Retrieval of Soil Organic Carbon in Cinnamon Mining Belt Subsidence Area Based on OLI and 6SV
ZHAO Xin1, XU Zhan-jun1*, YIN Jian-ping2, BI Ru-tian1, FENG Jun-fang1, LIU Pei3
1. College of Resources and Environment, Shanxi Agricultural University, Jinzhong 030801, China
2. Energy-Saving and Environment Protection Department, China Coal Pingshuo Group Co., Ltd., Shuozhou 036006, China
3. School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo 454000, China
摘要： 遥感反演已广泛应用于区域土壤理化性质的动态监测，但是鲜有针对有机碳含量低、下垫面不均一等土壤光谱特性不显著区域的研究。黄土高原褐土带地形多样，丘陵广布，有机碳含量低。采煤活动引起大面积土壤退化，土壤光谱特性受到强烈干扰，制约了区域尺度土壤有机碳(soil organic carbon)含量遥感反演精度。以山西省褐土带典型采煤沉陷区为例，借助地表反射率和室外实地采集的样本数据对褐土带煤矿开采沉陷区土壤有机碳含量进行反演。采用结合高空间、时间分辨率辅助气象数据的6SV(second simulation of a satellite signalin the solar spectrum-vector)模型和FLAASH(fast line-of-sight atmospheric analysis of spectral hypercubes)模型对研究区Landsat8 OLI影像的大气校正方法进行对比实验，分析其对褐土带采煤沉陷区土壤光谱曲线及有机碳含量的影响，识别敏感波段。选择原始光谱反射率(R)和平方根()、倒数的对数log(1/R)、一阶微分(R′)等数学变换形式，利用多元线性回归(MLR)、BP神经网络(BP neural net)和偏最小二乘回归(PLSR)建立土壤有机碳反演模型。结果表明：6SV模型大气校正的效果要优于FLAASH模型，可以有效消除大气、地形对于反射率的干扰，可见光波段反射率降低而近红外波段明显上升，不同有机质含量等级土壤反射光谱特性分明；640～670，850～880，1 570～1 600和2 110～2 290 nm波段对土壤有机碳含量指示性强；相较于多元线性回归(决定系数R2为0.765)、BP神经网络(R2为0.767)，偏最小二乘回归模型反演精度最高(R2为0.778)；结合高空间、时间分辨率辅助气象数据的6SV大气校正模型与偏最小二乘回归建模能显著提高褐土带采煤沉陷区土壤有机碳的反演精度。在此基础上预测研究区2013年—2015年土壤有机碳含量，研究发现：研究区土壤有机碳含量中部高，两侧低，复垦使土壤有机碳含量得到恢复。研究结果可用于揭示黄土高原褐土带采煤沉陷区土壤有机碳含量的时空分布特征，为改进区域土壤光谱分析、土地复垦评价、建立褐土带采煤沉陷区碳通量观测网络和土壤碳库估算提供理论和技术支持，对研究区域甚至全球范围褐土带生态可持续发展提供依据。
关键词：土壤有机碳；OLI；6SV；褐土带；采煤沉陷区
Abstract：Remote sensing retrieval has been widely used for dynamic monitoring of the physical and chemical properties of regional soil, but there are few studies on the areas with low organic carbon content and uneven underlying surface which have unremarkable soil spectral characteristics. The cinnamon soil belt in Loess Plateau has multiplicity topography, widely distributed hills and low organic matter content. Large areas soil degradation caused by mining activities has resulted in the fact that soil spectroscopy characteristics are strongly disturbed, which has some inhibiting effect on the remote sensing retrieval accuracy of soil organic carbon content at the regional scale. Based on cinnamon soil belt with typical coal mining subsidence area in Shanxi Province as an example, this research used the surface reflectance and outdoor sample data from the field of coal mining subsidence area to retrieve soil organic carbon content. Conducting comparative experiments on the atmospheric correction methods of the Landsat8 OLI image in the study area by the FLAASH model and the 6SV model combined with high spatial and temporal resolution aided meteorological data to analyze the effect on soil spectral curve and organic carbon content in the mining subsidence area of the cinnamon soil belt and recognize sensitive bands. Multiple linear regression(MLR), BP neural network(BP) and partial leas squares regression(PLSR) model were established to retrieve soil organic carbon content by using the original spectral reflectance R and mathematical transformation forms such as , log (1/R) and R′. The results showed that the atmospheric correction effect of the 6SV model was better than that of the FLAASH model which could effectively eliminate the interference of atmosphere and topography to reflectance. The reflectance of visible light decreased and the near-infrared rose obviously. The soil reflectance spectra of different organic matter content was clear. The bands of 640~670, 850~880, 1 570~1 600, 2 110~2 290 nm were highly indicative of soil organic carbon content. Compared with multiple linear regression (Coefficient of determination R2 was 0.765) and BP neural network (R2 was 0.767), the partial least-squares regression model had the highest retrieval accuracy (R2 was 0.778). It was found that the 6SV atmospheric correction model and partial least squares regression modeling combined with aided meteorological data which had high spatial and temporal resolution could significantly improve the retrieval accuracy of soil organic carbon in the mining subsidence area of the cinnamon belt. The soil organic carbon content in the study area from 2013 to 2015 was retrieved based on this model. Results showed that the soil organic carbon content in the middle of the study area was higher than that in both sides, and the soil organic carbon content was restored by reclamation. The results can be used to reveal the spatial-temporal distribution of soil organic carbon in the mining subsidence area of the cinnamon belt in the Loess Plateau, providing theoretical and technical support for improving regional soil spectral analysis, land reclamation evaluation, establishment of carbon flux observation network in mining subsidence area of the cinnamon belt and estimation of soil carbon pool, which provides the basis for the ecological sustainable development of the cinnamon belt in the regional and global scales.
赵 鑫，徐占军，尹建平，毕如田，冯俊芳, 刘 培. OLI与6SV的褐土带煤炭开采沉陷区土壤有机碳反演[J]. 光谱学与光谱分析, 2019, 39(03): 886-893.
ZHAO Xin, XU Zhan-jun, YIN Jian-ping, BI Ru-tian, FENG Jun-fang, LIU Pei. Retrieval of Soil Organic Carbon in Cinnamon Mining Belt Subsidence Area Based on OLI and 6SV. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(03): 886-893.
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