Regeneration of natural-forest species in plantations of fast-growing species in northeast Thailand

We examined the ‘catalyzing effect’, by which the establishment of indigenous species and secondary succession are facilitated in plantations. A tree census was conducted at two 24-year-old plantations (agroforestry and eucalyptus plots), and a grassland in northeast Thailand. Three natural forests adjacent to the two plantation plots and the grassland plot were also investigated to evaluate their possible influence on the catalyzing effect based on the differences in species diversity and the intensity of disturbance among the natural forests. The catalyzing effect seemed to be observed at the study site; the two plantations had more individuals and species of indigenous trees than the grassland, indicating faster natural regeneration of the formers than the latter. Although our results found the tendency of the catalyzing effect, further studies using sufficient plot replication are required to verify the generality of the effect.