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Fang W, Liu J, Lu N, Li R. The dynamics of nocturnal sap flow components of a typical revegetation shrub species on the semiarid Loess Plateau, China. FRONTIERS IN PLANT SCIENCE 2024; 15:1370362. [PMID: 38576789 PMCID: PMC10991760 DOI: 10.3389/fpls.2024.1370362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Accepted: 03/11/2024] [Indexed: 04/06/2024]
Abstract
Introduction The components of nighttime sap flux (En), which include transpiration (Qn) and stem water recharge (Rn), play important roles in water balance and drought adaptation in plant communities in water-limited regions. However, the quantitative and controlling factors of En components are unclear. Methods This study used the heat balance method to measure sap flow density in Vitex negundo on the Loess Plateau for a normal precipitation year (2021) and a wetter year (2022). Results The results showed that the mean values were 1.04 and 2.34 g h-1 cm-2 for Qn, 0.19 and 0.45 g h-1 cm-2 for Rn in 2021 and 2022, respectively, and both variables were greater in the wetter year. The mean contributions of Qn to En were 79.76% and 83.91% in 2021 and 2022, respectively, indicating that the En was mostly used for Qn. Although the vapor pressure deficit (VPD), air temperature (Ta) and soil water content (SWC) were significantly correlated with Qn and Rn on an hourly time scale, they explained a small fraction of the variance in Qn on a daily time scale. The main driving factor was SWC between 40-200 cm on a monthly time scale for the Qn and Rn variations. Rn was little affected by meteorological and SWC factors on a daily scale. During the diurnal course, Qn and Rn initially both declined after sundown because of decreasing VPD and Ta, and Qn was significantly greater than Rn, whereas the two variables increased when VPD was nearly zero and Ta decreased, and Rn was greater than Qn. Discussion These results provided a new understanding of ecophysiological responses and adaptation of V. negundo plantations to increasing drought severity and duration under climate changes.
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Affiliation(s)
- Weiwei Fang
- Key Research Institute of Yellow Civilization and Sustainable Development and Collaborative Innovation Center of Henan Province, Henan University, Kaifeng, China
| | - Jianbo Liu
- Tianjin Key Laboratory of Water Resources and Environment, Tianjin Normal University, Tianjin, China
| | - Nan Lu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ruiping Li
- Key Research Institute of Yellow Civilization and Sustainable Development and Collaborative Innovation Center of Henan Province, Henan University, Kaifeng, China
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Nadal-Sala D, Medlyn BE, Ruehr NK, Barton CVM, Ellsworth DS, Gracia C, Tissue DT, Tjoelker MG, Sabaté S. Increasing aridity will not offset CO 2 fertilization in fast-growing eucalypts with access to deep soil water. GLOBAL CHANGE BIOLOGY 2021; 27:2970-2990. [PMID: 33694242 DOI: 10.1111/gcb.15590] [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: 12/03/2020] [Accepted: 03/07/2021] [Indexed: 06/12/2023]
Abstract
Rising atmospheric [CO2 ] (Ca ) generally enhances tree growth if nutrients are not limiting. However, reduced water availability and elevated evaporative demand may offset such fertilization. Trees with access to deep soil water may be able to mitigate such stresses and respond more positively to Ca . Here, we sought to evaluate how increased vapor pressure deficit and reduced precipitation are likely to modify the impact of elevated Ca (eCa ) on tree productivity in an Australian Eucalyptus saligna Sm. plantation with access to deep soil water. We parameterized a forest growth simulation model (GOTILWA+) using data from two field experiments on E. saligna: a 2-year whole-tree chamber experiment with factorial Ca (ambient =380, elevated =620 μmol mol-1 ) and watering treatments, and a 10-year stand-scale irrigation experiment. Model evaluation showed that GOTILWA+ can capture the responses of canopy C uptake to (1) rising vapor pressure deficit (D) under both Ca treatments; (2) alterations in tree water uptake from shallow and deep soil layers during soil dry-down; and (3) the impact of irrigation on tree growth. Simulations suggest that increasing Ca up to 700 μmol mol-1 alone would result in a 33% increase in annual gross primary production (GPP) and a 62% increase in biomass over 10 years. However, a combined 48% increase in D and a 20% reduction in precipitation would halve these values. Our simulations identify high D conditions as a key limiting factor for GPP. They also suggest that rising Ca will compensate for increasing aridity limitations in E. saligna trees with access to deep soil water under non-nutrient limiting conditions, thereby reducing the negative impacts of global warming upon this eucalypt species. Simulation models not accounting for water sources available to deep-rooting trees are likely to overestimate aridity impacts on forest productivity and C stocks.
