關刀溪森林生態系之倒木孔隙更新

Studies on the Tree-fall Gap Regeneration in Guandaushi Forest Ecosystem

本研究在關刀溪森林生態系之倒木孔隙設置永久樣區，進行植群、種實雨、土壤種子庫、小苗組成及微氣候等之長期監測。初步結果發現種實雨主要來自現生植群之上木。土壤種子庫發芽試驗發現種子庫中的植物組成與現生植群不同，主要以陽性植物為主，其密度為1.129株/m2。調查孔隙中胸高直徑大於1cm的所有上木，發現以1-5cm徑級的為主，顯示森林植群主要以小苗庫或苗木庫的形式存在林下，等待填補小干擾孔隙所釋放的空間。相似性指數分析的結果，發現小孔隙中土壤種子庫的植物組成與種實雨、小苗及胸高直徑大於1cm的樹木間的相似性很低，在0至6.9%間，顯示土壤種子庫的組成分子對倒木孔隙更新的影響力並不明顯。小孔隙的更新來源應為孔隙產生前原存的小苗庫，或由種實雨落下迅速萌發的小苗庫，這些小苗將等待機會取代原有樹木或透過競爭將孔隙填補，達成森林孔隙的更新。 Tree-fall gaps in the close canopy induce gap regeneration. We measured the seed rain. Seedlings, soil seed bank and all the tree species greater than 1 cm in DBH at the small disturbance gaps created by fallen trees in Guandaushi forest ecosystem. The density of germinated seedlings of' soil seed bank is 1,129 plant/m2. The species composition of soil seed bank are almost pioneer species which are different from that of the site vegetation. The trees in gaps are mostly 1-5cm in DBH. It indicates that the forest vegetation is mainly presented by the seedling bank which will take the space released by gap. The similarity indices between the species composition of soil seed bank and seed rain, seedlings, tree species greater than 1 cm in DBH are very low (0-6.9 %). For the regeneration of tree-fall gaps in Guandaushi forest ecosystem, the seedlings or sapling bank, instead of the soil seed bank, would be the major source for the recruitment of upper canopy species.

Tree-fall gaps in the close canopy induce gap regeneration. We measured the seed rain. Seedlings, soil seed bank and all the tree species greater than 1 cm in DBH at the small disturbance gaps created by fallen trees in Guandaushi forest ecosystem. The density of germinated seedlings of' soil seed bank is 1,129 plant/m2. The species composition of soil seed bank are almost pioneer species which are different from that of the site vegetation. The trees in gaps are mostly 1-5cm in DBH. It indicates that the forest vegetation is mainly presented by the seedling bank which will take the space released by gap. The similarity indices between the species composition of soil seed bank and seed rain, seedlings, tree species greater than 1 cm in DBH are very low (0-6.9 %). For the regeneration of tree-fall gaps in Guandaushi forest ecosystem, the seedlings or sapling bank, instead of the soil seed bank, would be the major source for the recruitment of upper canopy species.