The enrichment of (18)O in leaf water under natural conditions.

The enrichment of (18)O in the water of transpiring leaves under natural conditions is described. In the first series two, later three species at the same location and at the same time are compared (birch Betula pubescens L., oak Quercus robur Ehrh., larch Larix decidua Mill., and spruce Picea abies Karst). All four show parallel enrichment properties. In addition two beeches (Fagus silvatica L.) were observed, one at Jülich, the other at the Solling hills. They show similar (18)O/(16)O ratio fluctuation in their leaves during the time of observation. Three plant communities (beech forest B1, spruce forest F1, and meadow W, sites of the "Solling-Project", German Research Foundation, part of International Biological Program, at the Solling hills) show a daily course of the (18)O enrichment comparable to each other.