how imaging spectrometry estimates of ecosystem composition can constrain and improve terrestrial biosphere model predictions of regional carbon, water, and energy fluxes, and biomass dynamics.
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Affiliation(s)
| | - Stacy A Bogan
- Department of Geography, Sussex University, Brighton, UK
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Michael L Goulden
- Department of Earth Sciences, University of California, Irvine, California, USA
| | - Paul R Moorcroft
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
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9
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Bradford JB, Shriver RK, Robles MD, McCauley LA, Woolley TJ, Andrews CA, Crimmins M, Bell DM. Tree mortality response to drought‐density interactions suggests opportunities to enhance drought resistance. J Appl Ecol 2021. [DOI: 10.1111/1365-2664.14073] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- John. B. Bradford
- Southwest Biological Science Center U.S. Geological Survey Flagstaff AZ USA
| | - Robert K. Shriver
- Department of Natural Resources and Environmental Science University of Nevada Reno NV USA
| | - Marcos D. Robles
- Center for Science and Public Policy The Nature Conservancy Tucson AZ USA
| | - Lisa A. McCauley
- Center for Science and Public Policy The Nature Conservancy Tucson AZ USA
| | - Travis J. Woolley
- Center for Science and Public Policy The Nature Conservancy Tucson AZ USA
| | - Caitlin A. Andrews
- Southwest Biological Science Center U.S. Geological Survey Flagstaff AZ USA
| | - Michael Crimmins
- Department of Environmental Science University of Arizona Tucson AZ USA
| | - David M. Bell
- Pacific Northwest Research Station USDA Forest Service Corvallis OR USA
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10
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Baeza A, Martin RE, Stephenson NL, Das AJ, Hardwick P, Nydick K, Mallory J, Slaton M, Evans K, Asner GP. Mapping the vulnerability of giant sequoias after extreme drought in California using remote sensing. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2021; 31:e02395. [PMID: 34164888 DOI: 10.1002/eap.2395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 01/07/2021] [Accepted: 02/04/2021] [Indexed: 06/13/2023]
Abstract
Between 2012 and 2016, California suffered one of the most severe droughts on record. During this period Sequoiadendron giganteum (giant sequoias) in the Sequoia and Kings Canyon National Parks (SEKI), California, USA experienced canopy water content (CWC) loss, unprecedented foliage senescence, and, in a few cases, death. We present an assessment of the vulnerability of giant sequoia populations to droughts that is currently lacking and needed for management. We used a temporal trend of remotely sensed CWC obtained between 2015 and 2017, and recently georeferenced giant sequoia crowns to quantify the vulnerability of 7,408 individuals in 10 groves in the northern portion of SEKI. CWC is sensitive to changes in liquid water in tree canopies; therefore, it is a useful metric for quantifying the response of sequoia trees to drought. Temporal trends indicated that 9% of giant sequoias had a significant decline or consistently low CWC, suggesting these trees were likely operating at low photosynthetic capacity and potentially at high risk to drought stress. We also found that 20% of the giant sequoias had an increase or consistently high level of CWC, indicating these trees were at low risk to drought stress. These vulnerability categories were used in a random forest model with a combination of topographic, fire-related, and climate variables to generate high-resolution vulnerability risk maps. These maps show that higher risk is associated with lower elevation and higher climate water deficit. We also found that sequoias at higher elevations but located near meadows had higher vulnerability risk. These results and the vulnerability maps can identify vulnerable sequoias that may be difficult to save or locations of refugia to be protected, and thus may aid forest managers in preparation for future droughts.
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Affiliation(s)
- Andres Baeza
- Center for Global Discovery and Conservation Science, Arizona State University. Tempe, Arizona, USA
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, USA
| | - Roberta E Martin
- Center for Global Discovery and Conservation Science, Arizona State University. Tempe, Arizona, USA
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, USA
| | - Nathan L Stephenson
- U.S. Geological Survey, Western Ecological Research Center, Three Rivers, California, USA
| | - Adrian J Das
- U.S. Geological Survey, Western Ecological Research Center, Three Rivers, California, USA
| | - Paul Hardwick
- Sequoia and Kings Canyon National Parks, Division of Resources Management and Science, Three Rivers, California, USA
| | - Koren Nydick
- Sequoia and Kings Canyon National Parks, Division of Resources Management and Science, Three Rivers, California, USA
| | - Jeff Mallory
- USDA Forest Service, Pacific Southwest Region, Remote Sensing Laboratory, McClellan, California, USA
| | - Michèle Slaton
- USDA Forest Service, Pacific Southwest Region, Remote Sensing Laboratory, McClellan, California, USA
| | - Kirk Evans
- 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
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11
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Dudney J, Willing CE, Das AJ, Latimer AM, Nesmith JCB, Battles JJ. Nonlinear shifts in infectious rust disease due to climate change. Nat Commun 2021; 12:5102. [PMID: 34429405 PMCID: PMC8385051 DOI: 10.1038/s41467-021-25182-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 07/09/2021] [Indexed: 11/09/2022] Open
Abstract
Range shifts of infectious plant disease are expected under climate change. As plant diseases move, emergent abiotic-biotic interactions are predicted to modify their distributions, leading to unexpected changes in disease risk. Evidence of these complex range shifts due to climate change, however, remains largely speculative. Here, we combine a long-term study of the infectious tree disease, white pine blister rust, with a six-year field assessment of drought-disease interactions in the southern Sierra Nevada. We find that climate change between 1996 and 2016 moved the climate optimum of the disease into higher elevations. The nonlinear climate change-disease relationship contributed to an estimated 5.5 (4.4-6.6) percentage points (p.p.) decline in disease prevalence in arid regions and an estimated 6.8 (5.8-7.9) p.p. increase in colder regions. Though climate change likely expanded the suitable area for blister rust by 777.9 (1.0-1392.9) km2 into previously inhospitable regions, the combination of host-pathogen and drought-disease interactions contributed to a substantial decrease (32.79%) in mean disease prevalence between surveys. Specifically, declining alternate host abundance suppressed infection probabilities at high elevations, even as climatic conditions became more suitable. Further, drought-disease interactions varied in strength and direction across an aridity gradient-likely decreasing infection risk at low elevations while simultaneously increasing infection risk at high elevations. These results highlight the critical role of aridity in modifying host-pathogen-drought interactions. Variation in aridity across topographic gradients can strongly mediate plant disease range shifts in response to climate change.
