丹江口库区不同土地利用土壤碳氮含量的变化

Changes in Soil Carbon and Nitrogen Concentration Under Land Use Change in Danjiangkou Reservoir Area, China

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0～10 cm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 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.