中文摘要：

设置了两种土壤施氮水平（150和300mg·kg^-1），3个生长时期（喇叭期、开花期和成熟期）收获玉米植株的土壤盆栽试验，采用同位素质谱法测定玉米植株和土壤有机碳的δ^13C值，以研究玉米植株生长和施氮水平对土壤有机碳更新的影响．结果表明。玉米植株的δ^13C值为-12．9‰-13．2‰，受玉米生长时期和施氮水平的影响不显著；种植玉米后，土壤有机碳含量增加，说明在供试土壤上，玉米生长促进了土壤碳汇的作用；玉米生长和施氮水平显著影响土壤有机碳的δ^13C值和土壤有机碳的更新．根据土壤有机碳δ^13C变化计算，玉米根际碳沉积对土壤有机碳的贡献为4％-25％，随玉米生长时间的延长，玉米根际碳沉积对土壤有机碳的贯献增大．种植一季玉米后，低氮处理的土壤有机碳的δ^13C值大于施用高氮的处理，但土壤总有机质含量低于高氮处理．由此说明，在养分不足的条件下，玉米根分泌物可能更能激发土壤原有机质的矿化，从土壤中获得更多的养分．

英文摘要：

In order to understand the effect of growing maize and N application on the renewal of soil organic carbon （SOC）, a pot experiment with two N application rates （ 150 and 300 mg·kg^ -1 ） and harvesting maize at three growing stages （ trumpeting, flowering, and ripening stage, respectively） was conducted and the values of δ^13C in maize plant and SOC was determined by mass spectrometer. The results showed that the values of δ^13C in maize plant were - 12.9‰ - - 13.2‰, which were not affected by growing stages and N application rates. The SOC content was increased after maize planting, but decreased in the hare soil, indicating that growing maize enhanced the function of soil as a carbon pool. And growing maize and N application rates influenced obviously the value of δ^13C and renewal of SOC. Based on the changes in δ^13C, the contribution of rhizodeposition to SOC was calculated to be from 4% to 25% , increased with the maize growing time. After the maize harvesting, the contribution of rhizodeposition to SOC was larger in low N application rate than in high N application rate, but the total content of SOC was higher in high N application rate than in low N application rate. The results indicated that the mineralization of the original SOC was accelerated by maize root exudations more significantly in low N application rate than in high N application rate, which was probably due to more N demands from soil organic matter in the case of low N application rate.