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Affiliation(s)
- Joan Dudney
- Department of Plant Sciences, UC Davis, Davis, CA, USA. .,Department of Environmental Science Policy and Management, University of California, Berkeley, Berkeley, CA, USA.
| | - Claire E Willing
- Department of Environmental Science Policy and Management, University of California, Berkeley, Berkeley, CA, USA.,Department of Biology, Stanford University, Stanford, CA, USA
| | - Adrian J Das
- U.S. Geological Survey, Western Ecological Research Center, Three Rivers, CA, USA
| | | | | | - John J Battles
- Department of Environmental Science Policy and Management, University of California, Berkeley, Berkeley, CA, USA
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12
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Thom D, Seidl R. Accelerating Mountain Forest Dynamics in the Alps. Ecosystems 2021; 25:603-617. [PMID: 35509678 PMCID: PMC9016046 DOI: 10.1007/s10021-021-00674-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 06/18/2021] [Indexed: 11/25/2022]
Abstract
Climate change alters forest development pathways, with consequences for ecosystem services and biodiversity. As the rate of warming increases, ecosystem change is expected to accelerate. However, ecosystem dynamics can have many causes unrelated to climate (for example, disturbance and stand development legacies). The compound effects of multiple drivers remain largely unclear. Here, we assessed forest dynamics over 28 years at Berchtesgaden National Park (BGNP), Germany, quantifying the spatiotemporal patterns and unraveling the drivers of forest change. We analyzed high-density forest inventory data, consisting of three consecutive censuses of 3759 permanent sample plots (132,866 tree records in total). We used semi-variograms to analyze spatial patterns of change, and boosted regression trees to quantify the effect of 30 covariates on changes in nine indicators of forest structure and composition. Over the 28 years investigated, the forests of BGNP were becoming denser, structurally more complex, and more species rich. Changes in forest structure were more pronounced and spatially correlated on the landscape than changes in tree species composition. Change rates of all indicators increased over time, signifying an acceleration of forest dynamics since the 1980s. Legacies and climate were the most important drivers of change, but had diverging impacts. Although forest change accelerated with increasing temperature, high legacy levels typical for late development stages dampened it. We here provide evidence for accelerating forest dynamics in mountain forests of the Alps, with potentially far-reaching consequences for biodiversity and ecosystem processes. We highlight that unmanaged forest development toward old-growth conditions could counteract climate-mediated acceleration of forest change.
