中文摘要：

以河北曲周县原状草地土壤和农田土壤为研究对象，分析了土地利用方式、秸秆还田、耕作方式和施肥水平对土壤有机碳特性的影响。研究表明，华北原状草地改变为农田后（34年），土壤砂粒、颗粒有机碳的含量和总有机碳的比例、轻组土壤和轻组土壤有机碳都显著降低，且以秸秆还田影响最大。经过8年的耕作，施加底肥、免耕和秸秆整株还田等农艺措施，明显提高了土壤颗粒有机碳含量。秸秆还田使得0～20cm土壤颗粒有机碳含量明显增加，且整株还田比粉碎还田更能增加10～20cm土壤颗粒的有机碳含量，而免耕对土壤颗粒有机碳的增加主要表现在0～10cm。土壤非保护性有机碳的比例也会显著降低，且非保护性有机碳主要分布在0～5cm土层。

英文摘要：

In Quzhou County, Hebei Province where now intensive farming system is operated, original grassland and farming land under different tillage, crop straw return and fertilization measures were studied for the analysis of the impact on soil organic carbon properties, espe cially on light fraction organic carbon, sand and particle organic carbon. The research indicated that after change into farmland（34 years）, light fraction organic carbon, sand and particle organic carbon were significantly reduced and maize straw had the most influence. After 8 years of farming, fertilization, no-tillage, and maize straw return significantly increased particle organic carbon. Crop straw significantly increased the particle organic carbon in 0-20 cm soil layer, but whole-straw return had higher increase of 10-20 cm soil particle organic carbon than grinding straw return. The increase of particle organic carbon induced by no tillage mainly happened in 0-10 cm soil. After changed into farmland from grassland, non-protective organic carbon were significantly reduced and it mainly happened in 0-5 cm soil layer.