重庆市主城区景观格局演变的样带响应与驱动机制差异

Gradient Analysis and Comparison of Landscape Pattern along Different Transects in the Main Urban Area of Chongqing City

为深入研究地形地貌和经济背景对快速城市化地区景观格局演变进程与时空差异的影响程度,以重庆市主城区为研究对象,借助于Arc GIS 9.3和Fragstats 4.2软件,采用样带梯度分析和景观格局分析相结合方法,基于研究区独特地貌特征和不同经济环境,设置南北向和东西向等7条样带,对1995—2014年研究区景观格局演变的样带响应和驱动机制进行对比分析。结果表明:1)就相同时期同向样带景观破碎度和景观多样性整体变化特征而言,靠近城市中心的南北向样带c和东西向样带f的斑块密度PD和香农多样性指数SHDI值分别呈最低值和最高值,远离城市中心的样带却恰好相反,可见各样带整体景观特征差异受同期城市化水平、地形因素、政策驱动影响明显;2)随着与城区中心(或丘陵、台地)距离的增加,南北向样带和东西向样带景观破碎度和景观多样性不断提高,景观聚集度却不断降低,斑块之间的连通性变差。2001年之后城市化对研究区景观格局影响程度增强,地形因素减弱,以耕地景观为主导的景观格局也逐步向以城市景观为优势的方向转变;3)在1995—2014年期间,南北向c样带南段18km和东西向f样带西段8 km附近城乡居民点最大斑块指数LPI值均为最高,随城市向外蔓延,c样带北段6 km处LPI值出现100%,由于2001年之后老城区内部改造,南北向c样带南段18km和东西向f样带西段8 km附近的面积加权平均斑块分维数AWMPFD也多由波峰值降为最低值(接近于1),且城市化空间推进过程中不均匀性特征显著。

The paper studies the influence of topography and economics on the evolution process of landscape pattern and its spatial-temporal difference in the rapid urbanization area, taking the main urban area of Chongqing City as the research object. Seven transects in north-south direction and east-west direction were selected on the basis of the unique geomorphologic characteristics and the economic environment in the study area. With the help of the Fragstats 4.2 and ArcGIS 9.3, the responses of transacts to the evolution of landscape pattern in the period of 1995-2014 in the study area were compared and the driving mechanism was analyzed with combined methods of gradient analysis and landscape pattern analysis. Results are shown as follows： 1） In terms of the change characteristics of landscape fragmentation and landscape diversity in the same period and direction transects, the values of PD and SHDI of the north- south transect c and the east-west transect f were the lowest and the highest values near the urban center, but away from the city center of the same direction transects are just the opposite. It is obvious that the differences of the whole landscape features are influenced by the urbanization level, terrain factors and policy-driven in the same period. 2） With the increased distance from the center of city （or hills and plateaus）, the landscape fragmentation and landscape diversity of both the north-south and east-west transects continued increasing, while the landscape aggregation continued decreasing, and the connectivity between patches decreased. After the year of 2001, the impact of urbanization on the landscape pattern in the study area enhanced, but the impact of terrain factors weakened, and the dominant landscape changed from farmland to urban landscape. 3） During the period of 1995-2014, in the southern 18 km section of north- south transect c and the western 8 km section of east- west transect f where it is close to the urban and rural residents, the values of LPI were the highest. With urban sprawl, the LPI value became 100% at 6 km in the north of north-south transect c. Because of internal renovation of the old urban area since 2001, the AWMPFD values at 18 km in the south of north-south transect c and at 8 km in the west of east-west transect f dropped from the peak value to the lowest value close to 1. The research results show that the evolution of landscape pattern of Chongqing city has significant characteristics of spatial heterogeneity.