Tree regeneration in a subtropical humid forest: Effect of cultural disturbance on seed production, dispersal and germination

1. The subtropical humid forest of Meghalaya, India, has been exposed to various kinds of cultural disturbance of varying magnitude during recent years. In order to analyse the effect of disturbance on natural regeneration of a few dominant and commercially important tree species, viz. Schima khasiana and the oaks Lithocarpus dealbatus and Quercus griffithii, a study on seed production, dispersal and germination was carried out in three stands, differing in degree of disturbance, during the years 1988-91. 2. Seed production in L. dealbatus and S. khasiana varied significantly between the three stands and increased with increasing disturbance. It increased with increase in d.b.h. of the trees in all three species. Heavy seeding occurred in different years in different species. 3. Lithocarpus and Quercus spp. produced heavier seeds in the disturbed stands than in the undisturbed stand. 4. The number of seeds dispersed from the trees decreased with distance from the parent tree. The dispersal distance for Lithocarpus and Quercus was greater in the disturbed stands than in the undisturbed stand. However, the dispersal distance in the forest was very low irrespective of degree of disturbance. 5. Seed predation decreased and germination increased with distance from the parent tree in all three stands, suggesting that distance-related seed predation was not influenced by disturbance. 6. In an experiment with four treatments the greatest germination of seeds was observed on the moss layer, irrespective of species and forest stand. The presence of litter inhibited germination of seeds to a great extent in all the species. Germination of Lithocarpus and Quercus was better in the undisturbed stand than in the disturbed stands, while that of Schima khasiana was better in the disturbed stands. 7. An analysis of the fate of seed populations of the oak species revealed that loss of seeds caused through consumption by rodents and insects and transportation by various agents accounted for more than 98% of the seeds, while fewer than 1% of them germinated. 8. The findings of the study are discussed in relation to their potential application in management of the disturbed subtropical forests.