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Affiliation(s)
- Daniel Nadal-Sala
- Ecology Section, Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona (UB), Barcelona, Spain
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Belinda E Medlyn
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
| | - Nadine K Ruehr
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
| | - Craig V M Barton
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
| | - David S Ellsworth
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
| | - Carles Gracia
- Ecology Section, Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona (UB), Barcelona, Spain
- CREAF (Center for Ecological Research and Forestry Applications, Cerdanyola del Vallès, Spain
| | - David T Tissue
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
| | - Mark G Tjoelker
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia
| | - Santi Sabaté
- Ecology Section, Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona (UB), Barcelona, Spain
- CREAF (Center for Ecological Research and Forestry Applications, Cerdanyola del Vallès, Spain
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Rumman R, Atkin OK, Bloomfield KJ, Eamus D. Variation in bulk-leaf 13 C discrimination, leaf traits and water-use efficiency-trait relationships along a continental-scale climate gradient in Australia. GLOBAL CHANGE BIOLOGY 2018; 24:1186-1200. [PMID: 28949085 DOI: 10.1111/gcb.13911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Accepted: 08/22/2017] [Indexed: 06/07/2023]
Abstract
Large spatial and temporal gradients in rainfall and temperature occur across Australia. This heterogeneity drives ecological differentiation in vegetation structure and ecophysiology. We examined multiple leaf-scale traits, including foliar 13 C isotope discrimination (Δ13 C), rates of photosynthesis and foliar N concentration and their relationships with multiple climate variables. Fifty-five species across 27 families were examined across eight sites spanning contrasting biomes. Key questions addressed include: (i) Does Δ13 C and intrinsic water-use efficiency (WUEi ) vary with climate at a continental scale? (ii) What are the seasonal and spatial patterns in Δ13 C/WUEi across biomes and species? (iii) To what extent does Δ13 C reflect variation in leaf structural, functional and nutrient traits across climate gradients? and (iv) Does the relative importance of assimilation and stomatal conductance in driving variation in Δ13 C differ across seasons? We found that MAP, temperature seasonality, isothermality and annual temperature range exerted independent effects on foliar Δ13 C/WUEi . Temperature-related variables exerted larger effects than rainfall-related variables. The relative importance of photosynthesis and stomatal conductance (gs ) in determining Δ13 C differed across seasons: Δ13 C was more strongly regulated by gs during the dry-season and by photosynthetic capacity during the wet-season. Δ13 C was most strongly correlated, inversely, with leaf mass area ratio among all leaf attributes considered. Leaf Nmass was significantly and positively correlated with MAP during dry- and wet-seasons and with moisture index (MI) during the wet-season but was not correlated with Δ13 C. Leaf Pmass showed significant positive relationship with MAP and Δ13 C only during the dry-season. For all leaf nutrient-related traits, the relationships obtained for Δ13 C with MAP or MI indicated that Δ13 C at the species level reliably reflects the water status at the site level. Temperature and water availability, not foliar nutrient content, are the principal factors influencing Δ13 C across Australia.
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Affiliation(s)
- Rizwana Rumman
- Terrestrial Ecohydrology Research Group, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia
| | - Owen K Atkin
- ARC Centre of Excellence in Plant Energy Biology, Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Keith J Bloomfield
- Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | - Derek Eamus
- Terrestrial Ecohydrology Research Group, School of Life Sciences, University of Technology Sydney, Sydney, NSW, Australia
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Gharun M, Possell M, Vervoort RW, Adams MA, Bell TL. Can a growth model be used to describe forest carbon and water balance after fuel reduction burning in temperate forests? THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 615:1000-1009. [PMID: 29751404 DOI: 10.1016/j.scitotenv.2017.09.315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 09/05/2017] [Accepted: 09/29/2017] [Indexed: 06/08/2023]
Abstract
Empirical evidence from Australia shows that fuel reduction burning significantly reduces the incidence and extent of unplanned fires. However, the integration of environmental values into fire management operations is not yet well-defined and requires further research and development. WAVES, a plant growth model that incorporates Soil-Vegetation-Atmosphere Transfer, was used to simulate the hydrological and ecological effects of three fuel management scenarios on a forest ecosystem. WAVES was applied using inputs from a set of forest plots for one year after three potential scenarios: (1) all litter removed, (2) all litter and 50% of the understorey removed, (3) all litter and understorey removed. Modelled outputs were compared with sites modelled with no-fuel reduction treatment (Unburnt). The key change between unburnt and fuel reduced forests was a significant increase in soil moisture after fire. Predictions of the recovery of aboveground carbon as plant biomass were driven by model structure and thus variability in available light and soil moisture at a local scale. Similarly, effects of fuel reduction burning on water processes were mainly due to changes in vegetation interception capacity (i.e. regrowth) and soil evaporation. Predicted effects of fuel reduction burning on total evapotranspiration (ET) - the major component of water balance - were marginal and not significant, even though a considerable proportion of ET had effectively been transferred from understorey to overstorey. In common with many plant growth models, outputs from WAVES are dictated by the assumption that overstorey trees continue to grow irrespective of their age or stage of maturity. Large areas of eucalypt forests and woodlands in SE Australia are well beyond their aggrading phase and are instead over-mature. The ability of these forests to rapidly respond to greater availability of water remains uncertain.
