基于缓冲带的贵港市城市景观格局梯度分析

运用景观格局指数与城市建成区缓冲带划分相结合的方法,分析了广西贵港市近20a来城市建成区整体景观与主要城市景观类型（公共设施用地、工业用地、居住用地及农田）的圈层梯度变化特征.分析结果表明：贵港市城市建成区可以看作是居住用地与公共设施用地的镶嵌景观,但这种镶嵌景观随着城市化的发展,存在日趋不明显的特征;整个景观层面的指数20a来在31个梯度带内,表现出相似的变化趋势,斑块面积指数显示出贵港市城市建成区存在两个较为明显的商业金融中心;各梯度带内景观的平均面积增大,景观的形状日臻规则,景观多样性随景观类型及均匀度的增加显著上升.2004年主要城市景观类型在缓冲区中间各带能够很好的反映出格局的变化特征,其中工业用地和农田用地的斑块数和斑块密度随缓冲区梯度表现出较为一致的变化特征,而公共设施用地和居住用地的梯度变化趋势相似.各个梯度带中工业用地形状最为复杂,所占比重最低,平均斑块面积最大;公共设施和居住用地形状较为简单,在各带中所占比重较高,平均斑块面积较小;农田景观在各带中所占比例变化不大,近似连续分布,对城市生态环境的调节起到一定作用.

A gradient analysis based on the buffer zones of urban landscape pattern of the constructed area in Guigang City, Guangxi, China

Over the last century urbanization on the landscape has increased and intensified.Urban development has intense impacts on the environment on local,regional and even global scales.As a driving force in global change,the need to understand the dynamics of urban pattern and its change in an accurate and efficient manner is ever more pressing.Based on the aerial color infrared photograph in 1985 and the QuickBird satellite image in 2004 and according to the standard for plan and construction of city land use,Guigang City was divided into 11 landscape types.In the landscape classification maps,31 buffer zones,each being 200m wide,were divided.With the aid of GIS software ArcView 3.2 and landscape pattern analysis software FRAGSTATS 3.3,the landscape spatial patterns of each buffer zone were analyzed on the landscape level and class level.The landscape indices,such as patch size,patch fractal dimension,diversity index and evenness index,were calculated.The results indicated that:1.The total area of the residential land and the communal facilities land in 2004 covered 46.3% of the entire constructed area of Guigang City and the sum of patch number of the two patch types occupied about 39.7% of the total patch number,while the percentages were 48.2% and 45.4%,respectively,in 1985.This showed that the mosaic landscape with the residential land and the communal facilities land became more and more unobvious following the urban development and the landscape diversity.2.Based on the gradient analysis with the landscape-level index and the classlevel index,there were two business and finance centers existed in the constructed area.One was located in the urban center with a range of 0.8 km;the other was from the 10th to the 16th zone.In each buffer zone,the mean patch size was larger and the landscape shape was more regular in 2004 than in 1985.Furthermore,the Shannon diversity index of each buffer zone was rising in 2004 with the patch richness and the evenness index increasing.3.The landscape index computed for the main landscape types(communal facilities land,industrial estate land,residential land and farmland) in the middle of the buffer zones could reflect the urbanization changing well.The patch size and the patch number of industrial estate land and farmland showed the same changing tendency,while communal facilities land and residential land assumed another same changing tendency.In each gradient zone,the industrial estate land had the most complex shape,the lowest area percentage of each zone and the biggest mean patch size,whereas the communal facilities land and the residential land were opposite to the industrial estate land.The farmland had steady percentage along the buffer zone and its continuous distribution had an important effect on the urban eco-environment.4.How to relate the pattern changing characteristics along the buffer zone to the urban ecological process and the urban ecological planning remains to be studied further in the future.