Topographic and anthropogenic factors shaping subalpine Abies spectabilis forest in Langtang National Park, eastern Himalaya
2017
Tiwari, R.M. ((Hokkaido University, Sapporo (Japan). Graduate School of Environmental Science), (Tribhuvan University, Kirtipur, Kathmandu (Nepal). Central Department of Botany)) | Shrestha, B.B. | Kohyama, T.S.
Located in the Himalayas, and situated at the highest altitude worldwide, the subalpine forests have come under human pressure through means of timber logging, livestock farming and tourism, which has brought about the progress of degradation. Thus, it is essential to quantify how forest structure is determined by environmental factors over the range of subalpine zone for better management planning. We investigated the subalpine forest dominated by Abies spectabilis in Langtang National Park, Nepal Himalaya, by setting 80 plots of 10-by-10 m scattered over the range of subalpine forest from 3170 to 3810 m a.s.l. on a north-facing slope, and examined the relationship between topographic factors (e.g. altitude and slope inclination), anthropogenic factors (e.g. number of cut stumps and trampling intensity), and forest stand variables (e.g. woody species richness and composition, tree and juvenile density, basal area, and topsoil C/N content). Species richness decreased with altitude, number of fallen logs, and trampling intensity while at the same time, it increased with slope inclination and cut stump density. Stands in higher altitude showed lower tree density and basal area, while higher juvenile density of A. spectabilis. Juvenile density decreased with high basal area. Stands on steeper slopes had higher tree density with smaller maximum size on poorer soil. With increasing cut stumps, basal area and soil carbon content decreased while woody species richness and tree density increased, suggesting enhanced stand recovery in response to canopy removal. We conclude that Abies population is vulnerable to topsoil removal by trampling and cutting, and that altitude-dependent management is needed.
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