**Acknowledgements**

To the Austrian Research Council for the fellowship to M. Watzka and the Centro de Estudios Avanzados, IVIC, for providing housing facilities; Prof. Dr. H. Ziegler (University of Munich, Germany) helped with the determination of δ13C values of leaf samples. Analyzes of inorganic and organic osmolytes were conducted at the Center of Ecology of IVIC, in Caracas, and the Institute for Ecology and Environmental Conservation, University of Vienna, Austria. Dr. Ariel Lugo (IITF-Forest Service) provided critical comments to the original manuscript.
