南仁山亞熱帶雨林樹種分佈類型之研究

Abstract

本研究在探討萬?得山亞熱帶雨林三公頃永久樣區中樹種的分佈類型。研究中將樣區的樹木依照胸高直徑分成四個生長階段，並且比較整個樣區和各個生育地以及大樹及小樹中植物分佈類型的改變。 結果樣區中DBH?8cm且植株數量超過15株的種類有53種，這53種中有31種（58.5％）植物呈群聚分佈，其餘22種（41.5％）呈隨機分佈，沒有一種植物呈規則分佈；22種隨機分佈的植物多為株數較少的種類，株數較多的種類則多為群聚分佈。 各個生育地中胸高直徑?8cm大樹的分佈類型以隨機分佈的種類比例佔了大部分（75％以上），由此我們推測影響樣區中植物的分佈類型最明顯因數可能為各個生育地中的環境因數例如風或是地形上的因素，這些因數可能造成植物小苗無法發芽，或是小樹無法順利長成大樹。 在整個樣區中沒有任何一種植物呈規則分佈，而在各個生育地中也只有少數幾種大樹呈規則分佈，這可能是因為強烈的種內競爭發生在一小塊區域。 研究樣區中植物的分佈類型隨生長階段的變化中，多數的樹種是隨徑級增加而漸漸群聚性減少或偏向隨機及規則分佈，但仍有一些種類呈現其他分佈類型的變化，且同種植物於不同生育地中分佈類型的變化亦不同。 研究結果可以看出影響萬?得山樣區樹種分佈類型的因數頗多，如地形因數、空間影響、種內競爭及植物豐富度等。這些因數影響了植物在空間與時間上的分佈。

Spatial patterns of tree species were studied in a 3-ha subtropical rain forest plot in the Wanliteshan of southern Taiwan. The spatial patterns of tree groups at different growth stages from juveniles to adults were evaluated by dividing individuals of a species according to diameter (DBH) size. The spatial patterns of adult vs. juvenile tree, and whole plot vs. each habitat were compared. Out of the 53 adult (DBH?8cm) species occurring with ? 15 individuals in whole plot, 58.5% had an aggregated distribution, 41.5% were randomly distributed and no any species had a regular distribution. Rare species were generally less aggregated than common ones and most of the randomly distributed species were rare in whole plot. But in each habitat, most tree species display a random distribution. This suggest that habitat factors like wind and topography might affect the tree species distribution. These factors cause seed germination or juveniles growth varying from site to site. No adult tree species displayed a regular pattern in whole plot, and in each habitat, regular distributions were rarely found. This is probably due to intraspecific competition at a local scale. Most species shift from high clumping to looser intensity or random distribution when moving from juveniles to adults, while other species show different patterns of distribution. In addition, the distribution among conspecific trees may vary with habitats. This study suggests that the Wanlite forest is subjected to multiple controlling factor, e.g., topography, spacing effect, intraspecific competition and species rarity. The importance of any factor changes across spatial and temporal scales.