喀斯特城市石漠化遥感参数的时空变化

针对桂林喀斯特城市近20多年来快速扩展可能导致的喀斯特山峰石漠化,提出遥感像元裸土率的正比例估算方法,对该地区Landsat卫星1990~2015年8景遥感图像反演植被覆盖度、裸岩率的长时间序列数据,分析喀斯特山峰混合像元中植被、裸岩比例的时空变化规律。结果表明,研究区喀斯特山峰裸岩率高于0.7的面积比例低于15%,植被覆盖度高于0.5的面积在60%~85%之间。喀斯特山峰植被覆盖度、裸岩率的变化趋势主要受气候因素和人为因素等的影响,裸岩率高于0.7的面积比例变化受人为因素影响的程度较大。在1990~2006年呈略降低后基本维持平稳的趋势;但新区的建设使得2009年升高到最高值14.3%;2009~2015年缓慢下降到6.6%;植被覆盖度高于0.7的面积比例1990~1994年逐渐上升达到最高值56.0%,1994~2009年下降到最低值25.7%,2009~2015年上升到37.1%。研究结果可为进一步监测和预警喀斯特城市发展过程的喀斯特山峰石漠化提供科学数据。

Temporal and spatial changes of desertification remote sensing parameters in karst city

In order to analyze the impact of urban rapid expansion on karst hill desertification in Guilin city from 1990 to 2015, the long time series of vegetation coverage and bare rock percentage were derived from 12 Landsat images with the proposal of bare soil percentage estimation method in the mixed pixels on karst hills. Then the temporal and spatial change of vegetation coverage and bare rock percentage was analyzed. Result shows the area proportion with bare rock percentage more than 0.7 is below 15% and that with vegetation coverage more than 0.5 ranges from 60% to 85% on karst hills. The trends of vegetation coverage and bare rock percentage on karst hills are affected by climate and human being. The bare rock percentage area proportion more than 0.7 is mainly influenced by artificial factors and shows smooth trends from 1990 to 2006 after slightly lowering. However, it rises to 14.3%, the maximum, with the urban New Area development in 2009. And then it slowly declines to 6.6% from 2009 to 2015. Meanwhile the vegetation coverage area proportion more than 0.7 gradually rises to the maximum of 56.0% from 1990 to 1994. Then it declines to the minimum of 25.7% up-and-down from 1994 to 2009. Finally it rises to 37.1% from 2009 to 2015. The research results can provide scientific data for monitoring and alerting karst hill desertification in karst city development.