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Loik ME, Griffith AB, Alpert H, Concilio AL, Wade CE, Martinson SJ. Impact of intra- versus inter-annual snow depth variation on water relations and photosynthesis for two Great Basin Desert shrubs. Oecologia 2015; 178:403-14. [PMID: 25627409 DOI: 10.1007/s00442-015-3224-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 01/12/2015] [Indexed: 10/24/2022]
Abstract
Snowfall provides the majority of soil water in certain ecosystems of North America. We tested the hypothesis that snow depth variation affects soil water content, which in turn drives water potential (Ψ) and photosynthesis, over 10 years for two widespread shrubs of the western USA. Stem Ψ (Ψ stem) and photosynthetic gas exchange [stomatal conductance to water vapor (g s), and CO2 assimilation (A)] were measured in mid-June each year from 2004 to 2013 for Artemisia tridentata var. vaseyana (Asteraceae) and Purshia tridentata (Rosaceae). Snow fences were used to create increased or decreased snow depth plots. Snow depth on +snow plots was about twice that of ambient plots in most years, and 20 % lower on -snow plots, consistent with several down-scaled climate model projections. Maximal soil water content at 40- and 100-cm depths was correlated with February snow depth. For both species, multivariate ANOVA (MANOVA) showed that Ψ stem, g s, and A were significantly affected by intra-annual variation in snow depth. Within years, MANOVA showed that only A was significantly affected by spatial snow depth treatments for A. tridentata, and Ψ stem was significantly affected by snow depth for P. tridentata. Results show that stem water relations and photosynthetic gas exchange for these two cold desert shrub species in mid-June were more affected by inter-annual variation in snow depth by comparison to within-year spatial variation in snow depth. The results highlight the potential importance of changes in inter-annual variation in snowfall for future shrub photosynthesis in the western Great Basin Desert.
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Affiliation(s)
- Michael E Loik
- Department of Environmental Studies, University of California, 1156 High Street, Santa Cruz, CA, 95064, USA,
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Meinzer FC, Woodruff DR, Marias DE, McCulloh KA, Sevanto S. Dynamics of leaf water relations components in co-occurring iso- and anisohydric conifer species. PLANT, CELL & ENVIRONMENT 2014; 37:2577-86. [PMID: 24661116 DOI: 10.1111/pce.12327] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 03/13/2014] [Accepted: 03/17/2014] [Indexed: 05/20/2023]
Abstract
Because iso- and anisohydric species differ in stomatal regulation of the rate and magnitude of fluctuations in shoot water potential, they may be expected to show differences in the plasticity of their shoot water relations components, but explicit comparisons of this nature have rarely been made. We subjected excised shoots of co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis to pressure-volume analysis with and without prior artificial rehydration. In J. monosperma, the shoot water potential at turgor loss (Ψ(TLP)) ranged from -3.4 MPa in artificially rehydrated shoots to -6.6 MPa in shoots with an initial Ψ of -5.5 MPa, whereas in P. edulis mean Ψ(TLP) remained at ∼ -3.0 MPa over a range of initial Ψ from -0.1 to -2.3 MPa. The shoot osmotic potential at full turgor and the bulk modulus of elasticity also declined sharply with shoot Ψ in J. monosperma, but not in P. edulis. The contrasting behaviour of J. monosperma and P. edulis reflects differences in their capacity for homeostatic regulation of turgor that may be representative of aniso- and isohydric species in general, and may also be associated with the greater capacity of J. monosperma to withstand severe drought.
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Affiliation(s)
- Frederick C Meinzer
- USDA Forest Service, Pacific Northwest Research Station, Corvallis, OR, 97331, USA
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McDowell NG, Fisher RA, Xu C, Domec JC, Hölttä T, Mackay DS, Sperry JS, Boutz A, Dickman L, Gehres N, Limousin JM, Macalady A, Martínez-Vilalta J, Mencuccini M, Plaut JA, Ogée J, Pangle RE, Rasse DP, Ryan MG, Sevanto S, Waring RH, Williams AP, Yepez EA, Pockman WT. Evaluating theories of drought-induced vegetation mortality using a multimodel-experiment framework. THE NEW PHYTOLOGIST 2013; 200:304-321. [PMID: 24004027 DOI: 10.1111/nph.12465] [Citation(s) in RCA: 189] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 07/19/2013] [Indexed: 05/05/2023]
Abstract
Model-data comparisons of plant physiological processes provide an understanding of mechanisms underlying vegetation responses to climate. We simulated the physiology of a piñon pine-juniper woodland (Pinus edulis-Juniperus monosperma) that experienced mortality during a 5 yr precipitation-reduction experiment, allowing a framework with which to examine our knowledge of drought-induced tree mortality. We used six models designed for scales ranging from individual plants to a global level, all containing state-of-the-art representations of the internal hydraulic and carbohydrate dynamics of woody plants. Despite the large range of model structures, tuning, and parameterization employed, all simulations predicted hydraulic failure and carbon starvation processes co-occurring in dying trees of both species, with the time spent with severe hydraulic failure and carbon starvation, rather than absolute thresholds per se, being a better predictor of impending mortality. Model and empirical data suggest that limited carbon and water exchanges at stomatal, phloem, and below-ground interfaces were associated with mortality of both species. The model-data comparison suggests that the introduction of a mechanistic process into physiology-based models provides equal or improved predictive power over traditional process-model or empirical thresholds. Both biophysical and empirical modeling approaches are useful in understanding processes, particularly when the models fail, because they reveal mechanisms that are likely to underlie mortality. We suggest that for some ecosystems, integration of mechanistic pathogen models into current vegetation models, and evaluation against observations, could result in a breakthrough capability to simulate vegetation dynamics.
