Hydrogen and oxygen isotope ratios of tree ring cellulose for field-grown riparian trees
Hydrogen and oxygen isotope ratios of tree ring cellulose for field-grown riparian trees
复制标题
田间河岸树木年轮纤维素的氢氧同位素比
DOI：
10.1007/s004420000349
复制
发表时间：
2000
期刊：
影响因子：
2.7
通讯作者：
J. Ehleringer
中科院分区：
文献类型：
--
作者：
J. Roden;J. Ehleringer
摘要在不同水源水同位素组成和湿度的野外点，从小直径河岸带树木中获得了2年以上的树轮纤维素的同位素组成。 这些地点位于犹他州（凉爽和低湿度）、俄勒冈州（凉爽和高湿度）和亚利桑那州（温暖和低湿度），水源水同位素比值分别为-125/-15‰（δD/δ 18 O）、-48/-6‰和-67/-7‰。每月的环境测量包括温度和湿度沿着与大气水蒸气，流，茎，叶水的同位素比的测量。小型河岸树木只利用溪流水（茎和溪流水的δD和δ 18 O没有差异），但大气水蒸气和叶水的δ值在月间变化很大。不同地点之间的环境温度和湿度条件的差异导致叶水蒸发富集的实质性差异。这些水分差异导致树木年轮纤维素δD和δ 18 O值的差异，表明树木年轮记录了湿度信息。这些环境和同位素的测量被用来测试一个机械模型的因素，有助于在树轮纤维素δD和δ 18 O值。该模型进行了测试，在两个部分：（a）叶水模型，利用环境信息来预测叶水蒸发富集和（B）模型描述生化分馏事件和同位素交换与介质水。该模型充分占叶水和树轮纤维素的实地观察，表明控制实验的模型参数化是强大的，即使在不受控制的和可变的现场条件下。
Abstract The isotopic composition of tree ring cellulose was obtained over a 2-year period from small-diameter riparian-zone trees at field sites that differed in source water isotopic composition and humidity. The sites were located in Utah (cool and low humidity), Oregon (cool and high humidity), and Arizona (warm and low humidity) with source water isotope ratio values of –125/–15‰ (δD/δ18O), –48/–6‰, and –67/–7‰, respectively. Monthly environmental measurements included temperature and humidity along with measurements of the isotope ratios in atmospheric water vapor, stream, stem, and leaf water. Small riparian trees used only stream water (both δD and δ18O of stem and stream water did not differ), but δ values of both atmospheric water vapor and leaf water varied substantially between months. Differences in ambient temperature and humidity conditions between sites contributed to substantial differences in leaf water evaporative enrichment. These leaf water differences resulted in differences in the δD and δ18O values of tree ring cellulose, indicating that humidity information was recorded in the annual rings of trees. These environmental and isotopic measurements were used to test a mechanistic model of the factors contributing to δD and δ18O values in tree ring cellulose. The model was tested in two parts: (a) a leaf water model using environmental information to predict leaf water evaporative enrichment and (b) a model describing biochemical fractionation events and isotopic exchange with medium water. The models adequately accounted for field observations of both leaf water and tree ring cellulose, indicating that the model parameterization from controlled experiments was robust even under uncontrolled and variable field conditions.