土地利用方式变化对湘中丘陵区土壤碳氮含量的影响

对湘中丘陵区水田、旱地、农田、撂荒地和林地5种土地利用方式下土壤碳氮含量垂直分布特征进行比较分析。结果表明:5种土地利用方式下,土壤有机碳含量的空间垂直分布基本随着土层深度的增加而降低,水田的土壤全氮、有机碳平均含量、土壤容重均值均高于旱地土壤,水田土壤全氮含量、有机碳含量、土壤容重分别为2.03%、3.89 g/kg、1.20 g/cm~3;农田土壤的有机碳、全氮含量、碳氮比均高于撂荒地土壤的;水田转化为林地后,土壤全氮含量和有机碳含量分别比水田土壤低212.00%和80.80%,而土壤容重比水田的高7.69%,但林地土壤的容重高于农田;农田撂荒后,土壤的全氮含量变化规律呈现随土层深度增加而减少的趋势,最高值出现在0~5 cm土层,为0.314%,最低值出现在30~35 cm土层,为0.052%。

Soil carbon and nitrogen concentration under different land utilization method in central hilly area of Hunan Province

A comparative study was made of the vertical distribution characteristics of soil carbon and nitrogen contents of five kinds of land utilization types of paddy,upland,cultivated land abandoned land,and forest soil in the central hilly area of Hunan Province.The results show that the soil organic carbon content decreased gradually with the increase of soil depth on 5 kinds of land utilization types and according to the variation coefficient,TN,SOC content and soil bulk den-sity mean value of paddy soil are higher than those in upland soil,the value is 2.03%、3.89 g/kg、1.20 g/cm3 respec-tioely;Cultivated land TN,SOC content and soil bulk density mean value are higher than abandoned land soil.After paddy field convert into forest,TN content and SOC content respectively 212.00% and 80.80% lower than the paddy field,the soil bulk density is higher than paddy of 7.69%,but forest soil bulk density is higher than paddy soil;the soil TN of abandoned land reduce with the increase of soil thickness,peak value is found in 0 ~5 cm soil layer,is 0.314%,and the lowest value is found in 30 ~35 cm soil layer,is 0.052%.