Publication Date:
2011-11-24
Description:
The carbon ( 13 C) and oxygen ( 18 O) 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 13 C and 18 O 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 ( 18 O) and leaf assimilates ( 13 C and 18 O) to tree-ring wood via phloem-transported compounds over a whole growing season. Phloem and leaf samples for 13 C and 18 O analyses as well as soil water, xylem water, leaf water and atmospheric water vapour samples for 18 O analysis were taken approximately every 2 weeks during the growing season of 2007. The 13 C and 18 O samples from the tree rings were dated intra-annually by monitoring the tree growth with dendrometers. 18 O in the phloem organic matter and tree-ring whole wood was not positively related to leaf water evaporative enrichment and 18 O 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 13 C 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 13 C and 18 O 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.
Print ISSN:
0829-318X
Electronic ISSN:
1758-4469
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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