沙障对不同林龄雨养梭梭林冠下浅层土壤含水量的影响

[目的]分析不同林龄雨养梭梭林冠下浅层土壤含水量在布设沙障后的变化,为沙障生态功能的评价及梭梭生长发育状况的预测提供理论依据。[方法]对5年生幼年林和25年生中年林在布设沙障后冠下0—50cm的土壤含水量、表层结皮厚度、近地表风速等因子进行测定分析。[结果]沙障通过降低近地表气流流速,加速结皮形成等方式提高了梭梭冠下0—50cm的浅层土壤含水量。沙障对5年生梭梭冠下土壤含水量的空间分布格局影响不大,但使25年生梭梭冠下土壤含水量随着与主干距离的增加而单调增加,表现为"干岛效应"。在垂直分布上,25年生梭梭冠下土壤含水量在塑料网沙障区与对照区间呈显著相关(p0.05),而在麦草沙障区与对照区间相关性不显著,其最大土壤含水量的出现深度下降至30—40cm处。[结论]布设机械沙障对退化梭梭林的恢复将起到一定的促进作用,且对中年林梭梭土壤水分的影响大于对幼年林。

Influence of Sand Barriers on Shallow Soil Moisture Under Canopy of Rain-fed Haloxylon Ammodendron Forest with Different Ages

[Objective] By analyzing the changes of soil water content beneath the canopy of rain-fed Haloxylon ammodendron forest in which sand barriers were established, this paper aimed to provide theoretical basis for evaluating the ecological functions of sand barriers as well as forecasting the growth and development situation of the Haloxylon ammodendron forest. [Methods] Two sites of 5 and 25 years old Haloxylon ammodendron forests were selected to establish wheat straw and plastic net sand barriers. Wherein, soil water contents of 0-50 cm depth, crust thickness, near-surface wind speed beneath the canopy were measured and analyzed. [Results] Under the influence of sand barriers, soil water contents of 0-50 cm increased, air flow velocity in near-surface decreased and the formation of crust was speeded up. The sand barriers had no significant influence on the spatial distributional pattern of soil water contents beneath the 5 years old Haloxylon ammodendron canopy. Whereas, "dry island effect" was observed for the 25 years old Haloxylon ammodendron canopy, i.e., soil water contents decreased monotonically with the distance decreasing from the tree trunk. Soil water content in the vertical profile between plastic net sand barriers area and contrast area had a significant correlation(p<0.05), while had no evident correlation between wheat straw sand barriers area and contrast area. The depth with biggest soil water content in wheat straw sand barriers area descended to 30-40 cm. [Conclusion] Establishment of sand barriers had somewhat acceleration effects on the recovery of degenerated Haloxylon ammodendron forest, it was more obvious for the middle age forest than the young forest with regard to the effect on soil water.