Forest gaps structure and tree regeneration in a montane Guayanan forest, Sierra de Lema, Venezuela

Thesis submitted in partial fulfilment of the requirements of the degree of Dr. rer. nat of the Faculty of Forest and Environmental Sciences Albert­Ludwigs Universität, Freiburg im Breisgau, Germany

by

Cristabel Durán Rangel

Freiburg im Breisgau, July 2011 Dean: Prof. Dr. Juergen Bauhus

First advisor: Prof. Dr. Dr. h.c. Albert Reif Second reviewer: Prof. Dr. Siegfried Fink

Disputation term: 29 November 2011

for Aida, Haiddye and Moritz

for the majestics Tepuys and breathtaking Gran Sabana

Acknowledgments “caminante no hay camino, se hace camino al andar” “wanderer, there is no path, the path is made by walking” Antonio Machado (1875 – 1983), Poet.

This is the longest hike I ever wandered to reach the summit. The person who accompanied me from the planning of the journey to the end of this hike, is the person I most have to thank: mein lieber Doktorvater the Prof. Albert Reif. Thank you very much for your enormous support in all senses! I have been very lucky to meet you and share with you these years! My second adviser the Prof. Lionel Hernández introduce me in the scientific world and in the tropical ecology, I thank all your advice and understanding. I thank the Prof. Siegfried Fink for be my second reviewer.

Several institutions made this study possible. I thank to Prof. Juergen Bauhus, as the representer of the Silviculture Institute, for permit me to work here for a long time. The Centro de Investigaciones Ecológicas de Guayana, from the Universidad Nacional Experimental de Guayana provided me the institutional and logistic support in Venezuela. I also thank the Prof. Pelz and the Institute of Biometry for be working in their offices in the time of renovations at our institute. The Institute for National Parks in Venezuela, Petróleos de Venezuela and Parupa Research Station in Gran Sabana provided necessary logistical support for this study.

This study was partially financed by several institutions: the State Electricity Enterprise EDELCA C.A., in Venezuela and the International Promotions Program (IPP) of the Faculty of Forestry and Environmental Sciences at the University of Freiburg. The IPP paid the language correction of the thesis and scientific articles. The Wissenschaftliche Gesellschaft of the University of Freiburg supported this work funding my assistance to congresses in Venezuela. I received financial support through grants by the Verband der Freunde der Universitaet Freiburg, the Dr. Leo­Ricker­Stiftung in Freiburg im Breisgau and the Landesgraduiertenfoerderung, Baden­Wuerttemberg Ministry of Science, Research and Art, Germany.

A very specially thank goes for Stefanie Gaertner. You give me so much scientific input and understanding. We are happy to have you again between us! I thank the Prof. Miguel Acevedo for the time I spend improving my English and analyzing hemispherical pictures at the University of North Texas. You introduced me in the powerful and exiting world of R! The botanical identification was possible with the collaboration of Elio Sanoja, Roland Keller and Bruce Holst. Several person give advices during the realization of this study: Florian Straub, Peter van der Meer, David Butler Manning. Katja Seis translated the summary of this work in German. Nestor Gutiérrez checked the summary in Spanish and improved the format of the final document. A special thanks goes for the Dr. Sibel Vurgun for her effectively and valorously advising related to time management, thesis structure and self­confidence during the last phase of my work!

i I also thank to Markus Heck and the members of the GAUS­Group at the Fraunhofer­ISE for their understanding and flexibility in the time before the submission of my dissertation.

One of the biggest profits I had in this time was the learning of the Open Source Operation Systems and Softwares, specially Linux and R. I appreciate the encourage