近10年来蒙古高原植被覆盖变化对气候的响应

基于东亚干旱半干旱地区内蒙古和蒙古国67个气象站的观测资料和SPOTVEGETATION归一化植被指数(NDVI)数据,借助线性趋势、MK趋势性检验、最大化合成法和相关分析等常用数理统计方法,研究了内蒙古和蒙古国地区的植被覆盖变化和气候变化及其响应关系。结果表明:①近49年内蒙古和蒙古国地区年均气温显著上升,降水变化不明显。年均气温在空间上呈现出南高北低的空间分布格局,降水量表现出由西向东递增趋势。②空间分布上,内蒙的植被覆盖状况好于蒙古国。时间变化上,该地区植被覆盖变化分为2个阶段,1998—2001年NDVI呈整体退化趋势,2002—2012年波动上升,其中2009—2012年连续3a上升。空间变化上,内蒙古境内植被退化的区域主要集中在锡林郭勒盟周边地区,蒙古国境内退化的区域分布在中西部地区。③蒙古国境内荒漠和草原植被NDVI与降水呈正相关关系,与气温呈负相关。而对于内蒙古而言荒漠和草原植被的NDVI也与降水呈正相关关系,森林植被与气温呈正相关。就政策层面:内蒙古区域近年来受国家重大生态政策退耕还林、退牧还草的影响,大部分东部和西部植被恢复较快。在今后如果增强两国的文化和政策交流学习,将会对未来的游牧民族文化的保留和发展提供契机。

Response of vegetation coverage to climate change in Mongolian Plateau during recent 10 years

Vegetation in the arid/semi arid area is highly sensitive to climate change. The Mongolian Plateau climate is mainly controlled by the east Asia monsoon system. Hence both Inner Mongolia and the state of Mongolia (Hereafter: Mongolia) experience a similar arid/semi arid climate but have different anthropological influences via their separate social and economic development histories. In this study, we analyzed in-situ observations from 67 meteorological stations (50 stations in Inner Mongolia and 17 in Mongolia) and NDVI (Normalized Difference Vegetation Index) product from SPOT (Satellite pour l' observation de la Terre in French) using Mann-Kendall (MK) tests and Maximum Value Composition (MVC). Our results showed that: (1) Temperature is general higher in the south than the north, while precipitation ranges from low in the west to high in the east. There is a significant warming trend over the whole Mongolian Plateau region from 1961 to 2009, while no obvious trends were found for precipitation; (2) Vegetation coverage in Inner Mongolia was generally greater than that in Mongolia. The time series of vegetation coverage change in these two regions can be divided into two periods. The regional averaged NDVI decreased from 1998 to 2001, fluctuated greatly and then increased continuously from 2009 to 2012. The main degraded areas are located in the Xilingol league, central Inner Mongolia, while they are mostly located in the central and western Mongolia; (3) Positive correlations were found between NDVI and precipitation in desert, steppe vegetation and forest areas in Mongolia, while negative relationships were found for temperature. In Inner Mongolia, NDVI are also positively correlated with precipitation in desert and steppe vegetation areas and also positively correlated with temperature in forests. Recently several major national ecological projects were implemented in Inner Mongolia by national central and local governments, including "The Return Cropland to Forest", the "Return Grazing Land to Grassland" (Grain for Green), and the Three North Protection Forest Plantation Project. These projects improved the local environment by stopping grazing/cropping and planting trees. We believe that these policy actions contribute to the vegetation recovery in Inner Mongolia exhibited here in the NDVI. We attribute the different trends and dynamics of vegetation change in Inner Mongolia and Mongolia to human activities since the climate is similar in these two areas. However, the mechanism driving the changes requires further study particularly investigation of the socio-economic drivers of local land use changes. If formal/informal communication between Inner Mongolia and Mongolia are encouraged in scientific research, cultural exchange and policy making of environmental protection at different levels, it will provide more opportunity for preservation and enhancement of the nomadic culture.