1
|
Gui J, Li Z, Du F, Liu X, Xue J. Vegetation restoration strategies based on plant water use patterns. Sci Total Environ 2024; 924:171611. [PMID: 38462013 DOI: 10.1016/j.scitotenv.2024.171611] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 03/06/2024] [Accepted: 03/07/2024] [Indexed: 03/12/2024]
Abstract
The study on the water source of plants in alpine mountainous is of great significance to optimize the allocation and management of water resources, and can also provide important reference for ecological restoration and protection. However, the controls of water sources for different plants in alpine mountainous region remain poorly understood. Based on the advantages of stable isotope tracer and Bayesian (MixSIAR) model, the water source of plants in Qilian Mountains was quantitatively analyzed. The results showed that the water sources of plants in Qilian Mountain mainly included two parts: direct source and indirect source. The direct source is soil water, which provides most of the water that plants need. The highest contribution of soil water to shrubs was 80 %, followed by trees (73 %) and herbs (72 %). It is worth mentioning that trees mainly use deeper soil water (below 60 cm), shrubs mainly use surface and intermediate soil water (0-60 cm), and herbs mainly use surface soil water (0-40 cm). What is more noteworthy is that indirect sources, such as precipitation, glacier and snow meltwater, and groundwater, are also water sources that cannot be ignored for plant growth in study area. Shrubs and Herbs use more soil water in the range of 40-60 cm, which leads to the possibility of water competition between these two planting types. Therefore, attention should be paid to this phenomenon in the process of vegetation restoration and water resources management. Especially when planting or restoring artificial plants, it is necessary to consider the water use strategy of the two plants to avoid unnecessary water competition and water waste. This is of great significance for ecological stability and sustainable utilization of water resources in the study region.
Collapse
Affiliation(s)
- Juan Gui
- Observation and Research Station of Eco-Hydrology and National Park by Stable Isotope Tracing in Qilian Mountains/Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zongxing Li
- Observation and Research Station of Eco-Hydrology and National Park by Stable Isotope Tracing in Qilian Mountains/Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, China.
| | - Fa Du
- Observation and Research Station of Eco-Hydrology and National Park by Stable Isotope Tracing in Qilian Mountains/Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoyin Liu
- Observation and Research Station of Eco-Hydrology and National Park by Stable Isotope Tracing in Qilian Mountains/Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Jian Xue
- Observation and Research Station of Eco-Hydrology and National Park by Stable Isotope Tracing in Qilian Mountains/Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| |
Collapse
|
2
|
Dubbert M, Couvreur V, Kübert A, Werner C. Plant water uptake modelling: added value of cross-disciplinary approaches. Plant Biol (Stuttg) 2023; 25:32-42. [PMID: 36245305 DOI: 10.1111/plb.13478] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
In recent years, research interest in plant water uptake strategies has rapidly increased in many disciplines, such as hydrology, plant ecology and ecophysiology. Quantitative modelling approaches to estimate plant water uptake and spatiotemporal dynamics have significantly advanced through different disciplines across scales. Despite this progress, major limitations, for example, predicting plant water uptake under drought or drought impact at large scales, remain. These are less attributed to limitations in process understanding, but rather to a lack of implementation of cross-disciplinary insights into plant water uptake model structure. The main goal of this review is to highlight how the four dominant model approaches, that is, Feddes approach, hydrodynamic approach, optimality and statistical approaches, can be and have been used to create interdisciplinary hybrid models enabling a holistic system understanding that, among other things, embeds plant water uptake plasticity into a broader conceptual view of soil-plant feedbacks of water, nutrient and carbon cycling, or reflects observed drought responses of plant-soil feedbacks and their dynamics under, that is, drought. Specifically, we provide examples of how integration of Bayesian and hydrodynamic approaches might overcome challenges in interpreting plant water uptake related to different travel and residence times of different plant water sources or trade-offs between root system optimization to forage for water and nutrients during different seasons and phenological stages.
