上海市城市扩展格局及土壤无机碳分布特征分析

An Analysis on the Urban Expanding Patterns and Soil Inorganic Carbon Distribution in Shanghai

土地利用方式变更引起的土壤碳库变化对全球温室效应、全球碳循环有重大影响。基于1：250000多目标地球化学调查数据，利用RS影像和GIS统计技术研究了上海城市扩展进程中的土壤无机碳空间分布与演化特征。根据上海地区1980、2000．2005年3期遥感影像分析，上海市城区扩张以原市区为中心向周边快速扩展，1980～2005年间，城区面积由193．08km^2增加到1570．52km^2，城市用地面积比例由3．05％迅速上升到24．77％。比较城区，郊区、乡村地区土壤无机碳分布，城区表层土壤无机碳密度为（1．12±0．64）kg／m^2，深层土壤无机碳密度为（1．24±0．40）kg／m^2，表层土壤无机碳积累明显，深层土壤呈现轻度积累，城区土壤无机碳空间分布变异系数降低。比较1980年前建城区、1980～2000年建城区．2000～2005年建城区与郊区土壤无机碳密度分布，城区土壤无机碳分布呈现富集。并且随建城区年限的延长，土壤无机碳积累渐趋显著，城市土壤无机碳分布的空间异质性降低。本项研究提供城市化进程中的土壤无机碳分布演变趋势信息，可为土壤固定碳潜力研究提供数据支持，也为推动中国城市生态系统碳循环研究提供参考。

Soil carbon stock changes induced by land use changes play an essential role in global greenhouse effect and carbon circulation. The urban expanding patterns and spatial characteristics of soil inorganic carbon distribution and evolution in the course of urbanization in Shanghai were studied based on the data of 1：250 000 regional geochemical survey with the help of remote sensing （RS） images and geographic information system （GIS） technology. The urbanization process in Shanghai has been quickened greatly since the 1980s, i.e., the urban areas increased from 193.08 km^2 in 1980 to 1 570.52 km^2 in 2005, or the urban area proportion steeply rose up from 3.05% to 24.77% in the past 25 years. The urban region expansion circled the central urban area （till 1980） according to the RS images acquired in periods of 1980, 2000 and 2005. The urban soil inorganic carbon distribution showed low spatial variability by comparison among the urban, suburban and countryside areas. In the urban area, topsoil was obviously enriched with soil inorganic carbon at density of （1.12±0.64） kg/m^2, while deep layer soil （160-180 cm） was slightly enriched at （1.24±0.40） kg/m^2. By comparison of soil inorganic carbon distribution in the central urban area （before 1980） and expanded urban areas （1980-2000 and 2005-2005）, as well as in the rural areas, soil inorganic carbon in the urban areas had presented enrichment, furthermore, the density increased and spatial variability decreased along with the extending duration of urban land use. The evolution trends of soil inorganic carbon distribution in the course of urbanization could be provided as baseline to evaluate regional carbon fixation potentials and to push forward carbon circulation research on urban ecosystem in China.