区域碳收支能力估算的面向对象遥感分类方法

全球气候变暖问题是人类面临的最艰巨的挑战之一,通过先进的面向对象分类方法可以提高碳排放与碳汇能力的研究水平,对于控制区域气候变化具有推动作用。本文利用面向对象分类方法,以广西百色市右江区为研究区域,选取Landsat 8 OLI和Google Earth影像数据提取区域地物信息,并针对研究区地势复杂的特点,采用设置多种尺度参数的方法,选取最优尺度进行影像分割。同时,引入隶属度函数法、最邻近分类法和CART决策树分类器3种方法,基于影像光谱差异、几何形状、对象纹理等特征,逐层逐级地实施面向对象分类,随后加以针对性的精度评价分析并检验分类结果。通过总结分析前人的地物碳系数转换关系并结合高精度面向对象分类结果,构建了基于土地覆被类型的碳收支能力估算模型,并根据已有的基于CASA模型的碳收支能力估算方法加以精度校验,最终估算出右江区碳收支能力为-399.64万t。此外,本文结合右江区行政区划、人口分布、DEM等相关数据对区域碳收支能力进行了专题性剖析。结果表明,面向对象分类方法是研究小区域碳收支能力的有效途径,在区域碳循环评估中具有更好的准确性和预见性,有效促进碳收支平衡研究领域的发展。

Remote Sensing Estimation of the Carbon Balance Ability Based on the Object-Oriented Method for Guangxi Youjiang District

Global warming is one of the most daunting challenges that our humanity is facing. It has urged the action to study carbon emissions and carbon sequestration ability to control the regional climate change. Some studies show that human activities, especially the combustion of fossil fuel, cause the carbon emissions and the global climate warming. Therefore, it is important to work on energy saving and emission reduction. At the same time, the carbon sink capacity of forest, grassland, crops and other vegetations become one of the most powerful approaches to ease the global climate change. Thus, we conduct a research in this area, in order to improve the carbon source utilization efficiency, reduce the carbon intensity, prefect the energy-saving and emission-reduction works, and well manage the carbon budget capacity and some other problems. Taking Youjiang district of Baise city in Guangxi Province as the experimental area, this article uses the object-oriented classification technology and extracts the area geographic information from the Landsat 8 OLI and Google Earth images. Due to the complex terrain of the study area, different parameter settings of the multi-scale segmentation are used and the optimal scaling for the image segmentation is selected. We also use the membership function method, the closest classification method and the CART decision tree classifier method to complete the object-oriented classification layer by layer and evaluate the accuracy of the classification results, based on the spectral difference, geometric shapes, objects, texture and other characteristics. Through summarizing the conversion relationship between the land and carbon coefficient, combining with the high-precision object-oriented classification results, the estimation model of carbon budget capacity is built based on land-cover types. Finally, according to the CASA model of carbon budget capacity, we check the accuracy of the estimation method. The carbon budget capacity of Youjiang district is estimated to be -3996.4 kt, according to the coefficient that corresponds to the feature carbon conversion relationship. Integrated with the administrative planning, population distribution, DEM, and other relevant data, the carbon budget capacity of Youjiang district is analyzed thematically. The results showed that: (1) the use of RS and GIS technologies in the studies of regional carbon budget capacity reveals a distinct advantage. The multiscale segmentation and object classification method can efficiently eliminate the extraction error caused by spectral confusion, and solve problems such as the large quantity of spatial data faced by the traditional classification, the classification of "salt and pepper", the exact utilization of different classification methods, and the improvement of the classification accuracy of carbon. (2) We summarized the findings of the coefficients for carbon balance capacity from domestic and international researches, and applied it in the construction of carbon balance estimation model. The object-oriented method and carbon balance estimation model were used to interpret the land cover data to estimate the Youjiang area carbon balance capability. Results show that the high degree of forest land, grassland, cultivated land and other types of vegetation areas is responsible for the performance of carbon sink in the study area. At the same time the construction land consumes a lot of fossil fuel to play as a large source of carbon. But the overall carbon sink ability of Youjiang area is stronger than its carbon emissions. It is conducive to the stable development of the regional ecological system, and may ease the regional threat of climate change. (3) Combined with the administrative divisions of Youjiang district and DEM data, the spatial analysis was carried out. We summed up the overall characteristics of the carbon budget capacity in the Youjiang district. The carbon budget is large in quantity in the central districts. Moreover, studies have shown that the elevation, slope aspect and human activities could affect the carbon budget capacity. It specifically demonstrated that the areas of high-altitude, steep slopes and less human activity reveal a large amount of carbon sink and less carbon footprint. On the contrary, the areas of low-altitude, lower slopes and more human activity reveal a large carbon footprint and lower amount of carbon.