執行成果摘要
This study examined the effects of different thinning intensities on the dynamic occurrences of indigenous broadleaf species regeneration at the Fenggong Mountain Taiwania cryptomerioides Hay. plantation. The site was thinned in 1998 for the then 26-year-old trees. The control zone (no thinning), lightly thinned zone (with thinning intensity of 20%), and heavily thinned zone (with intensity of 40%) were compared. Each zone included 9 plots of 10×10 m2 for a total area of 900 m2. Natural seeding on the test plots was then observed.The results indicated that there were seedlings of 65 species of regenerated species belonging to 29 families. Of these, predominately 46% belonged to the Myrsinaceae family, it was followed by Rutaceae at 24%, and Lauraceae at 14%. Species-wise, Ardisia quinquegona occurred at 41% was the most numerous. For larger trees, Litsea accuminata at 7% was the most numerous.In the plots of different Taiwania plantation thinning intensity treatments, of the emerging plant species, lianas and herbaceous plants accounted for ca. 19~25%. The understory shrubs accounted for 23~26%. At the control zone plots, the proportions of sub-canopy and canopy predominant species were 54% and 2%, respectively. At the lightly thinned plots, the sub-canopy species reduced to 40% and the predominant species of the canopy layer made up 9%; and at the heavily thinned plots, predominant species of the canopy layer increased to 17%. The results indicated that thinning intensity of the Taiwania plantation trees had less effect on the lianas and herbaceous plants, and along with increased thinning intensity, shade-tolerant sub-canopy layer small trees reduced which in turn affected the sub-canopy layer predominant species to invade the gaps. When thinning intensity increased, density of Taiwania trees decreased and the release of environmental resources facilitated the invasion of seedlings of canopy layer predominant tree species.