杉木人工林樹冠結構與生物量之研究

Abstract

本研究旨在探討杉木人工林樹冠結構與生物量之相關問題，研究區域位於台灣中部八仙山事業區十文溪生態系經營示範區內第111林班之杉木人工林，調查林分之各項生長狀況，並採用16株樣木進行林木生長研究，以理論模式為基礎，以及應用森林測計學之方法，配合統計軟體，進行杉木林分與樣木之資料分析，來探討胸徑與樹冠之性態值間的關係，樹冠形態與結構之特性，並估算林木之淨生產力，以及分析葉面積量。研究所得主要結果分述如下： 在林木樹冠之垂直變化中，林木之樹冠長、枝下高和胸徑間之關係為線性關係，且隨胸徑之增大，樹冠長和枝下高之間，呈現漸次增大之趨勢，而其平均樹冠比約0.58。 杉木人工林之樹冠形態與結構中，其樹冠形呈現圓錐形或圓柱體，而葉量在垂直空間分佈，可以最大葉密度分佈來區分上層與下層樹冠，其杉木最大葉密度分佈約為1.7~2.0 kg/m，約在離頂端距離3~5 m。 杉木各部位淨生產量，隨著胸徑之增加，其幹量與枝量之淨生產量逐漸增加，地上部之淨生產量則是以直徑級Ⅱ達最大，約為1.46 ton/ha/yr。另外杉木幹量之生產構造，隨胸徑之增大，其增加的幅度愈大，枝條量在垂直分布上則逐漸往上移，葉量主要分布於中、上層樹冠，故以生產構造特性來說，葉量之分布類似闊葉型之生產構造。 杉木林平均單株葉面積隨直徑級增大而增加，直徑級Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ之平均單株葉面積分別為74.15, 104.13, 133.11, 164.31, 206.34 m2/tree，並由林分之資料推估可得知杉木林分葉面積指數約為3.87。而葉面積則與邊材面積具有較高之相關性，符合管束模式理論。 杉木人工林經營中，其修枝撫育作業在垂直方面，以修枝至葉密度分佈最高點位置，且維持樹冠比約0.20~0.30間為最適宜，另外以直徑級Ⅱ之葉空間密度，可使林木之生物量為最大，故可提供未來杉木人工林經營之重要參考資訊。

The purpose of this study was to discuss crown structure and biomass of mature China-fir (Cunninghamia lanceolata). The study area is location in the central part of Taiwan, at compartment no.111, Pa-Hsien-Sha working circle and Shyr-Wen-Shi demonstration zone. Data of this study were collected from stand and 16 sample trees of a mature China-fir plantation. This study is based on theory way, and use forest measure method and statistics software, to analysis the relationships of DBH and the other attributes, and characteristic of crown form and crown structure, and estimate the of net productivity, and analysis leaf area amount. The analyzed results are summarized as follows. In the vertical distribution of crown, the relationship among crown-length(LC), clear-length(HB) and tree DBH of open-growth tree were found positively linear. LC and HB were increased as DBH increased. The mean crown ratio(CR) about 0.58, which have certain proportionate relationships, and growth condition was very well. The crown form and crown structure of mature China-fir, which the crown form shown cone or cylinder, and the leaf weight can to discriminate upper crown and down crown by maximum leaf density distribution on vertical layer. The maximum leaf density distribution is 1.7~2.0 kg/m on the from top to 3~5 m. The net productivity of China-fir, the net production of stem and branch were increased as DBH increased, the maximum net productivity of aboveground was diameter classⅡ about 1.46 ton/ha/yr. The major dry-matter distributions of China-fir stem increase with DBH, the branch dry-matter increase with height on the vertical distribution, the leaf dry-matter was concentrated in the upper or middle parts of the crown, and it is similar to the broad leaf type dry-matter distribution. The crown leaf area of China-fir individual tree increase with diameter class, so diameter class Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ of leaf area were 74.15, 104.13, 133.11, 164.31, 206.34 m2/tree, respectively. And it is estimate China-fir leaf area index about 3.87. The highly positive correlations were found between leaf area and sapwood, accord with the pipe model theory. The pruning operation might be useful maximum leaf density distribution on the vertical distribution of the China-fir plantation, and CR keep to 0.20~0.30 was expediency. The leaf spatial density was diameter class Ⅱ, and it have maximum biomass. The results will provide detailed information for China-fir plantation management.