Can oxygen stable isotopes be used to track precipitation moisture source in vascular plant-dominated peatlands?
Can oxygen stable isotopes be used to track precipitation moisture source in vascular plant-dominated peatlands?
复制标题
DOI：
10.1016/j.epsl.2015.08.015
复制
发表时间：
2015-11-15
影响因子：
5.3
通讯作者：
Gallego-Sala, Angela V.
中科院分区：
文献类型：
--
作者：
Amesbury, Matthew J.;Charman, Dan J.;Gallego-Sala, Angela V.
降水同位素组成的变化是由分馏过程决定的，分馏过程发生在与蒸发和冷凝相关的温度和湿度相关的相变过程中。因此，氧稳定同位素比值经常被用作各种代用档案的古气候数据的来源，这些代用档案整合了随时间变化的信号。在全营养泥炭地，用于纤维素合成的水源水仅来自降水，其应用大多限于北方半球泥炭藓为主的沼泽，在南半球或以维管植物为主的泥炭地很少。新西兰（NZ）提供了一个理想的地点进行实证研究，在维管泥炭地的氧同位素分馏，因为可以很容易地进行单一分类群的分析，特别是使用保存的根基质的restionaceous线灯心草（假眼鲷属）。形成了遍布全国的深层全新世泥炭沉积。此外，大梯度的平均同位素组成的降水横跨新西兰，主要是由不同的气候模式的相对影响所造成的。在这里，我们测试是否三角洲O-18的Empodisma α-纤维素在新西兰的雨养restiad泥炭地可以提供一种方法，开发古气候记录过去的降水三角洲O-18。地表植物、水和降水样本是在空间（6个地点跨越10度以上纬度）和时间（一年内每月测量）梯度上采集的。根相关的水的同位素组成，最有可能的水源植物生长，和降水在两个dataset. Back轨迹模拟降雨前几天的降水水分源采样显示出明确的季节性的时间数据，反映在根相关的水的联系。源水和植物纤维素之间的联系不太清楚，虽然机械建模预测的平均纤维素值在公布的误差范围内的两个数据集。改进的生理理解和三角洲O-18在restiad泥炭地的建模，应使使用这种方法作为一个新的来源的古气候数据，以重建过去的大气环流的变化。(C)2015作者由爱思唯尔公司出版
Variations in the isotopic composition of precipitation are determined by fractionation processes which occur during temperature- and humidity-dependent phase changes associated with evaporation and condensation. Oxygen stable isotope ratios have therefore been frequently used as a source of palaeoclimate data from a variety of proxy archives, which integrate this signal over time. Applications from ombrotrophic peatlands, where the source water used in cellulose synthesis is derived solely from precipitation, have been mostly limited to Northern Hemisphere Sphagnum-dominated bogs, with few in the Southern Hemisphere or in peatlands dominated by vascular plants. New Zealand (NZ) provides an ideal location to undertake empirical research into oxygen isotope fractionation in vascular peatlands because single taxon analysis can be easily carried out, in particular using the preserved root matrix of the restionaceous wire rush (Empodisma spp.) that forms deep Holocene peat deposits throughout the country. Furthermore, large gradients are observed in the mean isotopic composition of precipitation across NZ, caused primarily by the relative influence of different climate modes. Here, we test whether delta O-18 of Empodisma alpha-cellulose from ombrotrophic restiad peatlands in NZ can provide a methodology for developing palaeoclimate records of past precipitation delta O-18. Surface plant, water and precipitation samples were taken over spatial (six sites spanning >10 degrees latitude) and temporal (monthly measurements over one year) gradients. A link between the isotopic composition of root-associated water, the most likely source water for plant growth, and precipitation in both datasets was found. Back-trajectory modelling of precipitation moisture source for rain days prior to sampling showed clear seasonality in the temporal data that was reflected in root-associated water. The link between source water and plant cellulose was less clear, although mechanistic modelling predicted mean cellulose values within published error margins for both datasets. Improved physiological understanding and modelling of delta O-18 in restiad peatlands should enable use of this approach as a new source of palaeoclimate data to reconstruct changes in past atmospheric circulation. (C) 2015 The Authors. Published by Elsevier B.V.