Assessing biodiversity and the spatial structures of forest ecosystems are important for forestry and nature conservation. However, tropical forests of Bangladesh are only sparsely investigated. Here we determined biodiversity (alpha, beta and gamma), spatial species turnover and stand characteristics of one of the few last remnant tropical forest in Bangladesh. Two differently protected areas of Satchari forest were compared.

We recorded tree species composition, in a systematic plot design, measured diameter at breast height for each individual tree (to asses basal area), and calculated decay in similarity of tree species composition with geographical distance. The distance-decay was assessed separately for the whole study area and for two subsamples from Satchari National Park and Satchari Reserve Forest. Satchari National Park (strictly protected) had, despite its smaller area, a higher Alpha- and Gamma diversity, but a lower Beta diversity than Satchri Reserved Forest. Variation in species composition was not significantly between the two differently protected areas. Basal area increased significantly with protection status although tree individuals were of equal size in both areas. Plots in the Reserve Forest were associated with higher species turnover than in the National Park.

We suggest anthropogenic disturbances, that occur in the less strictly protected Reserved Forest, to be the main driver for the detected spatial heterogeneity in species composition.

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