ALVARO CAÑADAS1, OLEG NENADIC2, ANDREAS BOLTE3
1Georg-August-Universität Göttingen, Institute of Forest Management, Germany
2Georg-August-Universität Göttingen, Institute for Statistics and Econometrics, Germany
3Georg-August-Universität Göttigen, Institute of Silviculture, Germany
Studies on site and forest history provide many useful insights into the effects of human activities on Neotropical forest structure and functions. However, we are still unable to develop a deterministic model to simulate how land use history influences tropical forest structure and succession. The present study aims to enhance our ability both to predict and to manage tropical forest succession. Three forest sites (Rukullacta, Villano and Wawa Sumaco) with different colonization date and use intensity were selected. The age of the forest ranges from 3 and 22 years. At each site, plots of 500 m2 surface (20 x 25m) were installed with four repetitions. Within the plots, all trees above 5cm DBH were identified and measured. According to the results, a regional model was developed to determine the driving factors of secondary forest succession. The number of occurring species depends on the sample area, stand age and land use intensity. The species/area curves of the different sites differ significantly; a correlation between land use intensity and species richness could be observed. Multivariate analysis procedures (Principal Component Analysis) were used in order to determinate the patterns of species replacement and show that land use affect floristic composition following abandonment. A noticeable floristic affinity exist, with an intensive land use in different phases of succession. Stand structure analysis showed differences in aggregation and desegregation due to the succession. The DBH distribution (Weibull function) of the forests is influenced by the grade of anthropogenic disturbance. The Correspondence Analysis is used for describing the potentiality of the Secondary Forest in different sites. The forests under middle and low intensity of the use, the commercial species exceed 38% in comparison with the forests exhibiting high intensity of use.
Keywords: Correspondence analysis, neotropical forest, land use intensity , Weibull function, principal component analysis, regional models, Ecuador, biodiversity index