不同种植年限紫花苜蓿人工草地土壤有机碳及土壤酶活性垂直分布特征

Vertical distribution characters of soil organic carbon and soil enzyme activity in alfalfa field with different growing years

通过测定土壤容重、土壤有机碳含量和土壤酶活性,探讨了不同种植年限(1,3,4,5和8年)紫花苜蓿人工草地剖面土壤有机碳含量、土壤碳密度及土壤酶活性的垂直分布差异。结果表明,1)1～8年0～100cm土壤平均SOC含量分别为4.519,4.865,5.120,5.348和3.334g/kg,各土壤剖面SOC含量主要集中在0～40cm深度内,分别占0～100cm土壤有机碳含量的69.7%,65.8%,73.8%,70.0%和67.2%,SOC含量自40cm以下急剧下降。2)1～8年0～100cm土壤平均SOC密度分别为1.148,1.217,1.231,1.398和0.840kg/m2,表层0～40cm约占54.8%～61.8%;0～100cm SOC含量及其密度均以种植5年苜蓿地最高,依次为8年(19.9g/kg和5.04kg/m2)<1年(27.7g/kg和6.77kg/m2)<3年(29.7g/kg和7.26kg/m2)<4年(30.4g/kg和7.38kg/m2)<5年(32.2g/kg和8.53kg/m2)。3)3种土壤酶活性都随着土层加深和种植年限的增加而降低,土壤表层(0～10cm)及次表层(10～20cm)酶活性显著降低,土壤酶活性主要集中在0～20cm深度内,表现出表聚性。

Through comparing the concentration and inventory of soil organic carbon（SOC） and soil enzyme activity under different plant ages（1,3,4,5 to 8 years） of alfalfa at the foot of Helan mountain in Ningxia,the SOC and soil enzyme activity vertical distribution characters were explored.1）With the increase of soil depth and plant time,from 0 to 100 cm soil mean SOC concentration were 4.519,4.865,5.120,5.348 and 3.334 g/kg from 1 to 8 years,the soil profile SOC concentration mainly showed a significant accumulation in the 0 to 40 cm depth,accounted for 69.7%,65.8%,73.8%,70.0% and 67.2% from 0 to 100 cm,but it sharply declined below 40 cm;2）0-100 cm soil mean SOC density were 1.148,1.217,1.231,1.398 and 0.840 kg/m^2 from 1 to 8 years,and the surface soil（0-40 cm） accounted for about 54.8% to 61.8%,the highest SOC content and its density was five-year alfalfa,the order of the concentration and density of SOC in the 0-100 cm soil layer were 8 years（19.9 g/kg and 5.04 kg/m^2）〈1 year（27.7 g/kg and 6.77 kg/m^2）〈3 years（29.7 g/kg and 7.26 kg/m^2）〈4 years（30.4 g/kg and 7.38 kg/m^2）〈5 years（32.2 g/kg and 8.53 kg/m^2）.3） Three kinds of soil enzyme activity decreased with the increase of soil depth and plant time,the soil surface（0-10 cm） and subsurface（10-20 cm） enzyme activity decreased significantly,soil enzyme activity was mainly concentrated in the 0-20 cm depth,showed the surface gathering.