近30年来呼伦贝尔地区草地植被变化对气候变化的响应

Responses of Vegetation Changes to Climatic Variations in Hulun Buir Grassland in Past 30 Years

基于1981-2006年的GIMMSNDVI数据和2000-2009年的MODISNDVI数据反演呼伦贝尔地区草地变化,结合1981-2009年该地区7个气象站点的气温和降水数据,分别从年际变化、季节变化和月变化角度分析该地区草地变化对气候变化的响应。结果表明,从年际变化来看,降水是驱动草地植被年际变化的主要因素;从季节变化来看,草地植被生长在不同季节对水热条件变化的敏感性不同,春季草地植被生长对气温变化的敏感性较降水变化高,夏季和秋季草地植被的生长对降水变化的敏感性则高于对气温变化的敏感性,其中以夏季最为显著;从月变化来看,4月和5月草地植被变化受气温变化影响较明显;5-8月与前一月降水变化关系密切,说明植被生长对降水变化具有一定的滞后性;4月正值草本植物萌芽期,而4月份草地生长与年气温变化关系最为密切,一定程度上说明4月份表征植被生长的NDVI值增加可能是由于气候变暖引起的草地植被生长季提前产生的。综上所述,通过植被与气候要素月变化的关系可以具体地揭示气温和降水对草地植被生长的季节韵律控制。

Global warming,a global concern,has led to significant vegetation changes especially in the past 30 years.The Hulun Buir Grassland in Inner Mongolia,one of the world＇s three prairies,is undergoing a process of prominent warming and drying.It is necessary to investigate the effects of climatic variations（temperature and precipitation） on vegetation changes for a better understanding of acclimation to climatic change.NDVI（Normalized Difference Vegetation Index）,which can reflect characteristics of plant growth,vegetation coverage,biomass,and so on,is used as an indicator in monitoring vegetation changes.GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation change conditions in Hulun Buir.The responses of vegetation coverage changes to climatic variations from the yearly,seasonal and monthly time scales were analyzed combined with temperature and precipitation data of seven meteorological sites.In the past 30 years,vegetation coverage change was closely correlated with climatic factors,and the correlations were different on different time scales.Annual average of vegetation change was better correlated with precipitation,suggesting that rainfall was the main factor for driving vegetation change.Correlations between seasonal average of vegetation coverage and climatic factors showed that the sensitivity of vegetation growth to hydrothermal condition change was different in different seasons.The sensitivity of vegetation growth to temperature in summer was higher than in the other seasons,while that of vegetation growth to rainfall in both summer and autumn was higher,especially in summer.Correlations between monthly average of vegetation coverage and climatic factors during growing seasons showed that the response of vegetation change to temperature in April and May was stronger,indicating that the temperature effect occurred in the early stage of vegetation growth.Correlations between NDVI of the current month and precipitation of the month before the current month were better from May to August,showing a hysteresis response of vegetation growth to rainfall.Grasses turned green and began to grow in April,and the impacts of temperature on grass growth was obvious,therefore,the increase of NDVI in April might be due to an advanced growing season caused by climatic warming.In summary,relationships between annual variation of monthly vegetation and climatic factors represent temporal rhythm controls of temperature and precipitation on grass growth.