不同程度的擾動環境下森林生態系樹形與林冠特徵之分化

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題名:	不同程度的擾動環境下森林生態系樹形與林冠特徵之分化
其他題名:	Differentiation Of Tree Architectural And Crown Traits In Two Hardwood Forests Under Distinct Disturbance Regimes
作者:	陳思瑋 Chen, Szuwei
貢獻者:	江智民 Chiang, Jyhmin 東海大學生命科學系
關鍵詞:	功能特徵組成;植物功能特徵;森林動態樣區;異速生長函數;擾動特性 Plant Functional Trait;Forest Dynamic Plot;Allometric Function;Disturbance Regimes;Functional Composition
日期:	2012
上傳時間:	2013-01-02T09:01:59Z (UTC)
摘要:	擾動如何影響生態系的特性是近年來生態研究者所關注的議題。颱風為影響臺灣森林生態系重要的擾動因子之一。過去20年颱風侵襲的資料顯示台灣不同地區長期以來累計不同程度的颱風擾動，這提供了良好的環境來探討不同程度的長期擾動環境對森林結構及植物適應策略的影響。近年來，研究者以植物的功能特徵作為探討大尺度生態問題的工具。植物功能特徵為相對易於廣泛量測的特徵如比葉面積、樹高、木質密度等。這些特徵可反映植物生長與生存的權衡。本研究比較颱風擾動頻繁與相對不頻繁的福山及蓮華池森林動態樣區內植物功能特徵組成，以三個層次探討長期颱風擾動環境對於森林生態系結構及植物適應策略的影響：(1) 物種層次：兩樣區之共同樹種是否因長期擾動環境不同而有特徵的分化？(2) 樣方層次：兩樣區之冠層高度是否因長期擾動環境不同而隨著地形有特定的空間分布？(3) 樣區層次：兩樣區之特徵組成是否因長期擾動環境不同而有不同的分化？本研究於兩個25公頃樣區內(每樣區含有625個20 ? 20m之樣方)各選出重要指標累計前70%的物種，每種約40棵，測量樹冠特徵(冠幅面積、長度及深度)和樹形結構(樹高、第一枝條高、木質密度)。以最大概似估計法推算特徵間的異速生長函數，使用共變數分析(Analysis of covariance)、最小化平方法(Generalized least square)及主成分分析(Principal component analysis)檢定特徵是否因長期擾動環境不同而有分化。結果顯示：(1)相同胸徑下位於福山的共同樹種有較矮的樹高，相同樹高下，位於福山的共同樹種有較大的冠幅。(2) 福山樣區的平均冠層高度小於蓮華池樣區，福山的冠層高度與地形凹凸度呈顯著負相關，蓮華池樣區的冠層高度與海拔高度呈顯著正相關。(3) 福山傾向於形成較大的冠幅及較矮胖的樹型，蓮華池的功能特徵組成則較為多樣。綜觀以上所述，植物為適應長期颱風擾動頻繁的福山樣區可能發展出的適應策略為：隨著地勢高低形成矮且一致的冠層高度，降低強風的傷害，因為沒有突出的樹冠及較為矮胖的樹型而形成寬廣的冠幅以提升光的攔截率。植物適應長期颱風擾動較不頻繁的蓮華池樣區所發展的策略較為多樣：如木質密度小、最大樹高高且細長的樹型，或木質密度大、較深的冠幅但較矮胖的樹型。此研究顯示，在不同程度的擾動環境下，種內特徵的分化、林冠結構的變化以及多樣化的群聚功能特徵組成能反映出森林面對不同擾動程度的適應策略。 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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