林木位置圖應用於香杉之疏伐業務

Application of Individual Tree Location Map in the Thinning Operation of Luanta-fir

林分的蓄積與生長是經營木材生產的核心，亦是森林經營計畫擬定的重要依據。在一定的生育地條件下，林分密度是決定木材收穫的數量與品質之最重要因子之一，所以在森林的撫育作業中，疏伐作業的實施更顯得格外迫切，因為疏伐作業是控制林分密度的一項重要環節和技術手段。而在整個疏伐施業計劃中，需考量的幾個問題：何時疏伐、疏伐數量、疏伐木的選擇、主伐時間等，以往遭遇到此類問題時，大都以經驗為憑來作決策，缺乏一套簡易而有系統的量化模式。本研究係利用GIS 配合林木位置圖，以惠蓀林場之150 m × 30 m香杉採穗園為研究材料，以生產大徑材為目的的考量下，針對疏伐木之選擇，利用隨機法、寺崎渡氏法、胸徑級法、樹冠競爭指數法等四種方法加以模擬、評估、探討。各種疏伐方法的準則皆有其目的，利用GIS 工具配合林木位置圖及單株林木資料庫，可相當方便地提供做決策的具體量化、圖形化的模擬結果。 The information of growing stock and stand growth is the core of timber production, there are the important clues to forest management, too. In the same site quality of forest land, stand density is the key factor of affecting the quantity and quality of timber harvest. Thinning is the key point of density controlling in the forest tending operation. In the process of thinning, there are few questions we have to face. Those questions are: the amount of thinning, the time intervals between thinning, how to select the thinned trees, and deciding rotation age. In dealing with these questions, we used to make decisions by our experiences generally. It's necessary to have a simple and systematic digital model in thinning decisionmaking. In the paper, the tree location map of 150 m×30 m Luanta-fir in Hui-Sun Forest Experimental Station were digitized in GIS and thinning simulation by random, Telathaki-Wadali-Chi, DBH class and crown competition index method. Alternative methods could be evaluated with thinning criteria, the database of individual tree map and tree attributes table with GIS tool under different purpose of timber production. GIS could be used efficiently to support the simulation results of digital map and information for decision- making.

The information of growing stock and stand growth is the core of timber production, there are the important clues to forest management, too. In the same site quality of forest land, stand density is the key factor of affecting the quantity and quality of timber harvest. Thinning is the key point of density controlling in the forest tending operation. In the process of thinning, there are few questions we have to face. Those questions are: the amount of thinning, the time intervals between thinning, how to select the thinned trees, and deciding rotation age. In dealing with these questions, we used to make decisions by our experiences generally. It's necessary to have a simple and systematic digital model in thinning decisionmaking. In the paper, the tree location map of 150 m×30 m Luanta-fir in Hui-Sun Forest Experimental Station were digitized in GIS and thinning simulation by random, Telathaki-Wadali-Chi, DBH class and crown competition index method. Alternative methods could be evaluated with thinning criteria, the database of individual tree map and tree attributes table with GIS tool under different purpose of timber production. GIS could be used efficiently to support the simulation results of digital map and information for decision- making.