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Zhao L, Liu X, Wang N, Barbeta A, Zhang Y, Cernusak LA, Wang L. The determining factors of hydrogen isotope offsets between plants and their source waters. New Phytol 2024; 241:2009-2024. [PMID: 38178796 DOI: 10.1111/nph.19492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 11/22/2023] [Indexed: 01/06/2024]
Abstract
A fundamental assumption when using hydrogen and oxygen stable isotopes to understand ecohydrological processes is that no isotope fractionation occurs during plant water uptake/transport/redistribution. A growing body of evidence has indicated that hydrogen isotope fractionation occurs in certain environments or for certain plant species. However, whether the plant water source hydrogen isotope offset (δ2 H offset) is a common phenomenon and how it varies among different climates and plant functional types remains unclear. Here, we demonstrated the presence of positive, negative, and zero offsets based on extensive observations of 12 plant species of 635 paired stable isotopic compositions along a strong climate gradient within an inland river basin. Both temperature and relative humidity affected δ2 H offsets. In cool and moist environments, temperature mainly affected δ2 H offsets negatively due to its role in physiological activity. In warm and dry environments, relative humidity mainly affected δ2 H offsets, likely by impacting plant leaf stomatal conductance. These δ2 H offsets also showed substantial linkages with leaf water 18 O enrichment, an indicator of transpiration and evaporative demand. Further studies focusing on the ecophysiological and biochemical understanding of plant δ2 H dynamics under specific environments are essential for understanding regional ecohydrological processes and for conducting paleoclimate reconstructions.
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Affiliation(s)
- Liangju Zhao
- Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an, 710069, China
| | - Xiaohong Liu
- School of Geography and Tourism, Shaanxi Normal University, Xi'an, 710119, China
| | - Ninglian Wang
- Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an, 710069, China
| | - Adrià Barbeta
- BEECA, Department of Evolutionary Biology, Ecology and Environmental Sciences, Universitat de Barcelona, Barcelona, Catalonia, 08007, Spain
| | - Yu Zhang
- School of Geography and Tourism, Shaanxi Normal University, Xi'an, 710119, China
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, QLD, 4878, Australia
| | - Lixin Wang
- Department of Earth and Environmental Sciences, Indiana University Indianapolis (IUI), Indianapolis, IN, 46202, USA
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Barbeta A, Martínez-Sancho E. Origin and fate of carbon and nitrogen reserves in trees. Tree Physiol 2024; 44:tpae021. [PMID: 38349799 DOI: 10.1093/treephys/tpae021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 02/07/2024] [Indexed: 02/15/2024]
Affiliation(s)
- Adrià Barbeta
- Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, Edifici Margalef, Facultat de Biologia, Diagonal, 643, E-08028 Barcelona, Catalonia, Spain
| | - Elisabet Martínez-Sancho
- Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, Edifici Margalef, Facultat de Biologia, Diagonal, 643, E-08028 Barcelona, Catalonia, Spain
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Gimeno TE, Stangl ZR, Barbeta A, Saavedra N, Wingate L, Devert N, Marshall JD. Water taken up through the bark is detected in the transpiration stream in intact upper-canopy branches. Plant Cell Environ 2022; 45:3219-3232. [PMID: 35922889 DOI: 10.1111/pce.14415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 07/29/2022] [Accepted: 08/02/2022] [Indexed: 06/15/2023]
Abstract
Alternative water uptake pathways through leaves and bark complement water supply with interception, fog or dew. Bark water-uptake contributes to embolism-repair, as demonstrated in cut branches. We tested whether bark water-uptake could also contribute to supplement xylem-water for transpiration. We applied bandages injected with 2 H-enriched water on intact upper-canopy branches of Pinus sylvestris and Fagus sylvatica in a boreal and in a temperate forest, in summer and winter, and monitored transpiration and online isotopic composition (δ2 H and δ18 O) of water vapour, before sampling for analyses of δ2 H and δ18 O in tissue waters. Xylem, bark and leaf waters from segments downstream from the bandages were 2 H-enriched whereas δ18 O was similar to controls. Transpiration was positively correlated with 2 H-enrichment. Isotopic compositions of transpiration and xylem water allowed us to calculate isotopic exchange through the bark via vapour exchange, which was negligible in comparison to estimated bark water-uptake, suggesting that water-uptake occurred via liquid phase. Results were consistent across species, forests and seasons, indicating that bark water-uptake may be more ubiquitous than previously considered. We suggest that water taken up through the bark could be incorporated into the transpiration stream, which could imply that sap-flow measurements underestimate transpiration when bark is wet.