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Affiliation(s)
- Mana Gharun
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Bushfire and Natural Hazards Cooperative Research Centre, East Melbourne, VIC 3002, Australia.
| | - Malcolm Possell
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Bushfire and Natural Hazards Cooperative Research Centre, East Melbourne, VIC 3002, Australia
| | - R Willem Vervoort
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Mark A Adams
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Bushfire and Natural Hazards Cooperative Research Centre, East Melbourne, VIC 3002, Australia
| | - Tina L Bell
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia; Bushfire and Natural Hazards Cooperative Research Centre, East Melbourne, VIC 3002, Australia
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Fisher RA, Koven CD, Anderegg WRL, Christoffersen BO, Dietze MC, Farrior CE, Holm JA, Hurtt GC, Knox RG, Lawrence PJ, Lichstein JW, Longo M, Matheny AM, Medvigy D, Muller-Landau HC, Powell TL, Serbin SP, Sato H, Shuman JK, Smith B, Trugman AT, Viskari T, Verbeeck H, Weng E, Xu C, Xu X, Zhang T, Moorcroft PR. Vegetation demographics in Earth System Models: A review of progress and priorities. GLOBAL CHANGE BIOLOGY 2018; 24:35-54. [PMID: 28921829 DOI: 10.1111/gcb.13910] [Citation(s) in RCA: 183] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/12/2017] [Accepted: 08/17/2017] [Indexed: 05/24/2023]
Abstract
Numerous current efforts seek to improve the representation of ecosystem ecology and vegetation demographic processes within Earth System Models (ESMs). These developments are widely viewed as an important step in developing greater realism in predictions of future ecosystem states and fluxes. Increased realism, however, leads to increased model complexity, with new features raising a suite of ecological questions that require empirical constraints. Here, we review the developments that permit the representation of plant demographics in ESMs, and identify issues raised by these developments that highlight important gaps in ecological understanding. These issues inevitably translate into uncertainty in model projections but also allow models to be applied to new processes and questions concerning the dynamics of real-world ecosystems. We argue that stronger and more innovative connections to data, across the range of scales considered, are required to address these gaps in understanding. The development of first-generation land surface models as a unifying framework for ecophysiological understanding stimulated much research into plant physiological traits and gas exchange. Constraining predictions at ecologically relevant spatial and temporal scales will require a similar investment of effort and intensified inter-disciplinary communication.
