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(＞2 mm、0.25 ～2 mm、0.053 ～ 0.25 mm和＜0.053 mm)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～ 10 cm土层＞2 mm土壤颗粒所占百分比显著高于农田(P＜0.05),0.053 ～ 0.25 mm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 ～2 mm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 ～ 10 cm土层＞2 mm、0.25 ～2 mm和＜0.053 mm土壤颗粒,以及10 ～ 30 cm土层＞2 mm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δ13C和δ15N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入和土壤分解速率,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.%In this study soil particles (＞2mm,0.25-2 mm,0.053-0.25 mm and ＜0.053 nun),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 δ13C and δ15N values.In the 0-10cm soil layer,soil particles (＞2 mm) 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 mm) 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 δ13C and δ15N 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 δ13C and δ15N values.
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