县域尺度红壤丘陵区水稻土有机碳模拟

区域尺度土壤有机碳储量的时空变化及其管理是全球气候变化和农业可持续发展研究的重要内容。本文以中亚热带红壤丘陵区的江西省余江县为例,基于12a的长期试验和1998年、2001年的野外定位采样对比研究,利用反硝化分解模型?DNDC(Denitrification-Decomposition)在田块和县域尺度研究了县域尺度表层(0~20 cm)水稻土有机碳储量的时空变化规律。结果表明,以长期试验数据验证,DNDC模型可以较好地模拟水稻土表层有机碳的长期动态变化。2001年农田水稻土(面积为3.6×108m2)表层(0~20 cm)有机碳总储量为2.9×109kg,平均土壤有机碳密度为6.0 kg m-2。1998年至2001年余江县水稻土表层土壤有机碳库逐年增加,年际平均变化量为3.0×107kg。通过对余江县水稻田模拟不同碳投入的情景,分析预测1998年至2017年土壤有机碳储量,种植绿肥提高秸秆还田比率同时减少化肥的投入,可有效地增加红壤区域有机碳蓄积。

The spatial-temporal dynamic change and simulation of county-scale paddy soil organic carbon in red soil hilly region

A research using the Denitrification-Decomposition (DNDC) model was carried out to study spatial-temporal variation of SOC storage at both field and county scales, based on the data of a long-term (12 a) fertilization experiment in paddy field and the comparison of two field surveys in 1998 and 2001 in Yujiang County. Results show that the model simulated well the variation of SOC in the long-term experiment. The total SOC storage in the surface layer (0~20 cm) of paddy field in Yujiang County was estimated at 2.9×10⁹ kg and the average SOC density was 6.0 kg m^-2 in 2001. The SOC storage in the surface layer increased annually on average by 3.0×10⁷ kg from 1998 to 2001. Scenario analysis of the period from 1998 to 2017 show that SOC storage could be effectively improved by planting green manure, increasing straw returning rate and reducing chemical fertilizer application rate.