Micro-topographic Differentiation of the Tree Species Composition in a Subtropical Submontane Rainforest in Northeastern Taiwan

台灣東北部亞山地雨林樹木組成之微地形分化現象

10.7075/TJFS.201003.0063

蘇聲欣(Sheng-Hsin Su)；謝長富(Chang-Fu Hsieh)；張楊家豪(Chia-Hao Chang-Yang)；呂佳陵(Chia-Ling Lu)；關秉宗(Biing T. Guan)

生境分化 ； 微地形 ； 指標種 ； 生育地關聯性 ； 福山森林動態樣區 ； niche differentiation ； micro-topography ； indicator species ； habitat association ； Fushan Forest Dynamics Plot

臺灣林業科學

25卷1期（2010 / 03 / 01）

63 - 80

英文

為了探討森林組成在細微尺度異質環境下的變化，本研究於台灣東北部天然闊葉林中設立一處25公頃的永久樣區，進行微地形高程測量工作，並完成區內所有胸高直徑達到1 cm以上樹木的每木調查工作。本研究採用迴歸樹狀模式與指標種分析法，以分析森林組成在微地形上的分化以及個別樹種對於生育地的關聯性。分析結果顯示，在這個連續的森林區域內，近30%的樹木組成變化可歸因於微地形因子。其中以坡面曲度、坡度與方位角為最關鍵的生境分化因子。而在所有的受測樹種中，超過九成的樹種對於特定的生育地具有指標能力，但是在不同樹種之間則呈現強弱與幅度不等的生育地關聯性。而除了微地形分化作用之外，其他潛在的生態過程亦可能共同影響此處森林的樹木分布變化。綜言之，本研究證實在這處亞熱帶雨林中，微地形上的變化梯度可反映出生境組合律對於樹種多樣性與森林結構的影響力。

In this study, we investigated how the forest composition varies across fine-scale environmental heterogeneity. We established a 25-ha permanent plot, surveyed the micro-topography, and censused all trees with diameter at breast height of ≥ 1 cm within a natural broad-leaved forest in northeastern Taiwan. The micro-topographic differentiation of the forest composition and habitat association of individual species were analyzed using regression tree models and indicator species analysis. Our results demonstrated that nearly 30% of the variation in the tree species composition was attributable to micro-topographic factors in this contiguous forest region. Slope curvature, inclination, and aspect were the decisive factors of micro-topographic niche differentiation. Over 9/10 of the examined species were shown to be indicative of a specific habitat, but each species performed dissimilarly in both the magnitude and breadth of its habitat associations. In addition to niche differentiation, other underlying processes might also be jointly regulating this forest community. In conclusion, our results confirm the control of the niche-assembly rule on tree species diversity and forest structure along micro-topographic gradients in this subtropical rainforest.