RESTORATION OF NATURAL VEGETATION IN DEGRADED IMPERATA-CYLINDRICA GRASSLAND - UNDERSTOREY DEVELOPMENT IN FOREST PLANTATIONS

Reclamation of former, degraded forest lands occupied by Imperata cyli ndrica is one of the crucial environmental and forestry issues in the humid tropics, notably Southeast Asia. We suggest that it is possible to gradually restore the original natural forest cover with the help o f a sacrifice fallow crop of fast-growing exotic tree species. Recentl y, a set of suitable fast-growing plantation tree species has been ide ntified and stand establishment methods developed for this purpose. We assessed the regeneration of natural vegetation in stands of differen t plantation tree species and evaluated the ecological impact of speci es composition in the plantation understorey. PCA ordination, regressi on analysis and analysis of covariance were applied at different stage s of the study. We found a marked vegetational resemblance between sta nds dominated by Acacia mangium: they had the highest number of indige nous trees in their understorey, whereas stands of other plantation tr ees supported more diverse grass and herb vegetation. A high proportio n of evergreen woody vegetation reduces the risk of fire and grass com petition and enhances secondary succession towards natural forest.