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Affiliation(s)
- Teresa E Gimeno
- CREAF, 08193 Bellaterra (Cerdanyola del Vallès), Catalonia, Spain
- Basque Centre for Climate Change (BC3), Leioa, Spain
| | - Zsofia R Stangl
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden
| | - Adrià Barbeta
- BEECA, Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Noelia Saavedra
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden
| | | | | | - John D Marshall
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden
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Cernusak LA, Barbeta A, Bush RT, Eichstaedt (Bögelein) R, Ferrio JP, Flanagan LB, Gessler A, Martín‐Gómez P, Hirl RT, Kahmen A, Keitel C, Lai C, Munksgaard NC, Nelson DB, Ogée J, Roden JS, Schnyder H, Voelker SL, Wang L, Stuart‐Williams H, Wingate L, Yu W, Zhao L, Cuntz M. Do 2 H and 18 O in leaf water reflect environmental drivers differently? New Phytol 2022; 235:41-51. [PMID: 35322882 PMCID: PMC9322340 DOI: 10.1111/nph.18113] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 02/06/2022] [Indexed: 06/01/2023]
Abstract
We compiled hydrogen and oxygen stable isotope compositions (δ2 H and δ18 O) of leaf water from multiple biomes to examine variations with environmental drivers. Leaf water δ2 H was more closely correlated with δ2 H of xylem water or atmospheric vapour, whereas leaf water δ18 O was more closely correlated with air relative humidity. This resulted from the larger proportional range for δ2 H of meteoric waters relative to the extent of leaf water evaporative enrichment compared with δ18 O. We next expressed leaf water as isotopic enrichment above xylem water (Δ2 H and Δ18 O) to remove the impact of xylem water isotopic variation. For Δ2 H, leaf water still correlated with atmospheric vapour, whereas Δ18 O showed no such correlation. This was explained by covariance between air relative humidity and the Δ18 O of atmospheric vapour. This is consistent with a previously observed diurnal correlation between air relative humidity and the deuterium excess of atmospheric vapour across a range of ecosystems. We conclude that 2 H and 18 O in leaf water do indeed reflect the balance of environmental drivers differently; our results have implications for understanding isotopic effects associated with water cycling in terrestrial ecosystems and for inferring environmental change from isotopic biomarkers that act as proxies for leaf water.
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Affiliation(s)
- Lucas A. Cernusak
- College of Science and EngineeringJames Cook UniversityCairnsQld4878Australia
| | - Adrià Barbeta
- BEECADepartment of Evolutionary Biology, Ecology and Environmental SciencesUniversitat de BarcelonaBarcelonaCatalonia08028Spain
| | - Rosemary T. Bush
- Department of Earth and Planetary SciencesNorthwestern UniversityEvanstonIL60208USA
| | | | - Juan Pedro Ferrio
- ARAID‐Departamento de Sistemas AgrícolasForestales y Medio AmbienteCentro de Investigación y Tecnología Agroalimentaria de Aragón (CITA)Zaragoza50059Spain
| | - Lawrence B. Flanagan
- Department of Biological SciencesUniversity of LethbridgeLethbridgeABT1K 3M4Canada
| | - Arthur Gessler
- WSL Swiss Federal Institute for Forest, Snow and Landscape ResearchBirmensdorf8903Switzerland
| | - Paula Martín‐Gómez
- INRAEBordeaux Sciences AgroUMR ISPAVillenave d'Ornon 33140France
- Centre Tecnològic Forestal de Catalunya (CTFC)SolsonaCatalonia25280Spain
| | - Regina T. Hirl
- Technische Universität MünchenLehrstuhl für GrünlandlehreFreising‐Weihenstephan85354Germany
| | - Ansgar Kahmen
- Department of Environmental Sciences–BotanyUniversity of BaselBasel4056Switzerland
| | - Claudia Keitel
- School of Life and Environmental SciencesSydney Institute of AgricultureThe University of SydneyCamdenNSW2006Australia
| | - Chun‐Ta Lai
- Department of BiologySan Diego State UniversitySan DiegoCA92182USA
| | - Niels C. Munksgaard
- College of Science and EngineeringJames Cook UniversityCairnsQld4878Australia
| | - Daniel B. Nelson
- Department of Environmental Sciences–BotanyUniversity of BaselBasel4056Switzerland
| | - Jérôme Ogée
- INRAEBordeaux Sciences AgroUMR ISPAVillenave d'Ornon 33140France
| | - John S. Roden
- Department of BiologySouthern Oregon UniversityAshlandOR97520USA
| | - Hans Schnyder
- Technische Universität MünchenLehrstuhl für GrünlandlehreFreising‐Weihenstephan85354Germany
| | - Steven L. Voelker
- College of Forest Resources and Environmental ScienceMichigan Technological UniversityHoughtonMI49931USA
| | - Lixin Wang
- Department of Earth SciencesIndiana University–Purdue University IndianapolisIndianapolisIND46202USA
| | | | - Lisa Wingate
- INRAEBordeaux Sciences AgroUMR ISPAVillenave d'Ornon 33140France
| | - Wusheng Yu
- Key Laboratory of Tibetan Environmental Changes and Land Surface ProcessesInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing100101China
| | - Liangju Zhao
- Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying CapacityCollege of Urban and Environmental SciencesNorthwest UniversityXi'an 710127China
| | - Matthias Cuntz
- Université de LorraineAgroParisTechINRAEUMR SilvaNancy54000France
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Barbeta A, Burlett R, Martín-Gómez P, Fréjaville B, Devert N, Wingate L, Domec JC, Ogée J. Evidence for distinct isotopic compositions of sap and tissue water in tree stems: consequences for plant water source identification. New Phytol 2022; 233:1121-1132. [PMID: 34767646 DOI: 10.1111/nph.17857] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 11/04/2021] [Indexed: 06/13/2023]
Abstract
The long-standing hypothesis that the isotopic composition of plant stem water reflects that of source water is being challenged by studies reporting bulk water from woody stems with an isotopic composition that cannot be attributed to any potential water source. The mechanism behind such source-stem water isotopic offsets is still poorly understood. Using a novel technique to extract selectively sap water from xylem conduits, we show that, in cut stems and potted plants, the isotopic composition of sap water reflects that of irrigation water, demonstrating unambiguously that no isotopic fractionation occurs during root water uptake or sap water extraction. By contrast, water in nonconductive xylem tissues is always depleted in deuterium compared with sap water, irrespective of wood anatomy. Previous studies have shown that isotopic heterogeneity also exists in soils at the pore scale in which water adsorbed onto soil particles is more depleted in deuterium than unbound water. Data collected at a riparian forest indicated that sap water matches best unbound soil water from depth below -70 cm, while bulk stem and soil water differ markedly. We conclude that source-stem isotopic offsets can be explained by micrometre-scale heterogeneity in the isotope ratios of water within woody stems and soil micro-pores.
