Seasonal variations in the isotopic composition of leaf and stem water from an arid region of Southeast Asia

Abstract

in the isotopic composition of leaf and stem water from an arid region of Southeast Asia. Hydrol. Sci. J. 55(5), 844-848.Abstract Stable isotopes are powerful research tools in environmental sciences and their use in ecosystem research is increasing. Stable isotope measurements allow the study of evapotranspiration fluxes, soil evaporation and leaf transpiration phenomena. Soil water and leaf water are the sources of the evapotranspiration that transfers large quantities of water from land to the atmosphere; as a result the isotopic composition of water left in the leaves is modified towards enrichment. Evaporation also changes the isotopic composition of water bodies creating a natural isotopic signal. The isotopic identity of soil water affects the oxygen isotopic signature of leaf and stem water. In this paper we present the isotopic data of bulk leaf water, showing the enrichment in isotopic value of oxygen due to evapotranspiration from leaves in conjunction with the isotopic signal of rainwater and other environmental factors such as humidity and temperature. Results suggest that the variation in the values of d 18 O of Eucalyptus citriodora, Dalbergia sissoo, Melia azedarach and Pinus roxburghii is due to the seasonal changes in the d 18 O of the source water for plants, i. e. rain. It is further observed that leaf water d 18 O values are depleted during the months of July, August and September. This occurs due to the following reasons: (a) the sampling areas receive about 50% of the average annual rain during these months, and (b) rainfalls during these months are isotopically depleted compared with winter rains.

Validation and application of a cryogenic vacuum extraction system for soil and plant water extraction for isotope analysis

“…In plant ecology stable water isotopes provide a powerful method for determining seasonal changes in plant water uptake (Corbin et al, 2005;Eggemeyer et al, 2009;Butt et al, 2010;Liu et al, 2010), intra-and interspecific resource competition of plants (Williams and Ehleringer, 2000;Yang et al, 2011), partitioning evaporation and transpiration (Wang and Yakir, 2000;Phillips and Gregg, 2003;Rothfuss et al, 2010Rothfuss et al, , 2012, partitioning of water resources between plants ( Stratton et al, 2000;Rossatto et al, 2012), and community wateruse patterns or the zones of root activity in soils (Ehleringer and Dawson, 1992;Thorburn and Ehleringer, 1995;Dawson and Pate, 1996;Liu et al, 2011). Plant water uptake is considered as a non-fractionating process (Wershaw et al, 1966;Dawson and Ehleringer, 1991;Walker and Richardson, 1991;Thorburn et al, 1993;Dawson and Ehleringer, 1993) for non-saline conditions (Lin and Sternberg, 1993), implying that the isotopic signature of the source water remains the same during soil water uptake and water transport through plants (White et al, 1985).…”

Leaf water δD and δ¹⁸O enrichment process and influencing factors in spring maize (Zea mays) grown in the middle reaches of Heihe River Basin

“…速率, T则决定着平衡分馏效应 Butt et al, 2010)。Pendall等 ( (Roden & Ehleringer, 1999)或者 模型研究 (Lai et al, 2008;Welp et al, 2008;Song et al, 2015)…”

“…O 和δD (δ l,b ) (Farquhar & Cernusak, 2005)。然而, δ l,e 只 能依赖模型模拟获得, 仅δ l,b 可以直接观测或模型模 拟 (Craig & Gordon, 1965;Dongmann et al, 1974;Farquhar & Cernusak, 2005) Farquhar & Cernusak, 2005)。目前, 基于控制实验 Roden & Ehleringer, 1999;Ripullone et al, 2008)或野外试验获得的δ l,b 实测数 据量较少, 通常仅作为模型验证数据 (Cernusak et al, 2002;Welp et al, 2008;Xiao et al, 2012), 缺乏 基于野外试验条件的δ l,b 控制机制的相关研究。 目前, Farquhar et al, 1993;Pendall et al, 2005)。植物叶片水Δ l,b 主要受植 物自身生理调控过程和环境条件变化影响 (Craig & Gordon, 1965;Dongmann et al, 1974;Farquhar et al, 1993;Farquhar & Cernusak, 2005) Roden & Ehleringer, 1999;Yakir & Sternberg, 2000; www.plant-ecology.com 2006; Welp et al, 2008;Kahmen et al, 2009;Lee et al, 2009)。其中影响Δ l,b 的生物因素主要是气孔导 度。气孔导度影响蒸腾速率和动力学分馏效应, 而 蒸腾速率影响叶片水周转速率 (Lee et al, 2007)。大 Farquhar et al, 2007;Butt et al, 2010) & Ehleringer, 1999;Helliker & Griffiths, 2007;Lai et al, 2006Lai et al, , 2008Welp et al, 2008;Butt et al, 2010)。 稳定同位素红外光谱技术(IRIS)的发展克 服了大气水汽冷阱/同位素质谱仪技术的缺点, 实 现了大气水汽δ v 的原位连续观测 (Lee et al, 2005;Wen et al, , 2012Huang & Wen, 2014), 促进了 植物叶片水δ 18 O和δD富集过程和机制方面的研究 (Yakir & Sternberg, 2000;Lee et al, 2005;Xiao et al, 2012)。 黑河流域位于中国西北干旱区, 属于典型温带 大陆性干旱气候。黑河中游地区是中国规模最大的 玉米(Zea mays)制种基地, 农业灌溉消耗了全流域 80%-90%的水资源 <...>…”

What do Plants Leave after Summer on the Ground? The Effect of Afforested Plants in Arid Environments

“…The isotope signature of the absorbed water is not modified by plant uptake until the water reaches the photosynthetic tissues. Here, the leaf tissues will become enriched by the escape of lighter isotopes [38]. Althought the roots do not modify the soil water during uptake, the isotope signature of xylem water is affected by mixing processes when different water sources are used by the same plant.…”