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Affiliation(s)
- Rosie A Fisher
- National Center for Atmospheric Research, Boulder, CO, USA
| | | | | | | | - Michael C Dietze
- Department of Earth and Environment, Boston University, Boston, MA, USA
| | - Caroline E Farrior
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
| | | | - George C Hurtt
- Department of Geographical Sciences, University of Maryland, College Park, MD, USA
| | - Ryan G Knox
- Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | | | | - Marcos Longo
- Embrapa Agricultural Informatics, Campinas, Brazil
| | - Ashley M Matheny
- Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, USA
| | - David Medvigy
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | | | | | - Shawn P Serbin
- Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Hisashi Sato
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan
| | | | - Benjamin Smith
- Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden
| | - Anna T Trugman
- Program in Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, USA
| | - Toni Viskari
- Smithsonian Tropical Research Institute, Panamá, Panamá
| | - Hans Verbeeck
- Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
| | - Ensheng Weng
- Center for Climate Systems Research, Columbia University, New York, NY, USA
| | - Chonggang Xu
- Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Xiangtao Xu
- Department of Geosciences, Princeton University, Princeton, NJ, USA
| | - Tao Zhang
- Department of Biology, University of Florida, Gainesville, FL, USA
| | - Paul R Moorcroft
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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6
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Jia G, Liu Z, Chen L, Yu X. Distinguish water utilization strategies of trees growing on earth-rocky mountainous area with transpiration and water isotopes. Ecol Evol 2017; 7:10640-10651. [PMID: 29299245 PMCID: PMC5743539 DOI: 10.1002/ece3.3584] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 10/01/2017] [Accepted: 10/08/2017] [Indexed: 11/05/2022] Open
Abstract
Water stress is regarded as a global challenge to forests. Unlike other water-limited areas, the water use strategies of rocky mountainous forests, which play an important ecohydrological role, have not received sufficient attention. To prove our hypothesis that species adopt different water use strategies to avoid competition of limited water resources, we used site abiotic monitoring, sap flow and stable isotope method to study the biophysiological responses and water use preferences of two commonly distributed forest species, Pinus tabuliformis (Pt) and Quercus variabilis (Qv). The results showed that Pt transpired higher than Qv. Pt was also prone to adopt isohydric water use strategy as it demonstrated sensitive stomatal control over water loss through transpiration. Qv developed cavitation which was reflected by the dropping Ec in response to high vapor pressure deficit, concentrated peak sap flux density (Js), and enlarged hysteresis loop. Considering the average soil depth of 52.8 cm on the site, a common strategy shared by both species was the ability to tap water from deep soil layers (below 40 cm) when soil water was limited, and this contributed to the whole growing season transpiration. The contribution of surface layer water to plant water use increased and became the main water source for transpiration after rainfall. Qv was more efficient at using water from surface layer than Pt due to the developed surface root system when soil water content was not stressed. Our study proves that different water-using strategies of co-occurring species may be conducive to avoid competition of limited water resources to guarantee their survival. Knowledge of water stress-coping strategies of trees has implications for the understanding and prediction of vegetation composition in similar areas and can facilitate forest management criteria for plantations.
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Affiliation(s)
- Guodong Jia
- Key Laboratory of State Forestry Administration on Soil and Water ConservationBeijing Forestry UniversityBeijingChina
- Beijing Engineering Research Center of Soil and Water ConservationBeijing Forestry UniversityBeijingChina
- School of Soil and Water ConservationBeijing Forestry UniversityBeijingChina
| | - Ziqiang Liu
- School of Soil and Water ConservationBeijing Forestry UniversityBeijingChina
| | - Lixin Chen
- Key Laboratory of State Forestry Administration on Soil and Water ConservationBeijing Forestry UniversityBeijingChina
- Beijing Engineering Research Center of Soil and Water ConservationBeijing Forestry UniversityBeijingChina
- School of Soil and Water ConservationBeijing Forestry UniversityBeijingChina
| | - Xinxiao Yu
- Key Laboratory of State Forestry Administration on Soil and Water ConservationBeijing Forestry UniversityBeijingChina
- Beijing Engineering Research Center of Soil and Water ConservationBeijing Forestry UniversityBeijingChina
- School of Soil and Water ConservationBeijing Forestry UniversityBeijingChina
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Modelling Seasonal and Inter-annual Variations in Carbon and Water Fluxes in an Arid-Zone Acacia Savanna Woodland, 1981–2012. Ecosystems 2016. [DOI: 10.1007/s10021-015-9956-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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8
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Chen L, Zhang Z, Zeppel M, Liu C, Guo J, Zhu J, Zhang X, Zhang J, Zha T. Response of transpiration to rain pulses for two tree species in a semiarid plantation. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2014; 58:1569-81. [PMID: 24510059 DOI: 10.1007/s00484-013-0761-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Revised: 10/23/2013] [Accepted: 10/23/2013] [Indexed: 05/14/2023]
Abstract
Responses of transpiration (Ec) to rain pulses are presented for two semiarid tree species in a stand of Pinus tabulaeformis and Robinia pseudoacacia. Our objectives are to investigate (1) the environmental control over the stand transpiration after rainfall by analyzing the effect of vapor pressure deficit (VPD), soil water condition, and rainfall on the post-rainfall Ec development and recovery rate, and (2) the species responses to rain pulses and implications on vegetation coverage under a changing rainfall regime. Results showed that the sensitivity of canopy conductance (Gc) to VPD varied under different incident radiation and soil water conditions, and the two species exhibited the same hydraulic control (-dG c/dlnVPD to Gcref ratio) over transpiration. Strengthened physiological control and low sapwood area of the stand contributed to low Ec. VPD after rainfall significantly influenced the magnitude and time series of post-rainfall stand Ec. The fluctuation of post-rainfall VPD in comparison with the pre-rainfall influenced the Ec recovery. Further, the stand Ec was significantly related to monthly rainfall, but the recovery was independent of the rainfall event size. Ec enhanced with cumulative soil moisture change (ΔVWC) within each dry-wet cycle, yet still was limited in large rainfall months. The two species had different response patterns of post-rainfall Ec recovery. Ec recovery of P. tabulaeformis was influenced by the pre- and post-rainfall VPD differences and the duration of rainless interval. R. pseudoacacia showed a larger immediate post-rainfall Ec increase than P. tabulaeformis did. We, therefore, concluded that concentrated rainfall events do not trigger significant increase of transpiration unless large events penetrate the deep soil and the species differences of Ec in response to pulses of rain may shape the composition of semiarid woodlands under future rainfall regimes.
