Age Structure and Regeneration of Rhododendron arboreum Sm. along an Altitudinal Gradient of Manaslu Conservation Area, Nepal Himalaya
The age structure and regeneration of Rhododendron arboreum Smith. was studied along an altitudinal gradient of Manaslu Conservation Area, Nepal Himalaya ranging from 2180m to 3180m. Vegetation sampling was done by using quadrate method. Five plots of 10mX10m were located in each transect with vertical distance of 200m and horizontal distance of 100m. Altogether six tree species were recorded in the study area. R. arboreum was dominant followed by Pinus wallichiana. Altogether 46 cores from 27 trees and 10 stumps of R. arboreum were collected. In the population of R. arboreum, seedling accounted for 38.51%, sapling 33.33% and tree 28.14%, showing successful life cycle of the species. The regeneration status of R. arboreum was good at 2380m, fair at 2180m, 2580m and 2780m and poor regeneration at upper limit i.e. 3180m. The oldest and youngest cored trees recorded were 127 and 19 years respectively. A reverse J-shaped distribution was found in DBH class, age class and height class. The height of tallest and shortest Rhododendron arboreum recorded in the study area were 7m and 0.1m respectively. The correlation between age and DBH of R. arboreum was statistically significant(r=0.763, p<0.00001). The mean annual radial growth of R. arboreum was 1.65mm.