- 作者: 楊榮啟
- 作者服務機構: 國立臺灣大學森林學系
- 中文摘要: 經營集約之人工林,從樹冠開始競爭以至主伐期間需要實施數次疏伐,疏伐主要為促進留存林木之材積生長及改進木材品質,兼能提早收擭充裕木材工業原料。臺灣為供應發展木材工業所需原料,積極擴大造林,所以疏伐之重要性是與日俱增。 本研究應用臺灣大學實驗林疏伐試驗永久樣區賢料研究疏伐對於林木生長的影響,所得結果可供本省人工林經營之依據參考。根據疏伐強度實施A、B、G、D四種不同疏伐方法實驗,比較探討其在發育過程上之林木生長及林分構成狀態。摘其重要結果如下: (1)疏伐方法對於林木平均胸高直徑生長之效果非常顯著,強度疏伐者皆大於弱度疏伐者。 中)疏伐方法對於林木平均樹高生長之影響甚微。 (3)林木株數之遞減度與疏伐度之強弱成比例,疏伐度愈強,其遞減度愈烈,最後所殘存之株數也愈少。 (4)各種疏伐方怯在46年生時之林木(殘存林木)材積,A種為591立方公尺,B種次之為460立方公尺,C種及D種最少各為413及422立方公尺,可見疏伐強弱對於殘存林木之材積數量有相當之影響。林木三次疏伐量合計,以強度之C種及D種最多各為344及309立方公尺,B種次之為244立方公尺,A種最少為136平方公尺。 (5)實施強度疏伐之林分,其樹幹形狀常比弱度疏伐者尖削。 (O林木按胸高直徑級之株數分布,皆近似常態分布,隨林齡之增加而向右推移並趨於扁平“大徑木所佔之比率,強度疏伐老比弱度疏伐者為多。 (7)林木按樹高級之株數分布“也皆近似常態分布,隨林齡之增加而向右推移,但其變域逐漸縮小及成為狹?狀。各樹高級之林木株數所佔比率,受疏伐度之影響不甚顯著。 (s)各種疏伐度之樹高隨胸高直徑變化的曲線(樹高曲線),皆近似直線,而各年次在同胸高直徑級中,均以強度疏伐之樹高為低。
- 英文摘要: In the plantation with intensive management, several thinnings shouldbe undertaken from the time of crown competition until the final harvesting.The aim of thinning is to increase volume and improve timber quality oftrees to reserve for final harvesting, and at the same time produce treesfor raw material of forest industry. Recently, positive efforts were made toenlarge the afforestation in order to supply the wood raw material for thedevelopment of forest industry. The thinning treatment therefore must beemphasized both in the national and private owned forest. This paper is to study the change in growth in response to thinning byusing the data from the permanent sample plots of thinning in the Experi-mental Forest '.of Taiwan University. The results of this study providesguidance on the management of plantation in Taiwan. Four differentthinning treatments, based on the thinning intensity, were carried out tostudy the growth and stand structure at different developing stages. Theimportant results of this study may be summarized as follows'.(1)The effect of thinning on the growth of average diameter of trees was highly significant. The heavier thinnings, the greater was the average diameter.(2) Thinning had little effect on the growth of average height.(3) The reduction in number of trees per unit area was proportional to the intensity of thinning: the heavier thinnings made the reduction not only serious, but also less trees, than the lighter thinnings.(4) The volume per hectare for the four thinning treatments at 47 years: treatment A was 591 cubic meters in the first place, treatment B was 460 cubic meters in the second; while treatments C and D were the last with 413 and 422 cubic meters respectively. So, the intensity of thinning has considerable effect on total volume of trees left. The total thinned volume of three repeated thinnings: C and D gave the most with 344 and 309 cub--c‘meters respectively, B gave the second with 244 cubic meters, and A gave the least with 136 cubic meters.(5) The heavier thinnings produced tapering trees than the lighter thinnings.(6) The diameter distribution of all four thinning treatments approximated the normal distribution.All of them moved to the right一and flattened out with advancing of age. Heavier thinnings produced more relatively large trees than lighter thinnings.(7) The height distribution of all four thinning treatments also approximated the normal distribution. All of them moved to the right and the range became narrow with advancing of age.(8) The curve of height on diameter for all four thinning treatments approximated to a straight line, and the height in the same diameter class of heavy thinnings are always low.
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