Insights into plant water uptake from xylem-water isotope measurements in two tropical catchments with contrasting moisture conditions
Insights into plant water uptake from xylem-water isotope measurements in two tropical catchments with contrasting moisture conditions
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DOI：
10.1002/hyp.10841
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发表时间：
2016-08-30
影响因子：
3.2
通讯作者：
Chun, Kwok P.
中科院分区：
文献类型：
--
作者：
Evaristo, Jaivime;McDonnell, Jeffrey J.;Chun, Kwok P.
长期以来，人们一直认为树木蒸腾的水分来自于地下水的补给和径流。然而，最近的调查使用双重水稳定同位素显示出明显的生态水文分离之间的树木蒸腾水和溪流水。在这里，我们提出的证据，这种生态水文分离在两个热带环境中的波多黎各降水季节性相对较低，降水与初级生产力呈正相关。测定了30株桃花心木（Swietenia spp.）树木采样在两个时期的对比水分状况。我们的研究结果表明，蒸散水和地下水补给/径流水之间的分离可能与水文输入和初级生产力的时间定相有关，更多的是驱动蒸发同位素富集土壤基质内残留土壤水的基本过程。在研究区的地下水和溪流的蒸发签名的缺乏表明，这些水平衡组件有一个水源，被迅速运送到更深的地下存储相比，树木使用的沃茨。贝叶斯混合模型用于分区源水木质部水的比例表明，地下水的贡献是大于谷底，河岸树木比脊顶树木。地下水的贡献也更大，在干旱的网站比在mesic-hydroxy网站。这些模型的结果（1）强调了一个简单的线性混合模型的效用，实施贝叶斯推理框架，在量化源水的贡献与对比地形特征的网站，和（2）突出明智的判断，应在解释混合模型的结果，进口特别是在调查地下水利用模式的植被从区域到全球范围。版权所有（c）2016约翰威利父子有限公司
Water transpired by trees has long been assumed to be sourced from the same subsurface water stocks that contribute to groundwater recharge and streamflow. However, recent investigations using dual water stable isotopes have shown an apparent ecohydrological separation between tree-transpired water and stream water. Here we present evidence for such ecohydrological separation in two tropical environments in Puerto Rico where precipitation seasonality is relatively low and where precipitation is positively correlated with primary productivity. We determined the stable isotope signature of xylem water of 30 mahogany (Swietenia spp.) trees sampled during two periods with contrasting moisture status. Our results suggest that the separation between transpiration water and groundwater recharge/streamflow water might be related less to the temporal phasing of hydrologic inputs and primary productivity, and more to the fundamental processes that drive evaporative isotopic enrichment of residual soil water within the soil matrix. The lack of an evaporative signature of both groundwater and streams in the study area suggests that these water balance components have a water source that is transported quickly to deeper subsurface storage compared to waters that trees use. A Bayesian mixing model used to partition source water proportions of xylem water showed that groundwater contribution was greater for valley-bottom, riparian trees than for ridge-top trees. Groundwater contribution was also greater at the xeric site than at the mesic-hydric site. These model results (1) underline the utility of a simple linear mixing model, implemented in a Bayesian inference framework, in quantifying source water contributions at sites with contrasting physiographic characteristics, and (2) highlight the informed judgement that should be made in interpreting mixing model results, of import particularly in surveying groundwater use patterns by vegetation from regional to global scales. Copyright (c) 2016 John Wiley & Sons, Ltd.