| Summary: | 碩士 === 國立臺灣師範大學 === 生命科學研究所 === 101 === Forest gaps can promote canopy tree regeneration thereby maintain forest species diversity. Gaps provide space and light for rapid growth of understory plants, especially shade-tolerant species, thus help them reach the canopy. This regeneration process has been well described in tropical and temperate forests, but is rarely studied in subtropical forests. Forests in Taiwan which is located at the west side of North Pacific, is influenced by frequent typhoons as such the forests have structural adaptation to typhoon disturbance. This study examined gap characteristics in a subtropical forest of northeastern Taiwan, the Fushan Experimental Forest. Frequent typhoon disturbance causes regular defoliation, and thereby increases understory light availability allowing seedlings of shade-tolerant species to reach the canopy. It is questionable that in such a forest, if gap dynamics also plays an important role on canopy tree regeneration. To address this question, 7 transects were set up at watershed #1 in Fushan Experimental Forest. The gaps intersected the transect lines were surveyed and gap characteristics including area size, age, and turnover time were compared to the study conducted in 1995 following the disturbance of 6 typhoons of 1994. Seedling composition and understory light environment were also investigated to examine their relation to gap and non-gap understory. A total 17 gaps were recorded and the area of individual gaps ranged from 1 to 36 m2. Both the numbers and size of the gaps were less/smaller than those reported before. The calculated turnover time is 197 and 398 years when gaps < 1 and ≦ 9 years, respectively, were include and is much longer than the 51 and 175 years reported in the 1995 study. Understory light availability showed no significant difference between gap and non-gap understory and this contributed to the high similarity of seedling composition between the two environments. Moreover, non-gap understory encompasses all seedling species recorded in gaps. Thus, seedling regeneration in Fushan may not rely on gaps.
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