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Affiliation(s)
- Dominik Thom
- Ecosystem Dynamics and Forest Management Group, School of Life Sciences, Technical University of Munich, Hans-Carl-von-Carlowitz-Platz 2, 85354 Freising, Germany
- Department of Forest- and Soil Sciences, Institute of Silviculture, University of Natural Resources and Life Sciences (BOKU) Vienna, Peter-Jordan-Straße 82, 1190 Vienna, Austria
- Gund Institute for Environment, University of Vermont, 617 Main Street, Burlington, Vermont 05405 USA
| | - Rupert Seidl
- Ecosystem Dynamics and Forest Management Group, School of Life Sciences, Technical University of Munich, Hans-Carl-von-Carlowitz-Platz 2, 85354 Freising, Germany
- Department of Forest- and Soil Sciences, Institute of Silviculture, University of Natural Resources and Life Sciences (BOKU) Vienna, Peter-Jordan-Straße 82, 1190 Vienna, Austria
- Berchtesgaden National Park, Doktorberg 6, 83471 Berchtesgaden, Germany
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13
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Ordway EM, Elmore AJ, Kolstoe S, Quinn JE, Swanwick R, Cattau M, Taillie D, Guinn SM, Chadwick KD, Atkins JW, Blake RE, Chapman M, Cobourn K, Goulden T, Helmus MR, Hondula K, Hritz C, Jensen J, Julian JP, Kuwayama Y, Lulla V, O’Leary D, Nelson DR, Ocón JP, Pau S, Ponce‐Campos GE, Portillo‐Quintero C, Pricope NG, Rivero RG, Schneider L, Steele M, Tulbure MG, Williamson MA, Wilson C. Leveraging the NEON Airborne Observation Platform for socio‐environmental systems research. Ecosphere 2021. [DOI: 10.1002/ecs2.3640] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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14
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Fine PVA, Salazar D, Martin RE, Metz MR, Misiewicz TM, Asner GP. Exploring the links between secondary metabolites and leaf spectral reflectance in a diverse genus of Amazonian trees. Ecosphere 2021. [DOI: 10.1002/ecs2.3362] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Paul V. A. Fine
- Department of Integrative Biology and Jepson and University Herbaria University of California, Berkeley 3040 Valley Life Sciences Building #3140 Berkeley California94720USA
| | - Diego Salazar
- Department of Biological Sciences, Institute of the Environment, and International Center for Tropical Botany Florida International University 11200 S.W. 8th Street Miami Florida33199USA
| | - Roberta E. Martin
- School of Geographical Sciences and Urban Planning Arizona State University P.O. Box 875302 Tempe Arizona85287USA
- Center for Global Discovery and Conservation Science Arizona State University Tempe Arizona85287USA
| | - Margaret R. Metz
- Department of Biology Lewis & Clark College 615 S Palatine Hill Rd Portland Oregon97219USA
| | - Tracy M. Misiewicz
- Department of Integrative Biology and Jepson and University Herbaria University of California, Berkeley 3040 Valley Life Sciences Building #3140 Berkeley California94720USA
| | - Gregory P. Asner
- School of Geographical Sciences and Urban Planning Arizona State University P.O. Box 875302 Tempe Arizona85287USA
- Center for Global Discovery and Conservation Science Arizona State University Tempe Arizona85287USA
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15
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Climate Change Effects on Trophic Interactions of Bark Beetles in Inner Alpine Scots Pine Forests. FORESTS 2021. [DOI: 10.3390/f12020136] [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
Increased tree mortality has become a widespread phenomenon and is largely attributed to climate change. Little field research has addressed the complex interactions between trees, herbivores, and their natural enemies as affected by temperature. We recorded the densities of bark insects and their natural enemies emerging from felled trees in Scots pine forests at 17 study sites along 6 elevation gradients encompassing different temperature ranges in 3 regions in Switzerland and Italy. We additionally measured tree resin defense at different elevations. The density of aggressive bark beetles decreased with increasing temperatures while that of non-aggressive species did not respond to temperature. Contrasting patterns were also found for natural enemies, with the densities of most predatory taxa decreasing with increasing temperature whereas densities of parasitoids increased. Consequently, bark beetle mortality by predators decreased and that by parasitoids increased with temperature. Exudation of resin increased with temperature. As the number of resin ducts did not change with temperature, this is assumed a physical effect of reduced viscosity. Despite lower densities of aggressive bark beetles and improved tree resin flow under higher temperatures, the currently experienced drought-induced reduction in tree vigor is likely to increase tree mortality under the ongoing climate warming.
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16
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Reed CC, Hood SM. Few generalizable patterns of tree-level mortality during extreme drought and concurrent bark beetle outbreaks. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 750:141306. [PMID: 32846245 DOI: 10.1016/j.scitotenv.2020.141306] [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: 05/18/2020] [Revised: 07/14/2020] [Accepted: 07/26/2020] [Indexed: 06/11/2023]
Abstract
Tree mortality associated with drought and concurrent bark beetle outbreaks is expected to increase with further climate change. When these two types of disturbance occur in concert it complicates our ability to accurately predict future forest mortality. The recent extreme California USA drought and bark beetle outbreaks resulted in extensive tree mortality and provides a unique opportunity to examine questions of why some trees die while others survive these co-occurring disturbances. We use plot-level data combined with a three-proxy tree-level approach using radial growth, carbon isotopes, and resin duct metrics to evaluate 1) whether variability in stand structure, tree growth or size, carbon isotope discrimination, or defenses precede mortality, 2) how relationships between these proxies differ for surviving and now-dead trees, and 3) whether generalizable risk factors for tree mortality exist across pinyon pine (Pinus monophylla), ponderosa pine (P. ponderosa), white fir (Abies concolor), and incense cedar (Calocedrus decurrens) affected by the combination of drought and beetle outbreaks. We find that risk factors associated with mortality differ between species, and that few generalizable patterns exist when bark beetle outbreaks occur in concert with a particularly long, hot drought. We see evidence that both long-term differences in physiology and shorter-term beetle-related selection and variability in defenses influence mortality susceptibility for ponderosa pine, whereas beetle dynamics may play a more prominent role in mortality patterns for white fir and pinyon pine. In contrast, incense cedar mortality appears to be attributable to long-term effects of growth suppression. Risk factors that predispose some trees to drought and beetle-related mortality likely reflect species-specific strategies for dealing with these particular disturbance types. The combined influence of beetles and drought necessitates the consideration of multiple, species-specific risk factors to more accurately model forest mortality in the face of similar extreme events more likely under future climates.
