| Summary: | 碩士 === 東海大學 === 生命科學系 === 100 === The impact of disturbance on the ecosystem characteristics has been an important topic in ecological studies. In Taiwan, typhoons are perhaps the most important disturbance agent in forest ecosystems. The meteorological records of typhoon raid during past 20 years show distinct typhoon disturbance regime in different regions of Taiwan. Such heterogeneity in disturbance regime provides ideal environment for investigating the importance of typhoon disturbance in shaping the community structure of forests. Recently, various plant functional traits are widely measured for investigating the large-scale ecological questions. Functional traits are generally easy to measure and thus make extensive measurements possible. Some common traits include specific leaf area, tree height and wood density. These traits can reflect trade-offs of various strategies for the growth and survival of plants. In order to understand how typhoons influence the structure of forest ecosystem, I will compare functional traits related to wind disturbance in two Forest Dynamics Plot (FDP): one at FuShan (FS) which has frequent typhoon disturbance and the other at LienHuaChih (LHC) where typhoon disturbance is relatively infrequent. My research questions are organized into: (1) Species level: are there any differentiations of functional traits between shared species of two plots under different disturbance regimes? (2) Quadrat level: do canopy heights of two sites exhibit differentiations that reflect different level of wind disturbance? (3) Site level: is there any difference in functional composition between two different disturbance regimes? I used the importance value (IV; %) to selected the most important species for each of the two 25ha plots (each plot has 625 20 × 20m quadrates) that constitute 70% of the total IV. For each species I selected approximately 40 trees to measure crown and architectural traits (e.g. crown area, crown depth, tree height and wood density). I used Maximum Likelihood method to model the allometric relationships between different trait values. Analysis of covariance (ANCOVA), generalized least square (GLS) model and principal component analysis (PCA) were used to test whether there were trait differentiations under different disturbance regimes. The results showed: (1) At a given diameter at breast height (DBH), shared species tended to have lower tree height in FS. At a given tree height, shared species tended to have greater crown area in FS. (2) Mean canopy height in FS was significantly lower than in LHC. Canopy height was negatively correlated with convexity in FS, but positively correlated with elevation in LHC. (3) FS tended to form higher maximum tree height and slender trunk, but functional composition in LHC was more diverse than in FS. The adaptation strategies in frequently disturbed FS tended to be conservative: lower but consistent canopy height can reduce the damage from high wind blow, and wider crown area can compensate the relatively low light condition. The adaptation strategies in less frequently disturbed LHC were diverse: ranging from lower wood density with slender tree form to higher wood density with greater crown depth, shorter and thicker tree form. This research indicated intraspecific trait differentiations, variation of canopy structure and diversity of functional composition can reflect different adaptation strategies between distinct typhoon disturbance regimes.
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