奧萬大天然闊葉林枯落物與養分迴歸量之季節變化

Seasonal Variation on Litterfall and Nutrient Recycling Amount of Natural Hardwoods Stands in Ou-Wan-Ta

自 2001 年 8 月至 2003 年 3 月止為期 20 個月，以枝葉袋收集網調查奧萬大天然闊葉林之枯落物，探討每月枯落物量及養分迴歸量的季節性變化。結果顯示本試驗地的年枯落總量為 9.14 t/ha/yr，各組成分以葉部為最大量 6.05 t/ha/yr，依序為枝條 1.78 t/ha/yr 與其他0.82 t/ha/yr，繁殖體為最小，僅有 0.45 t/ha/yr。枯落物總量的季節性變化，主要受葉部影響而變動，呈 5 至 7 月為最高量的單一高峰凋落類型。試驗期間枯落物量因受當年娜克莉颱風的影響，使得此月無論是在枯落物總量或枯落物養分含量均達最高，尤其枝條枯落物顯著高於其他月份，可達 5~114 倍之多。枯落物各組成成分的養分濃度以其他部位濃度最高，繁殖體次之。養分濃度高低呈碳＞氮＞鈣＞鉀＞鎂＞磷＞鈉＞鐵＞錳濃度，各組成成分養分濃度的月變動情形，大致呈現 4~6 月及 10~1 月為養分濃度較高的時期。枯落物養分年迴歸量，均以葉部顯著高於其他各個組成分，顯然本試驗地以葉部為林地養分迴歸主要來源。 The purpose of this study was to explicate how the seasonal variation of litterfall and nutrient recycling amount of the natural hardwoods in Ou-Wan-Ta. The content and concentration of litterfall were investigated monthly from August 2001 to March 2003 by using littertrap method. The results showed that the amount of litterfall in this site was 9.14 t/ha yearly. Most of the litterfall were composed of leaves (6.05 t/ha/yr), followed by branch (1.78 t/ha/yr), others (0.82 t/ha/yr) and reproduction (0.45 t/ha/yr). The seasonal variability of litterfall showed a uni-modal distribution pattern. In this study period, the litterfall variability was due to the strong typhoon, Nakri, which might have led to increased more than 5 to 114 times branch litter compared with other months. Nutrient concentration of litterfall was in the order as C > N > Ca > K > Mg > P > Na > Fe > Mn, and the concentration of litterfall was highest in other component, followed by reproduction component. The seasonal concentration of nutrients was the highest during April-June and October-January. In addition, nutrient returned to the soil through litterfall was greatest in leave component.

The purpose of this study was to explicate how the seasonal variation of litterfall and nutrient recycling amount of the natural hardwoods in Ou-Wan-Ta. The content and concentration of litterfall were investigated monthly from August 2001 to March 2003 by using littertrap method. The results showed that the amount of litterfall in this site was 9.14 t/ha yearly. Most of the litterfall were composed of leaves (6.05 t/ha/yr), followed by branch (1.78 t/ha/yr), others (0.82 t/ha/yr) and reproduction (0.45 t/ha/yr). The seasonal variability of litterfall showed a uni-modal distribution pattern. In this study period, the litterfall variability was due to the strong typhoon, Nakri, which might have led to increased more than 5 to 114 times branch litter compared with other months. Nutrient concentration of litterfall was in the order as C > N > Ca > K > Mg > P > Na > Fe > Mn, and the concentration of litterfall was highest in other component, followed by reproduction component. The seasonal concentration of nutrients was the highest during April-June and October-January. In addition, nutrient returned to the soil through litterfall was greatest in leave component.