黄土丘陵区小叶杨林地土壤水分过耗动态

Excessive Depletive Dynamic of Soil Water of Pupulus simonii in Loess Hilly Region

针对黄土丘陵区土壤水分不足,小叶杨林生长发育不良的特点,进行了长期定位监测。结果表明,在黄土丘陵区小叶杨的生长影响因子较多,其主要影响因子是土壤水分不足和大气干燥抑制了树木的快速生长与正常发育,这一特点在黄土丘陵区的坡面林地上更加明显。在丰水年小叶杨林地土壤贮水量与荒山相比减少28～101.91mm;平水年土壤贮水量与荒山相比减少41.2～66.6mm;干旱年土壤贮水量与荒山相比减少37.9～57.3mm。生长在峁顶的小叶杨林0～500cm土壤贮水量亏缺为302～612.2mm;生长在山坡中部的小叶杨林土壤贮水量亏缺为394.4～588.6mm;生长在山坡下部的小叶杨林土壤贮水量亏缺为346.6～574.3mm。从小叶杨林地土壤水分的变化和干层的形成看,4～16年生小叶杨林地土壤干层的分布深度平均在80～350cm,干层厚度为270cm,土壤含水量平均不足5.0%,远低于凋萎湿度,所以,从目前黄土丘陵区小叶杨林地土壤水分的变化来看,仅能维持其生命,要想获得较高的生态和经济效益,必须采取工程整地等措施,发展集流林业。

Due to the soil water shortage in loess hilly region and slow growth of Pupulus simonii, the longterm fixingposition monitoring and investigating were conducted. The results showed that lots of factors influenced the growth of Pupulus simonii in loess hilly region, and soil water shortage and atmosphere drought was the principle factors inhibiting fast growth and normal development trees of trees, which was a obvious characteristic of forests in slope land of the loess hilly region. Soil waterstorage capacity of Pupulus simonii decreased 28~101.91 mm in abundant precipitation year, 41.2~66.6 mm in equal precipitation year and 37.9~57.3 mm in low precipitation year compared to the barren hill. The deficit of soil water storage capacity(0~500 cm) of Pupulus simonii in the top of hills were 302~612.2 mm, 394.4~588.6 mm in the middle of slope and 346.6~574.3 mm in the bottom of slope. The conditions of soil water variations and soil drylayer formation were as follows: the distributive depth of soil drylayer of Pupulus simonii that has grown for 4~16 years was average 80~350 cm, its thickness was 270 cm, and soil water content was below 5.0% that was far lower than languish humidity .So soil water only kept survival of Pupulus simonii. If higher ecological and economic benefit was obtained, engineering measures, developing gatheringstream forestry and other measures must be taken. 