干旱区冷凉型绿洲景观格局变化分析

Change of Landscape Patterns in a Cold Oasis in Arid Zone

冷凉型绿洲是干旱区的主要景观类型之一,其景观结构的变化机制是理解干旱区生态环境变化的重要补充。位于祁连山北麓的冷凉绿洲(张掖市民乐县)是干旱区具有代表性的区域,在黑河流域具有重要的生态功能。据此,本文以1987、1995、2000、2005年的TM数据为信息源,采用景观结构的分析方法,分析了该绿洲1987—2005年间的景观变化。结果表明:在干旱区的冷凉型绿洲中,农田是景观优势斑块类型,斑块面积占研究区的比例为28.6%~34.6%。景观斑块类型的转化主要发生在农田和草地之间,1987—2005年间农田转换为草地的比例为43.6%,而草地转换为农田高达72.9%。与同期平原型绿洲景观变化特点相比较,冷凉型绿洲的农田面积扩增速度大于平原型绿洲。分布面积最小的水域和居工地斑块有最高的景观变化速率,说明该干旱区河流水文过程季节性变化和持续的城镇化过程对该类景观类型的影响显著。

The dynamic mechanism of cold oasis landscape is an important section and supplement for best understanding regional environmental change.Minle County,a representativeness of the cold oasis in the arid zone,located in northern slope or Qilian Mountain,plays an important role of ecological function in the Heihe River Basin.We analyzed landscape change mechanism by employing the landscape structure analysis method in 1987,1995,2000,and 2005 based on TM data.Cropland was a dominant landscape type in the cold oasis and,the cropland patch area occupied28.6%-34.6%of total area during study period.Three was significant conversion between cropland and grassland patches among landscape types and,ratio was 43.6% form cropland to grassland and72.9%from grassland to cropland,respectively.Comparing to the plain oasis landscape characteristic in the Heihe Basin,the cropland patch area increased more quickly in the cold oasis. For landscape change ratio,the water and the residential area that areas were least had highest values,this indicated that they impacted by the seasonal change of river hydrological and the continued urbanization process,respectively.