欖仁溪樣區低地雨林之樹種分佈類型

Distribution Patterns of Tree Species in the Lanjenchi Lowland Rain Forest

本研究探討臺灣南端的欖仁溪低地雨林5.88公頃樣區之樹種分佈類型。研究中將樹木依胸高直徑分成四個生長階段，並比較整個樣區及各生育地及不同徑級大小植物分佈類型之差異。在整個樣區中植株數量超過15株的種類有88種，以兩公尺的範圍來看，有87.5%的種類呈現聚集分佈，9.1%呈現隨機分佈，3.6%的種類在此範圍內不具任何同種植株。若以植株數量而言，株數較少的種類較數量多的種類更加聚集。至於不同徑級大小，35.5%的物種隨著徑級增加而由高度聚集的分佈類型逐漸轉移到較低強度的聚集或呈現隨機分佈，但有11.3%的物種呈現相反的結果。當比較樣區中各生育地之分佈類型時，則聚集強度隨著風力梯度的增加（即溪谷到迎風坡）而增強。在所有的分析中沒有任何物種表現出規則分佈。本研究顯示欖仁溪樣區之物種分佈類型與各生育地的異質性有關，但其他如種子傳播的限制也可能是影響植物分佈的因子之一。

Spatial patterns of trees in a lowland rainforest in the 5.88-ha Lanjenchi plot of the southernmost Taiwan were evaluated. Among the 88 species with more than 15 individuals, 87.5% had an aggregated distribution pattern, and 9.1% species were randomly distributed. Rare species tended to be more aggregated than common species at all distance scales. As for different DBH size classes, 35.5% species shifted from highly aggregated patterns to a low level of aggregation or random distribution with an increase in tree size, and 11.3% species had an inverse pattern. When comparing spatial patterns among different habitats within the plot, the aggregation intensity increased along a wind-stress gradient from the sheltered creek to the most exposed slopes. No species displayed a regular pattern in any size class or habitat type. This study revealed that distribution of most species within the Lanjenchi forest was related to habitat heterogeneity. Other factors, such as dispersal limitation, however, may also play a role in determining the distribution patterns.