Spatial distribution characteristics of soil organic matter and nitrogen of three shrub lands in Loess Plateau | 黄土高原3种灌木林地土壤有机质及氮素的空间分布特征

صينى. 分析研究黄土高原地区3种灌木林地土壤的有机质和氮素在剖面不同土层深度、坡向及坡位间的分布特征，为黄土高原灌木林地土壤的培育提供基础依据。通过野外采样、室内土壤分析并结合数理统计的方法，以荒草地作为对照，对黄土高原地区的柠条、沙棘林地和天然次生林地的有机质和氮素含量在不同土层深度(0~20，20~40，40~60，60~80 cm)、不同坡向(阳坡、半阴半阳坡、阴坡)和不同坡位(坡上部、坡中部、坡下部)的变化进行了研究。3种灌木林地土壤有机质含量随土层深度的增加而递减，不同土层间差异显著；各土层间土壤全氮含量差异不明显；碱解氮含量以表层显著高于20~80 cm土层，表层以下各土层差异较小；从坡上部、坡中部到坡下部，柠条林地土壤有机质含量差异很小，沙棘林地的土壤有机质含量呈降低趋势，而天然次生林地的土壤有机质含量却呈逐渐增大趋势；全氮含量总体呈现出坡上部-坡中部-坡下部逐渐下降的趋势，但天然次生林地土壤全氮含量则呈先上升后下降的变化规律；土壤有机质和土壤全氮含量在不同坡向的变化趋势相同，均为阴坡半阴半阳坡阳坡，而碱解氮含量却无明显规律性。黄土高原地区灌木林地有机质、全氮和碱解氮含量基本处于“中等”水平，且在土壤剖面及不同坡向、不同坡位之间具有一定的分布规律。

إنجليزي. This paper analyzed the spatial distribution characteristics of soil organic matter and nitrogen of three shrub lands on different soil layers of profile, different slope aspects and different slope positions in Loess Plateau and provided basic data for soil cultivation. Using the wild grass land as contrast, the spatial distribution characteristics of organic matter and nitrogen of Caragana korshinskii Kom. land (CKK), Hippophae rhamnoides L. land (HRL) and Natural Secondary Forest land (NSF) on different soil layers of profile (0－20, 20－40, 40－60, and 60－80 cm), different slope aspects (sunny slope, half sunny slope, and shady slope) and different slope positions (upper slope, middle slope, and lower slope) were studied by field investigation and sampling, soil analysis, and mathematical statistics. The organic matter contents of the three shrub lands decreased from topsoil to basement soil and the differences of any two layers were significant. There was no marked difference in total nitrogen contents between different layers, meanwhile the alkali-hydrolyzed nitrogen content of topsoil was higher than 20－80 cm soil layer, but no marked differences between 20－40, 40－60, and 60－80 cm soil layers. The organic matter of CKK had no significant differences between upper, middle, and lower slope, while that of HRL decreased and that of NSF increased from upper to middle and lower slope. The total nitrogen contents gradually decreased from upper to middle and lower slope except that of NSF increased at first then decreased. The contents of organic matter and total nitrogen on different slope aspects were similar (shady slopehalf sunny slopesunny slope), but the alkali-hydrolyzed nitrogen on different slope aspects showed no obvious variation trend. Most of the organic matter, total nitrogen and alkali-hydrolyzed nitrogen contents of shrub lands in Loess Plateau were “middle” grade, and had different spatial distribution characteristics between different soil layers on profile, different slope aspects and positions.