1982-2003年内蒙古植被带和植被覆盖度的时空变化

Spatial and Temporal Variations of Vegetation Belts and Vegetation Cover Degrees in Inner Mongolia from 1982 to 2003

利用内蒙古地区1982-2003年遥感归一化差值植被指数(NDVI)数据,对植被带进行了分时段的划分,并以典型草原植被带为例,分析植被覆盖度时空变化及其与水热因子的关系。结果表明:在整个研究期间,典型草原带的面积呈增加的趋势,荒漠草原带的面积呈减少的趋势,森林带、森林草原带和荒漠带的面积趋势变化不明显。总体上看,从时段1(1982-1987年)到时段2(1988-1992年)植被带进化演变的面积占优势,从时段2(1988-1992年)到时段3(1993-1998年)进化和退化演变的面积相当,从时段3(1993-1998年)到时段4(1999-2003年)退化演变的面积占优势。在典型草原带内,多年平均植被覆盖度具有明显的季节变化,从5月上半月返青开始到8月下半月达到年最大值,其空间演进以大兴安岭两翼为中心,逐渐向东南的西辽河平原和向西的乌兰察布高原扩展。前期降水量与覆盖度季节增量年际变化之间呈正相关,显著正相关的区域位于锡林郭勒高原西部和乌兰察布高原,而气温与覆盖度季节增量年际变化的相关一般不显著。典型草原年最大覆盖度线性趋势降低与升高的面积分别占52.6%和47.4%,其中,呼伦贝尔高原西部边缘以及大兴安岭山麓两侧的年最大覆盖度呈显著降低的趋势,而西辽河平原西南部和努鲁儿虎山东段的年最大覆盖度呈显著升高的趋势。年降水量是影响年最大覆盖度的主要因子,而年均温对年最大覆盖度的影响不明显。

The Normalized Difference Vegetation Index （NDVI） data in Inner Mongolia during 1982 to 2003 were used to classify the vegetation belts in four time periods and reveal spatial shifts of the vegetation belts between two sequential periods. Then, we analyzed the spatial and temporal variations of the vegetation cover degree and its relation to thermal-moisture factors taking the tpical steppe belt as an example. During the study period, the area of the typical steppe belt showed an increscent tendency, whereas the area of the desert steppe belt indicated a decreasing tendency. Otherwise, areas of the forest belt, the forest steppe belt and the desert belt did not represent any apparent tendency. Generally speaking, an evolution succession of vegetation belts was dominant during period 1 （1982-1987） to period 2 （1988-1992）, whereas a degradation succession of vegetation belts （following succession orders of forest→forest steppe→typical steppe→desert steppe→desert） was dominant during period 3 （1993-1998） to period 4 （1999-2003）. In between, evolution and degradation successions of vegetation belts were counterbalanced during period 2 （1988-1992） to period 3 （1993-1998）. A significantly positive correlation appeared in the western part of the Xilingol Tableland and the Ulanqab Tableland. In contrast to precipitation, the correlation between the vegetation cover degree increment and air temperature was less significant. From 1982 to 2003, areas with decreasing and increasing linear trends of the annual maximum vegetation cover degree accounted for 52.6% and 47.4% of the entire Inner Mongolia, respectively, of which significantly decreasing trends appeared at the western edge of the Hulun Buir Tableland and the both sides of the Da Hinggan Mountains.