| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 98 === Macroecologists have often suggested that environmental factors such as climate and topography exert great influences on woody plant species richness. However, studies which have empirically documented the link between biological determinants and species richness are scant, e.g. the ecotone effect and the mass effect. Few studies have reported on an East Asian landscape too. Therefore, the aim of this article attempts to explore how species richness and independent environmental descriptors are related in the scale of Taiwan Island. Generalized linear models (GLM) were used to correlate species richness of woody plants per quadrat (400 m2) with three sets of variables, which are topographic, climatic and vegetation variables. Regression models were constructed by a manually operated forward stepwise procedure as the following process: the reduction of collinearity among variables, the model selection based on the percentage of deviance change (D2) and a Chi-squared significant test. The best explanatory model consists of nine variables. Including quadratic and cubic forms of temperature, the model explains about 53% of the deviance. Maximum woody plant species richness occurs at higher annual average temperatures with larger temperature ranges, in a potential ecotone, with higher maximum monthly rainfall, with less rock outcrops and fewer vegetation formations. Our results could be explained by the species-energy hypothesis, the environmental favorableness hypothesis and the ecotone effect. Stressful conditions, stability of climate, environmental heterogeneity and the mass effect proved to be of minor importance for determining regional patterns of species richness. We conclude that climate-driven process and ecotones are primary determinants of woody plant species richness in Taiwan Island. It is recommended using several sets of predictors and the methods that we proposed to capture the underlying complexity of biodiversity.
|
|---|
