内蒙古温带草原区植被盖度变化及其与气象因子的关系

Change in vegetation coverage and its relationships with climatic factors in temperate steppe,Inner Mongolia

利用1982-1999年内蒙古地区NOAA/AVHRR的NDVI数字遥感影像,对内蒙古温带草原区植被盖度进行了反演,探讨了近20a来温带草原植被盖度的变化情况,并对植被盖度与不同组合方式的降水及气温数据进行了相关分析,探讨了植被盖度与气象因子的关系。结果表明:①近20a来温带草原植被盖度呈上升趋势,占总面积72%的草原植被盖度发生了增长,3种不同草原类型中典型草原盖度上升趋势最为明显;②温带草原生长季平均盖度、逐月盖度与降水成正相关关系,与气温呈负相关关系,其中降水对盖度的影响存在着时滞及累积效应;③3种草原类型植被盖度对气象因子的敏感性不同,荒漠草原植被盖度与气温和降水相关性最强,其次为典型草原与草甸草原。

Vegetation coverage is an important physiological parameter for describing the growing status of vegetation,and plays a key role in some ecological processes such as evapotranspiration,soil erosion,and photosynthesis etc. So vegetation coverage is considered to be an important indicator of ecosystem change. In this paper,the temperate steppe of Inner Mongolia was chose as study area,and following two questions were brought forward and expected to be solved：（a） how were the changes in vegetation coverage happened temporally and spatially？ （b） What kinds of relationships exist between vegetation coverage changes and some climatic factors,including air temperature and precipitation？ In order to understand these two questions,the NDVI product images of NOAA/AVHRR were used to calculate vegetation coverage in temperate steppe of Inner Mongolia from 1982 to 1999,and then correlation coefficients between vegetation coverage and climate factors were calculated. Climatic factors were combined into different patterns based on the observed time periods and time lags for finding out the temporal responses of vegetation coverage to climate fluctuation or change. The main findings were as follows：（a） Increasing trend of vegetation coverage in whole study area is clearly during last 18 years. The vegetation coverage in 72% of total area has been increased during last 18 years,and the most obvious increase was occurred in the typical steppe areas among three types of steppe; （b） The average vegetation coverage of growing season and monthly vegetation coverage have positive correlation with precipitation,and negative correlation with temperature. The impacts of precipitation on vegetation coverage show in time-delay and cumulative effects. （c） The sensitivities of vegetation coverage to climate factors were different among three kinds of steppes,and vegetation coverage was most strongly related to climate factors in desert steppe.