人工針葉林與天然闊葉林孔隙更新動態研究(4/4)

(一)在不同大小(10~200㎡)的林冠層孔隙中，幼苗型態變化相當大，種的發生端視該孔隙四周的母樹而定。孔隙中央常出現先驅樹種，但存活不佳。人工林林床幼苗發生數量與種類和天然林的距離有相關，但數量最多的種類多是小型漿果類樹種。
(二)台灣櫸苗木在13%透光下苗木形質較佳，超過25%光照則分枝數增加;牛樟耐蔭性較台灣櫸為佳，但在4.5%以下(相較於林地地被遮蔽的環境)則存活不良，小西氏賽楠在三種之中具最佳的耐蔭性。
(三)人工針葉林之幼苗發生以陽性樹種之山胡椒、雀不踏為主，但長葉木薑子、瓊楠、長尾柯、紅楠等多以根株萌芽更新為主要形式。
(四)就調查資料顯示，針葉人工林內天然更新闊葉樹幼苗的種類與數量，已可具有混合林多樣性之價值潛能。透過人工林的期中撫育，除改善留存木形質外，同時營造適宜林下光環境，用以促進天然更新幼苗之生長，促進林分組成與結構之多樣性。

(1) In canopy gaps ranging from 10 to 200 ㎡ in size, seedling morphology varies considerably. The occurrence of each tree species is determined by the mother trees surrounding the respective gap. Pioneer tree species frequently emerge in the center of these gaps yet exhibit poor survival rates. The number and species composition of seedlings on the forest floor of artificial planted forests correlate with their distance from adjacent natural forests, while the most numerically dominant species are mostly small berry-producing tree taxa.
(2) For *Zelkova formosana* seedlings, their functional traits are optimal under 13% light transmittance; when light transmittance exceeds 25%, the number of branches increases. *Cinnamomum kanehirae* has better shade tolerance than *Zelkova formosana*, but its survival rate is poor when light transmittance is below 4.5% compared to the shaded understory environment of forest land. *Nothaphoebe konishii* exhibits the strongest shade tolerance among the three species.
(3) In artificial coniferous forests, seedling establishment is primarily dominated by light-demanding tree species such as *Lindera glauca* and *Zanthoxylum ailanthoides*, whereas other species including *Litsea elongata*, *Beilschmiedia erythrophloia*, *Lithocarpus longicaudatus*, and *Machilus thunbergii* mainly rely on stump sprouting as their primary regeneration strategy.
(4) Survey data indicate that the species richness and abundance of naturally regenerated broadleaved tree seedlings in coniferous planted forests already hold the potential to deliver the diversity value of mixed forests. Through intermediate thinning of planted forests, in addition to improving the traits of residual standing trees, suitable understory light environments can be constructed to promote the growth of naturally regenerated seedlings, thereby enhancing stand composition and structural diversity.