杉木人工林疏伐後原生種樹苗之天然更新

植物群落未來的組成與結構決定於現階段小苗的天然更新狀況。本研究透過剖析人工林砍伐跡地原生樹種的小苗組成、結構與微環境因子間之關係，以提出經營與復育策略。研究地點在台灣中部惠蓀林場杉木林行列疏伐跡地。伐木後此地林冠層尚有殘留的杉木，而次林冠層則有天然更新的原生樹種。本研究於伐木結束一年半後，設立30個1×2 m樹苗小樣方。樣方內共調查到121株樹苗。依樹苗的物種組成及數量，小樣方內由樹苗所組成的植物群落可分成三群：第一群的優勢物種為中度耐陰的灌木樹種琉球雞屎樹，主要分布在上層植被（林冠層及次林冠層）覆蓋度較高處；第二群優勢物種為先驅喬木樹種白匏子，主要分布在上層植被覆蓋度較低且蕨類植物覆蓋度較高處；第三群優勢物種為中度耐陰性的喬木香楠，主要在地表蕨類植物覆蓋度低處。在群落結構上，樹苗的植株密度以及物種多樣性皆和次林冠層覆蓋度呈顯著負相關。杉木殘材的覆蓋度對物種組成、植株密度和物種多樣性皆無顯著影響。因此本研究推測，人工林砍伐跡地天然更新的樹苗物種組成主要受到林冠層、次林冠層和地被層植物覆蓋度之綜合影響，而樹苗群落結構（密度和多樣性）則主要受到次林冠層覆蓋度之影響。本研究建議若欲以被動策略復育人工林砍伐跡地時，有必要維持林冠層和次林冠層的覆蓋度異質性，以促進不同更新策略樹種小苗的共存，進而提高物種多樣性。

關鍵字

惠蓀實驗林場；人工林伐木跡地；原生樹種小苗；天然更新；次生演替

並列摘要

Natural regeneration of native seedlings is important to the future composition and structure of forests. In this study, we investigated relationships between microenvironmental variables and native tree seedlings (including their composition and structure) in a logged China fir (Cunninghamia lanceolata) plantation, in order to propose management and restoration strategies. Our study site was located in the Huisun Experimental Forest Station, central Taiwan. After logging practices, the canopy and subcanopy layers were respectively dominated by residual China fir and naturally regenerated native trees. We set up 30 seedling subquadrats (each 1×2 m) in this plantation. The communities in these subquadrats could be clustered into 3 groups based on the species composition and abundance of 121 tree seedlings recorded in censuses. The first group was dominated by the moderately shade-tolerant shrub species, Lasianthus fordii, and was located at the habitat with high overstory (canopy and subcanopy) cover. The second group was dominated by the shade-intolerant tree species, Mallotus paniculatus, and the habitat of the group was characterized by low overstory cover and high understory fern cover. The third group was dominated by the moderately shade-tolerant tree species, Machilus zuihoensis, and its habitat was characterized by low understory fern cover. In terms of community structure, seedling density and diversity indices were significantly negatively correlated with subcanopy cover. Residual coarse woody debris of China fir had no significant effects on species composition, stem density, or species diversity. Regeneration of native trees was mainly influenced by the canopy, subcanopy, and understory cover, while the seedling community structure (stem density and species diversity) was mainly influenced by the subcanopy cover. We proposed that it is necessary to maintain the heterogeneity of overstory cover when managing logged plantations through passive strategies, since habitat heterogeneity facilitates the coexistence of seedlings with different regeneration needs and in turn maintains species diversity.

並列關鍵字

Huisun Experimental Forest ； logged plantation ； native tree seedling ； natural regeneration ； secondary succession

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杉木人工林疏伐後原生種樹苗之天然更新

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