Tree regeneration and seedling survival patterns in old-growth lowland tropical rainforest in Namdapha National Park, north-east India

The tree structure and regeneration was studied in the buffer zone area comprising lowland evergreen and semi-evergreen forests in the Namdapha National Park, one of the largest remaining tract of pristine rainforests in the Eastern Himalayan biodiversity hotspot in India. The investigations were conducted in the three forest stands, viz. Altingia-mixed species, Shorea-Dipterocarp, and Albizia forests that are most dominant forest types in the lowland areas of the park. A total of 98, 54 and 20 species have been recorded at tree stratrum, while 87, 44 and 15 species at regeneration stratum for three stands, respectively. The cumulative regenerating density (seedlings + saplings) was estimated 17,648, 16,110 and 768 individual ha−1 for respective stands. It was interesting to note that of the total regenerating species, 44–47% species were new to different stands, which mainly comprised middle storey species. Low-dominant and rare species also contributed significantly in the regeneration of the forest stands. The expanding population structure of forest stands indicated higher survival of the mid- and the low-canopy species than the top-canopy species. The data revealed that the future composition of these stands will highly depended on the potential regenerative status of species in each of the stand and such information would be crucial for forest management. Since the park contributed significantly to the regional biodiversity by depicting species assemblages for both wet evergreen and semi-evergreen biomes, such last remnants of rainforest should be integrally protected from anthropogenic disturbances.