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Affiliation(s)
- Charlotte C Reed
- USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, 5775 US Highway 10 W, Missoula, MT 59808, USA.
| | - Sharon M Hood
- USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, 5775 US Highway 10 W, Missoula, MT 59808, USA
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17
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Liu X, Biondi F. Transpiration drivers of high-elevation five-needle pines (Pinus longaeva and Pinus flexilis) in sky-island ecosystems of the North American Great Basin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 739:139861. [PMID: 32544678 DOI: 10.1016/j.scitotenv.2020.139861] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/24/2020] [Accepted: 05/29/2020] [Indexed: 06/11/2023]
Abstract
We investigated the interaction between soil water supply and atmospheric evaporative demand for driving the seasonal pattern of transpiration in sky-island high-elevation forest ecosystems. Sap flow measurements were collected at 10-minute intervals for five consecutive years (2013-2017) on two co-occurring subalpine conifers, i.e. limber pine (Pinus flexilis) and bristlecone pine (Pinus longaeva). Our study site is part of the Nevada Climate-ecohydrological Assessment Network (NevCAN), and is located at 3355 m a.s.l. within an undisturbed mixed-conifer stand. We found that seasonal changes in soil moisture regulated transpiration sensitivity to atmospheric conditions. Sap flow density was mainly limited by evaporative demands under non-water limiting conditions, but was influenced only by soil moisture when water availability decreased. Daily sap flow density increased with radiation and soil moisture in June and July when soil moisture was generally above 10%, but correlated only with soil moisture in August and September when soil drought occurred. Sap flow sensitivity to vapor pressure deficit and solar radiation was therefore reduced under decreasing soil moisture conditions. Transpiration peaked in mid-to-late June during both dry and wet years, with a lower peak in late summer during wet years. Normalized mean daily canopy conductance of both species declined with decreasing soil moisture (i.e., increasing soil drought). Severe soil drying (i.e., soil moisture <7% at 20 cm depth), which was rarely detected in wet summers (2013-2014) but occurred more frequently in dry summers (2015-2017), induced a minimum in crown conductance with unchanged low-level sap flow, which might potentially trigger hydraulic failure. The minimum sap flow level under severe soil drought was higher for limber pine than bristlecone pine, possibly because of wider tracheids in limber compared to bristlecone pine. Our findings provide insights into physiological mechanisms of drought-induced stress for iconic sky-island five-needle pines located at high elevation in xeric environments.
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Affiliation(s)
- Xinsheng Liu
- College of Tourism and Geography, Jiujiang University, East Qianjin Road No. 551, Jiujiang 332005, China; DendroLab, Department of Natural Resources and Environmental Science, University of Nevada, Reno, NV 89557, USA
| | - Franco Biondi
- DendroLab, Department of Natural Resources and Environmental Science, University of Nevada, Reno, NV 89557, USA.
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18
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Lambrecht SC, Gujral AK, Renshaw LJ, Rosengreen LT. Evolutionary and plastic changes in a native annual plant after a historic drought. Ecol Evol 2020; 10:4570-4582. [PMID: 32551044 PMCID: PMC7297769 DOI: 10.1002/ece3.6156] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/24/2020] [Accepted: 02/14/2020] [Indexed: 01/27/2023] Open
Abstract
Severe droughts are forecast to increase with global change. Approaches that enable the study of contemporary evolution, such as resurrection studies, are valuable for providing insights into the responses of populations to global change. In this study, we used a resurrection approach to study the evolution of the California native Leptosiphon bicolor (true babystars, Polemoniaceae) across populations differing in precipitation in response to the state's recent prolonged drought (2011-2017). In the Mediterranean climate region in which L. bicolor grows, this historic drought effectively shortened its growing season. We used seeds collected both before and after this drought from three populations found along a moisture availability gradient to assess contemporary evolution in a common garden greenhouse study. We coupled this with a drought experiment to examine plasticity. We found evolution toward earlier flowering after the historic drought in the wettest of the three populations, while plasticity to experimental drought was observed across all three. We also observed trade-offs associated with earlier flowering. In the driest population, plants that flowered earlier had lower intrinsic water-use efficiency than those flowering later, which was an expected pattern. Unexpectedly, earlier flowering plants had larger flowers. Two populations exhibited evolution and plasticity toward smaller flowers with drought. The third exhibited evolution toward larger flowers, but displayed no plasticity. Our results provide valuable insights into differences among native plant populations in response to drought.