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Affiliation(s)
- Lixin Chen
- Key Laboratory Soil and Water Conservation and Desertification Combating, Ministry of Education, College of Soil and Water Conservation, Beijing Forestry University, Qinghua East Road 35#, Haidian District, Beijing, 100083, People's Republic of China,
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9
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Contrasting Hydraulic Strategies during Dry Soil Conditions in Quercus rubra and Acer rubrum in a Sandy Site in Michigan. FORESTS 2013. [DOI: 10.3390/f4041106] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Skelton RP, West AG, Dawson TE, Leonard JM. External heat-pulse method allows comparative sapflow measurements in diverse functional types in a Mediterranean-type shrubland in South Africa. FUNCTIONAL PLANT BIOLOGY : FPB 2013; 40:1076-1087. [PMID: 32481175 DOI: 10.1071/fp12379] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 03/23/2013] [Indexed: 06/11/2023]
Abstract
There has been limited application of sapflow technology to small-stemmed species and across co-existing functional types, restricting its use in diverse floras such as the Mediterranean-type shrubland in South Africa. Our main objective was to test whether sapflow may provide an alternative to traditional gas-exchange measurements, which would permit comparative evaluation of transpiration at a previously unattained temporal resolution. We tested miniature external heat ratio method (HRM) sapflow gauges on three co-occurring functional types with contrasting stem or culm anatomies and examined the relationship between sapflow and shoot- and leaf-level water loss in both a controlled and field environment. Our sapflow gauges captured dynamic patterns of transpiration in both settings for all three functional types. In a controlled environment the relationship between sapflow and transpiration was linear in all three species with r2 values ranging from 0.78 for Cannomois congesta Mast. (Restionaceae) to 0.96 for Protea repens (L.) L. (Proteaceae) and Erica monsoniana L.f. (Ericaceae). In the field, r2 values were lower, ranging from 0.59 for C. congesta to 0.74 for P. repens. We discuss the efficacy and potential of this methodology to cast light on patterns of community ecology in functionally diverse shrublands by capturing continuous variation in transpiration.