Collapse
Affiliation(s)
- M Dubbert
- Isotope Biogeochemistry and Gasfluxes, Leibniz Institute of Agricultural Landscape Research (ZALF), Müncheberg, Germany
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
| | - V Couvreur
- Earth and Life Institute, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - A Kübert
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
- Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, Helsinki, Finland
| | - C Werner
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
| |
Collapse
|
3
|
Xiangyang S, Genxu W, Juying S, Shouqin S, Zhaoyong H, Chunlin S, Shan L. Contrasting water sources used by a coniferous forest in the high-altitude, southeastern Tibetan Plateau. Sci Total Environ 2022; 849:157913. [PMID: 35948127 DOI: 10.1016/j.scitotenv.2022.157913] [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: 05/04/2022] [Revised: 08/04/2022] [Accepted: 08/04/2022] [Indexed: 06/15/2023]
Abstract
Forest trees use various water sources to adapt to environmental conditions in mountainous regions. However, water resources variances along elevational gradients are not clearly understood. This limits the assessment of the ecosystem responses to climate change. In this study, stable oxygen and hydrogen isotopes were used to investigate the spatiotemporal patterns of water sources for Faber's fir in a humid high-altitude elevational gradient (ranging between 2800 m.a.s.l. and 3700 m.a.s.l.) on the southeastern Tibetan Plateau. The results indicated that 27 ± 8.3 % of the xylem water was from previous winter snowmelt between May and June. In contrast, almost all xylem water was from current summer precipitation between July and October. Faber's fir at the lower elevation (2800 m.a.s.l.) primarily relied on water derived from winter precipitation during May and June. Yet, trees located near the tree line (3700 m.a.s.l.) were mostly dependent on current precipitation over the entire growing season. However, when statistically analyzing data from all seven different elevation gradients in this study, the contribution of winter precipitation to xylem water was not elevation dependent. Precipitation contributed to a large proportion (59.86 % ± 33.43 %) of xylem water between May and October. Meanwhile, no linear contribution ratio of precipitation to trees was identified in this high-altitude elevational gradient. The replenishment of soil water and the soil water storage determine the spatiotemporal patterns of water sources. Climate change has the possibility of reducing winter precipitation at high altitudes on the Tibetan Plateau. Thus, tree water use at different altitude gradients will play varied roles in influencing the evolution of forest composition under ongoing climate change.
Collapse
Affiliation(s)
- Sun Xiangyang
- State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China.
| | - Wang Genxu
- State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China; Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China.
| | - Sun Juying
- State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China; Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
| | - Sun Shouqin
- State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Hu Zhaoyong
- State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Song Chunlin
- State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Lin Shan
- State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China
| |
Collapse
|
4
|
Finkenbiner CE, Good SP, Renée Brooks J, Allen ST, Sasidharan S. The extent to which soil hydraulics can explain ecohydrological separation. Nat Commun 2022; 13:6492. [PMID: 36310234 PMCID: PMC9618555 DOI: 10.1038/s41467-022-34215-7] [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] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 10/11/2022] [Indexed: 12/25/2022] Open
Abstract
Field measurements of hydrologic tracers indicate varying magnitudes of geochemical separation between subsurface pore waters. The potential for conventional soil physics alone to explain isotopic differences between preferential flow and tightly-bound water remains unclear. Here, we explore physical drivers of isotopic separations using 650 different model configurations of soil, climate, and mobile/immobile soil-water domain characteristics, without confounding fractionation or plant uptake effects. We find simulations with coarser soils and less precipitation led to reduced separation between pore spaces and drainage. Amplified separations are found with larger immobile domains and, to a lesser extent, higher mobile-immobile transfer rates. Nonetheless, isotopic separations remained small (<4‰ for δ2H) across simulations, indicating that contrasting transport dynamics generate limited geochemical differences. Therefore, conventional soil physics alone are unlikely to explain large ecohydrological separations observed elsewhere, and further efforts aimed at reducing methodological artifacts, refining understanding of fractionation processes, and investigating new physiochemical mechanisms are needed.