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Affiliation(s)
- Susan C. Lambrecht
- Department of Biological SciencesSan Jose State UniversitySan JoseCalifornia
| | - Anjum K. Gujral
- Department of Biological SciencesSan Jose State UniversitySan JoseCalifornia
| | - Lani J. Renshaw
- Department of Biological SciencesSan Jose State UniversitySan JoseCalifornia
| | - Lars T. Rosengreen
- Department of Biological SciencesSan Jose State UniversitySan JoseCalifornia
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19
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Denney DA, Jameel MI, Bemmels JB, Rochford ME, Anderson JT. Small spaces, big impacts: contributions of micro-environmental variation to population persistence under climate change. AOB PLANTS 2020; 12:plaa005. [PMID: 32211145 PMCID: PMC7082537 DOI: 10.1093/aobpla/plaa005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 02/06/2020] [Indexed: 05/05/2023]
Abstract
Individuals within natural populations can experience very different abiotic and biotic conditions across small spatial scales owing to microtopography and other micro-environmental gradients. Ecological and evolutionary studies often ignore the effects of micro-environment on plant population and community dynamics. Here, we explore the extent to which fine-grained variation in abiotic and biotic conditions contributes to within-population variation in trait expression and genetic diversity in natural plant populations. Furthermore, we consider whether benign microhabitats could buffer local populations of some plant species from abiotic stresses imposed by rapid anthropogenic climate change. If microrefugia sustain local populations and communities in the short term, other eco-evolutionary processes, such as gene flow and adaptation, could enhance population stability in the longer term. We caution, however, that local populations may still decline in size as they contract into rare microhabitats and microrefugia. We encourage future research that explicitly examines the role of the micro-environment in maintaining genetic variation within local populations, favouring the evolution of phenotypic plasticity at local scales and enhancing population persistence under global change.
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Affiliation(s)
- Derek A Denney
- Department of Plant Biology, University of Georgia, Athens, GA, USA
| | - M Inam Jameel
- Department of Genetics, University of Georgia, Athens, GA, USA
| | - Jordan B Bemmels
- Department of Genetics, University of Georgia, Athens, GA, USA
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Mia E Rochford
- Department of Plant Biology, University of Georgia, Athens, GA, USA
| | - Jill T Anderson
- Department of Genetics, University of Georgia, Athens, GA, USA
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20
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Steel EJ, Fontaine JB, Ruthrof KX, Burgess TI, Hardy GESJ. Changes in structure of over- and midstory tree species in a Mediterranean-type forest after an extreme drought-associated heatwave. AUSTRAL ECOL 2019. [DOI: 10.1111/aec.12818] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Emma J. Steel
- Environment and Conservation Science; College of Science, Health, Engineering and Education; Murdoch University; Murdoch Western Australia 6150 Australia
| | - Joseph B. Fontaine
- Environment and Conservation Science; College of Science, Health, Engineering and Education; Murdoch University; Murdoch Western Australia 6150 Australia
| | - Katinka X. Ruthrof
- Environment and Conservation Science; College of Science, Health, Engineering and Education; Murdoch University; Murdoch Western Australia 6150 Australia
- Department of Biodiversity; Conservation and Attractions; Kensington Western Australia Australia
| | - Treena I. Burgess
- Environment and Conservation Science; College of Science, Health, Engineering and Education; Murdoch University; Murdoch Western Australia 6150 Australia
| | - Giles E. St. J. Hardy
- Environment and Conservation Science; College of Science, Health, Engineering and Education; Murdoch University; Murdoch Western Australia 6150 Australia
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21
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Remotely Sensed Water Limitation in Vegetation: Insights from an Experiment with Unmanned Aerial Vehicles (UAVs). REMOTE SENSING 2019. [DOI: 10.3390/rs11161853] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Unmanned aerial vehicles (UAVs) equipped with multispectral sensors present an opportunity to monitor vegetation with on-demand high spatial and temporal resolution. In this study we use multispectral imagery from quadcopter UAVs to monitor the progression of a water manipulation experiment on a common shrub, Baccharis pilularis (coyote brush) at the Blue Oak Ranch Reserve (BORR) ~20 km east of San Jose, California. We recorded multispectral imagery at several altitudes with nearly hourly intervals to explore the relationship between two common spectral indices, NDVI (normalized difference vegetation index) and NDRE (normalized difference red edge index), leaf water content and water potential as physiological metrics of plant water status, across a gradient of water deficit. An examination of the spatial and temporal thresholds at which water limitations were most detectable revealed that the best separation between levels of water deficit were at higher resolution (lower flying height), and in the morning (NDVI) and early morning (NDRE). We found that both measures were able to identify moisture deficit across treatments; however, NDVI was better able to distinguish between treatments than NDRE and was more positively correlated with field measurements of leaf water content. Finally, we explored how relationships between spectral indices and water status changed when the imagery was scaled to courser resolutions provided by satellite-based imagery (PlanetScope).We found that PlanetScope data was able to capture the overall trend in treatments but unable to capture subtle changes in water content. These kinds of experiments that evaluate the relationship between direct field measurements and UAV camera sensitivity are needed to enable translation of field-based physiology measurements to landscape or regional scales.
