臺灣中部大雪山地區紅檜人工林於不同疏伐強度下林木健康及林下植群之探討

Effects of Understorey Vegetation and Tree Health by Different Thinning Intensity at ＂Chamaecyparis Formosensis＂ Matsum Plantations in Dasyueshan Area, Central Taiwan

蘇柏羽(Po-Yu Su) ； 郭家和(Chia-Ho Kuo) ； 陳朝圳(Chaur-Tzuhn Chen) ； 陳建璋(Jian- Zhang Chen)

《中華林學季刊》 48卷2期 (2015/06) Pp. 137-153

摘要

疏伐為森林經營重要作業之一，透過適當疏伐有助於立木生長及提升林木材質。紅檜（＂Chamaecyparis formosensis Matsum＂）為台灣及亞洲地區重要經濟樹種之一，以往研究中都著重於疏伐對紅檜林分生長、直徑分布等影響，較少綜合探討不同疏伐強度處理下健康狀態及林下植群狀況。因此，本研究以林務局大安溪事業區內紅檜人工林疏伐樣區為研究範圍。透過健康評估表進行評估不同疏伐處理下，紅檜人工林健康度及林下植群狀態。研究結果顯示，藉由林木外觀評估法選取10項林木指標並透過因素分析萃取4個紅檜健康解釋因素；其中以冠層綜合指標的解釋力最高。此結果說明紅檜人工林受到競爭下，樹冠密度、樹冠枯梢程度等對於紅檜健康程度具有一定影響。此外，樣木健康等級分布情況中，以中度疏伐佔健康等級比例（44%）較高，死亡比例方面則以未疏伐（7.6%）最高；此結果顯示透過適當疏伐確實能有助於人工林分健康度提升。不同疏伐強度下，草本植物多樣性除均勻度之外，其他包括物種豐富度、Shannon多樣性指數及Simpson多樣性指數，強度疏及中度疏伐與未疏伐呈現極顯著差異。在木本植物多樣性方面，不同疏伐強度下四個指數皆呈現不顯著。由結果能得知，疏伐作業能除能使林木之健康程度有所改變之外，也能增進地表草本層植物多樣性與物種歧異度。

關鍵字

紅檜人工林 ； 疏伐 ； 林木健康 ； 地被多樣性

並列摘要

Thinning is an important and constructive process for forest plantation tending operation. Proper thinning will help the stand density management, the tree growth and enhance the stumpage values. The ＂Chamaecyparis formosensis Matsum＂ are important forestry resources in Taiwan and Asia. Previous studies of red cypress plantation mostly focused on the establishment of different growth harvesting model, thinning effects of individual tree and stands growth, and diameter distributions by thinning in different site. There was very few comprehensive discussion on the health condition of trees under different thinning levels. In this study, we used the tree health assessment and understory vegetation for different forest thinning treatments in C. ＂formosensis＂ Matsum thinning demonstration area, Daanshi working circle of Forestry Bureau, northeast Taiwan. Visual tree assessment was used to select 10 forest health indicators and factor analysis was further applied to extract 4 explanatory factors of Formosan Cypress forest health, among which the crown composite indicator exhibited the strongest explanatory power. The result demonstrated that the health of Formosan Cypress plantation forest under the situation of forest competition was affected by the characteristics of the crown including the crown density and dieback. Analysis of health Formosan Cypress forest distribution with different thinning intensity showed that moderate thinning forest had highest proportion (44%) of healthy trees, and no thinning forest had highest percentage (7.6%) of tree death. Analysis of the understory in Formosan Cypress forests showed that except for species evenness, the indices of herbaceous plant diversity including the species richness, Shannon diversity index and Simpson diversity index of no thinning forest were significantly different from those of moderate and severe thinning forests. In contrast, no significant difference was found in the 4 above-mentioned indices of woody plant diversity between Formosan Cypress forests with different thinning intensity. The results of this study indicated that properly conducted thinning operation might have a good impact on the forest health and increase the understory herbaceous plant diversity.

並列關鍵字

Taiwan red cypress plantation ； Thinning ； Tree health ； Vegetation diversity