The long way down-are carbon and oxygen isotope signals in the tree ring uncoupled from canopy physiological processes?
The long way down-are carbon and oxygen isotope signals in the tree ring uncoupled from canopy physiological processes?
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DOI：
10.1093/treephys/tpr093
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发表时间：
2011-10-01
期刊：
影响因子：
4
通讯作者：
Gessler, Arthur
中科院分区：
文献类型：
--
作者：
Offermann, Christine;Pedro Ferrio, Juan;Gessler, Arthur
碳（δ C-13）和氧（δ O-18）稳定同位素组成被广泛用于获得各种时间尺度上环境驱动因素与树木生理学之间联系的信息。树木年轮档案尤其可以用来重建气候和生理的年际和年内变化。然而，缺乏信息的过程中可能影响三角洲C-13和三角洲O-18的方式从同化的树叶到树轮。因此，本研究的目的是追踪欧洲山毛榉（Fagus sylvatica L.）在整个生长季中，叶片水（δ O-18）和叶片同化物（δ C-13和δ O-18）通过韧皮部运输的化合物进入年轮材。在2007年的生长季节期间，大约每两周采集一次用于δ C-13和δ O-18分析的韧皮部和叶片样品以及用于δ O-18分析的土壤水、木质部水、叶片水和大气水蒸气样品。从树木年轮中提取的δ C-13和δ O-18样品，通过用测树仪监测树木生长来测定年内年龄。韧皮部有机质和年轮全木的δ O-18与叶片水分蒸发富集和冠层有机质库的δ O-18之间不存在正相关。这一发现意味着部分解耦的年轮氧同位素信号冠层生理。与此同时，内部碳储存和再动员生理最有可能阻止三角洲C-13在树木年轮全木密切相关的环境驱动程序的年内变化。考虑到光合作用后的同位素分馏过程，不仅在树轮，但也在韧皮部碳水化合物，以及在树内部生理变化的年内时间的变化，δ C-13和δ O-18的改变，可能有助于更好地理解的意义，树轮同位素信号，不仅在内部，而且每年。
The carbon (delta C-13) and oxygen (delta O-18) stable isotope composition is widely used to obtain information on the linkages between environmental drivers and tree physiology over various time scales. The tree-ring archive can especially be exploited to reconstruct inter- and intra-annual variation of both climate and physiology. There is, however, a lack of information on the processes potentially affecting delta C-13 and delta O-18 on their way from assimilation in the leaf to the tree ring. As a consequence, the aim of this study was to trace the isotope signals in European beech (Fagus sylvatica L.) from leaf water (delta O-18) and leaf assimilates (delta C-13 and delta O-18) to tree-ring wood via phloem-transported compounds over a whole growing season. Phloem and leaf samples for delta C-13 and delta O-18 analyses as well as soil water, xylem water, leaf water and atmospheric water vapour samples for delta O-18 analysis were taken approximately every 2 weeks during the growing season of 2007. The delta C-13 and delta O-18 samples from the tree rings were dated intra-annually by monitoring the tree growth with dendrometers. delta O-18 in the phloem organic matter and tree-ring whole wood was not positively related to leaf water evaporative enrichment and delta O-18 of canopy organic matter pools. This finding implies a partial uncoupling of the tree-ring oxygen isotopic signal from canopy physiology. At the same time, internal carbon storage and remobilization physiology most likely prevented delta C-13 in tree-ring whole wood from being closely related to intra-annual variation in environmental drivers. Taking into account the post-photosynthetic isotope fractionation processes resulting in alterations of delta C-13 and delta O-18 not only in the tree ring but also in phloem carbohydrates, as well as the intra-annual timing of changes in the tree internal physiology, might help to better understand the meaning of the tree-ring isotope signal not only intra- but also inter-annually.