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Affiliation(s)
- Nate G McDowell
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Rosie A Fisher
- Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO, 80305, USA
| | - Chonggang Xu
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - J C Domec
- University of Bordeaux, Bordeaux Sciences Agro, UMR INRA-TCEM 1220, 33140, Villenave d'Ornon, France
- Nicholas School of the Environment, Duke University, Box 90328, Durham, NC, 27708, USA
| | - Teemu Hölttä
- Department of Forest Sciences, University of Helsinki, PO Box 24, 00014, Helsinki, Finland
| | - D Scott Mackay
- Department of Geography, State University of New York at Buffalo, 105 Wilkeson Quadrangle, Buffalo, NY, 14261, USA
| | - John S Sperry
- Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112, USA
| | - Amanda Boutz
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131-0001, USA
| | - Lee Dickman
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Nathan Gehres
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131-0001, USA
| | - Jean Marc Limousin
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131-0001, USA
| | - Alison Macalady
- School of Geography and Development and Laboratory of Tree-Ring Research, University of Arizona, 1215 Lowell Street, Tucson, AZ, 85721-0058, USA
| | - Jordi Martínez-Vilalta
- CREAF, Cerdanyola del Vallès, 08193, Spain
- Univ Autònoma Barcelona, Cerdanyola del Vallès, 08193, Spain
| | - Maurizio Mencuccini
- ICREA at CREAF, Cerdanyola del Vallès, 08193, Spain
- School of GeoSciences, University of Edinburgh Crew Building, West Mains Road, Edinburgh, EH9 3JN, UK
| | - Jennifer A Plaut
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131-0001, USA
| | - Jérôme Ogée
- INRA, UR1263 EPHYSE, F-33140, Villenave d'Ornon, France
| | - Robert E Pangle
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131-0001, USA
| | - Daniel P Rasse
- Bioforsk - Norwegian Institute for Agricultural and Environmental Research, Ås, Norway
| | - Michael G Ryan
- Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO, 80523-1499, USA
- USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO, 80526, USA
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Richard H Waring
- College of Forestry, Oregon State University, Corvallis, OR, 97331-5704, USA
| | - A Park Williams
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Enrico A Yepez
- Departamento de Ciencias del Agua y del Medio Ambiente, Instituto Tecnológico de Sonora, Ciudad Obregón, Sonora, 85000, Mexico
| | - William T Pockman
- Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131-0001, USA
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Plaut JA, Wadsworth WD, Pangle R, Yepez EA, McDowell NG, Pockman WT. Reduced transpiration response to precipitation pulses precedes mortality in a piñon-juniper woodland subject to prolonged drought. THE NEW PHYTOLOGIST 2013; 200:375-387. [PMID: 23844951 DOI: 10.1111/nph.12392] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 05/27/2013] [Indexed: 06/02/2023]
Abstract
Global climate change is predicted to alter the intensity and duration of droughts, but the effects of changing precipitation patterns on vegetation mortality are difficult to predict. Our objective was to determine whether prolonged drought or above-average precipitation altered the capacity to respond to the individual precipitation pulses that drive productivity and survival. We analyzed 5 yr of data from a rainfall manipulation experiment in piñon-juniper (Pinus edulis-Juniperus monosperma) woodland using mixed effects models of transpiration response to event size, antecedent soil moisture, and post-event vapor pressure deficit. Replicated treatments included irrigation, drought, ambient control and infrastructure control. Mortality was highest under drought, and the reduced post-pulse transpiration in the droughted trees that died was attributable to treatment effects beyond drier antecedent conditions and reduced event size. In particular, trees that died were nearly unresponsive to antecedent shallow soil moisture, suggesting reduced shallow absorbing root area. Irrigated trees showed an enhanced response to precipitation pulses. Prolonged drought initiates a downward spiral whereby trees are increasingly unable to utilize pulsed soil moisture. Thus, the additive effects of future, more frequent droughts may increase drought-related mortality.
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Affiliation(s)
- Jennifer A Plaut
- Department of Biology, 1 University of New Mexico, MSC03 2020, Albuquerque, NM, 87131-0001, USA
| | - W Duncan Wadsworth
- Department of Statistics, Rice University, MS 138, PO Box 1892, Houston, TX, 77251, USA
| | - Robert Pangle
- Department of Biology, 1 University of New Mexico, MSC03 2020, Albuquerque, NM, 87131-0001, USA
| | - Enrico A Yepez
- Departamento de Ciencias del Agua y del Medio Ambiente, Instituto Tecnológico de Sonora, Ciudad Obregón Sonora, 85000, Mexico
| | - Nate G McDowell
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - William T Pockman
- Department of Biology, 1 University of New Mexico, MSC03 2020, Albuquerque, NM, 87131-0001, USA
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