Informing Community Forest Management: A Retrospective Analysis of an Old Silvicultural Trial in Nepal

摘要

This study demonstrates a simple method to gather information from old demonstration trials. It was undertaken in the context of a 32-year-old thinning trial in a naturally regenerating stand of Shorea robusta Gaertn. f. in a community forest in the Sindhupalchok district of Nepal. The trial was established by the Nepal-Australia Forestry Project in 1983 and the only documentation of the trial is a report of measurements undertaken in 2005. The site has been relatively untouched, apart from the collection of non-timber forestry products (NTFPs) by the Community Forest User Group (CFUG) that manages the site. The 1983 project had 6 treatments including: pruning, selective thinning, and mechanical harvesting. The impacts of the six treatments were measured by pairing the treatment plots with comparison plots at the same position on the slope in the surrounding forest. Measurements taken were: height, diameter at breast height, canopy cover, and species distribution and count to compare with the area of forest outside the treatment plots using the slope position as strata. Evidence of a remaining treatment effect from 1983 was found for only two of the original thinning treatments. These treatments were the most intensely thinned, and had either positive or negative impacts on S. robusta growth, depending on their position on the slope, indicating the overriding influence of slope position. Using information from measurements taken in 2005 and 2015, it is recommended: that a 4 m x 4 m target spacing should be used as the basis for silvicultural treatments for regenerating S. robusta forests; this density be maintained with planned removal of regenerating saplings; this target be modified with sensitivity to the position on slope; and it should be a staged harvest done in coordination with the community's annual needs.