Variation of δC of wood and foliage with canopy height differs between evergreen and deciduous species in a temperate forest.

We investigated post-photosynthetic fractionation and carbon transfer mechanisms of different plant functional types growing under the same climatic conditions in North-eastern China. The variations in δC of trunk and branches were compared with leaf δC at different canopy heights of Pinus koraiensis (evergreen coniferous species), Larix gmelinii (deciduous coniferous species) and Quercus mongolica (deciduous broad-leaved species). Results showed that δC of leaves increased (became more enriched) with increasing canopy height for both coniferous species ( P. koraiensis, L. gmelinii) but not for Q. mongolica (a deciduous broad-leaved species). δC of both trunk and branches also increased with sampling height for the evergreen conifer P. koraiensis but did not significantly vary for either of the deciduous species ( L. gmelinii or Q. mongolica), except a significant increase in branch δC for L. gmelinii. Similarly, δC of trunk and branches were strongly correlated with leaf δC only in the evergreen conifer, P. koraiensis. C was consistently more enriched in trunk, branches, and roots compared to leaves in all three species. Our findings suggest that, even under the same climatic conditions, different plant functional types may exhibit different carbon transfer mechanisms. This is contrary to the previous hypothesis that different carbon transfer mechanisms operate in forests of different climatic zones, especially in tropical and temperate forests. Particularly, the differences occur predominantly between evergreen and deciduous trees rather than between coniferous and broad-leaved trees. The significant difference in δC between leaves and wood tissues confirms a previous post-photosynthetic isotope fractionation in temperate forests. [ABSTRACT FROM AUTHOR]