Nature and Extent of Forest Degradation in Central Himalayas

Abstract

Forest degradation is widespread in developing countries, as poor people depend on forest biomass collection on a “day-to-day” basis, giving little respite to forest ecosystems to recover. In the Himalayas, collection of firewood, tree leaf fodder, and leaf litter from forest floor is one of the main causes of forest degradation, particularly in oak (Quercus leucotrichophora) and pine (Pinus roxburghii) elevation belt (1000–2200 m elevation) of the Western and Central Himalayas. In this area, whole tree cutting is uncommon, but most trees are lopped until they become severely denuded, with little crown left. Compared to healthy forests, generally such degraded forests have 40–50% less biomass but about 80% less net primary productivity and 86.4% less leaf area. As degradation progresses, the biomass extracted from the forest declines, but in proportional terms it increases, resulting in a rapid disintegration of ecosystem structure and functions. Some of the observed effects are (1) reduction of soil carbon and nitrogen by 40–50%; (2) desiccation of oak acorns lying on forest floor well before the arrival of monsoon; (3) about 40% reduction in leaf litter decomposition; (4) 35% reduction in ectomycorrhizal association with roots, as indicated by fungal sporocarp density; and (5) 25% reduction in soil water holding capacity and 25% increase in soil bulk density (these values are in comparison to a relatively undisturbed forest). Recovery of a degraded forest (chronic disturbance) has not yet been investigated but is likely to be slower than that of a clear-cut (acute disturbance) forest. However, some interventions can result in a faster recovery.