The impacts of CENTURY model initialization scenarios on soil organic carbon dynamics simulation in French long-term experiments
The impacts of CENTURY model initialization scenarios on soil organic carbon dynamics simulation in French long-term experiments
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DOI：
10.1016/j.geoderma.2017.09.038
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发表时间：
2018-02
期刊：
影响因子：
6.1
通讯作者：
Bassem Dimassi;B. Guenet;N. Saby;F. Muñoz;M. Bardy;F. Millet;M. Martin
中科院分区：
文献类型：
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作者：
Bassem Dimassi;B. Guenet;N. Saby;F. Muñoz;M. Bardy;F. Millet;M. Martin
基于过程的生态系统模型越来越多地用于评估农业实践对不同尺度土壤有机碳（SOC）储量的影响。在这些模型中，误差和预测不确定性的主要来源之一是初始SOC池大小的规格。然而，很少有研究审查随着时间的推移和各种农业实践的错误和不确定性。我们研究的主要目的是1）检查初始化情景对世纪模型V4.5性能的影响，2）量化初始化对世纪模型总误差方差的贡献。我们模拟了6个充分表征的长期实验（LTE）的SOC动态，在法国各地进行了25种处理，测试了各种农业实践（即，在保持标准参数不变的情况下，使用世纪模型计算了各种作物（包括无机和有机施肥、各种作物轮作以及秸秆和残留物的去除）。我们应用了九个初始化方案，每个方案的特点是作物管理和放松程序的独特组合。这些放松程序包括在初始化阶段结束时改变模拟SOC和氮水平，直到它们与实验开始时的库存相匹配。在初始化阶段结束时，SOC池的分布模式在所有LTE的所有场景中是相似的。慢池占总SOC储量的比例最大（平均值为61.5%），而主动和被动池平均分别为5.3%和27.9%。对世纪绩效的总体分析表明，SOC存量预测结果合理（9种初始化情景的R2值在0.50和0.75之间），但SOC变化预测结果较弱（9种初始化情景的R2值在0.1和0.36之间）。均方根误差（RMSE）值是中等的总测量SOC股票和他们的置信区间相比。RMSE值介于6.22 Mg ha− 1和15.24 Mg ha− 1之间，分别相当于所有LTE初始平均总SOC存量的13.1%和32.1%。记录了无松弛程序的最高值。世纪模型误差（即，模拟-观测SOC存量）分析显示对初始化情景有轻微的敏感性（约占世纪误差总方差的6%）。不过，场景与LTE的二阶交互贡献了33.6%。与此同时，与其他因素相比，农业实践对世纪误差的方差影响最大（44.7%）。我们的研究结果表明，在预计SOC变化的不确定性的初始化的贡献是可以忽略不计的模型本身和模拟系统特性的不确定性相比。
Process-based ecosystem models are used increasingly to evaluate the impacts of agricultural practices on soil organic carbon (SOC) stocks at various scales. One of the major sources of error and projection uncertainty in these models is the specification of the initial SOC pools sizes. However, few studies have examined errors and uncertainty over time and for various agricultural practices. The main purposes of our study were 1) to examine the impacts of initialization scenarios on CENTURY model V4.5 performance and 2) to quantify the initialization contribution to the total variance of error of the CENTURY model. We simulated the SOC dynamics of six well-characterized long-term experiments (LTEs) with 25 treatments across France, testing various agricultural practices (i.e., inorganic and organic fertilization, various crop rotations and straw and residues removed) using the CENTURY model while keeping the standard parameters unchanged. We applied nine initialization scenarios, each characterized by a unique combination of crop management and relaxation procedures. These relaxation procedures consisted of shifting simulated SOC and nitrogen levels at the end of the initialization period until they matched the stocks at the beginning of the experiment. At the end of the initialization period, the distribution pattern of SOC pools was similar in all scenarios for all LTEs. The slow pool represented the largest proportion of total SOC stocks (average value of 61.5%), whereas the active and passive pools averaged 5.3% and 27.9%, respectively. The overall analysis of CENTURY performance indicated fair results for SOC stocks prediction (R2values of the nine initialization scenarios ranged between 0.50 and 0.75) but weak results for SOC change prediction (R2values of the nine initialization scenarios, ranged between 0.1 and 0.36). The root mean square error (RMSE) values were moderate compared to the total measured SOC stocks and their confidence intervals. The RMSE values ranged between 6.22 Mg ha− 1and 15.24 Mg ha− 1, which corresponded to 13.1% and 32.1% of the initial average total SOC stock for all LTEs, respectively. The highest values were recorded for the no relaxation procedures. CENTURY model errors (i.e., simulated - observed SOC stocks) analysis showed a slight sensitivity to the initialization scenarios (approximately 6% of the total variance of the CENTURY error). However, the second-order interaction of scenarios and LTE contributed by 33.6%. Meanwhile, agricultural practices had the greatest impact on the variance of the CENTURY error (44.7%) compared to other factors. Our findings suggest that the contribution of the initialization to the uncertainty in projected SOC changes is negligible compared to the uncertainty related to the model itself and simulated systems characteristics.