Evaporative enrichment and time lags between δ18O of leaf water and organic pools in a pine stand
Evaporative enrichment and time lags between δ18O of leaf water and organic pools in a pine stand
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DOI：
10.1111/j.1365-3040.2007.01654.x
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发表时间：
2007-05-01
影响因子：
7.3
通讯作者：
Buchmann, Nina
中科院分区：
文献类型：
--
作者：
Barnard, Romain L.;Salmon, Yann;Buchmann, Nina
了解生态系统的水通量越来越受到关注，因为气候情景预测世界许多地区的环境将更加干燥。基于最近建立的机理模型，叶水中O-18（Delta O-18）的蒸发富集和随后植物有机质的富集可用于表征控制蒸发的环境和生理因素。在樟子松林，我们测量了氧同位素组成（δ O-18）的动态，每6小时为4天的大气水蒸气，木质部汁液，叶水和水溶性有机质在当前（N）和前一年（N-1）针叶，韧皮部汁液，连同叶气体交换池N和N-1针叶，和相关的微气象变量。叶片水δ O-18表现出较强的昼夜周期性，而大气水蒸气和木质部汁液中的δ O-18变化不大。Delta O-18始终低于N-1针叶，可能与物候期有关。模拟叶水三角洲O-18表现出良好的协议与测量值时，应用非稳态蒸发富集模型，包括Peclet效应。我们确定的时间滞后三角洲O-18信号从叶水到水溶性叶面有机物和韧皮部汁液在不同位置的树干，这清楚地表明了考虑这些时间滞后效应的相关性碳运输，源-汇和碳通量分配研究。
Understanding ecosystem water fluxes has gained increasing attention, as climate scenarios predict a drier environment for many parts of the world. Evaporative enrichment of O-18 (Delta O-18) of leaf water and subsequent enrichment of plant organic matter can be used to characterize environmental and physiological factors that control evaporation, based on a recently established mechanistic model. In a Pinus sylvestris forest, we measured the dynamics of oxygen isotopic composition (delta O-18) every 6 h for 4 d in atmospheric water vapour, xylem sap, leaf water and water-soluble organic matter in current (N) and previous year (N-1) needles, phloem sap, together with leaf gas exchange for pooled N and N-1 needles, and relevant micrometeorological variables. Leaf water delta O-18 showed strong diel periodicity, while delta O-18 in atmospheric water vapour and in xylem sap showed little variation. The Delta O-18 was consistently lower for N than for N-1 needles, possibly related to phenological stage. Modelled leaf water Delta O-18 showed good agreement with measured values when applying a non-steady state evaporative enrichment model including a Peclet effect. We determined the time lags between delta O-18 signals from leaf water to water-soluble foliar organic matter and to phloem sap at different locations down the trunk, which clearly demonstrated the relevance of considering these time-lag effects for carbon transport, source-sink and carbon flux partitioning studies.