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Affiliation(s)
- Robert P Skelton
- University of Cape Town - Botany, HW Pearson Building Upper Campus, Cape Town, Western Cape 7700, South Africa
| | - Adam G West
- University of Cape Town - Botany, HW Pearson Building Upper Campus, Cape Town, Western Cape 7700, South Africa
| | - Todd E Dawson
- University of California Berkeley - Dept of Integrative Biology, 3060 Valley Life Sciences Building, Berkeley, CA 94720, USA
| | - Jenny M Leonard
- University of Cape Town - Botany, HW Pearson Building Upper Campus, Cape Town, Western Cape 7700, South Africa
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Eamus D, Boulain N, Cleverly J, Breshears DD. Global change-type drought-induced tree mortality: vapor pressure deficit is more important than temperature per se in causing decline in tree health. Ecol Evol 2013; 3:2711-29. [PMID: 24567834 PMCID: PMC3930053 DOI: 10.1002/ece3.664] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 06/03/2013] [Accepted: 06/04/2013] [Indexed: 11/30/2022] Open
Abstract
Drought-induced tree mortality is occurring across all forested continents and is expected to increase worldwide during the coming century. Regional-scale forest die-off influences terrestrial albedo, carbon and water budgets, and land-surface energy partitioning. Although increased temperatures during drought are widely identified as a critical contributor to exacerbated tree mortality associated with "global-change-type drought", corresponding changes in vapor pressure deficit (D) have rarely been considered explicitly and have not been disaggregated from that of temperature per se. Here, we apply a detailed mechanistic soil-plant-atmosphere model to examine the impacts of drought, increased air temperature (+2°C or +5°C), and increased vapor pressure deficit (D; +1 kPa or +2.5 kPa), singly and in combination, on net primary productivity (NPP) and transpiration and forest responses, especially soil moisture content, leaf water potential, and stomatal conductance. We show that increased D exerts a larger detrimental effect on transpiration and NPP, than increased temperature alone, with or without the imposition of a 3-month drought. Combined with drought, the effect of increased D on NPP was substantially larger than that of drought plus increased temperature. Thus, the number of days when NPP was zero across the 2-year simulation was 13 or 14 days in the control and increased temperature scenarios, but increased to approximately 200 days when D was increased. Drought alone increased the number of days of zero NPP to 88, but drought plus increased temperature did not increase the number of days. In contrast, drought and increased D resulted in the number of days when NPP = 0 increasing to 235 (+1 kPa) or 304 days (+2.5 kPa). We conclude that correct identification of the causes of global change-type mortality events requires explicit consideration of the influence of D as well as its interaction with drought and temperature. This study disaggregates the influence of temperature and vapour pressure deficit on net primary productivity of an Australian woodland and their interactions with drought as potential causal agents in recent widespread forest mortality.
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Affiliation(s)
- Derek Eamus
- Plant Biology and Climate Change Research Cluster, University of Technology SydneyBroadway, PO Box 123, Sydney, New South Wales, 2007, Australia
- National Centre for Groundwater Research and Training, University of Technology SydneyBroadway, PO Box 123, Sydney, New South Wales, 2007, Australia
| | - Nicolas Boulain
- Plant Biology and Climate Change Research Cluster, University of Technology SydneyBroadway, PO Box 123, Sydney, New South Wales, 2007, Australia
| | - James Cleverly
- Plant Biology and Climate Change Research Cluster, University of Technology SydneyBroadway, PO Box 123, Sydney, New South Wales, 2007, Australia
| | - David D Breshears
- School of Natural Resources and the Environment, University of ArizonaTucson, Arizona, 85721
- Department of Ecology and Evolutionary Biology, University of ArizonaTucson, Arizona, 85721
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12
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Wright JK, Williams M, Starr G, McGee J, Mitchell RJ. Measured and modelled leaf and stand-scale productivity across a soil moisture gradient and a severe drought. PLANT, CELL & ENVIRONMENT 2013; 36:467-483. [PMID: 22882366 DOI: 10.1111/j.1365-3040.2012.02590.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Environmental controls on carbon dynamics operate at a range of interacting scales from the leaf to landscape. The key questions of this study addressed the influence of water and nitrogen (N) availability on Pinus palustris (Mill.) physiology and primary productivity across leaf and canopy scales, linking the soil-plant-atmosphere (SPA) model to leaf and stand-scale flux and leaf trait/canopy data. We present previously unreported ecophysiological parameters (e.g. V(cmax) and J(max)) for P. palustris and the first modelled estimates of its annual gross primary productivity (GPP) across xeric and mesic sites and under extreme drought. Annual mesic site P. palustris GPP was ∼23% greater than at the xeric site. However, at the leaf level, xeric trees had higher net photosynthetic rates, and water and light use efficiency. At the canopy scale, GPP was limited by light interception (canopy level), but co-limited by nitrogen and water at the leaf level. Contrary to expectations, the impacts of an intense growing season drought were greater at the mesic site. Modelling indicated a 10% greater decrease in mesic GPP compared with the xeric site. Xeric P. palustris trees exhibited drought-tolerant behaviour that contrasted with mesic trees' drought-avoidance behaviour.
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Affiliation(s)
- J K Wright
- School of Geosciences, University of Edinburgh, Edinburgh, UK.
