稻田土壤有机碳变化的模拟:SCNC模型检验

Simulation of Changes of Soil Organic Carbon in Paddy Soils: SCNC Model Validation

应用自主建立的土壤碳循环模型(SCNC)模拟了中亚热带地区6个稻田长期定位试验土壤有机碳15年间的变化。结果表明,SCNC模型较为准确地模拟了各处理土壤有机碳的变化趋势,在所有模拟值与实测值的比较中,相对误差的绝对值<5%的比率占43.89%,<10%的则占71.11%。监测点土壤有机碳实测值和模拟值的相关性均达到了极显著水平,二者相关曲线的斜率均在0.95￣1.05之间。说明SCNC模型适合于我国亚热带稻田土壤有机碳的模拟,但模拟结果也表明,模型在一定程度上(<20%)低估了不施肥处理的有机碳积累量,需要进一步改进。

Paddy field is the main production system in the subtropical region of China. Due to waterlogged condition, the turnover of soil organic C （SOC） is different with dry upland. Based on the Soil Organic Carbon and Nitrogen Cycling Model （SCNC） built by us, we developed a simulation model for paddy soils. Here we simulated the changes of SOC in 6 long-term field experiments with 4 types of fertilization. Without any fertilizer incorporated, SOC showed no declining trend during the experimental period. Chemical fertilizer application enhanced the accumulation of soil organic C in half of the experiments. Soil organic C under middle-level manure （M-M） and high-level manure （H-M） treatments increased significantly, and the effect of H-M was obviously higher than that of L-M. The changes of soil organic C were simulated by SCNC paddy sub-model accurately. According to the statistics of relative errors between simulated and observed values, about 43.89% of relative errors were less than 5%, 71.11% less than 10%. The correlation between simulated and observed values was significant （p〈0.01）. The slopes of 6 sites were all between 0.95- 1.05. All these proved that SCNC model was suitable for the simulation of soil organic C changes in subtropical paddy soils. But the simulating results also showed that the model underestimated the accumulation of soil organic C in NIL treatment, and needed to be improved.