檜木林經營模式對於地被植物多樣性與林木天然更新之影響

森林經營對於天然檜木林生態之影響過去在台灣曾引起重大爭議，相關研究亦未有定論，因此仍需投入更多研究工作進行驗證。本研究在具有長久林業經營歷史而且仍保有廣大天然檜木林的棲蘭山區，選擇4種不同經營模式下的檜木林分進行地被植群及天然更新樹苗調查，以比較不同林型之植物多樣性與林下更新狀態。調查結果發現，枯立倒木整理後老齡林具有較高的地被植物多樣性，天然老齡林則具有較高的樹苗多樣性，而擇伐後天然更新林無論在地被植物或樹苗的多樣性皆為最低。從物種組成來看，天然老齡林的地被植物及樹苗物種均與其他林型存有明顯的區隔。不同林型的天然更新狀態也有極明顯的差異，其中以天然老齡林的樹苗量最高，分別在全部樹種以及檜木(均為台灣扁柏)樹苗上佔有77、87%。此外，91%檜苗是建立在木質殘材之上，顯見與其他樹種具有不同的生長基質偏好。本研究顯示不同的經營模式對於檜木林的地被植群、林木天然更新具有長期的影響，人為作業過之林分雖歷經20~40年的恢復，仍未發展出近似天然老齡林的狀態。我們建議應保護及長期監測天然老齡林之生態，並可運用枯立倒木整理林內之不同植生階段來增加生物棲地種類，進而提升天然林之整體生物多樣性。至於皆伐後人工栽植林與擇伐後更新林，應積極進行中、後期撫育工作以促進林木生長並改善林況。

關鍵字

台灣扁柏；枯立倒木整理；檜木林；地被植群；天然更新

並列摘要

The impact of forest management on the ecology of natural Chamaecyparis (cypress) forests previously caused momentous disputes in Taiwan. However, the scientific questions behind this issue have never been settled and thus require further investigations. This study was conducted in the Chilanshan area of northeastern Taiwan, where there is a long history of forest management, and extensive natural Chamaecyparis forests are still preserved. We investigated the ground vegetation and naturally regenerating seedlings in stands under 4 different management regimes to compare their plant diversity and tree regeneration. Our results showed that the diversity of ground vegetation was higher in the old-growth forest where snags and logs had previously been harvested, while the diversity of tree seedlings was higher in the natural old-growth forest. The lowest diversities of ground vegetation and seedlings were both observed in the naturally regenerated stand established after selective cutting. The natural old-growth forest was also distinct from the other stand types in terms of the species composition. The natural regeneration of seedlings significantly differed among stand types. The natural old-growth forest contained the greatest amount of both cypress seedlings (all of which were Chamaecyparis obtusa var. formosana; 87%) and overall seedlings (77%). Moreover, 91% of cypress seedlings were established on coarse woody debris, revealing a distinct substrate preference from the other species. Our study indicated long-term impacts of management regimes on the ground vegetation and natural regeneration in Chamaecyparis forests. After 20~40 yr of recovery, stands that had experienced management practices were still dissimilar to natural old-growth forests. Therefore, we would argue that natural old-growth forests should be protected and ecologically monitored, and that old-growth forests where snags and logs had previously been removed could offer various vegetation stages to create more-heterogeneous habitats and thus enhance the overall biological diversity. As for plantations and naturally regenerated stands, middle- or later-stage tending practices should promptly be applied to improve tree growth and stand conditions.

並列關鍵字

Chamaecyparis obtusa var. formosana ； removing snags and logs ； Chamaecyparis forest (cypress forest) ； ground vegetation ； natural regeneration

國際替代計量

檜木林經營模式對於地被植物多樣性與林木天然更新之影響

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