關刀溪森林生態系三種林分氮的沉降

Nitrogen Deposition in Three Stands of Guandaushi Forest Ecosystem

本試驗在臺灣中部關刀溪試驗集水區相鄰的杉木林、次生林及天然林三種不同林分內，評估雨水流經此三種不同林分後，在穿落水及幹流水的不同型態的N沉降及季節變化（1996年1月到1998年12月）。雨水的總氮年平均沉降為12.30 kg ha-1yr-1，穿落水的總氯年平均沉降在杉木林、次生林及天然林則分別為20.94 kg ha-1yr-1, 21.19 kg ha-1yr-1, 和19.24 kg ha-1yr-1，幹流水則分別為3.89 kg ha-1yr-1, 1.23 kg ha-1yr-1，及0.69 kg ha-1yr-1。有機氮在杉木林穿落水及幹流水都有較高比例的沉降，NO3-N在天然林穿落水的沉降較杉木林和次生林低。不同型態N沉降的季節變化顯示，在冬天乾季時，其沉降量特別高，此證明乾沉降對此森林生態系氮沉降的重要性。淨沉降在杉木林、次生林及天然林則分別為12.53 kg ha-1yr-1, 10.13 kg ha-1yr-1, 和7.63 kg ha-1yr-1。 A study was undertaken in 3 types of forest stands, a China-fir (Cunninghamia lanceolata) plantation, a secondary hardwood stand, and a natural hardwood stand in Guandaushi Forest, central Taiwan, from January 1996 to December 1998. We assessed the effect of different stands on the form, quantity and seasonal variation of N deposition through precipitation, throughfall and stemflow. The total N deposition by precipitation was 12.30 kg ha-1yr-1, and that by throughfall was 20.94 kg ha-1yr-1, 21.19 kg ha-1yr-1, and 19.24 kg ha-1yr-1 in a China-fir plantation, a secondary hardwood, and a natural hardwood, respectively. The quantities of total N deposited through stemflow in the three stands were 3.89 kg ha-1yr-1, 1.23 kg ha-1yr-1, and 0.69 kg ha-1yr-1, respectively. The gross N deposition via throughfall and stem flow was 20.94 and 3.89 kg ha-1yr-1, respectively. The organic-N contributed the maximum deposition of the gross N deposition via throughfall and stemflow in the China-fir plantation. At the natural hardwood stand, had lower NO3-N deposition than the other two stands. The monthly concentrations of NH4--N. NO3-N, organic-N and total N revealed that maximum concentration occurred in winter, when the months were the driest. It suggested a significant contribution of dry N deposits into the Guandaushi forest ecosystem. The annual net N depositions were 12.53 kg ha-1yr-1, 10.13 kg ha-1yr-1, and 7.63 kg ha-1yr-1 at the China-fir plantation, the secondary hardwood, and the natural hardwood, respectively.

A study was undertaken in 3 types of forest stands, a China-fir (Cunninghamia lanceolata) plantation, a secondary hardwood stand, and a natural hardwood stand in Guandaushi Forest, central Taiwan, from January 1996 to December 1998. We assessed the effect of different stands on the form, quantity and seasonal variation of N deposition through precipitation, throughfall and stemflow. The total N deposition by precipitation was 12.30 kg ha-1yr-1, and that by throughfall was 20.94 kg ha-1yr-1, 21.19 kg ha-1yr-1, and 19.24 kg ha-1yr-1 in a China-fir plantation, a secondary hardwood, and a natural hardwood, respectively. The quantities of total N deposited through stemflow in the three stands were 3.89 kg ha-1yr-1, 1.23 kg ha-1yr-1, and 0.69 kg ha-1yr-1, respectively. The gross N deposition via throughfall and stem flow was 20.94 and 3.89 kg ha-1yr-1, respectively. The organic-N contributed the maximum deposition of the gross N deposition via throughfall and stemflow in the China-fir plantation. At the natural hardwood stand, had lower NO3-N deposition than the other two stands. The monthly concentrations of NH4--N. NO3-N, organic-N and total N revealed that maximum concentration occurred in winter, when the months were the driest. It suggested a significant contribution of dry N deposits into the Guandaushi forest ecosystem. The annual net N depositions were 12.53 kg ha-1yr-1, 10.13 kg ha-1yr-1, and 7.63 kg ha-1yr-1 at the China-fir plantation, the secondary hardwood, and the natural hardwood, respectively.