Collapse
Affiliation(s)
- Catherine E. Finkenbiner
- grid.4391.f0000 0001 2112 1969Department of Biological & Ecological Engineering, Oregon State University, Corvallis, OR USA ,grid.4391.f0000 0001 2112 1969Water Resources Graduate Program, Oregon State University, Corvallis, OR USA
| | - Stephen P. Good
- grid.4391.f0000 0001 2112 1969Department of Biological & Ecological Engineering, Oregon State University, Corvallis, OR USA ,grid.4391.f0000 0001 2112 1969Water Resources Graduate Program, Oregon State University, Corvallis, OR USA
| | - J. Renée Brooks
- grid.418698.a0000 0001 2146 2763Pacific Ecological Systems Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Corvallis, OR USA ,grid.4391.f0000 0001 2112 1969Department of Forest Ecosystems & Society, Oregon State University, Corvallis, OR USA
| | - Scott T. Allen
- grid.266818.30000 0004 1936 914XDepartment of Natural Resources & Environmental Science, University of Nevada, Reno, NV USA
| | - Salini Sasidharan
- grid.4391.f0000 0001 2112 1969Department of Biological & Ecological Engineering, Oregon State University, Corvallis, OR USA
| |
Collapse
|
5
|
Haberstroh S, Lobo‐do‐Vale R, Caldeira MC, Dubbert M, Cuntz M, Werner C. Plant invasion modifies isohydricity in Mediterranean tree species. Funct Ecol 2022. [DOI: 10.1111/1365-2435.14126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Simon Haberstroh
- Ecosystem Physiology, Faculty of Environment and Natural Resources University Freiburg 79110 Freiburg Germany
- Forest Research Centre School of Agriculture University of Lisbon, 1349‐017 Lisbon Portugal
| | - Raquel Lobo‐do‐Vale
- Forest Research Centre School of Agriculture University of Lisbon, 1349‐017 Lisbon Portugal
| | - Maria C. Caldeira
- Forest Research Centre School of Agriculture University of Lisbon, 1349‐017 Lisbon Portugal
| | - Maren Dubbert
- Ecosystem Physiology, Faculty of Environment and Natural Resources University Freiburg 79110 Freiburg Germany
- Leibniz Centre for Agricultural Landscape Research (ZALF), Isotope Biogeochemistry and Gas Fluxes, 15374 Müncheberg Germany
| | - Matthias Cuntz
- Université de Lorraine AgroParisTech, INRAE, UMR Silva, 54000 Nancy France
| | - Christiane Werner
- Ecosystem Physiology, Faculty of Environment and Natural Resources University Freiburg 79110 Freiburg Germany
| |
Collapse
|
6
|
Haberstroh S, Caldeira MC, Lobo-do-Vale R, Martins JI, Moemken J, Pinto JG, Werner C. Nonlinear plant-plant interactions modulate impact of extreme drought and recovery on a Mediterranean ecosystem. New Phytol 2021; 231:1784-1797. [PMID: 34076289 DOI: 10.1111/nph.17522] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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: 04/14/2021] [Accepted: 05/20/2021] [Indexed: 06/12/2023]
Abstract
Interaction effects of different stressors, such as extreme drought and plant invasion, can have detrimental effects on ecosystem functioning and recovery after drought. With ongoing climate change and increasing plant invasion, there is an urgent need to predict the short- and long-term interaction impacts of these stressors on ecosystems. We established a combined precipitation exclusion and shrub invasion (Cistus ladanifer) experiment in a Mediterranean cork oak (Quercus suber) ecosystem with four treatments: (1) Q. suber control; (2) Q. suber with rain exclusion; (3) Q. suber invaded by shrubs; and (4) Q. suber with rain exclusion and shrub invasion. As key parameter, we continuously measured ecosystem water fluxes. In an average precipitation year, the interaction effects of both stressors were neutral. However, the combination of imposed drought and shrub invasion led to amplifying interaction effects during an extreme drought by strongly reducing tree transpiration. Contrarily, the imposed drought reduced the competitiveness of the shrubs in the following recovery period, which buffered the negative effects of shrub invasion on Q. suber. Our results demonstrate the highly dynamic and nonlinear effects of interacting stressors on ecosystems and urges for further investigations on biotic interactions in a context of climate change pressures.
