Topography and canopy openness influence spatial variations in mortality, recruitment, and growth of a subtropical tree community

森林樹木群落的動態受到許多因子的影響，其中地形和樹冠開闊度為兩個非常重要的因子，地形 因子可以反映森林內土壤及微氣候的變化，樹冠開闊度則與林下光量有關。然而，在經常受到颱風擾 動的地區，森林樹冠層較為破碎，林下光量也較高，我們尚不清楚樹冠開闊度對於森林樹木群落的影 響是否一如其他地區。本研究藉由分析位於台灣東北部福山森林動態樣區內樹木的死亡、新增與生長 情形，希望了解地形因子與樹冠開闊度對於樹木群落動態的影響。研究結果顯示地形因子與樹木的死 亡率、新增率、相對生長率均有顯著相關，樹冠開闊度則僅與新增率顯著相關，而且其影響效應與其 他地形因子相比明顯較小。這代表在經常受到颱風擾動的區域，其他因子(如地形)對於森林動態的影 響可能比樹冠開闊度所造成的光度變化更為重要。

Spatial variations in demographics of tree communities are influenced by multiple factors, among which topography and canopy openness are important elements. Topographic factors can serve as proxies that represent variations in the micro-climatic and edaphic factors in a forest. Canopy openness is closely associated with the light regime in the understory. However, in forests frequently disturbed by typhoons, canopy openness and understory light levels tend to be higher than in those without disturbances. It is not clear whether the effect of canopy openness remains the same in typhoon-disturbed forests as in other regions. In this study, we analyzed spatial variations in tree demographics of a subtropical rain forest to investigate the effects of topographic factors and canopy openness on forest dynamics. Our results showed that there were significant effects of topographic factors on tree mortality, recruitment, and relative growth rates. In contrast, canopy openness was only significantly correlated with tree recruitment, and its effect was weaker than the effects of topographic factors. These results imply that in frequently typhoon-disturbed forests, other factors such as topography may be more important in driving forest dynamics than light variations caused by canopy openness.

Abstract in Chinese and English; article only in Chinese.