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邱氏密度管理量表應用於柳杉林分生長評估及疏伐規劃之研究

Study of Applying Chiou's Density Management Diagram for Growth Evaluation and Thinning Planning of Cryptomeria japonica Plantations

摘要


本研究為柳杉人工林的現況評估與疏伐規劃,發展出一套僅使用林分胸徑與林分密度即能簡易操作的邱氏密度管理量表。量表的製作首先匯整林務局的永久樣區、臺大實驗林的長期試驗地進行資料庫形式的偵錯反饋,接著統計各齡級的林分密度、平均胸徑二次平均胸徑進行PR分級。再透過Schnute生長模式各適配一條代表該PR等級之生長曲線,分別組合成「林齡級-平均胸徑」、「林齡級-二次平均胸徑」與「林齡級-林分密度」此三種生長基線曲線組,作為建立邱氏密度管理量表之基礎,整體而言誤差率皆在0.16%以下,顯示該曲線能在其範圍內進行有效的模擬與應用。吾人能藉由PR50的生長基線為參考線,用以評估不同地區柳杉人工林生長優劣,也能利用各PR等級曲線參數預測生長,以作為各林分採取經營活動與評估資訊之基礎;進一步組合曲線組為「邱氏密度管理量表」,該量表包含「林齡級-平均胸徑-林分密度」與「林齡級-二次平均胸徑-林分密度」兩種林分胸徑的統計特性。我們能參考量表中點出目標林分的實際點位、相對應的基線點位與林地現況規劃應進行何種疏伐措施,進一步評估伐採後期望的生長軌跡,由此作為伐採強度的基準或是預定伐採的期程。

並列摘要


In this study, a set of Chiou's density management diagrams (CDMDs) was developed, which could be easily operated via the mean diameter at breast height (DBH), quadratic mean diameter (QMD), and stand density for assessment and thinning planning of Cryptomeria japonica plantations. At first, permanent plots of the Forestry Bureau and long-term experimental plots of National Taiwan University Experimental Forest were collected to debug feedback in the form of a database, and then we calculated the stand density, DBH, and QMD of each age-class for classification of the percentile rank (PR). Each of the growth curves representing PR classes were fitted through the Schnute model, and these were combined to form the basis for establishing age-DBH, age-QMD, and age-stand density from the baseline curve groups. Overall, the error was below 0.16%, which showed that the baseline curve groups could be effectively simulated and applied within the scope. As basic information for evaluation and management of each C. japonica plantation, the baseline PR50 served as a reference to assess the growth of C. japonica plantations in different regions, but we also used parameters of each PR curve to predict stand growth. The final curve groups were combined into CDMDs, which included two statistical characteristics of stand diameters as an age-DBH-density diagram and an age-QMD-density diagram. For thinning plans, we could refer to current stand structure, point out the practical positions of the target stand and the corresponding baseline positions from CDMDs, and further assess the expected growth trajectory after cutting, which could be used as a benchmark for the thinning intensity or as a schedule for thinning.

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