洛川塬土壤水分特征及其对土地利用变化的响应

Soil Moisture Characteristics and Their Responses to Land Use Change on Luochuan Loess Tableland

[目的]揭示洛川塬土壤水分特征及其对土地利用变化的响应,为优化黄土高原土地利用结构和土壤水分管理提供科学依据。[方法]测定农地、荒草地以及8,13,15,24,28和30a果龄的苹果园0—10m剖面的土壤水分,对比分析各样地的土壤含水率、土壤储水量及土壤干燥化特征。[结果](1)0—10m平均土壤水分含量:荒草地>农地≈8a果园>13a果园≈15a果园>24a果园≈30a果园>28a果园;≥24a果园土壤水分随深度增加逐渐减小,而其他样地的土壤水分随深度增加逐渐接近田间持水量。(2)以农地为参照,不同果园4—10m土壤水分减少量明显高于0—4m减少量,与农地的差异性随果龄增大而越发显著。(3)农地和荒草地转化为不同年限果园后出现水分亏缺现象,亏缺量占田间持水量的12%~46%。(4)24,28和30a果园分别出现轻度、中度和轻度干燥化现象。[结论]农地和荒草地转变成不同年限果园后,出现不同程度水分亏缺,并导致一定厚度的干层存在。

[Objective]Revealing the soil moisture characteristics and its response to land use change on Luochuan loess tableland,to provide scientific bases for optimizing land use structure and soil water management on the Loess Plateau.[Methods]Moisture contents in 0—10 msoil profiles under farmland,grassland,apple orchards with different ages（8,11,13,15,24,28,and 30 years old）were measured,respectively.Then this paper contrasted and analyzed the characteristics of soil moisture content,soil moisture storage and the desiccation of deep soil layer in various sampling sites.[Results]（1） The average soil water contents of different land use types in 0—10 mlayer have an order as grasslandfarmland≈8-year-old apple orchard13-year-old apple orchard≈15-year-old apple orchard24-year-old apple orchard≈30-year-old apple orchard28-year-old apple orchard.Soil moisture decreased with the increase of soil depth under apple orchard with apple trees older than 24 years,while it increased with the increase of depth in other sampling sites.（2） Compared with farmland,the decrease magnitudes of soil moisture within 4—10 mlayer were greater than those in 0—4 mlayer under apple orchards,and the differences between the two layers got increasing in older apple orchard.（3） The transformation of farmland and grassland into apple orchard can cause soil water storage gradually decreasing and hence worsen water deficit,which might account for 12% ~46% of the fieldcapacity.（4） 24-year,28-year and 30-year orchards caused mild or moderate desiccation with different thickness.[Conclusion]After farmlands and grasslands were turned into apple orchards,the soil water deficit appeared to some degree,and resulted in different thickness of dry layer.