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Vandegehuchte MW, Steppe K. Improving sap flux density measurements by correctly determining thermal diffusivity, differentiating between bound and unbound water. TREE PHYSIOLOGY 2012; 32:930-942. [PMID: 22543477 DOI: 10.1093/treephys/tps034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Several heat-based sap flow methods, such as the heat field deformation method and the heat ratio method, include the thermal diffusivity D of the sapwood as a crucial parameter. Despite its importance, little attention has been paid to determine D in a plant physiological context. Therefore, D is mostly set as a constant, calculated during zero flow conditions or from a method of mixtures, taking into account wood density and moisture content. In this latter method, however, the meaning of the moisture content is misinterpreted, making it theoretically incorrect for D calculations in sapwood. A correction to this method, which includes the correct application of the moisture content, is proposed. This correction was tested for European and American beech and Eucalyptus caliginosa Blakely & McKie. Depending on the dry wood density and moisture content, the original approach over- or underestimates D and, hence, sap flux density by 10% and more.
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Affiliation(s)
- Maurits W Vandegehuchte
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium.
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Fine Root Biomass and Its Relationship to Evapotranspiration in Woody and Grassy Vegetation Covers for Ecological Restoration of Waste Storage and Mining Landscapes. Ecosystems 2011. [DOI: 10.1007/s10021-011-9496-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Zeppel MJB, Lewis JD, Medlyn B, Barton CVM, Duursma RA, Eamus D, Adams MA, Phillips N, Ellsworth DS, Forster MA, Tissue DT. Interactive effects of elevated CO2 and drought on nocturnal water fluxes in Eucalyptus saligna. TREE PHYSIOLOGY 2011; 31:932-944. [PMID: 21616926 DOI: 10.1093/treephys/tpr024] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Nocturnal water flux has been observed in trees under a variety of environmental conditions and can be a significant contributor to diel canopy water flux. Elevated atmospheric CO(2) (elevated [CO(2)]) can have an important effect on day-time plant water fluxes, but it is not known whether it also affects nocturnal water fluxes. We examined the effects of elevated [CO(2)] on nocturnal water flux of field-grown Eucalyptus saligna trees using sap flux through the tree stem expressed on a sapwood area (J(s)) and leaf area (E(t)) basis. After 19 months growth under well-watered conditions, drought was imposed by withholding water for 5 months in the summer, ending with a rain event that restored soil moisture. Reductions in J(s) and E(t) were observed during the severe drought period in the dry treatment under elevated [CO(2)], but not during moderate- and post-drought periods. Elevated [CO(2)] affected night-time sap flux density which included the stem recharge period, called 'total night flux' (19:00 to 05:00, J(s,r)), but not during the post-recharge period, which primarily consisted of canopy transpiration (23:00 to 05:00, J(s,c)). Elevated [CO(2)] wet (EW) trees exhibited higher J(s,r) than ambient [CO(2)] wet trees (AW) indicating greater water flux in elevated [CO(2)] under well-watered conditions. However, under drought conditions, elevated [CO(2)] dry (ED) trees exhibited significantly lower J(s,r) than ambient [CO(2)] dry trees (AD), indicating less water flux during stem recharge under elevated [CO(2)]. J(s,c) did not differ between ambient and elevated [CO(2)]. Vapour pressure deficit (D) was clearly the major influence on night-time sap flux. D was positively correlated with J(s,r) and had its greatest impact on J(s,r) at high D in ambient [CO(2)]. Our results suggest that elevated [CO(2)] may reduce night-time water flux in E. saligna when soil water content is low and D is high. While elevated [CO(2)] affected J(s,r), it did not affect day-time water flux in wet soil, suggesting that the responses of J(s,r) to environmental factors cannot be directly inferred from day-time patterns. Changes in J(s,r) are likely to influence pre-dawn leaf water potential, and plant responses to water stress. Nocturnal fluxes are clearly important for predicting effects of climate change on forest physiology and hydrology.
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Affiliation(s)
- Melanie J B Zeppel
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
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Duursma RA, Barton CVM, Eamus D, Medlyn BE, Ellsworth DS, Forster MA, Tissue DT, Linder S, McMurtrie RE. Rooting depth explains [CO2] x drought interaction in Eucalyptus saligna. TREE PHYSIOLOGY 2011; 31:922-31. [PMID: 21571724 DOI: 10.1093/treephys/tpr030] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Elevated atmospheric [CO(2)] (eC(a)) often decreases stomatal conductance, which may delay the start of drought, as well as alleviate the effect of dry soil on plant water use and carbon uptake. We studied the interaction between drought and eC(a) in a whole-tree chamber experiment with Eucalyptus saligna. Trees were grown for 18 months in their C(a) treatments before a 4-month dry-down. Trees grown in eC(a) were smaller than those grown in ambient C(a) (aC(a)) due to an early growth setback that was maintained throughout the duration of the experiment. Pre-dawn leaf water potentials were not different between C(a) treatments, but were lower in the drought treatment than the irrigated control. Counter to expectations, the drought treatment caused a larger reduction in canopy-average transpiration rates for trees in the eC(a) treatment compared with aC(a). Total tree transpiration over the dry-down was positively correlated with the decrease in soil water storage, measured in the top 1.5 m, over the drying cycle; however, we could not close the water budget especially for the larger trees, suggesting soil water uptake below 1.5 m depth. Using neutron probe soil water measurements, we estimated fractional water uptake to a depth of 4.5 m and found that larger trees were able to extract more water from deep soil layers. These results highlight the interaction between rooting depth and response of tree water use to drought. The responses of tree water use to eC(a) involve interactions between tree size, root distribution and soil moisture availability that may override the expected direct effects of eC(a). It is essential that these interactions be considered when interpreting experimental results.
