基于Sentinel-2影像的城市植被土壤有机碳密度估算及空间分布特征

Estimation of the density and spatial distribution of soil organic carbon in urban vegetation based on Senti-nel-2 imagery data

土壤有机碳密度(soilorganiccarbondensity,SOCD)是评价土壤碳汇功能的重要指标,研究城市植被SOCD的空间分布对探究人类活动对碳循环的驱动作用及城市碳管理具有重要意义。本研究基于西安市主城区206个采样点(0~20cm)的SOCD数据和Sentinel-2遥感影像,采用多元线性、二次拟合以及指数模型,分别建立乔木、灌木、草地3种植被的最优SOCD估算模型,从而反演研究区植被SOCD,并分析其空间分布特征。结果表明:研究区植被SOCD为0~16.47kg·m^(-2),平均SOCD为3.24kg·m^(-2),总体呈现出“边缘高、中间低”的空间分布特征,具有较高空间异质性;不同植被类型SOCD存在较大差异,3种植被类型的平均SOCD为乔木(3.75kg·m^(-2))>灌木(2.72kg·m^(-2))>草地(2.04kg·m^(-2));城市植被SOCD与城市化强度存在负向相关关系(P<0.001),植被覆盖度较高的地区其平均SOCD越高;总的来说,西安市城市化对植被SOCD具有负面影响,提高城市植被覆盖度是提升SOCD的有效手段之一;遥感技术与样地实测调查方法相结合能够快速有效实现研究区乔木、灌木和草地SOCD反演,为未来城市发展中土壤碳管理提供了参考。

Soil organic carbon density(SOCD)is an important index to evaluate the carbon sink function of soil.Studying vegetation SOCD is of great significance for exploring the impacts of human activities on soil carbon cycle in urban areas.Based on the SOCD data of 206 sampling points(0-20 cm)and Sentinel-2 remote sensing images in the main urban area of Xi'an,we established the optimal SOCD estimation models of trees,shrubs,and grass-lands by using multiple linear,quadratic fitting,and exponential models.The vegetation SOCD in the study area was estimated based on the optimal models,the spatial distribution of vegetation SOCD were further analyzed.Re-sults showed that the SOCD of the urban vegetation ranged from 0 to 16.47 kg·m^(-2),with an average of 3.24 kg·m^(-2).Overall,the SOCD showed a spatial distribution characteristic of"high on the edge and low in the mid-dle",with high spatial heterogeneity.There were large differences in SOCD among different vegetation types.The average SOCD of the three vegetation types followed a pattern of trees(3.75 kg·m^(-2))>shrubs(2.72 kg·m^(-2))>grasslands(2.04 kg·m^(-2)).There was a negative correlation between urban vegetation SOCD and urbanization intensity(P<0.001),and the average SOCD was higher in areas with higher vegetation coverage.In general,urbanization had a negative impact on vegetation SOCD.Increasing urban vegetation coverage is one of the effective means to improve SOCD.The combination of remote sensing technology and field survey methods can quickly and effectively estimate SOCD of trees,shrubs and grasslands in the study area,which provides a reference for soil carbon management in future urban development.