藏北中部地区草地退化遥感监测

为了探讨藏北中部地区近20年来的草地退化状况及主要驱动力,基于1990、2000及2010年的Landsat影像,采用混合分类方法对研究区主要景观类型进行分类,并利用景观指数分析景观格局及草地退化特征。另外,基于气象数据,利用灰色关联度方法分析草地退化的主要驱动力。结果表明:草地退化面积在1990~2000年呈增加趋势,在2000~2010年呈减少趋势,2000年之后研究区草地退化状况趋于缓和。造成草地退化的主要气候因素为降水量、气温、日照时数、平均相对湿度和蒸发量等,其中,高寒草甸草地主要受平均相对湿度及降水量的影响,高寒草原草地受蒸发量、日照时数、平均最低气温、降水量、平均相对湿度和平均最高气温的影响均较大,高寒荒漠草地与平均最高气温、日照时数和蒸发量的关系最为密切。

Remote Sensing Monitoring of Grassland Degradation in the Central of the Northern Tibet

Northern Tibet is located in the hinterland of the Qinghai-Tibet Plateau,and abounds in grassland resources.While in recent years,Northern Tibet has experienced serious grassland degradation.In order to investigate the grassland degradation and its main driving factors in the central of the Northern Tibet during recent 20 years,the grassland landscape were classified using hybrid classification method and Landsat images for years of 1990,2000 and 2010.The classification accuracy was 78.0% based on the field data in 2010.The characteristics of the landscape patterns and grassland degradation were analyzed through calculating landscape indices,which included dominance index,evenness index,fragmentation index and diversity index.Finally,the main driving force for the grassland degradation was discussed using the Gray correlation method and the meteorological data.The results showed:the area of degraded grassland increased in 1990~2000,while decreased from 2000 to 2010.After the year of 2000,the grassland degradation is easing due to grassland restoration measures and grassland contract responsibility system.The change of climate has great influence on grassland degradation,and the major influence factors are precipitation,temperature,sunshine duration,and evaporation.The alpine meadows grass was mainly influenced by the average relative humidity and precipitation.The alpine grassland grass was mainly influenced by evaporation,the average relative humidity,precipitation,average minimum temperature,average maximum temperature,and sunshine duration.The desert grass has a close relationship with the average maximum temperature,sunshine duration,and evaporation.