Sap flow and plant water sources for typical vegetation in a subtropical humid karst area of southwest China

Water sources of woody plants in semi-arid or seasonally dry areas of China are little known. This study investigated the differences in water sources for plants due to seasonal changes (wet/transitional and dry seasons) in semi-arid areas. Stable isotope techniques were applied to determine plant water sources in different seasons. The results show that there is generally a switch of water sources from shallow depths in the rainy season to lower depths in the dry season. This study highlights how seasonal changes in climate in semi-arid China affect plant water uptake and suggests that further study with replicated systematic experiments are needed to better understand the responses in water use patterns to changes in environmental conditions in drought-prone areas.

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Potential effects of cryogenic extraction biases on inferences drawn from xylem water deuterium isotope ratios: case studies using stable isotopes to infer plant water sources

10.5194/hess-2020-683 ◽

2021 ◽

Author(s):

Scott T. Allen ◽

James W. Kirchner

Keyword(s):

Water Source ◽

Water Sources ◽

Plant Water ◽

Dual Isotope ◽

Cryogenic Vacuum ◽

Potential Impact ◽

End Members ◽

Plant Water Source ◽

Plant Water Sources ◽

The Impact

Abstract. Recent studies have demonstrated that plant and soilwater extraction techniques can introduce biases and uncertainties in stable isotope analyses. Here we show how recently documented δ2H biases resulting from cryogenic vacuum distillation of water from xylem tissues may have influenced the conclusions of five previous studies, including ours, that have used δ2H to infer plant water sources. Cryogenic extraction biases that reduce xylem water δ2H will also introduce an artifactual evaporation signal in dual-isotope (δ2H vs. δ18O) analyses. Calculations that estimate the composition of the source precipitation of xylem waters by compensating for their apparent evaporation will amplify the bias in δ2H, and also introduce new biases in the δ18O of the inferred pre-evaporation source precipitation. Cryogenic extraction biases may substantially alter plant water source attributions if the spread in δ2H among the potential end members is relatively narrow. By contrast, if the spread in δ2H among the potential end members is relatively wide, the impact of cryogenic extraction biases will be less pronounced, and thus suggestions that these biases universally invalidate inferences drawn from plant water δ2H are unwarranted. Nonetheless, until reliable correction factors for cryogenic extraction biases become available, their potential impact should be considered in studies using xylem water isotopes.

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An Assessment of Woody Plant Water Source Studies from across the Globe: What Do We Know after 30 Years of Research and Where Do We Go from Here?

Hydrology ◽

10.3390/hydrology6020040 ◽

2019 ◽

Vol 6 (2) ◽

pp. 40 ◽

Cited By ~ 3

Author(s):

Md. Shawkat I. Sohel ◽

Mohammed Abdus Salam ◽

John Herbohn

Keyword(s):

Woody Plant ◽

Global Climate ◽

Research Priorities ◽

Water Source ◽

The United States ◽

Agroforestry Systems ◽

Water Sources ◽

Future Research ◽

Plant Water ◽

Plant Water Sources

In the face of global climate change, water availability and its impact on forest productivity is becoming an increasingly important issue. It is therefore necessary to evaluate the advancement of research in this field and to set new research priorities. A systematic literature review was performed to evaluate the spatiotemporal dynamics of global research on woody plant water sources and to determine a future research agenda. Most of the reviewed studies were from the United States, followed by China and Australia. The research indicates that there is a clear variation in woody plant water sources in forests due to season, climate, leaf phenology, and method of measurement. Much of the research focus has been on identifying plant water sources using a single isotope approach. Much less focus has been given to the nexus between water source and tree size, tree growth, drought, water use efficiency, agroforestry systems, groundwater interactions, and many other topics. Therefore, a new set of research priorities has been proposed that will address these gaps under different vegetation and climate conditions. Once these issues are resolved, the research can inform forest process studies in new ways.

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Plant water sources in the cold semiarid ecosystem of the upper Kherlen River catchment in Mongolia: A stable isotope approach

Journal of Hydrology ◽

10.1016/j.jhydrol.2006.07.020 ◽

2007 ◽

Vol 333 (1) ◽

pp. 109-117 ◽

Cited By ~ 62

Author(s):

Sheng-Gong Li ◽

Hugo Romero-Saltos ◽

Maki Tsujimura ◽

Atsuko Sugimoto ◽

Lisa Sasaki ◽

...

Keyword(s):

Stable Isotope ◽

Water Sources ◽

Plant Water ◽

River Catchment ◽

Semiarid Ecosystem ◽

Plant Water Sources

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Unexplained hydrogen isotope offsets complicate the identification and quantification of tree water sources in a riparian forest

Hydrology and Earth System Sciences ◽

10.5194/hess-23-2129-2019 ◽

2019 ◽

Vol 23 (4) ◽

pp. 2129-2146 ◽

Cited By ~ 23

Author(s):

Adrià Barbeta ◽

Sam P. Jones ◽

Laura Clavé ◽

Lisa Wingate ◽

Teresa E. Gimeno ◽

...