Collapse
Affiliation(s)
- Simon Haberstroh
- Ecosystem Physiology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, 79110, Germany
- Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, 1349-017, Portugal
| | - Maria C Caldeira
- Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, 1349-017, Portugal
| | - Raquel Lobo-do-Vale
- Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, 1349-017, Portugal
| | - Joana I Martins
- Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, 1349-017, Portugal
| | - Julia Moemken
- Institute for Meteorology and Climate Research (IMK-TRO), Karlsruhe Institute of Technology (KIT), Karlsruhe, 76131, Germany
| | - Joaquim G Pinto
- Institute for Meteorology and Climate Research (IMK-TRO), Karlsruhe Institute of Technology (KIT), Karlsruhe, 76131, Germany
| | - Christiane Werner
- Ecosystem Physiology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, 79110, Germany
| |
Collapse
|
7
|
Xiang W, Si B, Li M, Li H, Lu Y, Zhao M, Feng H. Stable isotopes of deep soil water retain long-term evaporation loss on China's Loess Plateau. Sci Total Environ 2021; 784:147153. [PMID: 34088070 DOI: 10.1016/j.scitotenv.2021.147153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/08/2021] [Accepted: 04/11/2021] [Indexed: 06/12/2023]
Abstract
Evaporation from the land surface enriches heavy isotope ratios (2H/1H and 18O/16 O) in shallow soils, and downward water movement will carry the fractionation signal to deep soils. However, how to acquire the evaporation from water stable isotopes in deep soils remains untested. Here, we measured water stable isotope composition in the deep soils (2-10 m) across 20 sites on China's Loess Plateau. Our results show that the line-conditioned excess (lc-excess) in deep soils of these sites was invariable with depth at each site, but ranged between -14.0‰ and - 4.1‰ among these sites, indicating differing degree of enrichment in heavy water isotopes between sites. Moreover, the mean lc-excess in deep soils water was significantly correlated to mean annual precipitation (R2 = 0.57), potential evapotranspiration (R2 = 0.25), and the Budyko dryness (R2 = 0.68), indicating that deep soil water lc-excess reflects land surface climate conditions. Furthermore, the deep soils correspond to a timescale of approximately 100 years at one site and more than 27 years at the remaining sites. These results together indicate that stable isotopes of deep soil water retained long-term land surface evaporation effects. Further, by implementing the steady-state isotope mass balance model into the lc-excess framework, we derived a new method to estimate evaporation loss fraction (f). Our f estimates at these sites varied between 5% and 15%, which may represent the lower bound of the actual evaporation to precipitation ratio. Nevertheless, our work suggests that in these and the other similar regions, deep soil is a novel archive for long-term soil evaporation loss, and f may be estimated through a snapshot field campaign of stable isotope measurements.
Collapse
Affiliation(s)
- Wei Xiang
- College of Resources and Environmental Engineering, Ludong University, Yantai, China; Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Bingcheng Si
- College of Resources and Environmental Engineering, Ludong University, Yantai, China; Department of Soil Science, University of Saskatchewan, Saskatoon SK S7N 5A8, Canada; Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi Province 712100, China.
