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,结合稳定性碳同位素方法,分析不同秸秆还田方式、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 a）,土壤有机碳显著降低,且因农田栽培方式不同而异,1 m土层降低幅度在13.3%～35%之间,但降低显著发生在0～40 cm.经过8 a施加底肥,可以提高土壤有机碳0.83g.kg^-1.免耕方式可以显著提高土壤有机碳,且主要发生在0～10 cm土层.翻耕操作会引起10～15 cm和15～20 cm土层的土壤有机碳高于免耕处理的现象.土壤有机碳的δ^13C值的比变化主要发生在0～20 cm土层,玉米种植输入的有机碳主要集中在土壤0～20 cm层次.在土壤0～5 cm表层,源于农作物的土壤有机碳所占的最高比例为18%,到15～20 cm已经降到了5%左右.

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 using isotope carbon for the analysis of the impact on soil organic carbon（SOC） properties.The research indicated that after change into farmland（34 years）,SOC is significantly reduced and for 1m of soil layer,the scope of reduction is from 13.3%-35% and this decrease happens in 0-40 cm of soil layer.After 8 years of fertilization,SOC can be increased at 0.83 g.kg^-1.No-tillage can significantly increase the SOC especially in 0-10 cm but plough will increase the SOC at 10-15 cm and 15-20 cm.Change of δ13 C of SOC due to land use change mainly happens in 0-20 cm,where input of organic materials from maize stored.In soil layer of 0-5 cm,only maximum 18% of SOC is from crop residues and in 15-20 cm,this percentage is about 5%.