Keyword(s):

Soil Water ◽

Riparian Forest ◽

Stream Water ◽

Isotopic Fractionation ◽

Growing Season ◽

Water Sources ◽

Source Water ◽

Plant Water ◽

Deep Soil ◽

Plant Water Sources

Abstract. We investigated plant water sources of an emblematic refugial population of Fagus sylvatica (L.) in the Ciron river gorges in south-western France using stable water isotopes. It is generally assumed that no isotopic fractionation occurs during root water uptake, so that the isotopic composition of xylem water effectively reflects that of source water. However, this assumption has been called into question by recent studies that found that, at least at some dates during the growing season, plant water did not reflect any mixture of the potential water sources. In this context, highly resolved datasets covering a range of environmental conditions could shed light on possible plant–soil fractionation processes responsible for this phenomenon. In this study, the hydrogen (δ2H) and oxygen (δ18O) isotope compositions of all potential tree water sources and xylem water were measured fortnightly over an entire growing season. Using a Bayesian isotope mixing model (MixSIAR), we then quantified the relative contribution of water sources for F. sylvatica and Quercus robur (L.) trees. Based on δ18O data alone, both species used a mix of top and deep soil water over the season, with Q. robur using deeper soil water than F. sylvatica. The contribution of stream water appeared to be marginal despite the proximity of the trees to the stream, as already reported for other riparian forests. Xylem water δ18O could always be interpreted as a mixture of deep and shallow soil waters, but the δ2H of xylem water was often more depleted than the considered water sources. We argue that an isotopic fractionation in the unsaturated zone and/or within the plant tissues could underlie this unexpected relatively depleted δ2H of xylem water, as already observed in halophytic and xerophytic species. By means of a sensitivity analysis, we found that the estimation of plant water sources using mixing models was strongly affected by this δ2H depletion. A better understanding of what causes this isotopic separation between xylem and source water is urgently needed.

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The combined effects of a long‐term experimental drought and an extreme drought on the use of plant‐water sources in a Mediterranean forest

Global Change Biology ◽

10.1111/gcb.12785 ◽

2014 ◽

Vol 21 (3) ◽

pp. 1213-1225 ◽

Cited By ~ 120

Author(s):

Adrià Barbeta ◽

Monica Mejía‐Chang ◽

Romà Ogaya ◽

Jordi Voltas ◽

Todd E. Dawson ◽

...

Keyword(s):

Water Sources ◽

Extreme Drought ◽

Mediterranean Forest ◽

Plant Water ◽

Combined Effects ◽

Plant Water Sources

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Stable Oxygen and Deuterium Isotope Techniques to Identify Plant Water Sources

Journal of Water Resource and Protection ◽

10.4236/jwarp.2014.615137 ◽

2014 ◽

Vol 06 (15) ◽

pp. 1501-1508 ◽

Cited By ~ 4

Author(s):

M. Edwin ◽

S. Lubis ◽

I. Yani Harahap ◽

Taufiq C. Hidayat ◽

Y. Pangaribuan ◽

...

Keyword(s):

Water Sources ◽

Plant Water ◽

Isotope Techniques ◽

Stable Oxygen ◽

Plant Water Sources

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Unexplained hydrogen isotope offsets complicate the identification and quantification of tree water sources in a riparian forest

10.5194/hess-2018-631 ◽

2019 ◽

Cited By ~ 1

Author(s):

Adrià Barbeta ◽

Sam P. Jones ◽

Laura Clavé ◽

Lisa Wingate ◽

Teresa E. Gimeno ◽

...

Keyword(s):

Soil Water ◽

Riparian Forest ◽

Stream Water ◽

Isotopic Fractionation ◽

Growing Season ◽

Water Sources ◽

Source Water ◽

Plant Water ◽

Deep Soil ◽

Plant Water Sources

Abstract. We investigated plant water sources of an emblematic refugial population of Fagus sylvatica (L.) in the Ciron river gorges in South-Western France using stable water isotopes. It is generally assumed that no isotopic fractionation occurs during root water uptake, so that the isotopic composition of xylem water effectively reflects that of source water. However, this assumption has been called into question by recent studies that found that, at least at some dates during the growing season, plant water did not reflect any mixture of the potential water sources. In this context, highly resolved datasets covering a range of environmental conditions could shed light on possible plant-soil fractionation processes responsible for this phenomenon. In this study, the hydrogen (δ2H) and oxygen (δ18O) isotope compositions of all potential tree water sources and xylem water were measured fortnightly over an entire growing season. Using a Bayesian isotope mixing model (MixSIAR), we then quantified the relative contribution of water sources for F. sylvatica and Quercus robur (L.) trees. Based on δ18O data alone, both species used a mix of top and deep soil water over the season, with Q. robur using soil water relatively deeper than F. sylvatica. The contribution of stream water appeared to be marginal despite the proximity of the trees to the stream, as already reported for other riparian forests. Xylem water δ18O could always be interpreted as a mixture of deep and shallow soil waters, but the δ2H of xylem water was often more depleted than the considered water sources. We argue that an isotopic fractionation in the unsaturated zone and/or within the plant tissues could underlie this unexpected relatively depleted δ2H of xylem water, as already observed in halophytic and xerophytic species. By means of a sensitivity analysis, we found that the estimation of plant water sources using mixing models was largely affected by this δ2H depletion. A better understanding of what causes this isotopic separation between xylem and source water is urgently needed.

Download Full-text