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22
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Restaino C, Young DJN, Estes B, Gross S, Wuenschel A, Meyer M, Safford H. Forest structure and climate mediate drought-induced tree mortality in forests of the Sierra Nevada, USA. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2019; 29:e01902. [PMID: 31020735 DOI: 10.1002/eap.1902] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 01/09/2019] [Accepted: 02/01/2019] [Indexed: 05/25/2023]
Abstract
Extreme drought stress and associated bark beetle population growth contributed to an extensive tree mortality event in California, USA, resulting in more than 129 million trees dying between 2012 and 2016. Although drought is an important driver of this mortality event, past and ongoing fire suppression and the consequent densification of forests may have contributed. In some areas, land management agencies have worked to reduce stand density through mechanical treatments and prescribed fire to restore forests to less dense, more open conditions that are presumably more resilient to disturbance and changing climate. Here, we evaluate if stand structural conditions associated with treated (e.g., thinned and prescribed burned) forests in the Sierra Nevada of California conferred more resistance to the bark beetle epidemic and drought event of 2012-2016. We found that, compared to untreated units, treated units had lower stand densities, larger average tree diameters, and greater dominance of pines (Pinus), the historically dominant trees. For all tree species studied, mortality was substantially greater in climatically drier areas (i.e., lower elevations and latitudes). Both pine species studied (ponderosa pine [Pinus ponderosa] and sugar pine [Pinus lambertiana]) had greater mortality in areas where their diameters were larger, suggesting a size preference for their insect mortality agents. For ponderosa pine, the tree species experiencing greatest mortality, individual-tree mortality probability (for a given tree diameter) was significantly lower in treated stands. Ponderosa pine mortality was also positively related to density of medium- to large-sized conspecific trees, especially in areas with lower precipitation, suggesting that abundance of nearby host trees for insect mortality agents was an important determinant of pine mortality. Mortality of incense cedar (Calocedrus decurrens) and white fir (Abies concolor) was positively associated with basal area, suggesting sensitivity to competition during drought, but overall mortality was lower, likely because the most prevalent and effective mortality agents (the bark beetles Dendroctonus brevicomis and D. ponderosae) are associated specifically with pine species within our study region. Our findings suggest that forest thinning treatments are effective in reducing drought-related tree mortality in forests, and they underscore the important interaction between water and forest density in mediating bark beetle-caused mortality.
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Affiliation(s)
- Christina Restaino
- Department of Environmental Science and Policy, University of California, Davis, Davis, California, 95615, USA
| | - Derek J N Young
- Department of Environmental Science and Policy, University of California, Davis, Davis, California, 95616, USA
| | - Becky Estes
- USDA Forest Service, Pacific Southwest Region, Central Sierra Province, Placerville, California, 95667, USA
| | - Shana Gross
- USDA Forest Service, Pacific Southwest Region, Central Sierra Province, South Lake Tahoe, California, 96150, USA
| | - Amarina Wuenschel
- USDA Forest Service, Pacific Southwest Region, Southern Sierra Province, Clovis, California, 93611, USA
| | - Marc Meyer
- USDA Forest Service, Pacific Southwest Region, Southern Sierra Province, Bishop, California, 93514, USA
| | - Hugh Safford
- Department of Environmental Science and Policy, University of California, Davis, Davis, California, 95616, USA
- USDA Forest Service, Pacific Southwest Region, Vallejo, California, 94592, USA
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23
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Brodrick PG, Davies AB, Asner GP. Uncovering Ecological Patterns with Convolutional Neural Networks. Trends Ecol Evol 2019; 34:734-745. [PMID: 31078331 DOI: 10.1016/j.tree.2019.03.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 03/20/2019] [Accepted: 03/22/2019] [Indexed: 11/25/2022]
Abstract
Using remotely sensed imagery to identify biophysical components across landscapes is an important avenue of investigation for ecologists studying ecosystem dynamics. With high-resolution remotely sensed imagery, algorithmic utilization of image context is crucial for accurate identification of biophysical components at large scales. In recent years, convolutional neural networks (CNNs) have become ubiquitous in image processing, and are rapidly becoming more common in ecology. Because the quantity of high-resolution remotely sensed imagery continues to rise, CNNs are increasingly essential tools for large-scale ecosystem analysis. We discuss here the conceptual advantages of CNNs, demonstrate how they can be used by ecologists through distinct examples of their application, and provide a walkthrough of how to use them for ecological applications.
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Affiliation(s)
- Philip G Brodrick
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, AZ 85281, USA; Department of Global Ecology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA.
