岷江上游干旱河谷典型阳坡海拔梯度上土壤水分动态

DYNAMICS OF SOIL WATER CONTENTS ON SOUTH-FACING SLOPE OF DRY VALLEY AREA IN THE UPPER REACHES OF THE MINJIANG RIVER

结合气象观察和土壤质地的分析 ,监测和研究了岷江上游干旱河谷茂县段典型阳坡土壤水分动态 .结果表明 :1.土壤水分的季节变化可分为土壤水分亏缺期、土壤水分补偿期和土壤水分消退期 .2 .土壤含水量在旱季随土层深度的增加呈升高趋势 ,雨季中期出现相反的变化趋势 ,据变异系数可将土壤剖面分为剧变层、渐变层和相对稳定层 .3.相同土层深度含水量随海拔高度的增加先升高后降低 .4 .降雨和土壤特性是影响岷江上游干旱河谷土壤水分的主要因素 :降雨量与 0～ 10 0cm土层平均含水量的相关系数达到极显著水平 ,降雨对土壤含水量的影响随土层深度增加而减弱 ;大于 10mm的降雨对土壤水分的补充作用明显 ,气温及蒸发量较低时 ,连续的小于 10mm的降雨对土壤水分也有一定补充作用 ,降水可到达 5 0cm土层深度 .以沙质粘壤土为主的土壤含水量远高于以砂壤土为主的土壤含水量 .岷江上游干旱河谷造林时间在 4月为宜 ,以沙壤土为主的地段穴深在 4 5～ 6 0cm较好 ,以沙质粘壤土为主的地段穴深在 6 0～ 70cm比较适宜 .图 3表 3参

The spatio-temporal characters of soil moisture were studied in the dry valley area of Maoxian county in the upper reaches of the Minjiang River. The results showed that:(1) The seasonal variation of soil moisture could be divided into three periods: deficient period, compensatory period and lessen period.(2) Soil water content increased with soil depth increasing during dry period, whereas there was reverse instance in wet period. The soil profile could be characterized by three layers according to beta coefficient, i.e., drastically changing layer, gradually changing layer, relatively stable layer.(3) Soil water content increased first and then declined with altitude increasing.(4) Temporal variation of soil moisture and vertical variation of soil moisture content was greatly influenced by rainfall and soil texture. The correlation coefficient of precipitation and soil water content of 0～100 cm soil was very significant. Wet period and dry period of soil were basically identical with that of weather. The effect of rainfall to soil moisture weakened with soil depth increasing. Precipitation of hyper-10 cm influenced soil moisture obviously. Under low air temperature and transpiration, continuous rainfall under 10 mm had some compensation to soil moisture. And water of rainfall could get to 50 cm depth of soil. Soil texture was the determining factor which affected capacity of soil water, that is to say, sandy loam can keep much water than Sandy soil. April was the advisable time for planting sapling in dry valley area in the upper reaches of the Minjiang River. The advisable depth of planting sapling was 45～60 cm for sandy soil and 60～70 cm for sandy loam, respectively. Fig 3, Tab 3, Ref 16