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Affiliation(s)
- Adrià Barbeta
- INRAE, Bordeaux Sciences Agro, ISPA, Villenave d'Ornon, 33140, France
- BEECA, Universitat de Barcelona, Barcelona, Catalonia, 08028, Spain
| | - Régis Burlett
- Université de Bordeaux, INRAE, BIOGECO, Pessac, 33615, France
| | | | | | - Nicolas Devert
- INRAE, Bordeaux Sciences Agro, ISPA, Villenave d'Ornon, 33140, France
| | - Lisa Wingate
- INRAE, Bordeaux Sciences Agro, ISPA, Villenave d'Ornon, 33140, France
| | | | - Jérôme Ogée
- INRAE, Bordeaux Sciences Agro, ISPA, Villenave d'Ornon, 33140, France
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Barbeta A, Gimeno TE, Clavé L, Fréjaville B, Jones SP, Delvigne C, Wingate L, Ogée J. An explanation for the isotopic offset between soil and stem water in a temperate tree species. New Phytol 2020; 227:766-779. [PMID: 32239512 DOI: 10.1111/nph.16564] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 03/14/2020] [Indexed: 06/11/2023]
Abstract
A growing number of field studies report isotopic offsets between stem water and its potential sources that prevent the unambiguous identification of plant water origin using water isotopes. We explored the causes of this isotopic offset by conducting a controlled experiment on the temperate tree species Fagus sylvatica. We measured δ2 H and δ18 O of soil and stem water from potted saplings growing on three soil substrates and subjected to two watering regimes. Regardless of substrate, soil and stem water δ2 H were similar only near permanent wilting point. Under moister conditions, stem water δ2 H was 11 ± 3‰ more negative than soil water δ2 H, coherent with field studies. Under drier conditions, stem water δ2 H became progressively more enriched than soil water δ2 H. Although stem water δ18 O broadly reflected that of soil water, soil-stem δ2 H and δ18 O differences were correlated (r = 0.76) and increased with transpiration rates indicated by proxies. Soil-stem isotopic offsets are more likely to be caused by water isotope heterogeneities within the soil pore and stem tissues, which would be masked under drier conditions as a result of evaporative enrichment, than by fractionation under root water uptake. Our results challenge our current understanding of isotopic signals in the soil-plant continuum.
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Affiliation(s)
- Adrià Barbeta
- INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France
- BEECA, Department of Evolutionary Biology, Ecology and Environmental Sciences, Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Teresa E Gimeno
- INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France
- Basque Centre for Climate Change, 48940, Leioa, Spain
- IKERBASQUE, Basque Foundation for Science, 48008, Bilbao, Spain
| | - Laura Clavé
- INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France
| | | | - Sam P Jones
- INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France
- Instituto Nacional de Pesquisas da Amazônia, Manaus, CEP 69060-001, Brazil
| | - Camille Delvigne
- INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France
- Université Catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Lisa Wingate
- INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France
| | - Jérôme Ogée
- INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France
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Barbeta A, Peñuelas J. Increasing carbon discrimination rates and depth of water uptake favor the growth of Mediterranean evergreen trees in the ecotone with temperate deciduous forests. Glob Chang Biol 2017; 23:5054-5068. [PMID: 28544424 DOI: 10.1111/gcb.13770] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 05/04/2017] [Accepted: 05/16/2017] [Indexed: 05/17/2023]
Abstract
Tree populations at the low-altitudinal or -latitudinal limits of species' distributional ranges are predicted to retreat toward higher altitudes and latitudes to track the ongoing changes in climate. Studies have focused on the climatic sensitivity of the retreating species, whereas little is known about the potential replacements. Competition between tree species in forest ecotones will likely be strongly influenced by the ecophysiological responses to heat and drought. We used tree-ring widths and δ13 C and δ18 O chronologies to compare the growth rates and long-term ecophysiological responses to climate in the temperate-Mediterranean ecotone formed by the deciduous Fagus sylvatica and the evergreen Quercus ilex at the low altitudinal and southern latitudinal limit of F. sylvatica (NE Iberian Peninsula). F. sylvatica growth rates were similar to those of other southern populations and were surprisingly not higher than those of Q. ilex, which were an order of magnitude higher than those in nearby drier sites. Higher Q. ilex growth rates were associated with high temperatures, which have increased carbon discrimination rates in the last 25 years. In contrast, stomatal regulation in F. sylvatica was proportional to the increase in atmospheric CO2 . Tree-ring δ18 O for both species were mostly correlated with δ18 O in the source water. In contrast to many previous studies, relative humidity was not negatively correlated with tree-ring δ18 O but had a positive effect on Q. ilex tree-ring δ18 O. Furthermore, tree-ring δ18 O decreased in Q. ilex over time. The sensitivity of Q. ilex to climate likely reflects the uptake of deep water that allowed it to benefit from the effect of CO2 fertilization, in contrast to the water-limited F. sylvatica. Consequently, Q. ilex is a strong competitor at sites currently dominated by F. sylvatica and could be favored by increasingly warmer conditions.
