應用張力滲透計於林地土壤孔隙水通量之探討

Investigation on the Water Flux of Forest Soil Pores by Tension Infiltrometer Measurement

洪志遠(Chin-Yuan Hung) ； 陳明杰(Ming-Chieh Chen)

《中華林學季刊》 42卷4期 (2009/12) Pp. 541-555

https://doi.org/10.30064/QJCF.200912.0006

摘要

為了瞭解土壤試體取樣測定的孔隙率與實際的水分傳導孔隙率是否有差異，以及現地之土壤孔隙對水分傳導的貢獻，本研究在林業試驗所蓮華池四號集水區選擇19個樣點，使用張力滲透計測定土壤表層及深度20cm的入滲率，根據測定結果分析水力傳導度，並且引用Watson and Luxmoore(1986)方法（WL方法）計算現地土壤大、中孔隙的水通量比率以及導水孔隙率。另外，在每一個樣點附近採取深度0-10cm與20-30cm之不擾動土壤試體，使用加壓排水法測定土壤試體之大、中孔隙率。張力滲透計測定結果，經WL方法計算之大孔隙與中孔隙的水通量比率，表層分別為80.8%與18.8%，深度20cm分別為58.6%與36.1%；經WL方法計算之導水大孔隙率與中孔隙率，表層分別為0.047%與0.170%，深度20 cm分別為0.003%與0.027%。而土壤試體經測定結果，取樣深度0-10cm之大孔隙率（相當於壓力水頭大於－3cm測得的孔隙率）與中孔隙率（相當於壓力水頭介於－3~-10cm測得的孔隙率），19個試體的平均分別為8.8%與20.6%，取樣深度20-30cm則分別為5.6%與13.0%。研究結果顯示，計算之參與水分傳導的大孔隙率與中孔隙率明顯低於加壓排水法的測定結果，且土壤在飽和情形下，有90%以上的水通量經由相當於壓力水頭大於－10cm的大孔隙與中孔隙傳導。

關鍵字

水力傳導度 ； 蓮華池 ； 張力滲透計 ； 導水孔隙率 ； 水通量

並列摘要

The study was to evaluate the discrepancy of soil porosity between soil core samples and soil in situ that truly relate to water conducting, and to assess the contribution of soil porosity in situ for water conducting. There were 19 sample locations selected at Lienhuachih watershed No. 4 of Taiwan Forestry Research Institute. Based on the infiltration rates measured by tension infiltrometer for soil surface and in depth of 20 cm of the 19 locations, the hydraulic conductivity was derived. In addition, water flux ratio and water-conducting porosity of macropore and mesopore were estimated by Watson and Luxmoore (1986) approach. Undisturbed soil samples were also collected in depth of 0-10cm and 20-30cm around each sample location, at which the macroporosity and mesoporosity of soil could be measured with pressured extraction water method. According to the results of infiltration rates test, water flux ratios of soil macropore and mesopore in the soil surface were estimated about 80.8% and 18.8%, and in the depth of 20 cm were about 58.6% and 36.1%, respectively. Moreover, calculated water-conducting macroporosity and mesoporosity in the soil surface were about 0.047% and 0.170%, and in the depth of 20 cm were about 0.003% and 0.027%, respectively. Besides, average macroporosity (corresponding to water pressure head higher than -3 cm) and mesoporosity (corresponding to water pressure head between -3 cm and -10 cm) of the 19 locations in the soil depth of 0-10 cm were 8.8% and 20.6%, and in the soil depth of 20-30 cm were 5.6% and 13.0%, respectively. The study demonstrated that the water-conducting macroporosity and mesoporosity estimated were significantly lower than those measured by pressured extraction water method. Under saturated condition, more than 90% of water flux passed through the soil macropore and mesopore which were corresponded to water pressure head higher than -10 cm.

並列關鍵字

Hydraulic conductivity ； Lienhuachih ； Tension infiltrometer ； Water-conducting porosity ； Water flux