Evaluation of Thinning Project for Conifer Plantations in Timber Management Zone of Da-An Shi Working Circle

• Main Authors: Yi-Chih Chi, 紀儀芝
• Other Authors: Joou-Shian Lee
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/90872924372490273953

碩士 === 國立中興大學 === 森林學系 === 92 === Thinning operation is an important subject on forest tending. It not only increases timber growth and decreases competitions but also provides better growing space for trees and is considered an operation that should not be neglected. Traditional forest management has been overlooked since ecosystem management is more preferable to the world trend. However, forest tending is nowadays one of the major tasks for Taiwan Forest Bureau, by which many thinning demonstration areas have been established to observe the changes come after thinning operation, therefore forest thinning is once again under the spot light. Although thinning operation is a fundamental operation for timber management, the way to choose an appropriate project is even more important. The object of this research is to provide an evaluation method for choosing the appropriate thinning project. Conifer planations of six tree species in the timber management zone of Da-An Shi working circle were used as study subjects and attribute data of these planations were collected to calculate timber volumes in this research. Simple additive weighting method (SAW) was applied to integrate economic and public welfare criteria, different weight rates of 0.7:0.3, 0.5:0.5 and 0.3:0.7 were calculated as the two criteria to evaluate four different thinning projects. The four projects were accomplished by treatments of cutting stems as clear cutting(100%), heavy thinning(45%), intermediate thinning(35%) and without thinning(0%). The results are as follows: When compared under the economic criterion of net present value(NPV), the appropriate thinning project for Chamaecyparis formosensis, Chamaecyparis obtuse var. ofrmosana, Taiwania cryptomerioides and Picea morrisonicola turned out to be heavy thinning, and for Cunninghamia lanceolate and Cryptomeria japonica, clear cutting seemed to be more suitable. However, when the public welfare criterion was concerned, intermediate thinning appeared to be a better choice for the four former species, and clear cutting remain suitable for the latter two species. Along with all the weight rates, the final evaluation by SAW showed Chamaecyparis formosensis, Chamaecyparis obtuse var. formosana, and Taiwania cryptomerioides were more suitable for treatment without thinning, Picea morrisonicola were better to be treated with intermediate thinning and Cunninghamia lanceolate, Cryptomeria japonica were more suitable for heavy thinning and clear cutting, respectively.