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Affiliation(s)
- Remko A Duursma
- Hawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia.
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Zeppel M, Tissue D, Taylor D, Macinnis-Ng C, Eamus D. Rates of nocturnal transpiration in two evergreen temperate woodland species with differing water-use strategies. TREE PHYSIOLOGY 2010; 30:988-1000. [PMID: 20566582 DOI: 10.1093/treephys/tpq053] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Nocturnal fluxes may be a significant factor in the annual water budget of forested ecosystems. Here, we assessed sap flow in two co-occurring evergreen species (Eucalyptus parramattensis and Angophora bakeri) in a temperate woodland for 2 years in order to quantify the magnitude of seasonal nocturnal sap flow (E(n)) under different environmental conditions. The two species showed different diurnal water relations, demonstrated by different diurnal curves of stomatal conductance, sap flow and leaf water potential. The relative influence of several microclimatic variables, including wind speed (U), vapour pressure deficit (D), the product of U and D (UD) and soil moisture content, were quantified. D exerted the strongest influence on E(n) (r² = 0.59-0.86), soil moisture content influenced E(n) when D was constant, but U and UD did not generally influence E(n). In both species, cuticular conductance (G(c)) was a small proportion of total leaf conductance (G(s)) and was not a major pathway for E(n). We found that E(n) was primarily a function of transpiration from the canopy rather than refilling of stem storage, with canopy transpiration accounting for 50-70% of nocturnal flows. Mean E(n) was 6-8% of the 24-h flux across seasons (spring, summer and winter), but was up to 19% of the 24-h flux on some days in both species. Despite different daytime strategies in water use of the two species, both species demonstrated low night-time water loss, suggesting similar controls on water loss at night. In order to account for the impact of E(n) on pre-dawn leaf water potential arising from the influence of disequilibria between root zone and leaf water potential, we also developed a simple model to more accurately predict soil water potential (ψ(s)).
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Affiliation(s)
- Melanie Zeppel
- Plant Functional Biology and Climate Change Cluster and Department of Environmental Sciences, University of Technology, Sydney, NSW 2007, Australia
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Phillips NG, Lewis JD, Logan BA, Tissue DT. Inter- and intra-specific variation in nocturnal water transport in Eucalyptus. TREE PHYSIOLOGY 2010; 30:586-96. [PMID: 20332372 DOI: 10.1093/treephys/tpq009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
To identify environmental and biological drivers of nocturnal vapour exchange, we quantified intra-annual, intra- and inter-specific variation in nocturnal water transport among ecologically diverse Eucalyptus species. We measured sap flux (J(s)) and leaf physiology (leaf surface conductance (g(s)), transpiration (E) and water potential (Psi(l))) in three to five trees of eight species. Over 1 year, nocturnal J(s) (J(s,n)) contributed 5-7% of total J(s) in the eight species. The principal environmental driver of J(s,n) was the product of atmospheric vapour pressure deficit (D) and wind speed (U). Selected observations suggest that trees with higher proportions of young foliage may exhibit greater J(s,n) and nocturnal g(s) (g(s,n)). Compared with other tree taxa, nocturnal water use in Eucalyptus was relatively low and more variable within than between species, suggesting that (i) Eucalyptus as a group exerts strong nocturnal stomatal control over water loss and (ii) prediction of nocturnal flux in Eucalyptus may depend on simultaneous knowledge of intra-specific tree traits and nocturnal atmospheric conditions.
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Affiliation(s)
- Nathan G Phillips
- Centre for Plants and the Environment, University of Western Sydney, Richmond, NSW 2753, Australia.
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