Natural regeneration characteristics of some dominant tree species of broardleaf evergreen forests in Xuan Son National Park, Phu Tho province

Abstract

In Xuan Son National Park, the broardleaf evergreen forests have diverse and various tree species compositions, ranging from 56 to 104 tree species. Our study showed that the four species include Saraca dives, Aphanamixis polystachya, Amesiodendron chinense and Barringtonia macrocarpa were the most dominant tree species of the canopy layer. Their regeneration densities were higher under than beyond the shadow of the mother tree’s canopy, in which the density of A. polystachya was 635,833 individuals/ha that was 72 times higher, and 20.246 individuals/ha with 8 times, 13,100 individuals/ha with 3.6 times and 10,000 individuals/ha with 2.8 times higher for B. macrocarpa, A.chinense and S. dives, respectively. Most of regenerating trees were under 2 meters in height, which accounted for above 99.6% of the total of the regeneration individuals under and from 82.0% to 96.2% beyond the
shadow of the mother tree’s canopy. The rates of good quality regenerating trees reached from 87.4% to 99.7% for under and from 83.0% to 94.8% for beyond the mother tree’s canopy. Regeneration individuals derived mainly from seeds with above 96.7% and from 87.7% to 96.2% for under and beyond, respectively. The advanced regenerating trees (h ≥ 2m) accounted for from 3.8% to 18.0% beyond and only from 0.1% to 0.4% under the the shadow of the mother tree’s canopy. The study results suggested that the ratio of regeneration individuals growing up to the canopy layer was higher beyond than under the shadow of the mother tree’s canopy, which supports an important mechanism for the maintenance of tree species diversity in tropical forests