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Affiliation(s)
- Adrià Barbeta
- ISPA, Bordeaux Science Agro, INRA, Villenave d'Ornon, 33140, France
- Global Ecology Unit CREAF-CSIC-UAB, CSIC, E-08193, Bellaterra, Catalonia, Spain
- CREAF, E-08193, Cerdanyola del Vallès, Catalonia, Spain
| | - Josep Peñuelas
- Global Ecology Unit CREAF-CSIC-UAB, CSIC, E-08193, Bellaterra, Catalonia, Spain
- CREAF, E-08193, Cerdanyola del Vallès, Catalonia, Spain
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Turnbull MH, Ogaya R, Barbeta A, Peñuelas J, Zaragoza-Castells J, Atkin OK, Valladares F, Gimeno TE, Pías B, Griffin KL. Light inhibition of foliar respiration in response to soil water availability and seasonal changes in temperature in Mediterranean holm oak (Quercus ilex) forest. Funct Plant Biol 2017; 44:1178-1193. [PMID: 32480643 DOI: 10.1071/fp17032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 07/23/2017] [Indexed: 06/11/2023]
Abstract
In the present study we investigated variations in leaf respiration in darkness (RD) and light (RL), and associated traits in response to season, and along a gradient of soil moisture, in Mediterranean woodland dominated by holm oak (Quercus ilex L.) in central and north-eastern Spain respectively. On seven occasions during the year in the central Spain site, and along the soil moisture gradient in north-eastern Spain, we measured rates of leaf RD, RL (using the Kok method), light-saturated photosynthesis (A) and related light response characteristics, leaf mass per unit area (MA) and leaf nitrogen (N) content. At the central Spain site, significant seasonal changes in soil water content and ambient temperature (T) were associated with changes in MA, foliar N, A and stomatal conductance. RD measured at the prevailing daily T and in instantaneous R-T responses, displayed signs of partial acclimation and was not significantly affected by time of year. RL was always less than, and strongly related to, RD, and RL/RD did not vary significantly or systematically with seasonal changes in T or soil water content. Averaged over the year, RL/RD was 0.66±0.05s.e. (n=14) at the central Spain site. At the north-eastern Spain site, the soil moisture gradient was characterised by increasing MA and RD, and reduced foliar N, A, and stomatal conductance as soil water availability decreased. Light inhibition of R occurred across all sites (mean RL/RD=0.69±0.01s.e. (n=18)), resulting in ratios of RL/A being lower than for RD/A. Importantly, the degree of light inhibition was largely insensitive to changes in soil water content. Our findings provide evidence for a relatively constrained degree of light inhibition of R (RL/RD ~ 0.7, or inhibition of ~30%) across gradients of water availability, although the combined impacts of seasonal changes in both T and soil water content increase the range of values expressed. The findings thus have implications in terms of the assumptions made by predictive models that seek to account for light inhibition of R, and for our understanding of how environmental gradients impact on leaf trait relationships in Mediterranean plant communities.
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Affiliation(s)
- Matthew H Turnbull
- Centre for Integrative Ecology, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
| | - Romà Ogaya
- CREAF, Cerdanyola del Vallès, 08193, Catalonia, Spain
| | - Adrià Barbeta
- CREAF, Cerdanyola del Vallès, 08193, Catalonia, Spain
| | | | - Joana Zaragoza-Castells
- Geography, College of Life and Environmental Sciences, University of Exeter, Amory Building, Rennes Drive, Exeter EX4 4RJ, UK
| | - Owen K Atkin
- ARC Centre of Excellence in Plant Energy Biology, Division of Plant Sciences, Research School of Biology, Building 134, The Australian National University, Canberra, ACT 2601, Australia
| | - Fernando Valladares
- Museo Nacional de Ciencias Naturales, CSIC, Serrano 115, E-28006 Madrid, Spain
| | - Teresa E Gimeno
- Hawkesbury Institute for the Environment, University of Western Sydney, Locked bag 1797, Penrith, NSW 2751, Australia
| | - Beatriz Pías
- Departamento de Botánica, Universidad Complutense de Madrid, José Antonio Novais 2, 28040, Madrid, Spain
| | - Kevin L Griffin
- Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, 6 Biology, Palisades, NY 10964, USA
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Barbeta A, Peñuelas J. Relative contribution of groundwater to plant transpiration estimated with stable isotopes. Sci Rep 2017; 7:10580. [PMID: 28874685 PMCID: PMC5585407 DOI: 10.1038/s41598-017-09643-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 07/27/2017] [Indexed: 11/16/2022] Open
Abstract
Water stored underground in the saturated and subsurface zones below the soil are important sources of water for plants in water-limited ecosystems. The presence of deep-rooted plants worldwide, however, suggests that the use of groundwater is not restricted to arid and seasonally dry ecosystems. We compiled the available data (71 species) on the relative contribution of groundwater to plant water estimated using stable isotopes and mixing models, which provided information about relative groundwater use, and analyzed their variation across different climates, seasons, plant types, edaphic conditions, and landscape positions. Plant use of groundwater was more likely at sites with a pronounced dry season, and represented on average 49 per cent of transpired water in dry seasons and 28 per cent in wet seasons. The relative contribution of groundwater to plant-water uptake was higher on rocky substrates (saprolite, fractured bedrock), which had reduced groundwater uptake when this source was deep belowground. In addition, we found that the connectivity between groundwater pools and plant water may be quantitatively larger and more widespread than reported by recent global estimations based on isotopic averaged values. Earth System Models should account for the feedbacks between transpiration and groundwater recharge.
