| Summary: | 碩士 === 國立臺灣大學 === 生態學與演化生物學研究所 === 92 === Abstract
For study the regeneration of forest tree species at seedling stage in Fushan Subtropical Rain Forest in northern Taiwan, we set up 87 stations in a 25-ha permanent plot. Each station includes one 0.5m2 seed trap and three 1m2 seedling plots. The purposes of this study are to understand the temporal variation of tree species seedlings, the relationship between seed rain and seedling bank, the influences of understory vegetation on tree species seedlings established, and to probe into the regeneration strategies of the main tree species.
There were six seedling censuses from Sep. 2002 to Feb. 2004. A total of 5127 seedlings were found, belonging to 19 families, 28 genera and 32 species. Because of the mass germination of some species in a short period, there is a very large variation of seedling density with time. Numerous newborn seedlings were found in each recensus, especially in May 2003, and composed mainly of Myrsine sequinii, Pleocnemia rufinervis, Litsea acuminata, Glochidion acuminatum, Machilus thunbergii, Machilus zuihoensis and Engelhardtia roxburghiana. The tree species were divided into three groupsbased on the time between their seed fell and seedlings germination: 1. germinating quickly after seed fell, such as Pleocnemia rufinervis; 2. germinating with a short break, about 1 to 2 months, such as Litsea acuminate and Machilus thunbergii; 3. germinating after a dormancy of about half a year, such as Myrsine sequinii and Glochidion acuminatum.
The shrub layer vegetation was composed of 1729 shrubs, belonging to 6 families, 9 genera and 14 species. The most numerous species is Blastus cochinchinensis. The grass layer was composed of 91 species, belonging to 64 families and 71 genera. The dominant species include Diplazium dilatatum, Dicranopteris linearis and Elatostema lineolatum.
According to TWINSPAN analysis, the grass layer communities in the seedling plots could be divided into four groups, and each was named by the first dominant species and the second dominant species: 1. Dicranopteris linearis - Ardisia chinensis type, distributed over the ridge; 2. Diplazium dilatatum - Dicranopteris linearis type, most widespread; 3. Diplazium dilatatum - Elatostema lineolatum type, distributed along the stream; and 4. Elatostema lineolatum - Diplazium doederleinii type, distributed along the stream, but moister than type 3. According to χ2-test of goodness of fit, the relationship between tree seedlings mortality and understory communities are not obvious.
The regeneration strategies of tree species are different from each other. Myrsine sequinii seedlings have a higher survival rate; Schefflera octophylla and Glochidion acuminatum product a lot of seeds to ensure enough seedlings; Machilus thunbergii and Litsea acuminate seedlings can live under a shade canopy for a long time, waiting for the chance to grow upward. Limlia uraiana and Castanopsis carlesii have a few seedlings emerged from seed, their regeneration probably rely on sprouting from basal buds, sprouting maybe their mainly regenerated strategy.
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