全球環境現今變遷迅速且劇烈,為避免人為過度開發造成生物多樣性的下降,了解生物多樣性在不同空間尺度下的分布模式與影響因子便成為相當重要的課題。臺灣由於海拔跨幅大,因此相當適合進行生物多樣性在海拔梯度上變化模式的探討。過去在臺灣進行的相關研究尚缺乏對於低海拔鳥類物種豐富度的探討,因此本研究於臺灣中部地區,海拔梯度自平地延伸至合歡山的範圍內(183- 3110 m),於此海拔範圍選擇較少人為擾動的成熟林份,設立32個取樣站,調查鳥類群聚與植群組成。主要目的為了解在此海拔梯度內,初級生產力、鳥類族群密度、鳥類物種豐富度、木本植物物種豐富度與鳥類族群能量耗用的變化模式。此外,將更進一步探討鳥類物種豐富度與初級生產力之間的關係,以驗證其是否符合能量限制假說與其運作機制:(1)初級生產力與鳥類族群能量總耗用量的關係、(2)鳥類族群總耗用量與鳥類族群總密度的關係、(3)鳥類族群總密度與鳥類物種豐富度的關係。本研究更嘗試使用以綠葉覆蓋層次做為葉面積指數轉換的調查方式,並將此數據作為淨初級生產力的指標。野外調查於2009年至2010年間完成,結果發現鳥類物種豐富度與葉面積指數皆在中海拔地區最高,在海拔梯度上呈現駝峰狀分布。而木本植物物種豐富度則是在低海拔地區最高,並且隨著海拔梯度升高而遞減,本研究認為溫度是一重要的影響因素。鳥類物種豐富度與葉面積指數的分析結果支持能量限制假說,且在假說的運作機制部分皆完全符合,也就是鳥類物種豐富度與葉面積指數呈正相關,而各部機制部分也皆呈現正相關。因此,在海拔梯度的空間尺度下,能量的供給是影響鳥類物種豐富度的重要因子,同時,能量指標的選取以及分析方法的判定也都會是影響因素之一。在葉面積指數作為能量指標的部分,本研究亦針對數值轉換與調查法討論出建議的修正方法,以供後續選用此法的研究者參考。
With rapid global environment changes and growing human development, studying the distribution pattern of biodiversity at various spatial scales becomes a very important task to conserve biodiversity. Taiwan is an island with wide elevational range and is very suitable to study distribution of species richness along elevational gradient. Previous relevant studies in Taiwan seldom included bird species richness data below 1000 m. I conducted this study in old-growth forests from foothills to Mt. Ho-Haun (183- 3110 m a.s.l.) in central Taiwan in 2009 and 2010. I established 32 sampling stations to investigate community compositions of birds and trees along this elevational gradient. The objectives of this study were to (1) investigate the distribution patterns of primary productivity, bird density, bird species richness, tree species richness, and energy consumption of birds along elevational gradient, (2) examine the relationship between bird species richness and primary productivity, and (3) test three assumptions of energy limitation hypothesis. In this study, I estimated Leaf area index (LAI), an indicator of net primary productivity, by measuring leaf coverage. Results show that both bird species richness and LAI were hump-shaped along with the elevational gradient. However, tree species richness decreased with elevation. Results support energy limitation hypothesis and its three assumptions. I conclude that energy availability is a very important factor in determining bird species richness. In using LAI as index of primary productivity, I also discuss some corrections about the measurement of leaf coverage and the value transformation, which should be useful for future studies.