黄土高原丘陵沟壑区农业生态系统碳循环模拟研究

Simulation of soil carbon cycle in agro-ecosystem of hilly-gully areas on the Loess Plateau

利用甘肃农业大学定西旱农综合试验站的2001—2008年长期定位试验数据对DNDC模型进行了验证,结果表明:模型可以用于安定区县域尺度农田土壤有机碳储量及其变化的模拟。模拟不同处理间碳的循环结果显示,秸秆还田或覆盖可提高作物秸秆与根系残留的外源碳携入量,也能提高土壤异氧呼吸对内源碳的消耗。利用DNDC模型以及区域气象、土壤和作物资料,对该区域表层(0～20 cm)农田土壤碳循环进行模拟研究的结果表明,2008年农田土壤(面积为1.2×109 m2)表层(0～20 cm)有机碳总储量为2.8×109 kg,平均土壤有机碳密度为2.33 kg.m-2。通过对该区域农田土壤模拟不同碳投入的情景,分析预测2008年至2037年土壤有机碳储量,得出增加有机肥能够显著增加土壤有机碳的积累,其次为免耕同时增加秸秆还田率50%,而单独实施这两种措施,土壤有机碳的积累速度较慢。

DNDC（Denitrification Decomposition） model was validated using database of a long-term experiments on different tillage practices in Dingxi experimental station of Gansu Agricultural University.There was a high similarity between the simulated data and measured data,the DNDC model could be used to study spatio-temporal variation of soil organic carbon（SOC） storage at both farm land and county scales.The simulation results indicated that stubble retention or mulching could increase exogenous carbon input,which was brought into soil as crop residues and root exudates,it also could increase endogenous carbon consuming by soil heterotrophic respiration.Total SOC storage in the surface layer（0-10 cm） of farm land in Anding district was predicted at 2.8×109 kg,22710.51 kg·C·hm-2 in 2008,lower than the national average（40990 kg·C·hm-2）.Scenario analysis from 2008 to 2037 showed that SOC storage could be significantly improved by applying manure,and by no-tillage with increasing stubble retention rate by 50%.However,SOC accumulated slowly under the practice of no-tillage without straw cover,and conventional tillage with straw incorporated.