Human impacts on high-altitude forest structures in the Nangpa and Hinku Valleys, Sagarmatha and Makalu-Barun National Park, Nepal.

摘要

This study attempts to develop a better understanding of the role of human disturbances in shaping forest patterns in the Sagarmatha National Park. The Nangpa and Hinku valleys were selected as study sites to provide examples of a heavily disturbed and a less disturbed area respectively.; The two main aspects of the study include reconstructing the settlement and forest/land use history and determining the present forest patterns. The study compared human use and forest structures at three different levels. Firstly, a comparison between aspects (warm and cool) was made within the Nangpa and Hinku valleys. Secondly, variations in forest cover on the same aspects of the Nangpa valley were compared and causes for their variation were explored. Thirdly, stand level structural variations were examined and discussed.; The study showed that the warm and cool aspects of Hinku have similar forest composition and basal area coverage whereas similar comparison within the Nangpa found distinctly different forest structures. The variation in forest structure and composition on the same aspect of the Nangpa valley could not be explained entirely through variations in climate and site factors. Thus, it was concluded that much of the variation in forest structures in Nangpa Valley were caused by human modifications, and forests on warm and cool aspects could potentially develop to be similar in the absence of human disturbances. The variations in forest structures within warm aspect of Nangpa may be caused by a changes in land use pressure because settlements, which initially begun in the lower valley had later moved towards the head valley. Similarly, the variations in forest cover on across the cool aspect of the valley appear to be related partly to variations in collection and harvesting pressure.; The study suggests that humans disturbances became a significant forest influences in the Nangpa Valley mainly after the height of the Little Ice Age, which occurred about 250--300 years ago. Human-induced forest changes include substantial increase in stand initiation structure and decrease in old growth. These changes have led to mitigation responses such as establishment of the indigenous nawa forest protection system and introduction of modern conservation concepts such as protected areas establishment in Khumbu. The conservation measures coupled with alternative energy and off-farm employment opportunities appear to be causing a trend towards forest recovery.; A forest management system responsive to for multiple objectives of the Park, including habitats for biodiversity, resources for the resident people and aesthetic qualities for tourism is needed. Since, different forest structures are capable providing different values, one way to achieve these multiple objectives is to maintain the landscape in a variety of structures.