熱帶樹種的空間分布及形成過程可以反映出樹種之間或是與環境因子之間的交互關係，而這也被認為是樹種共存的機制之一。熱帶森林樹種在空間上大多呈現聚集分布，這可能是源自於樹種具有棲地偏好，使其在各類棲地間存活率不同，進而導致樹種在空間分布上並不均勻。因此，樹種族群的生長表現與棲地的關聯，是研究森林生態過程的重要問題。此外，植物的生理反應常被用於檢視環境因子對植物的影響，透過生理反應，可能可以輔助說明棲地對植物的影響。因此，本研究從族群與生理層次，探討熱帶喀斯特森林中的紅柴(Aglaia formosana)及黃心柿(Diospyros maritima)的棲地偏好。本研究的主要問題如下：(1)不同棲地下的小苗、小樹及大樹族群是否具有不同的存活表現及新增？(2)小樹族群在不同棲地下的生理表現是否有差異？並檢視在該森林中，不同季節的生理反應是否有差別。研究結果顯示，紅柴與黃心柿大樹死亡率，在不同棲地間沒有顯著差異。但在小樹階段，紅柴死亡風險在谷地較高，礁頂較低；而黃心柿小樹死亡風險則在礁頂較低。紅柴的小苗新增數量，在棲地間也有同樣的趨勢。因此，新增及存活率在兩樹種的小苗及小樹可看出具有棲地關聯，但是在大樹則無趨勢。在生理層次，小樹族群的有效光量子產量(ΔF/Fm’)，在谷地顯著較低，且有效光量子產量與土壤水分具備顯著二次式函數關係。透過這個結果，我們可以推斷小樹及小苗族群與棲地具有關聯，且土壤深度可能為重要的因子。綜合族群存活、新增表現與生理反應，可以更完整的解釋棲地關聯。本研究將有助於以生理生態學觀點出發的森林動態研究，並探討生理表現對解釋熱帶森林物種的族群動態、棲地與空間分布的可能性。 Spatial distribution and the formative process of tropical tree species can reflect the interaction between tree species or correlation with environmental factors. It is considered as one of the coexistence mechanisms for tropical forests. Many tropical tree species are aggregated in space. Such aggregation pattern may originate from habitat preference of tree species. Survival rates and recruitment of trees species may differ among habitats and lead to an uneven distribution among habitats. Therefore, understanding the habitat association of tree species is important to study forest dynamics. In addition, physiological performances have been using to evaluate the effect of environmental factors which may be used as indices to explore habitat association of tree species. The aim of this study is to understand the habitat association of two dominant species, Aglaia formosana and Diospyros maritima, at both demographic and physiological levels in a tropical karst forest. The specific objectives include (1) to compare mortality and recruitment rates of seedlings, saplings, and trees among habitat, (2) to study the physiological performance of saplings among habitats. Seasonal changes in environmental factors are also considered. The results indicated that mortality of trees did not differ significantly among habitats. Saplings of A. formosana in valleys were at a higher risk of mortality than those on slopes and top-reefs; saplings of D. maritima were at lower risk of mortality on top-reef. Recruitment of A. formosana exhibited a similar pattern with saplings. Therefore, the demographic hypothesis was supported with saplings and seedlings. Moreover, effective quantum yield (ΔF/Fm’) of saplings was significantly lower in valleys than the other two habitats. It can be best described by quadratic functions of soil moisture. In this study, we demonstrated that demographic performances of saplings and seedlings associated with habitat. Further, soil depth is critical for two study species in this forest. An integration of demographic and physiological data is usefully to explain habitat association of tree species. This study is valuable to evaluate researches of forest dynamics with eco-physiological perspective and understand coexistence mechanism of tree species in the tropical forest.
