Forest Structure and Regeneration of Quercus semecarpifolia in Api-Nampa Conservation area, Nepal

Abstract

Himalayan forest is dominated by different species of Oaks (Quercus spp.) at different altitudes. This work was carried out to study the forest structure and regeneration of Q. semecarpifolia along altitudinal gradient in Api-Nmpa Conservation Area. The vegetation data was collected from a total of 48 number of 20×20 m square quadrat for tree species in which plots were established at lower limit of Q. semecarpifolia i.e. 2489 masl to uppermost limit i.e 3636 masl. The Shrubs and tree saplings including lianas were recorded from the nested plot sized by 25 m2 and herbs and tree seedlings from the quadrat size of 4 m2 . Importance Value Index (IVI) of tree, shrub and herb species, distribution pattern of seedlings and saplings, and soil attributes were analyzed. Regeneration was assessed by density - diameter curve. Fourty eight soil samples were taken for laboratory analysis. A total of 188 species of woody and non woody species belonging to 67 families were recorded. Tree species richness in the forest decreased with increasing elevation. The most frequent and dense tree species in the forest was Q. semecarpifolia with important value index percent of about 19% (IVI=56) and it was present in 80% of the sampling plots. IP of Q. semecarpifolia in the lower elevation range was 8% and in middle and upper range 17% and 41% respectively. Seedling and sapling were present in 30.2% and 75% of sample plot in the forest. The tree density of Q. semecarpifolia in the forest area was 235stem/ha with basal area 42.22 m2 /hectare. Seedling and sapling density of Quercus semecarpifolia in the forest was 4010 stem/ha and 1058 stem/ha. All the tree, sapling and seedling density and basal area of Q. semecarpifolia were higher in the higher elevations. The average maximum DBH of Q. semecarpifolia was 46.72 cm and average maximum height was 18.61 m. Q. semecarpifolia above 2800 m elevation showed sustainable regeneration as evident from reverse J shaped curve. However it below 2800 m elevation showed weak regeneration as evident from bell shaped curve. Altitude was the main factor for unequal distribution of species along the altitude. Soil nutrient such as nitrogen and potassium showed positive but insignificant relationship with seedlings and saplings.