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Affiliation(s)
- Adrià Barbeta
- ISPA, Bordeaux Science Agro, INRA, 33140, Villenave d'Ornon, France. .,CSIC, Global Ecology Unit CREAF-CSIC-UAB, E-08193, Bellaterra (Catalonia), Spain. .,CREAF, E-08193, Cerdanyola del Vallès (Catalonia), Spain.
| | - Josep Peñuelas
- CSIC, Global Ecology Unit CREAF-CSIC-UAB, E-08193, Bellaterra (Catalonia), Spain.,CREAF, E-08193, Cerdanyola del Vallès (Catalonia), Spain
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Sperlich D, Barbeta A, Ogaya R, Sabaté S, Peñuelas J. Balance between carbon gain and loss under long-term drought: impacts on foliar respiration and photosynthesis in Quercus ilex L. J Exp Bot 2016; 67:821-33. [PMID: 26552882 PMCID: PMC4737074 DOI: 10.1093/jxb/erv492] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Terrestrial carbon exchange is a key process of the global carbon cycle consisting of a delicate balance between photosynthetic carbon uptake and respiratory release. We have, however, a limited understanding how long-term decreases in precipitation induced by climate change affect the boundaries and mechanisms of photosynthesis and respiration. We examined the seasonality of photosynthetic and respiratory traits and evaluated the adaptive mechanism of the foliar carbon balance of Quercus ilex L. experiencing a long-term rainfall-exclusion experiment. Day respiration (Rd) but not night respiration (Rn) was generally higher in the drought treatment leading to an increased Rd/Rn ratio. The limitation of mesophyll conductance (gm) on photosynthesis was generally stronger than stomatal limitation (gs) in the drought treatment, reflected in a lower gm/gs ratio. The peak photosynthetic activity in the drought treatment occurred in an atypical favourable summer in parallel with lower Rd/Rn and higher gm/gs ratios. The plant carbon balance was thus strongly improved through: (i) higher photosynthetic rates induced by gm; and (ii) decreased carbon losses mediated by Rd. Interestingly, photosynthetic potentials (Vc,max, Jmax, and TPU) were not affected by the drought treatment, suggesting a dampening effect on the biochemical level in the long term. In summary, the trees experiencing a 14-year-long drought treatment adapted through higher plasticity in photosynthetic and respiratory traits, so that eventually the atypical favourable growth period was exploited more efficiently.
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Affiliation(s)
- D Sperlich
- Departament d'Ecologia, Facultat de Biologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain CREAF, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain
| | - A Barbeta
- CREAF, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain CSIC, Global Ecology Unit CREAF-CSIC-UAB, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain
| | - R Ogaya
- CREAF, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain CSIC, Global Ecology Unit CREAF-CSIC-UAB, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain
| | - S Sabaté
- Departament d'Ecologia, Facultat de Biologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain CREAF, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain
| | - J Peñuelas
- CREAF, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain CSIC, Global Ecology Unit CREAF-CSIC-UAB, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain
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Liu D, Ogaya R, Barbeta A, Yang X, Peñuelas J. Contrasting impacts of continuous moderate drought and episodic severe droughts on the aboveground-biomass increment and litterfall of three coexisting Mediterranean woody species. Glob Chang Biol 2015; 21:4196-209. [PMID: 26149833 DOI: 10.1111/gcb.13029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 06/17/2015] [Accepted: 06/19/2015] [Indexed: 05/27/2023]
Abstract
Climate change is predicted to increase the aridity in the Mediterranean Basin and severely affect forest productivity and composition. The responses of forests to different timescales of drought, however, are still poorly understood because extreme and persistent moderate droughts can produce nonlinear responses in plants. We conducted a rainfall-manipulation experiment in a Mediterranean forest dominated by Quercus ilex, Phillyrea latifolia, and Arbutus unedo in the Prades Mountains in southern Catalonia from 1999 to 2014. The experimental drought significantly decreased forest aboveground-biomass increment (ABI), tended to increase the litterfall, and decreased aboveground net primary production throughout the 15 years of the study. The responses to the experimental drought were highly species-specific. A. unedo suffered a significant reduction in ABI, Q. ilex experienced a decrease during the early experiment (1999-2003) and in the extreme droughts of 2005-2006 and 2011-2012, and P. latifolia was unaffected by the treatment. The drought treatment significantly increased branch litterfall, especially in the extremely dry year of 2011, and also increased overall leaf litterfall. The drought treatment reduced the fruit production of Q. ilex, which affected seedling recruitment. The ABIs of all species were highly correlated with SPEI in early spring, whereas the branch litterfalls were better correlated with summer SPEIs and the leaf and fruit litterfalls were better correlated with autumn SPEIs. These species-specific responses indicated that the dominant species (Q. ilex) could be partially replaced by the drought-resistant species (P. latifolia). However, the results of this long-term study also suggest that the effect of drought treatment has been dampened over time, probably due to a combination of demographic compensation, morphological and physiological acclimation, and epigenetic changes. However, the structure of community (e.g., species composition, dominance, and stand density) may be reordered when a certain drought threshold is reached.