| | - Andrew B Davies
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, AZ 85281, USA; Department of Global Ecology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA; Present address: Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Ave, Cambridge, MA 02138, USA. https://twitter.com/andrewbdavies
| | - Gregory P Asner
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, AZ 85281, USA; Department of Global Ecology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA. https://twitter.com/greg_asner
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24
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Schwartz NB, Budsock AM, Uriarte M. Fragmentation, forest structure, and topography modulate impacts of drought in a tropical forest landscape. Ecology 2019; 100:e02677. [PMID: 30825323 DOI: 10.1002/ecy.2677] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 01/23/2019] [Accepted: 02/04/2019] [Indexed: 02/02/2023]
Abstract
Climate models predict increases in drought conditions in many parts of the tropics. Yet the response of tropical forests to drought remains highly uncertain, especially with regards to the factors that generate spatial heterogeneity in drought response across landscapes. In this study, we used Landsat imagery to assess the impacts of a severe drought in 2015 across an ~80,000-ha landscape in Puerto Rico. Specifically, we asked whether drought effects varied systematically with topography and with forest age, height, and fragmentation. We quantified drought impacts using anomalies of two vegetation indices, the enhanced vegetation index (EVI) and normalized difference water index (NDWI), and fit random forest models of these metrics including slope, aspect, forest age, canopy height, and two indices of fragmentation as predictors. Drought effects were more severe on drier topographic positions, that is, steeper slopes and southwest-facing aspects, and in second-growth forests. Shorter and more fragmented forests were also more strongly affected by drought. We also assessed which factors were associated with stronger recovery from drought. Factors associated with more negative drought anomalies were also associated with more positive postdrought anomalies, suggesting that increased light availability as a result of drought led to high rates of recovery in forests more severely affected by drought. In general, recovery from drought was rapid across the landscape, with postdrought anomalies at or above average across the study area. This suggests that forests in Puerto Rico might be resilient to a single-year drought, though vulnerability to drought varies depending on forest characteristics and landscape position.
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Affiliation(s)
- Naomi B Schwartz
- Department of Geography, University of British Columbia, 1984 West Mall, Vancouver, British Columbia, V6T 1Z2, Canada.,Department of Ecology, Evolution, and Behavior, University of Minnesota, 1479 Gortner Avenue, St. Paul, Minnesota, 55108, USA.,Department of Ecology Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, New York, New York, 10027, USA
| | - Andrew M Budsock
- Department of Ecology Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, New York, New York, 10027, USA
| | - María Uriarte
- Department of Ecology Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, New York, New York, 10027, USA
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Multispectral Approach for Identifying Invasive Plant Species Based on Flowering Phenology Characteristics. REMOTE SENSING 2019. [DOI: 10.3390/rs11080953] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Invasive plant species (IPS) are the second biggest threat to biodiversity after habitat loss. Since the spatial extent of IPS is essential for managing the invaded ecosystem, the current study aims at identifying and mapping the aggressive IPS of Acacia salicina and Acacia saligna, to understand better the key factors influencing their distribution in the coastal plain of Israel. This goal was achieved by integrating airborne-derived hyperspectral imaging and multispectral earth observation for creating species distribution maps. Hyperspectral data, in conjunction with high spatial resolution species distribution maps, were used to train the multispectral images at the species level. We incorporated a series of statistical models to classify the IPS location and to recognize their distribution and density. We took advantage of the phenological flowering stages of Acacia trees, as obtained by the multispectral images, for the support vector machine classification procedure. The classification yielded an overall Kappa coefficient accuracy of 0.89. We studied the effect of various environmental and human factors on IPS density by using a random forest machine learning model, to understand the mechanisms underlying successful invasions, and to assess where IPS have a higher likelihood of occurring. This algorithm revealed that the high density of Acacia most closely related to elevation, temperature pattern, and distances from rivers, settlements, and roads. Our results demonstrate how the integration of remote-sensing data with different data sources can assist in determining IPS proliferation and provide detailed geographic information for conservation and management efforts to prevent their future spread.
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26
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High-Resolution Mapping of Redwood (Sequoia sempervirens) Distributions in Three Californian Forests. REMOTE SENSING 2019. [DOI: 10.3390/rs11030351] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
High-resolution maps of redwood distributions could enable strategic land management to satisfy diverse conservation goals, but the currently-available maps of redwood distributions are low in spatial resolution and biotic detail. Classification of airborne imaging spectroscopy data provides a potential avenue for mapping redwoods over large areas and with high confidence. We used airborne imaging spectroscopy data collected over three redwood forests by the Carnegie Airborne Observatory, in combination with field training data and application of a gradient boosted regression tree (GBRT) machine learning algorithm, to map the distribution of redwoods at 2-m spatial resolution. Training data collected from the three sites showed that redwoods have spectral signatures distinct from the other common tree species found in redwood forests. We optimized a gradient boosted regression model for high performance and computational efficiency, and the resulting model was demonstrably accurate (81–98% true positive rate and 90–98% overall accuracy) in mapping redwoods in each of the study sites. The resulting maps showed marked variation in redwood abundance (0–70%) within a 1 square kilometer aggregation block, which match the spatial resolution of currently-available redwood distribution maps. Our resulting high-resolution mapping approach will facilitate improved research, conservation, and management of redwood trees in California.
