The evaluation of delta C-13 isotopes of trees to determine past regeneration environments

The effects of past regeneration environments and canopy position on delta C-13 signals in leaf and wood tissue were examined. Leaves were collected f rom various canopy positions both inside and outside of closed forest and f rom gaps ranging in size from 75 to 829 m(2). Trees of known recruitment en vironments were cored and wood was extracted from the outer rings and from the centre of the tree. Whole tissue was converted to holocellulose for iso topic analysis. An elevation of similar to1 parts per thousand in delta C-1 3 was associated with a conversion from whole wood to holocellulose. A regr ession of whole tissue vs, holocellulose produced an R-2=0.84. A significan t depression in delta C-13 values of leaf tissue was observed in areas unde r a closed canopy. Leaves sampled from open areas, or from a well-lit canop y position. had more positive delta C-13 values. In gaps, delta C-13 of the leaves increased with increasing gap size. The existence of a significant difference between delta C-13 of inner and outer woods within a tree indica tes that it is possible to distinguish between differing recruitment enviro nments with this technique. The data indicate that the regeneration environ ment confers a specific isotopic signal on a tree that can be detected late r in its life-span. The method can be used to determine recruitment environ ments and should allow for grouping of species into functional types. The p otential uses of this ecological tool are important for restoration ecology and the management of forest ecosystems. (C) 2001 Elsevier Science B.V. Al l rights reserved.