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Affiliation(s)
- Daijun Liu
- CSIC, Global Ecology Unit, CREAF-CEAB-CSIC-Universitat Autònoma de Barcelona, Cerdanyola del Vallés (Catalonia), E-08193, Spain
- CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
| | - Romà Ogaya
- CSIC, Global Ecology Unit, CREAF-CEAB-CSIC-Universitat Autònoma de Barcelona, Cerdanyola del Vallés (Catalonia), E-08193, Spain
- CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
| | - Adrià Barbeta
- CSIC, Global Ecology Unit, CREAF-CEAB-CSIC-Universitat Autònoma de Barcelona, Cerdanyola del Vallés (Catalonia), E-08193, Spain
- CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
| | - Xiaohong Yang
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, Southwest University, Chongqing, 400716, China
| | - Josep Peñuelas
- CSIC, Global Ecology Unit, CREAF-CEAB-CSIC-Universitat Autònoma de Barcelona, Cerdanyola del Vallés (Catalonia), E-08193, Spain
- CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
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12
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Martín-Gómez P, Barbeta A, Voltas J, Peñuelas J, Dennis K, Palacio S, Dawson TE, Ferrio JP. Isotope-ratio infrared spectroscopy: a reliable tool for the investigation of plant-water sources? New Phytol 2015; 207:914-27. [PMID: 25790288 DOI: 10.1111/nph.13376] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 02/11/2015] [Indexed: 05/16/2023]
Abstract
Stable isotopes are extensively used as tracers for the study of plant-water sources. Isotope-ratio infrared spectroscopy (IRIS) offers a cheaper alternative to isotope-ratio mass spectroscopy (IRMS), but its use in studying plant and soil water is limited by the spectral interference caused by organic contaminants. Here, we examine two approaches to cope with contaminated samples in IRIS: on-line oxidation of organic compounds (MCM) and post-processing correction. We assessed these methods compared to IRMS across 136 samples of xylem and soil water, and a set of ethanol- and methanol-water mixtures. A post-processing correction significantly improved IRIS accuracy in both natural samples and alcohol dilutions, being effective with concentrations up to 8% of ethanol and 0.4% of methanol. MCM outperformed the post-processing correction in removing methanol interference, but did not effectively remove interference for high concentrations of ethanol. By using both approaches, IRIS can overcome with reasonable accuracy the analytical uncertainties associated with most organic contaminants found in soil and xylem water. We recommend the post-processing correction as the first choice for analysis of samples of unknown contamination. Nevertheless, MCM can be more effective for evaluating samples containing contaminants responsible for strong spectral interferences at low concentrations, such as methanol.
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Affiliation(s)
- Paula Martín-Gómez
- Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Lleida, E-25198, Spain
| | - Adrià Barbeta
- Global Ecology Unit CREAF-CSIC-UAB, CSIC, Cerdanyola del Valles (Catalonia), E-08193, Spain
- CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
| | - Jordi Voltas
- Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Lleida, E-25198, Spain
| | - Josep Peñuelas
- Global Ecology Unit CREAF-CSIC-UAB, CSIC, Cerdanyola del Valles (Catalonia), E-08193, Spain
- CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
| | - Kate Dennis
- Product Manager for Isotopic Water, Picarro Inc., Santa Clara, CA, 95054, USA
| | - Sara Palacio
- Instituto Pirenaico de Ecología (IPE-CSIC), Jaca, E-22700, Spain
| | - Todd E Dawson
- Department of Integrative Biology, University of California, Berkeley, CA, 94720, USA
| | - Juan Pedro Ferrio
- Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Lleida, E-25198, Spain
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13
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Barbeta A, Mejía-Chang M, Ogaya R, Voltas J, Dawson TE, Peñuelas J. The combined effects of a long-term experimental drought and an extreme drought on the use of plant-water sources in a Mediterranean forest. Glob Chang Biol 2015; 21:1213-1225. [PMID: 25359123 DOI: 10.1111/gcb.12785] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 09/25/2014] [Indexed: 06/04/2023]
Abstract
Vegetation in water-limited ecosystems relies strongly on access to deep water reserves to withstand dry periods. Most of these ecosystems have shallow soils over deep groundwater reserves. Understanding the functioning and functional plasticity of species-specific root systems and the patterns of or differences in the use of water sources under more frequent or intense droughts is therefore necessary to properly predict the responses of seasonally dry ecosystems to future climate. We used stable isotopes to investigate the seasonal patterns of water uptake by a sclerophyll forest on sloped terrain with shallow soils. We assessed the effect of a long-term experimental drought (12 years) and the added impact of an extreme natural drought that produced widespread tree mortality and crown defoliation. The dominant species, Quercus ilex, Arbutus unedo and Phillyrea latifolia, all have dimorphic root systems enabling them to access different water sources in space and time. The plants extracted water mainly from the soil in the cold and wet seasons but increased their use of groundwater during the summer drought. Interestingly, the plants subjected to the long-term experimental drought shifted water uptake toward deeper (10-35 cm) soil layers during the wet season and reduced groundwater uptake in summer, indicating plasticity in the functional distribution of fine roots that dampened the effect of our experimental drought over the long term. An extreme drought in 2011, however, further reduced the contribution of deep soil layers and groundwater to transpiration, which resulted in greater crown defoliation in the drought-affected plants. This study suggests that extreme droughts aggravate moderate but persistent drier conditions (simulated by our manipulation) and may lead to the depletion of water from groundwater reservoirs and weathered bedrock, threatening the preservation of these Mediterranean ecosystems in their current structures and compositions.