| | - Min Li
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Han Li
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Yanwei Lu
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Minghua Zhao
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Hao Feng
- Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| |
Collapse
|
8
|
Ding Y, Nie Y, Chen H, Wang K, Querejeta JI. Water uptake depth is coordinated with leaf water potential, water-use efficiency and drought vulnerability in karst vegetation. New Phytol 2021; 229:1339-1353. [PMID: 32989748 DOI: 10.1111/nph.16971] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [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: 02/23/2020] [Revised: 09/10/2020] [Accepted: 09/14/2020] [Indexed: 06/11/2023]
Abstract
Root access to bedrock water storage or groundwater is an important trait allowing plant survival in seasonally dry environments. However, the degree of coordination between water uptake depth, leaf-level water-use efficiency (WUEi) and water potential in drought-prone plant communities is not well understood. We conducted a 135-d rainfall exclusion experiment in a subtropical karst ecosystem with thin skeletal soils to evaluate the responses of 11 co-occurring woody species of contrasting life forms and leaf habits to a severe drought during the wet growing season. Marked differences in xylem water isotopic composition during drought revealed distinct ecohydrological niche separation among species. The contrasting behaviour of leaf water potential in coexisting species during drought was largely explained by differences in root access to deeper, temporally stable water sources. Smaller-diameter species with shallower water uptake, more negative water potentials and lower WUEi showed extensive drought-induced canopy defoliation and/or mortality. By contrast, larger-diameter species with deeper water uptake, higher leaf-level WUEi and more isohydric behaviour survived drought with only moderate canopy defoliation. Severe water limitation imposes strong environmental filtering and/or selective pressures resulting in tight coordination between tree diameter, water uptake depth, iso/anisohydric behaviour, WUEi and drought vulnerability in karst plant communities.
Collapse
Affiliation(s)
- Yali Ding
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang, Guangxi, 547100, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yunpeng Nie
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang, Guangxi, 547100, China
| | - Hongsong Chen
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang, Guangxi, 547100, China
| | - Kelin Wang
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang, Guangxi, 547100, China
| | - José I Querejeta
- Soil and Water Conservation Department, Centro de Edafología y Biología Aplicada del Segura-Consejo Superior de Investigaciones Científicas (CEBAS-CSIC), Campus Universitario de Espinardo, Murcia, E30100, Spain
| |
Collapse
|
9
|
Chen Y, Helliker BR, Tang X, Li F, Zhou Y, Song X. Stem water cryogenic extraction biases estimation in deuterium isotope composition of plant source water. Proc Natl Acad Sci U S A 2020; 117:33345-50. [PMID: 33318208 DOI: 10.1073/pnas.2014422117] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hydrogen isotope ratio of water cryogenically extracted from plant stem samples (δ2Hstem_CVD) is routinely used to aid isotope applications that span hydrological, ecological, and paleoclimatological research. However, an increasing number of studies have shown that a key assumption of these applications-that δ2Hstem_CVD is equal to the δ2H of plant source water (δ2Hsource)-is not necessarily met in plants from various habitats. To examine this assumption, we purposedly designed an experimental system to allow independent measurements of δ2Hstem_CVD, δ2Hsource, and δ2H of water transported in xylem conduits (δ2Hxylem) under controlled conditions. Our measurements performed on nine woody plant species from diverse habitats revealed a consistent and significant depletion in δ2Hstem_CVD compared with both δ2Hsource and δ2Hxylem Meanwhile, no significant discrepancy was observed between δ2Hsource and δ2Hxylem in any of the plants investigated. These results cast significant doubt on the long-standing view that deuterium fractionation occurs during root water uptake and, alternatively, suggest that measurement bias inherent in the cryogenic extraction method is the root cause of δ2Hstem_CVD depletion. We used a rehydration experiment to show that the stem water cryogenic extraction error could originate from a dynamic exchange between organically bound deuterium and liquid water during water extraction. In light of our finding, we suggest caution when partitioning plant water sources and reconstructing past climates using hydrogen isotopes, and carefully propose that the paradigm-shifting phenomenon of ecohydrological separation ("two water worlds") is underpinned by an extraction artifact.
