Sub‐annual variability in historical water source use by Mediterranean riparian trees
Sub‐annual variability in historical water source use by Mediterranean riparian trees
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DOI：
10.1002/eco.1730
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发表时间：
2016-10
期刊：
影响因子：
2.6
通讯作者：
C. Sargeant;M. Singer
中科院分区：
文献类型：
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作者：
C. Sargeant;M. Singer
树木生根区内的季节性水供应可能是个体树木生长和整体森林健康的重要决定因素，特别是在易受水分胁迫的地中海气候区河岸走廊。在这里，我们提出了一种结合树突同位素和同位素建模的新方法，用于确定法国东南部罗讷河沿岸共生物种黑杨和白蜡树在连续 10 个生长季节（2000 年至 2010 年）内水源利用的变化。我们对树木年轮内的纤维素微切片进行了高分辨率 δ18O 分析，并使用生化分馏模型反算了生长时可用源水的 δ18O 特征。我们通过与渗流区和潜水区水域的 δ18O、降水和水流进行比较，将这些模式与推断的季节性水文分区联系起来。浅根水曲柳显示出更大的亚年源水变化，以及更大的同位素富集，反映了对降水衍生的渗流水分的利用。其早材主要由冬季降雨（δ18O 贫化）形成，而晚材则由生长季降水（δ18O 富集）形成。在杨树中，次年的水源用水量相对枯竭，表明使用了潜流水和区域地下水。从 2007 年起，这两个物种的水源吸收模式趋于一致，这是由于胡杨进入潜水的减少所致。这些结果表明，可以回顾性地确定水源利用的季节性变化，这种方法对于预测气候驱动的水文循环变化的未来后果可能很重要。 © 2016 作者。生态水文学由 John Wiley & Sons, Ltd 出版。
The seasonal availability of water within a tree's rooting zone may be an important determinant for individual tree growth and overall forest health, particularly in riparian corridors of Mediterranean climate zones that are vulnerable to water stress. Here, we present a new method that combines dendro‐isotopes and isotope modelling for determining how water source use varies over 10 consecutive growing seasons (2000–2010) for co‐occurring species Populus nigra and Fraxinus excelsior, along the Rhône River, south‐eastern France. We conducted highly resolved δ18O analysis of cellulose micro‐slices within tree‐rings and back‐calculated the δ18O signature of source water available at the time of growth using a biochemical fractionation model. We related these patterns to inferred seasonal hydrological partitioning through comparison with δ18O of waters from the vadose and phreatic zones, precipitation and streamflow. The shallowly rooted Fraxinus displayed greater sub‐annual source water variability, as well as greater isotopic enrichment, reflecting use of precipitation‐derived vadose moisture. Its earlywood was formed mainly from winter rainfall (δ18O depleted) whilst the latewood was composed from growing season precipitation (δ18O enriched). In Populus, the sub‐annual source water use was relatively depleted, suggesting use of hyporheic water and regional groundwater. From 2007, both species converged in their pattern of water source uptake which was attributed to a decline in phreatic water access for Populus. These results demonstrate that the seasonal variability in source water use can be identified retrospectively, a method which may prove important for anticipating the future consequences of climate‐driven changes to the hydrological cycle. © 2016 The Authors. Ecohydrology published by John Wiley & Sons, Ltd.