墾丁高位珊瑚礁森林樹冠疏開對二十種樹木種子發芽的影響

Effects of Canopy Opening on Seed Germination among Twenty Species of Uplifted Coral-Reef Forest Trees at Kenting, Taiwan

王相華(Hsiang-Hua Wang) ； 郭耀綸(Yau-Lun Kuo) ； 潘順勇(Shun-Yung Pan)

《台灣林業科學》 12卷3期 (1997/09) Pp. 299-307

https://doi.org/10.7075/TJFS.199709.0299

摘要

本研究探討墾丁高位珊瑚礁森林二十種主要組成樹種的種子發芽性狀及其與森林鬱閉度的關係。試驗方法為將種子播種在裝土的籃內，分別置於鬱閉林下、人為孔隙中央、孔隙邊界及苗圃空曠處，觀察各區各樹種種子的發芽率及發芽期間，並調查各區的光量。在夏季及秋季，林下、孔隙邊界及孔隙中央的平均光量分別為苗圃空地的0.5%-0.8%、5%-8%及12%-16%；冬季時因落葉量較多，該三處的相對光量會提高。在20個試驗樹種中，茄苳、紅柴、無患子、土楠、台灣赤楠、山柚、象牙樹、大葉楠、鐵色及樹青等10種在各區發芽率差異不顯著；黃心柿種子的發芽率以孔隙邊界最高，苗圃空曠地最低；其餘9種的發芽率均以林下最低，其中鐵冬青、血桐、蟲屎、欖仁，石朴及火筒樹等6個樹種在鬱閉林下種子無法發芽，後二種在孔隙邊界也無法發芽，但此6樹種在林下的種子移至苗圃空曠處後即可發芽，具機能性休眠特性。供試二十種林木中鐵冬青及石朴種子顯現內生性休眠特性，具有延遲發芽及發芽完成所需時間延長現象；其餘18個樹種除土楠外，種子發芽在5週內完成且發芽整齊。本研究發現林內孔隙及空曠地對陽性樹種種子的發芽有促進作用，各樹種種子發芽時對光環境的需求可能影響其在不同森林微環境的適應及更新狀況。

關鍵字

孔隙更新 ； 種子 ； 發芽 ； 休眠 ； 墾丁

並列摘要

Seeds of 23 species native to the uplifted coral-reef forest of Kenting in southern Taiwan were planted in trays with forest soils. The trays were then placed at 4 locations with different light conditions: forest understory, gap center, gap edge, and nursery opening. Germination ratio and duration as well as light intensity were monitored at each of the 4 locations. During summer and autumn seasons, the light intensity measured at the forest understory, gap edge, and gap center were, respectively, 0.5%-0.8%, 5%-8%, and 12%-16%, relative to the light intensity measured at nursery opening. In winter, relative light intensity rose as the amount of fallen leaves increased. The germination ratios of 10 species, Bischofia javanica, Aglaia formosana, Sapindus mukorossi, Cryptocarya concinna, Syzygium formosanum, Champereia manillana, Diospyros ferrea, Machilus japonica, Drypetes littoralis, and Pouteria obovata, showed no significant differences among the 4 locations. Seeds of Diospyros maritima had the highest germination ratio in gap edge and the lowest in the nursery opening. The other 9 species had the lowest germination ratio in the forest understory. We further observed that seeds of 6 species, llex rotunda, Macaranga tanarius, Celtis formosana, Melanolepis multiglandulosa, Terminalia catappa, and Leea guineensis, did not germinate while placed in the forest understory hut began rapidly germination when moved to the nursery opening. Apparently, these trees showed canopy-induced facultative dormancy of seeds. Seeds of most species germinated quickly and completed their germination duration within 5 wk except for those of C. formosana and I. rotunda, which showed endogenous seed dormancy. Results indicate that natural treefall gaps and nursery openings do not inhibit the germination of most species, but allow pioneer species to germinate and, therefore, promoting regeneration. Germination requirements might play an important role in controlling the species composition of regeneration in forest understory, gaps, and open fields.

並列關鍵字

gap regeneration ； seeds ； germination ； dormancy ； Kenting