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Affiliation(s)
- Adrià Barbeta
- CSIC, Global Ecology Unit CREAF-CSIC-UAB, Cerdanyola del Vallès (Catalonia), E-08193, Spain; CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
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14
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Ogaya R, Llusià J, Barbeta A, Asensio D, Liu D, Alessio GA, Peñuelas J. Foliar CO₂ in a holm oak forest subjected to 15 years of climate change simulation. Plant Sci 2014; 226:101-107. [PMID: 25113455 DOI: 10.1016/j.plantsci.2014.06.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 06/04/2014] [Accepted: 06/13/2014] [Indexed: 06/03/2023]
Abstract
A long-term experimental drought to simulate future expected climatic conditions for Mediterranean forests, a 15% decrease in soil moisture for the following decades, was conducted in a holm oak forest since 1999. Net photosynthetic rate, stomatal conductance and leaf water potential were measured from 1999 to 2013 in Quercus ilex and Phillyrea latifolia, two co-dominant species of this forest. These measurements were performed in four plots, two of them received the drought treatment and the two other plots were control plots. The three studied variables decreased with increases in VPD and decreases in soil moisture in both species, but the decrease of leaf water potential during summer drought was larger in P. latifolia, whereas Q. ilex reached higher net photosynthetic rates and stomatal conductance values during rainy periods than P. latifolia. The drought treatment decreased ca. 8% the net photosynthetic rates during the overall studied period in both Q. ilex and P. latifolia, whereas there were just non-significant trends toward a decrease in leaf water potential and stomatal conductance induced by drought treatment. Future drier climate may lead to a decrease in the carbon balance of Mediterranean species, and some shrub species well resistant to drought could gain competitive advantage relative to Q. ilex, currently the dominant species of this forest.
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Affiliation(s)
- Romà Ogaya
- CREAF, Cerdanyola del Vallès, E-08193 Catalonia, Spain; CSIC, Global Ecology Unit, CREAF-CEAB-CSIC, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, E-08193 Catalonia, Spain.
| | - Joan Llusià
- CREAF, Cerdanyola del Vallès, E-08193 Catalonia, Spain; CSIC, Global Ecology Unit, CREAF-CEAB-CSIC, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, E-08193 Catalonia, Spain
| | - Adrià Barbeta
- CREAF, Cerdanyola del Vallès, E-08193 Catalonia, Spain; CSIC, Global Ecology Unit, CREAF-CEAB-CSIC, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, E-08193 Catalonia, Spain
| | - Dolores Asensio
- CREAF, Cerdanyola del Vallès, E-08193 Catalonia, Spain; CSIC, Global Ecology Unit, CREAF-CEAB-CSIC, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, E-08193 Catalonia, Spain
| | - Daijun Liu
- CREAF, Cerdanyola del Vallès, E-08193 Catalonia, Spain; CSIC, Global Ecology Unit, CREAF-CEAB-CSIC, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, E-08193 Catalonia, Spain
| | - Giorgio Arturo Alessio
- CREAF, Cerdanyola del Vallès, E-08193 Catalonia, Spain; CSIC, Global Ecology Unit, CREAF-CEAB-CSIC, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, E-08193 Catalonia, Spain
| | - Josep Peñuelas
- CREAF, Cerdanyola del Vallès, E-08193 Catalonia, Spain; CSIC, Global Ecology Unit, CREAF-CEAB-CSIC, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, E-08193 Catalonia, Spain
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15
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Rico L, Ogaya R, Barbeta A, Peñuelas J. Changes in DNA methylation fingerprint of Quercus ilex trees in response to experimental field drought simulating projected climate change. Plant Biol (Stuttg) 2014; 16:419-27. [PMID: 23889779 DOI: 10.1111/plb.12049] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 04/11/2013] [Indexed: 05/22/2023]
Abstract
Rapid genetic changes in plants have been reported in response to current climate change. We assessed the capacity of trees in a natural forest to produce rapid acclimation responses based on epigenetic modifications. We analysed natural populations of Quercus ilex, the dominant tree species of Mediterranean forests, using the methylation-sensitive amplified polymorphism (MSAP) technique to assess patterns and levels of methylation in individuals from unstressed forest plots and from plots experimentally exposed to drought for 12 years at levels projected for the coming decades. The percentage of hypermethylated loci increased, and the percentage of fully methylated loci clearly decreased in plants exposed to drought. Multivariate analyses exploring the status of methylation at MSAP loci also showed clear differentiation depending on stress. The PCA scores for the MSAP profiles clearly separated the genetic from the epigenetic structure, and also significantly separated the samples within each group in response to drought. Changes in DNA methylation highlight the large capacity of plants to rapidly acclimate to changing environmental conditions, including trees with long life spans, and our results demonstrate those changes. These changes, although unable to prevent the decreased growth and higher mortality associated with this experimental drought, occurred together with a dampening in such decreases as the long-term treatment progressed.
