Rainfall Interception and its Chemical Composition in a Cryptomeria japonica Plantation at Xitou area

• Main Authors: Jing-Lun Huang, 黃敬倫
• Other Authors: Ming-Chieh Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/54567595333671331761

碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 103 === This study was conducted in the Cryptomeria japonica plantation located at Xitou tract, NTU Experimental Forest. The throughfall and stem flow were observed in the plantation and the canopy interception was calculated. Also, the ion gradients of precipitation, throughfall and stem flow were analyzed and thus calculated ion flux. This observation started from February 2012 to October 2014, data was collected about twice a month. The effective total rainfall was 2,270 ± 48.0 mm, throughfall was 2,022.7 ± 45.7 mm, stemflow was 55.5 ± 1.9 mm and interception was 191.8 ± 4.1 mm. The percentage of throughfall was 89.1%, stemflow was 2.5% and interception was 8.5%. The capacity of interception was low due to the low stem density of old stand and low LAI in study area. The linear regression equation between throughfall (y) and rainfall (x) was y = 0.9664x - 4.0271, r2 = 0.99, which indicated the amount of throughfall was highly positively related to rainfall. The percentage of throughfall also increased as rainfall increased, it was about 80% when the rainfall was 40 mm, 90% when the rainfall was 100 mm and close to 100% as the rainfall was 200 mm. The linear regression equation between stemflow (y) and rainfall (x) was y = 0.0372x - 0.3111, r2 = 0.87. The percentage of stemflow was also positively related to rainfall, however, the correlation was weaker (r2 = 0.37). The threshold of stemflow was 1.5 mm, and the saturation point of interception was about 3.9 mm. Higher gradient of cation led to no events of acidic rain in Xitou (pH = 5.56). Ca2+ was the most ion gradient in throughfall, stemflow and rainfall, and there were no significant difference in gradient of cation between throughfall and rainfall except K+. The gradient of anion in throughfall was significantly lower than that in rainfall, showing the effect on canopy of Cryptomeria japonica to buffer acid deposition. Because of more cation and less anion, the pH of throughfall was significantly higher than rainfall (pH = 6.24). Although the characters of ion gradient was similar to throughfall, the pH of stemflow was lower (pH = 4.29), which may be affected by other substance released from tree. Because of the canopy of Cryptomeria japonica in this study had capacity to buffer acid deposition, the acidic depositions (SO42- and NO3-) was fewer.