岩溶地区不同土地利用方式下土壤斥水性的空间变化

摘要

以广西桂林市农业科学院大豆、甘蔗及梨树植被覆盖的土壤为例,研究不同土地利用模式下土壤斥水性的空间变化.通过对每个试验区面积为135 m×105 m的100个测量点应用滴水穿透时间法(water droppenetration time,WDPT)进行土壤斥水性测量,利用土壤含水量确定干旱(0.062±0.025) cm3·cm-3、中等(0.151±0.045) cm3·cm-3和湿润(0.237土0.086)cm3·cm-3的土壤水分条件.运用地统计方式,对土壤斥水性进行空间变化分析.结果表明:在干旱和湿润水分条件下,WDPT的大小均表现出梨树地最大,甘蔗地次之,大豆地最小,与土壤含水量和有机质大小的变化一致,但是在中等水分条件下,WDPT均值大豆地高于甘蔗地,同时3个试验区的滴水入渗持续时间都达到最大.土壤斥水性的地统计分析结果表明,在3种水分条件下,3个试验区的空间结构比基本上大于75％,空间相关性较强.在土壤斥水性的高阈值空间分布上,甘蔗地的稳定性比大豆地强,而梨树的空间分布稳定性最弱.研究结果说明人类的活动会对土壤斥水性空间稳定性产生干扰,但土壤本身仍具有恢复其空间分布稳定性的能力.%Spatial distribution of water repellency of the soils from plots planted with different crops was studied under the dry,moderately or wet soil conditions.Soybeans,sugarcane or pear trees were grown on the plots in the karst region near Guilin Institute of Agricultural Sciences in Guangxi.The spatial distribution of water repellency in the soils from the plots was determined by using a geostatistical analysis on the plots of 135 m× 105 m in size.There were 100 sampling points on each plot for measurement of water drop penetration time (WDPT).The soils were also classified according to their moisture content as dry (0.062±0.025) cm3 · cm-3,moderately (0.151±0.045)cm3 · cm-3 or wet (0.237 ± 0.086) cm3 · cm-3.The results showed that,under dry and wet conditions,the greatest WDPT and contents of moisture and organic matters were found in the soil where pear trees were grown,while the lowest on the soybean plot.However,under the moderately wet soil condition,the lowest values on these parameters were on the sugarcane plot.Meanwhile,the water retention time reached a maximum for all plots.It appeared that geostatiatical analysis significant correlation existed among the spatial distribution of water repellencies in 3 planting plots under 3 soil conditions as the ratio was substantially greater than 75％.Due to the high threshold water repellency distribution,the soil at the sugarcane plot seemed to be more stable than that at the soybean field,while that at the pear tree plot being the weakest of all.It suggested that the soils might be able to recover spatial distribution of water repellency after being disturbed by human activity.