Collapse
|
10
|
Abstract
The ecohydrological-separation (ES) hypothesis is that the water used for plant transpiration and the water used for streams and groundwater recharge comes from distinct subsurface compartmentalized pools. The ES hypothesis was first proposed in a study conducted in the Mediterranean climate region, based on the stable isotope method in 2010. To date, the ES hypothesis has proven to be widespread around the world. The ES hypothesis is a new understanding of the soil water movement process, which is different from the assumption that only one soil reservoir in the traditional hydrology. It is helpful to clear the water sources of plants and establish a new model of the ecohydrological process. However, the theoretical basis and mechanism of the ES hypothesis are still unclear. Therefore, we analyzed the characteristics of ES phenomenon in different climatic regions, summarized the research methods used for the ES hypothesis, concluded the definitions of tightly bound water and mobile water, discussed the mechanism of isotopic differences of different reservoirs and their impacts on ES evaluation and pointed out the existing problems of the ES hypothesis. Future research should focus on the following three aspects: (a) detailed analysis of ES phenomenon characteristics of different plant species in different climatic regions; (b) further understanding of the ES phenomenon mechanism; (c) improvement of the experimental methods.
Collapse
|
11
|
Ripullone F, Camarero JJ, Colangelo M, Voltas J. Variation in the access to deep soil water pools explains tree-to-tree differences in drought-triggered dieback of Mediterranean oaks. Tree Physiol 2020; 40:591-604. [PMID: 32159804 DOI: 10.1093/treephys/tpaa026] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [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: 10/31/2019] [Accepted: 03/01/2020] [Indexed: 06/10/2023]
Abstract
Individual differences in the access to deep soil water pools may explain the differential damage among coexisting, conspecific trees as a consequence of drought-induced dieback. We addressed this issue by comparing the responses to a severe drought of three Mediterranean oak species with different drought tolerance, Quercus pubescens L. and Quercus frainetto Ten., mainly thriving at xeric and mesic sites, respectively, and Quercus cerris L., which dominates at intermediate sites. For each species, we compared coexisting declining (D) and non-declining (ND) trees. The stable isotope composition (δ2H, δ18O) of xylem and soil water was used to infer a differential use of soil water sources. We also measured tree size and radial growth to quantify the long-term divergence of wood production between D and ND trees and non-structural carbohydrates (NSCs) in sapwood to evaluate if D trees presented lower NSC values. The ND trees had access to deeper soil water than D trees except in Q. frainetto, as indicated by significantly more depleted xylem water values. However, a strong δ2H offset between soil and xylem water isotopes observed in peak summer could suggest that both tree types were not physiologically active under extreme drought conditions. Alternative processes causing deuterium fractionation, however, could not be ruled out. Tree height and recent (last 15-25 years) growth rates in all species studied were lower in D than in ND trees by 22 and 44%, respectively. Lastly, there was not a consistent pattern of NSC sapwood concentration; in Q. pubescens, it was higher in ND trees while in Q. frainetto, the D trees were the ones exhibiting the higher NSC concentration. We conclude that the vulnerability to drought among conspecific Mediterranean oaks depends on the differential access to deep soil water pools, which may be related to differences in rooting depth, tree size and growth rate.
Collapse
Affiliation(s)
- Francesco Ripullone
- School of Agricultural, Forest, Food and Environmental Sciences, University of Basilicata, Viale dell'Ateneo Lucano 10, Potenza I-85100, Italy
| | - J Julio Camarero
- Instituto Pirenaico de Ecología (IPE-CSIC), Avda Montañana 1005, Zaragoza E-50059, Spain
| | - Michele Colangelo
- School of Agricultural, Forest, Food and Environmental Sciences, University of Basilicata, Viale dell'Ateneo Lucano 10, Potenza I-85100, Italy
- Instituto Pirenaico de Ecología (IPE-CSIC), Avda Montañana 1005, Zaragoza E-50059, Spain
| | - Jordi Voltas
- Joint Research Unit CTFC-AGROTECNIO, Av. Alcalde Rovira Roure 191, Lleida 25198, Spain
- Department of Crop and Forest Sciences, University of Lleida, Av. Alcalde Rovira Roure 191, Lleida 25198, Spain
| |
Collapse
|