Assessing environmental and physiological controls over water relations in a Scots pine (Pinus sylvestris L.) stand through analyses of stable isotope composition of water and organic matter
Assessing environmental and physiological controls over water relations in a Scots pine (Pinus sylvestris L.) stand through analyses of stable isotope composition of water and organic matter
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DOI：
10.1111/j.1365-3040.2006.01609.x
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发表时间：
2007-01-01
影响因子：
7.3
通讯作者：
Gessler, Arthur
中科院分区：
文献类型：
--
作者：
Brandes, Elke;Wenninger, Jochen;Gessler, Arthur
本文研究了气象、土壤和生理因素对苏格兰松水分关系的影响，主要表现在吸收水分的来源、木质部运输以及新同化有机质的碳同位素辨别（δ C-13）和氧同位素富集（δ O-18）。在1年多的时间里，我们每两周量化潜在水源和木质部水分的δ H-2和δ O-18，以及树枝和树干韧皮部有机质的δ C-13和δ O-18，并将这些值与连续测量或模拟的气象参数、土壤含水量、林分蒸腾（ST）和冠层气孔导度（G(s)）联系起来。在生长季节，木质部水分的δ O-18和δ H-2与深度为2 ~ 20 cm的土壤水分基本相当。水分在管胞中停留的时间较长，使木质部和土壤水分的同位素信号在冬季不耦合。韧皮部有机质中的δ O-18直接指示了近期全年的环境状况，而δ C-13则不直接指示。δ O-18可以用一个模型来描述，该模型包括与叶片与大气之间的水分交换、有机质的产生以及蒸腾的影响相关的O-18分馏。韧皮部δ C-13被认为同时受到G(s)和光合有效辐射（PAR）的影响（PAR是光合能力的代表）。我们认为，同位素特征可以作为一种有效的工具(1)表征源水和木质部水分的季节动态，(2)评估环境对苏格兰松蒸腾和G(s)的影响，从而有助于了解和预测气候变化对树木和森林生态系统的潜在影响。
This study investigated the influence of meteorological, pedospheric and physiological factors on the water relations of Scots pine, as characterized by the origin of water taken up, by xylem transport as well as by carbon isotope discrimination (Delta C-13) and oxygen isotope enrichment (Delta O-18) of newly assimilated organic matter. For more than 1 year, we quantified delta H-2 and delta O-18 of potential water sources and xylem water as well as Delta C-13 and Delta O-18 in twig and trunk phloem organic matter biweekly, and related these values to continuously measured or modelled meteorological parameters, soil water content, stand transpiration (ST) and canopy stomatal conductance (G(s)). During the growing season, delta O-18 and delta H-2 of xylem water were generally in a range comparable to soil water from a depth of 2-20 cm. Long residence time of water in the tracheids uncoupled the isotopic signals of xylem and soil water in winter. Delta O-18 but not Delta C-13 in phloem organic matter was directly indicative of recent environmental conditions during the whole year. Delta O-18 could be described applying a model that included O-18 fractionation associated with water exchange between leaf and atmosphere, and with the production of organic matter as well as the influence of transpiration. Phloem Delta C-13 was assumed to be concertedly influenced by G(s) and photosynthetically active radiation (PAR) (as a proxy for photosynthetic capacity). We conclude that isotope signatures can be used as effective tools (1) to characterize the seasonal dynamics in source and xylem water, and (2) to assess environmental effects on transpiration and G(s) of Scots pine, thus helping to understand and predict potential impacts of climate change on trees and forest ecosystems.