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Affiliation(s)
- L Rico
- CSIC, Global Ecology Unit CREAF-CEAB-UAB, Catalonia, Spain; CREAF, Cerdanyola del Vallès, Catalonia, Spain
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Carnicer J, Barbeta A, Sperlich D, Coll M, Peñuelas J. Contrasting trait syndromes in angiosperms and conifers are associated with different responses of tree growth to temperature on a large scale. Front Plant Sci 2013; 4:409. [PMID: 24146668 PMCID: PMC3797994 DOI: 10.3389/fpls.2013.00409] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 09/26/2013] [Indexed: 05/18/2023]
Abstract
Recent large-scale studies of tree growth in the Iberian Peninsula reported contrasting positive and negative effects of temperature in Mediterranean angiosperms and conifers. Here we review the different hypotheses that may explain these trends and propose that the observed contrasting responses of tree growth to temperature in this region could be associated with a continuum of trait differences between angiosperms and conifers. Angiosperm and conifer trees differ in the effects of phenology in their productivity, in their growth allometry, and in their sensitivity to competition. Moreover, angiosperms and conifers significantly differ in hydraulic safety margins, sensitivity of stomatal conductance to vapor-pressure deficit (VPD), xylem recovery capacity or the rate of carbon transfer. These differences could be explained by key features of the xylem such as non-structural carbohydrate content (NSC), wood parenchymal fraction or wood capacitance. We suggest that the reviewed trait differences define two contrasting ecophysiological strategies that may determine qualitatively different growth responses to increased temperature and drought. Improved reciprocal common garden experiments along altitudinal or latitudinal gradients would be key to quantify the relative importance of the different hypotheses reviewed. Finally, we show that warming impacts in this area occur in an ecological context characterized by the advance of forest succession and increased dominance of angiosperm trees over extensive areas. In this context, we examined the empirical relationships between the responses of tree growth to temperature and hydraulic safety margins in angiosperm and coniferous trees. Our findings suggest a future scenario in Mediterranean forests characterized by contrasting demographic responses in conifer and angiosperm trees to both temperature and forest succession, with increased dominance of angiosperm trees, and particularly negative impacts in pines.
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Affiliation(s)
- Jofre Carnicer
- Community and Conservation Ecology Group, Centre for Ecological and Evolutionary Studies, University of GroningenGroningen, Netherlands
- CREAFBarcelona, Spain
- Global Ecology Unit, Consejo Superior de Investigaciones Científicas, CREAF-CEAB-CSIC-UABBarcelona, Spain
| | - Adrià Barbeta
- CREAFBarcelona, Spain
- Global Ecology Unit, Consejo Superior de Investigaciones Científicas, CREAF-CEAB-CSIC-UABBarcelona, Spain
| | - Dominik Sperlich
- CREAFBarcelona, Spain
- Global Ecology Unit, Consejo Superior de Investigaciones Científicas, CREAF-CEAB-CSIC-UABBarcelona, Spain
- Department of Ecology, University of BarcelonaBarcelona, Spain
| | - Marta Coll
- CREAFBarcelona, Spain
- Global Ecology Unit, Consejo Superior de Investigaciones Científicas, CREAF-CEAB-CSIC-UABBarcelona, Spain
| | - Josep Peñuelas
- CREAFBarcelona, Spain
- Global Ecology Unit, Consejo Superior de Investigaciones Científicas, CREAF-CEAB-CSIC-UABBarcelona, Spain
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Barbeta A, Ogaya R, Peñuelas J. Dampening effects of long-term experimental drought on growth and mortality rates of a Holm oak forest. Glob Chang Biol 2013; 19:3133-44. [PMID: 23712619 DOI: 10.1111/gcb.12269] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 04/23/2013] [Indexed: 05/10/2023]
Abstract
Forests respond to increasing intensities and frequencies of drought by reducing growth and with higher tree mortality rates. Little is known, however, about the long-term consequences of generally drier conditions and more frequent extreme droughts. A Holm oak forest was exposed to experimental rainfall manipulation for 13 years to study the effect of increasing drought on growth and mortality of the dominant species Quercus ilex, Phillyrea latifolia, and Arbutus unedo. The drought treatment reduced stem growth of A. unedo (-66.5%) and Q. ilex (-17.5%), whereas P. latifolia remained unaffected. Higher stem mortality rates were noticeable in Q. ilex (+42.3%), but not in the other two species. Stem growth was a function of the drought index of early spring in the three species. Stem mortality rates depended on the drought index of winter and spring for Q. ilex and in spring and summer for P. latifolia, but showed no relation to climate in A. unedo. Following a long and intense drought (2005-2006), stem growth of Q. ilex and P. latifolia increased, whereas it decreased in A. unedo. Q. ilex also enhanced its survival after this period. Furthermore, the effect of drought treatment on stem growth in Q. ilex and A. unedo was attenuated as the study progressed. These results highlight the different vulnerabilities of Mediterranean species to more frequent and intense droughts, which may lead to partial species substitution and changes in forest structure and thus in carbon uptake. The response to drought, however, changed over time. Decreased intra- and interspecific competition after extreme events with high mortality, together with probable morphological and physiological acclimation to drought during the study period, may, at least in the short term, buffer forests against drier conditions. The long-term effects of drought consequently deserve more attention, because the ecosystemic responses are unlikely to be stable over time.Nontechnical summaryIn this study, we evaluate the effect of long-term (13 years) experimental drought on growth and mortality rates of three forest Mediterranean species, and their response to the different intensities and durations of natural drought. We provide evidence for species-specific responses to drought, what may eventually lead to a partial community shift favoring the more drought-resistant species. However, we also report a dampening of the treatment effect on the two drought-sensitive species, which may indicate a potential adaptation to drier conditions at the ecosystem or population level. These results are thus relevant to account for the stabilizing processes that would alter the initial response of ecosystem to drought through changes in plant physiology, morphology, and demography compensation.
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Affiliation(s)
- Adrià Barbeta
- CSIC, Global Ecology Unit CREAF-CEAB-CSIC-UAB, Cerdanyola del Vallès (Catalonia), E-08193, Spain; CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain
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