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Whitebark and Foxtail Pine in Yosemite, Sequoia, and Kings Canyon National Parks: Initial Assessment of Stand Structure and Condition. FORESTS 2019. [DOI: 10.3390/f10010035] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Inventory & Monitoring Division of the U.S. National Park Service conducts long-term monitoring to provide park managers information on the status and trends in biological and environmental attributes including white pines. White pines are foundational species in many subalpine ecosystems and are currently experiencing population declines. Here we present results on the status of whitebark and foxtail pine in the southern Sierra Nevada of California, an area understudied relative to other parts of their ranges. We selected random plot locations in Yosemite, Sequoia, and Kings Canyon national parks using an equal probability spatially-balanced approach. Tree- and plot-level data were collected on forest structure, composition, demography, cone production, crown mortality, and incidence of white pine blister rust and mountain pine beetle. We measured 7899 whitebark pine, 1112 foxtail pine, and 6085 other trees from 2012–2017. All factors for both species were spatially highly variable. Whitebark pine occurred in nearly-pure krummholz stands at or near treeline and as a minor component of mixed species forests. Ovulate cones were observed on 25% of whitebark pine and 69% of foxtail pine. Whitebark pine seedlings were recorded in 58% of plots, and foxtail pine seedlings in only 21% of plots. Crown mortality (8% in whitebark, 6% in foxtail) was low and significantly higher in 2017 compared to previous years. Less than 1% of whitebark and zero foxtail pine were infected with white pine blister rust and <1% of whitebark and foxtail pine displayed symptoms of mountain pine beetle attack. High elevation white pines in the southern Sierra Nevada are healthy compared to other portions of their range where population declines are significant and well documented. However, increasing white pine blister rust and mountain pine beetle occurrence, coupled with climate change projections, portend future declines for these species, underscoring the need for broad-scale collaborative monitoring.
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Martin J, Looker N, Hoylman Z, Jencso K, Hu J. Differential use of winter precipitation by upper and lower elevation Douglas fir in the Northern Rockies. GLOBAL CHANGE BIOLOGY 2018; 24:5607-5621. [PMID: 30192433 DOI: 10.1111/gcb.14435] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 08/13/2018] [Accepted: 08/20/2018] [Indexed: 06/08/2023]
Abstract
In temperate regions such as the American west, forest trees often exhibit growth sensitivity to climatic conditions of a particular season. For example, annual tree ring growth increments may correlate well with winter precipitation, but not with summer rainfall, suggesting that trees rely more on winter snow than summer rain. Because both the timing and character of seasonal western climate patterns are expected to change considerably over coming decades, variation in the importance of different seasonal moisture sources for trees can be expected to influence how different forest trees respond to climate change as a whole, with shifts in seasonality potentially benefitting some trees while challenging others. In this study, we inferred patterns of tree water use in Douglas fir trees from the Northern Rockies for 2 years using stable water isotopes, while simultaneously quantifying and tracking precipitation inputs to soil moisture across a vertical soil profile. We then coupled water source use with daily measurements of radial growth to demonstrate that soil moisture from winter precipitation accounted for 87.5% and 84% of tree growth at low and high elevations, respectively. We found that prevailing soil moisture conditions drive variation in the depth at which trees access soil water, which in turn determines which seasonal precipitation inputs are available to support tree growth and function. In general, trees at lower elevations relied more on winter precipitation sourced from deep soils while trees at higher elevations made better use of summer rains sourced from near-surface soil layers. As both the timing of seasons and phase of precipitation (rain vs. snow) are likely to change considerably across much of the west, such patterns in tree water use are likely to play a role in determining the evolution of forest composition and structure in a warming climate.
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Affiliation(s)
- Justin Martin
- Department of Ecology, Montana State University, Bozeman, Montana
| | - Nathaniel Looker
- Department of Soil, Water, and Climate, University of Minnesota, St. Paul, Minnesota
| | - Zachary Hoylman
- Montana Climate Office, University of Montana, Missoula, Montana
| | - Kelsey Jencso
- Montana Climate Office, University of Montana, Missoula, Montana
| | - Jia Hu
- School of Natural Resources and Environment, University of Arizona, Tucson, Arizona
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Abstract
Forest densification, wildfires, and disease can reduce the growth and survival of hardwood trees that are important for biological and cultural diversity within the Pacific Northwest of USA. Large, full-crowned hardwoods that produce fruit and that form large cavities used by wildlife were sustained by frequent, low-severity fires prior to Euro-American colonization. Shifts in fire regimes and other threats could be causing declines in, large hardwood trees. To better understand whether and where such declines might be occurring, we evaluated recent trends in Forest Inventory and Analysis (FIA) data from 1991–2016 in California and southern Oregon. We included plots that lay within areas of frequent fire regimes during pre-colonial times and potential forest habitats for fisher, a rare mammal that depends on large live hardwoods. We analyzed changes in basal area for eight hardwood species, both overall and within size classes, over three time periods within ecoregions, and in public and private land ownerships. We found the basal area to generally be stable or increasing for these species. However, data for California black oak suggested a slight decline in basal area overall, and among both very large trees and understory trees; that decline was associated with fire mortality on national forest lands. In addition, mature trees with full crowns appeared to sharply decline across all species. Many trends were not statistically significant due to high variation, especially since more precise data from remeasured trees were only available for the two most recent time periods. Continued analysis of these indicators using remeasured trees will help to evaluate whether conservation efforts are sustaining large, full-crowned trees and their associated benefits.
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