干旱矿区土壤呼吸时空动态变化分析

Analysis of spatiotemporal dynamics of soil respiration in arid mining areas

  • 摘要: 了解荒漠化露天矿开采活动对土壤呼吸(Soil Respiration, Rs)的影响,对评估生态脆弱的露天矿区生态系统碳循环至关重要。目前对矿区Rs的研究多是采用实地采样等手段,难以实现大尺度、多时相的Rs遥感估算。以红沙泉露天矿及其周边区域为研究对象,以无人机(Unmanned Aerial Vehicle, UAV) Rs估算结果作为建模的样本数据,采用多元线性回归(Multiple Linear Regression,MLR)、随机森林(Random Forest,RF)、反向传播神经网络(Back Propagation Neural Network,BPNN)、支持向量机(Support Vector Machine,SVM)、粒子群优化的支持向量机(Support Vector Machine for Particle Swarm Optimization,PSO-SVM)和堆叠自编码器(Stacked Auto Encoder,SAE)6种方法构建最优Rs估算模型,实现矿区范围的Rs空间分布估算,并分析不同采矿年限Rs的强度和范围变化。结果表明:基于RF的Rs估算模型精度最高,验证集决定系数(Coefficient of determination,R2)、均方根误差(Root mean square error,RMSE)和赤池信息准则(Akaike’s information criterion,AIC)分别为0.762、0.514 μmol/(m2·s)和5714.1。利用土壤有机碳指数(Soil Organic Carbon Index,SOCI)验证了不同年份下估算结果的可靠性,结果显示3个年份的Rs与SOCI具有显著正相关关系,说明UAV的估算数据可以作为卫星建模的样本数据,实现卫星尺度Rs估算。采煤活动导致的土壤剥离和煤粉沉降显著提升了矿区Rs强度,采坑及其周边区域的Rs均值达到2.71 μmol/(m2·s),较未采矿区域高出约5%。随着采矿年限的增加,矿区周边裸地的Rs值由2.35 μmol/(m2·s) (2019年)升高至2.55 μmol/(m2·s) (2023年),增幅约10%。随着采矿年限的增加,采坑对Rs的影响范围从小于3 km增加到3 km以上,表明采矿活动对Rs的影响范围不仅局限于采坑周边,还延伸至更广泛的区域,影响距离约为3 km。综上所述,UAV估算结果可作为卫星尺度Rs估算的样本数据,结合不同年限的卫星影像实现矿区Rs遥感估算,进而厘清矿区Rs的变化规律,明晰不同采矿年限下采坑对Rs的影响范围,为矿区乃至更广泛区域的碳排放监测和管理提供科学依据。

     

    Abstract: Understanding the impact of open-pit mining activities in desertified areas on soil respiration (Rs) is crucial for assessing the carbon cycle in the fragile ecosystems of open-pit mining areas. Current studies on Rs in mining areas mostly rely on field sampling methods, which are difficult to achieve large-scale and multi-temporal Rs remote sensing estimation. The Hongshaquan open-pit mine and its surrounding areas are taken as the research object, with Rs estimation results from unmanned aerial vehicles (UAVs) used as the sample data for modeling. Six methods—including multiple linear regression (MLR), random forest (RF), back propagation neural network (BPNN), support vector machine (SVM), particle swarm optimization-based support vector machine (PSO-SVM), and stacked auto encoder (SAE)—are employed to construct the optimal Rs estimation model. This model aims to estimate the spatial distribution of Rs in the mining area and analyze the changes in Rs intensity and range with different mining years. The results show that: The Rs estimation model based on RF has the highest accuracy, with a coefficient of determination (R2), root mean square error (RMSE), and Akaike's information criterion (AIC) of 0.762, 0.514 μmol/(m2·s), and 5714.1, respectively, in the validation set. The reliability of the estimation results in different years was verified using the soil organic carbon index (SOCI). The results show that Rs in the three years has a significant positive correlation with SOCI, indicating that the UAV estimation data can be used as sample data for satellite modeling to achieve satellite-scale Rs estimation. The soil stripping and coal dust deposition caused by coal mining activities significantly increase the Rs intensity in the mining area. The mean Rs in the mining pit and its surrounding areas reaches 2.71 μmol/(m2·s), which is about 5% higher than that in the unmined areas. With the increase in mining years, the Rs value of the bare land around the mining area increases from 2.35 μmol/(m2·s) in 2019 to 2.55 μmol/(m2·s) in 2023, with an increase of about 10%. With the increase in mining years, the influence range of the mining pit on Rs increases from less than 3 km to more than 3 km, indicating that the impact of mining activities on Rs is not only limited to the surrounding areas of the mining pit but also extends to a wider area, with an influence distance of approximately 3 km. In conclusion, the UAV estimation results can be used as sample data for satellite-scale Rs estimation. Combined with satellite images of different years, it can achieve Rs remote sensing estimation in the mining area, clarify the variation pattern of Rs, and determine the influence range of the mining pit on Rs under different mining years, providing a scientific basis for carbon emission monitoring and management in the mining area and even wider regions.

     

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