Modelling anthropogenic impacts on the growth of tropical rain forests - using an individual oriented forest growth model for the analyses of logging and fragmentation in three case studies

For answering questions concerning anthropogenic impacts on tropical forest developmentthe individual-oriented and process-based forest growth model Formind2.0 wasdeveloped. It simulates the spatio-temporal dynamics of uneven-aged mixed forest standsin areas of one hectare to several km^2. The model describes forest dynamics as a mosaicof interacting forest patches of 20 m^2×20 m^2 in size. Within these patches trees are notspatial-explicitly distributed, and thus all compete for light and space following the gapmodel approach. Tree species diversity is aggregated into 5-20 plant functional types(PFT) on the basis of species maximum tree height and successional status. The carbonbalance of each individual tree including photosynthesis and respiration is modelled explicitly.Thus, we can match measured diameter increment for different PFT, size and light conditionsaccurately. Allometric relationships connect above-ground biomass, stem diameter,tree height and crown dimensions. Beside increasing mortality through self-thinning indense plots one of the main processes of mortality is gap creation by falling of large trees.This process as well as seed dispersal from mature trees interlinks neighbouring plots witheach other.The model was parametrised for three different sites in South-East Asia and South-America:Sabah (Malaysia), Venezuela, and French Guiana. Model accuracy is testedwith growth data from permanent sampling plots in Sabah. Sensitivity of various resultvariables on variation of most parameter values is tested and give important insights intogeneral model behaviour.Two examples of anthropogeneous impacts on tropical forest dynamics are managementpractise and fragmentation, both of major concern. Following applications are performed:Growth and yield of Venezuelan rain forest under various logging methods, intensitiesand cycles are analysed for their ustainability.Effects of logging (method and cycles), fragmentation and recruitment assumptionson forest dynamics in Sabah are discussed.Finally, fragmentation impacts on mortality and recruitment are simulated and theireffects on forest dynamic and biomass loss are evaluated for a forest site in French Guiana.