Population Structure, Allometry and Above-Ground Biomass of Avicennia marina Forest at the Chishui River Estuary, Tainan County, Taiwan

台南縣急水溪口海茄苳林分族群結構、相對生長及地上部生物量

This study investigates the structure and above-ground biomass of an Avicennia marina forest located at the mouth of the Chishui River, in Tainan County, Taiwan. Four mangrove stands with various characteristics and density were studied, including sea edge pioneer (Stand Tat the northern river bank) and young mangroves (Stands II and III at the northern river bank; Stand IV at the southern river bank). The tree heights of these four mangrove stands varied from 0.9 to 1.2 m, diameter at breast height (DBH) ranged from 2.4 to 5.1 cm, and tree density ranged from 5,029 to 17,000 trees ha^(-1). The distribution of DBH was skewed to small classes, and all sampled trees showed reverse J-shaped distributions, which suggested an active regeneration in these populations. The allometric relationships derived by regressions of leaves, stems, branches, and total above-ground biomass vs. DBH of A. marina trees, for each tree component were highly significant, with R^2 values from 0.750 to 0.956. Total above-ground biomass was estimated as a power function of the DBH as an independent variable, W(subscript T)-0.1012 (DBH^2) + 0.5402 (DBH)-1.5674, where W(subscript T)-above-ground biomass (kg). The allometrie relationship was used to estimate total above-ground biomass, which varied from 10.3 ton ha^(-1) for the pioneer stage (Stand I, near the river mouth) to 22.7 ton ha^(-1) for a more mature mangrove at the upstream of the river, indicating that this A. marina forest at the Chishui River estuary mouth has less above-ground biomass than these forests elsewhere in the world. 本研究調查台南縣急水溪口海茄苳（Avicennia marina）林分之結構與地上部生物量，所調查4個不同特性及密度之林分，包括向海之先驅林分（北岸之Stand I）及幼齡林（北岸之Stand II及III；南岸之Stand IV）。四個林分之樹高在0.9-1.2m間，胸高直徑（DBH）在2.4-5.1cm間，而林分密度則為5, 029-17, 000trees ha^(-1)。林木胸高直徑分布多為小徑木，而所有樣木胸徑分布呈反J形，顯示此族群呈現更新良好狀態。本研究建立海茄苳葉部、莖部、枝條、總地上部生物量與DBH之異速生長回歸式，顯示林木各部位乾重之R^2值在0.750-0.956間。而利用推估地上部生物量之最佳函數DBH為獨立變數，以W（下標T）=0.1012（DBH^2）+0.5402（DBH）-1.5674公式計算地上部生物量（W（下標T））結果顯示，先驅林分（Stand I，近河口處）之生物量為10.3tonha^(-1)，河流上游較成熟林分為22.7ton ha^(-1)，急水溪口海茄藝林分地上部生物量較世界其他國家為低。

本研究調查台南縣急水溪口海茄苳（Avicennia marina）林分之結構與地上部生物量，所調查4個不同特性及密度之林分，包括向海之先驅林分（北岸之Stand I）及幼齡林（北岸之Stand II及III；南岸之Stand IV）。四個林分之樹高在0.9-1.2m間，胸高直徑（DBH）在2.4-5.1cm間，而林分密度則為5, 029-17, 000trees ha^(-1)。林木胸高直徑分布多為小徑木，而所有樣木胸徑分布呈反J形，顯示此族群呈現更新良好狀態。本研究建立海茄苳葉部、莖部、枝條、總地上部生物量與DBH之異速生長回歸式，顯示林木各部位乾重之R^2值在0.750-0.956間。而利用推估地上部生物量之最佳函數DBH為獨立變數，以W（下標T）=0.1012（DBH^2）+0.5402（DBH）-1.5674公式計算地上部生物量（W（下標T））結果顯示，先驅林分（Stand I，近河口處）之生物量為10.3tonha^(-1)，河流上游較成熟林分為22.7ton ha^(-1)，急水溪口海茄藝林分地上部生物量較世界其他國家為低。