东北地区旱地土壤全氮空间变异性对幅度拓展的响应

土壤氮素不仅是作物必需的营养元素,还是重要的生态元素。不同幅度上土壤全氮含量空间变异的研究是正确评价土壤质量和精确估算土壤氮库的基础。基于中国东北地区第二次土壤普查的1 041个旱地剖面数据,设定三种类型的幅度,即行政区幅度(县、市、省和大区)、土壤分类幅度(土属、亚类、土类和土纲)和土壤类型(地带性土壤和非地带性土壤)-行政区幅度,研究了该区旱地土壤表层(0～20 cm)和剖面(0～100 cm)全氮含量的变异性及其对幅度拓展的响应。结果表明,三种类型幅度上,表层和剖面的平均土壤全氮含量变异性均随着幅度的拓展而增大。在行政区幅度,旱地面积或行政区面积与平均土壤全氮含量变异系数具有较强的对数关系。在土壤分类幅度上,不同土纲的平均土壤全氮含量的变异随幅度变化的趋势、变幅等均存在差异。在土壤类型—行政区幅度,地带性土壤与非地带性土壤的全氮含量随幅度的变化趋势一致,但变化速率有差别,旱地面积与平均非地带性土壤全氮含量变异系数有较强的对数关系。该结果可为东北地区不同幅度下基于土壤类型聚类的旱地土壤氮库估算、土壤资源调查时采样数目的确定提供理论指导。

Response of spatial variability of soil total nitrogen to expansion of uplands in scale in Northeast China

Soil nitrogen is not only an essential nutrient element for crops, but also an important ecological element. The study on spatial variability of soil total nitrogen content at different scales is the basis for evaluating soil quality and predicting nitrogen storage in soil accurately. Based on the data of 1 041 soil profiles obtained during the second soil survey in Northeast China, three scales were set in this study, namely, administration region scale (county, city, province and region), soil taxonomy scale (family, sub-group, great group and order of soil) and soil type- administration scale (zonal soil and intrazonal and azonal soil), to study variability of soil total nitrogen (STN) content in the surface soil layer (0~20cm) and the soil profile (0~100cm) and its response to expansion of upland in scale. Results show that variability of STN content in the surface layer and in the profile increased with the expansion of scale. At the administration scale, a strong logarithmic relationship was found between the area of uplands or of the administrative region and the mean CV of STN content. At the taxonomy scale, though the mean CV of STN content of each soil order increased with the extension of scale from family to order, amplitude of the variation varied. At the soil type-administration region scale, zonal, intrazonal and azonal soils displayed a similar trend in variability of STN content, but differed in variation rate, and a strong logarithmic relationship between the area of uplands and the mean CV of intrazonal and azonal STN content was observed. These findings may provide a basis for assessing soil nitrogen storage in uplands clustered by soil type at various scales in Northeast China, and some theoretical guidance for determining the number of soil samples to be taken in investigation of soil resources in that region.