中文摘要：

应用土壤物理分馏方法和同位素技术，对丹江口库区清塘河小流域林地、灌木地和农田的土壤颗粒组成（〉2mm、0．25～2mm、0．053～0．25mm和〈0．053mm）和其有机碳、全氮含量以及碳氮同位素值进行了研究。结果表明：不同土地利用下土壤颗粒组成、有机碳和全氮含量，以及碳氮同位素值均有明显差异。林地和灌木地0～10cm土层〉2mm土壤颗粒所占百分比显著高于农田（P〈0．05），0．053～0．25mm土壤颗粒则显著低于农田（P〈0．05）。林地和灌木地0～10cm土层0．25～2mm和〈0．053／mm土壤颗粒的有机碳含量显著高于农田（P〈0．05）。灌木地0～10cm土层〉2mm、0．25～2mm和〈0．053mm土壤颗粒，以及10～30cm土层〉2mm土壤颗粒的全氮含量显著高于林地和农田（P〈0．05）。同位素分析显示，3种土地利用类型土壤的δ^13C和δ^15N值在各粒径中大小顺序均为：农田〉灌木地〉林地。研究结果表明，土地利用类型的变化会改变植物碳的输人和土壤分解速率，进而会影响到土壤颗粒组成、土壤碳氮含量及其同位素值的变化。

英文摘要：

In this study soil particles （〉2mm, 0.25-2 ram, 0.053-0.25 mm and 〈0.053 mm）, soil organic carbon （SOC） and total soil nitrogen （TN） following land use changes （farmland, shrubland and woodland） in the Danjiangkou Reservoir area by soil fractionation and stable C and N isotopes were investigated. Land use change significantly changed soil particles, SOC and TN concentrations, and δ^13C and δ^15N values. In the 0-10cm soil layer, soil particles （〉2 ram） in the woodland and shrubland were significantly higher than that in the farmland （P〈0.05）, while particles （0.053-0.25 mm） showed opposite trends （P〈0.05）. SOC concentrations of soil particles （0.25-2 mm and 〈0.053 mm ） in the 0-10 cm soil layer were significantly higher in the woodland and shrubland than in the farmland （P〈0.05）. TN of soil particles （〉2 mm, 0.25-2 mm and 〈0.053 mm） in the 0-10 cm soil layer and particles （〉2 ram） in the 10-30cm soil layer were significantly higher in the shrubland than in the woodland and farmland （P〈0.05）. The isotope analysis showed that both δ^13C and δ^15N values of soil particles in all three land use types followed the same order： farmland 〉 shrubland 〉 woodland. The results suggested that land use change could change plant carbon input and soil carbon decomposition and hence impact soil particles, soil C and N and the δ^13C and δ^15N values.