不等林木間距對平地造林地闊葉林立木生長之影響

The Effect of Trees Spacing on the Growth of Trees in Afforested Broadleaf Stands on Cltivated Farmland

林金樹(Chin-Su Lin) ； 王子嘉(Ju-Jie Wang)

《中華林學季刊》 46卷3期 (2013/09) Pp. 311-326

摘要

本研究以台南市白河農場平地造林地的光蠟樹（Fraxinus griffithii Hay.）、小葉欖仁（Terminalia mamtalyi Tul.）及苦揀（Melia azedarach L.）林分為研究材料，利用數位航測法分層選取林分中不同林木間距（2-，3-，或4m）的林木為對象，評估林木的立木特徵及生長量的差異。結果顯示：苦揀林分的林木擁有較快速的直徑生長以及高生長速率，光蠟樹的生長速率最小。光蠟樹及苦揀林木的胸高直徑隨林木間距而增，4m間距（大間距）林木的胸高直徑為2m間距（小間距）林木的1.10倍；間距對不同樹種樹高的影響不同，大間距可以提高苦揀樹高約5－8%，對光蠟樹作用不明顯，但會降低小葉欖仁樹高約5－9%。三個樹種的林木樹冠投影面積三年定期增加量明顯的隨林木間距增大而顯著的增加。林木的樹高胸徑比（HDR）會隨林木間距增大而提高，樹形改善現象以光蠟樹及小葉欖仁最明顯，大間距可以有效降低林木的競爭壓力約40－70%。適度的擴大平地造林的林木間距，將可有效促進林木冠層枝葉面積的效應，促進平地造林闊葉樹林的生長，並避免早期疏伐作業對林木造成可能的干擾。

關鍵字

立木間距 ； 生長 ； 樹形 ； 競爭指數

並列摘要

This study aimed to explore the adaptation of tree parameters and tree growth to tree spacing in afforested broadleaf forest. The stands of Fraxinus griffithill Hay, Terminalia mantalyi Tul., and Melia azedarach L (abbreviated as Fraxinus, Terminalia, and Melia respectively) in Baihe Farm which locates on Baihe District, Tainan City were selected as the study site. Trees with 2-, 3-, or 4-m spacing in stands were individually picked as the samples using the stratified sampling by aerial photogrammetry technique. Results showed that Melia has a higher rate of tree diameter (DBH) growth and height growth then Terminalia and Fraxinus. DBHs of the Fraxinus and Melia trees are positively related to tree spacing. The tree with 4m spacing (big spacing) whose DBH is about 1.10 times higher than the trees with 2m spacing (small spacing). On the contrary, the spacing effect on the height of trees changes dramatically among the species. The height of Fraxinus trees is almost same among the spacing. In contrast to the small spacing, the big spacing can improve the height of Melia trees by 0.05-0.08 times while decreases the height of Terminalia trees by 0.05-0.09 times. A three-year periodical increment of the projected crown area is also increased as the spacing extended from 2m to 4m. The height to diameter ratio of trees decreased as tree spacing increased in particular for the Fraxinus and Terminalia Tree shape can be improved significantly. The value of Hegyi competition index can be reduced by 40-70% for the tested species. It is concluded that canopy foliage area and tree growth will be improved meanwhile the thinning practice can be omitted, as a result no damage impact will caused by thinning disturbance if trees are initially planted with appropriate spacing.

並列關鍵字

tree spacing ； growth ； tree shape ； competition index