土地利用类型对黄土塬区深层土壤含水量的影响——以长武塬区为例

Effect of land use types on the deep soil moisture of the loess tableland- A case of Changwu

对长武塬区不同土地利用类型条件下深层土壤水分特征及其生态环境效应进行了研究。结果表明:各土地利用类型测定范围内土壤平均含水量总体上呈涝池>裸地>小麦地>12年生果园>20年生果园的趋势,其值分别为:21.41、19.71、18.55、17.92和17.84%、15.42和14.07%。在相同树龄条件下,12龄果园不同样点之间土壤剖面水分存在较大差异,耗水深度可达10-13m,耗水深度因果树生长差异而有所差别;而20龄果园不同样点间土壤含水量的差异较小,耗水影响深度可达19m,形成了深厚的生物利用型干层,限制了降水入渗补给地下水。裸地和涝池土壤含水量总体上高于其他土地利用类型下土壤含水量。裸地在丰水年或者较大规模集中连续降水情况下,降水有可能通过1360cm的深厚土层继续向下补给;涝池在积水后快速入渗补给地下水,之后经过近一年的较长时间再分布后,在土体内水势梯度作用下重新趋于相对平衡。

Soil moisture characteristics in deep soil layers under different land use types（ pond,bare land,wheat land,12- years apple orchard（ two sites） and 20- years apple orchard（ two sites）） on the Changwu loess tableland area were studied. Results showed that the average soil water content under different land use types was pond 〉bare land 〉wheat land 〉12- years apple orchard 〉20- years apple orchard,and the average values of which were 21. 41%,19. 71%,18. 55%,19. 71% and 18. 55%,15. 42% and 14. 07%,respectively. The variation of soil water contents between two sampled sites in 12- years- old apple orchard was large,while that was small in 20- years- old apple orchard. The depths of soil water consumption by 12- years- old apple trees root were 10- 13m,varied among different growth conditions. And the depths of soil water consumption by 20-years- old apple trees root could reach 19m. There were deep dry layers as affected by biota use,which shut down the pathway of rainfall percolating to groundwater. The soil moisture in bare land and pond were higher than that of other land use types. The precipitations might be infiltrated and redistributed downward through 1360cm deep soil layer and recharge lower- layer soil water in rainy year or larger continuous precipitation in bare land. Precipitation,when converged into the pond,infiltrated quickly and recharged to groundwater. The soil water in pond redistributed by soil water potential gradient for a long time during the dry seasons and tended to be relatively balanced again.