- 期刊
福山林地土壤飽和與不飽和水力傳導度的特性
Characteristics of Saturated and Unsaturated Hydraulic Conductivity of Forest Soils in Fushan Area
摘要
本研究為探討森林土壤飽和與不飽和滲透的特性，採取福山試驗林地之直徑20 cm、長40 cm 的不擾動土壤試體三個，使用變水頭測定法測定飽和水力傳導度(K(下標 s))，以及使用穩定態流束控制法在模擬降雨強度條件下，測定不飽和水力傳導度(K(下標 u))，供比較不同深度層次之水力傳導度的差異，並分析不飽和水力傳導度的變化與壓力水頭的關係。飽和水力傳導度測定結果，三個試體之K(下標 s)值介於5.5~10.9×10^(-3) cm sec^(-1)，每一個試體之深度0~10 cm、10~20 cm、20~30 cm 三個層次的Ks 差異不大，由於受深度30~40 cm 的K(下標 s)大幅降低的影響，使整體試體的K(下標 s)值呈現降低的情形。不飽和水力傳導度測定結果，各個深度層次的K(下標 u)隨模擬降雨強度的增大而增大，然而深度0~10 cm的變化較為緩和。當模擬降雨強度達36 mm/hr時，各個深度層次的Ku仍小於Ks，顯示試體仍處於不飽和狀態。其次，應用Gardner method與Brooks and Coreymethod兩種方法分析K(下標 u)與壓力水頭的關係，並探討森林土壤的孔隙大小分佈參數(η)與限界毛管水頭(ψ(下標 c))的特性，經計算結果兩種方法差異不大。應用Brooks and Corey method 計算結果之η值介於0.87~11.10，ψ(下標 c)絕對值介於0.09~8.27 cm，計算結果顯示林地土壤的孔隙結構呈不均質的特徵。
並列摘要
Characteristics of saturated and unsaturated permeability of forest soil at a slope near watershed No. 1, Fushan Experimental forest was investigated. Three undisturbed soil samples with 20 cm diameter and 40 cm length were collected to measure saturated hydraulic conductivity (K(subscript s)) by falling head control method and unsaturated hydraulic conductivity (K(subscript u)) by steady state flux control method. Using permeability test, K(subscript s) at different soil depths of soil samples were compared with each other and K(subscript u) related to water pressure head was analyzed. From saturated permeability test results, K(subscript s) of three samples were between 5.5×10^(-3) cm sec^(-1) to 10.9×10^(-3) cm sec^(-1). In each sample, K(subscript s) at depth 0-10 cm, 10-20 cm and 20-30 cm were similar, but K(subscript s) at depth 30-40 cm were significantly smaller than values at other depths. The low values of K(subscript s) at depth 30-40 cm decreased the K(subscript s) of the overall soil sample. From unsaturated permeability test results, K(subscript u) at depth 0-10 cm, 10-20 cm and 20-30 cm increased with increasing simulated rainfall intensity, but K(subscript u) at depth 0-10 cm slowly increased. As the simulated rainfall intensity reached 36 mm/hr, K(subscript u) values of soil sample at each depth were smaller than K(subscript s) values, with the soil sample still unsaturated. Furthermore, Gardner method and Brooks and Corey method were used to analyze the relationship between Ku values and water pressure head, and to estimate soil pore size distribution parameter (η) and critical capillary head (ψ c). The results estimated by Gardner method and Brooks and Corey method were about the same. Based on Brooks and Corey method, the η values were from 0.87 to 11.10 and the absolute values of ψ c were about 0.09 to 8.27 cm. The results reveal that the pore size structure of forest soil at the study site was heterogeneous.