Vegetation and structure of forest gaps in the cloud forests of Sierra de Lema, Gran Sabana, Venezuela

Summary

The PhD is part of the general project “ecology and diversity of the cloud forest of Sierra de Lema, Gran Sabana, Venezuela” which has as main research objective the abiotic and biotic characteristics of the forest ecosystems along an altitudinal gradient in Sierra de Lema, and how such characteristics vary with time. Sierra de Lema forests are situated in Venezuela´s south east, in the eastern sector of the Canaima National Park. Gaps, as small disturbances in forests, generate dynamism in the forest community. Their formation induces changes in the forest’s environmental conditions (as light, nutrients, space), and partitions the forest resources. According to the gap partitioning theory, plant species spezialise more or less to the different range of conditions created by gaps. The chance hypothesis states, that the regeneration process in gaps is stochastic, depending on environmental factors prior to gap occurrence. The aims of this research are the description of the gap structures, characterization of woody and palm species regeneration in gaps, and the characterization of the environment factors light supply and microhabitat structures. The study was designed to answer the research questions: Which is the specific gap structure in Sierra de Lema? Does the floristic composition differ between microhabitats? Which are the relations between light conditions and forest understory? The woody regeneration was recorded on 62 plots in 22 gaps as well some environmental characteristics like the light availability. Results of this PhD thesis, together with those of other studies in the region, will improve the understanding of the ecosystem dynamics in the cloud forest of Sierra de Lema and La Gran Sabana.