民勤沙井子典型固沙植被区土壤水分动态与降水再分配研究

利用智能中子水分仪定时测定土壤水分的方法,在2006-2007年测定并分析了不同固沙灌木林地0-200cm深土壤共10个层次的水分时空变化特征和降水人渗再分配,结果表明:(1)民勤沙井子不同固沙灌木林地土壤水分季节变化表现为消耗期(6-7月);积累期(8-9月和4-5月),消退期(10月)-稳定期(11月-翌年3月).(2)土壤水分垂直变化为20cm土层含水量最低,60cm土层最高; 120-200 cm土层含水量随林地的不同而呈现减少、增加或保持稳定,(3)生长季节,土壤有效储水量0-40cm土层变化最频繁; 5种灌木林地0-200cm土层有效储水量.固定白刺沙包最高,97.9 mm.固定柽柳沙包最低,66.8mm.(4)降水在土壤中人渗深度和入渗历时不但取决于降水量,而且取决于降水强度,1.7 mm/h雨强平均湿润锋深度是0.7 mm/h的1.8倍,说明降水量相近,强度较大的降雨有利于水分向深层渗透.(5)降雨后水分在林地表层土壤中入渗增加,同时较深层的水分却表现为消耗,土壤水分的储存与消耗随着降水量和林地的不同而有差异.

Dynamics of Soil Water and Redistributions 0f Precipitation in the Main Sand-fixing Shrub Woodlands in Shajingzi of Minqin

The lack of surface water and the excessive pumping of groundwater have impacted seriously the sand-fixing functions of vegetations in Minqin oasis since 1970.However,to study the soil water dynamics and precipitation redistributions in 0-200 cm deep soll layer which is divided each 20cm into one layer in the woodlands of fixing and semi-fixing Haloxylon ammodendron,of fixing Tamarix ramosissima as well of fixing and semi-fixing Nitraria tangutorum,have an important meaning for the vegetative restoration and rebuilding in sandy area.The soil moistures were measured from June in 2006 to July in 2007 on five shrub woodlands with CN503DR Neutron Moisture Probe.The results were as follows:(1)The seasonal dynamics of soil moistures in 0-200 cm deep soil could be divided into four stages which were the consuming from June to July,the accumulating from August to September and from April to May,the subsidizing in October and the stable from November to March next year.(2)The soil moistures in vertical profile were the lowest at about 20 cm depth,and the highest at 60cm depth,as well from 120 cm to 200 cm in depth decreasing,increasing or stable with shrub woodlands.(3)The available soil water for plant growing from 0 to 40 cm in depth changed frequently in growing season.The biggest available soil water was hold by the fixing N.tangutorum woodland,reaching 97.9 mm,the smallest by fixing T.ramosissima woodland.being 66.8mmfrom 0 to 200 cm deep soiIin five shrub woodlands.(4)The depth and duration of precipitation infiltration into soil depended on not only the amount of precipitation,but the rainfall intensity.The mean wetting depth at 1.7 mm/h rainfall intensity in four woodlands was 1.8 time deeper than that at 0.7 mm/h intensity,which implied that the infi ltration in soil under the larger rainfall intensity was deeper than that under the smaller with the similar amount of precipitation.(5)While the water content accumulated after rainfall in shallow soils in different shrub woodlands,it imposed on consuming in deeper soils,showing that the processes of soil water accumulation and consuming were of difference with precipitation and woodlands.