气候变化和人类活动对蒙古高原植被覆盖变化的影响

基于全球监测与模型研究组（GIMMS）归一化植被指数(NDVI)，对蒙古高原地区1981-2006年植被覆盖的时空变化进行了研究，并从气候变化和人类活动的角度，分析了植被覆盖变化的原因。1981-2006年蒙古高原的植被覆盖时空分布具有明显的地带性特征,森林区及荒漠区植被覆盖呈现小幅下降趋势，草原区呈现上升趋势，蒙古高原NDVI分布从东北向西南、从高原南北边缘地带向中心地带呈明显的规律性变化：高原东北部的大兴安岭地区NDVI最高，蒙古国北部的杭爱山脉次之，西南部荒漠区的NDVI最低。研究表明: 植被覆盖变化是气候变化和人类活动共同作用的结果，蒙古高原地区的降水变化是植被覆盖变化的重要原因，森林砍伐、河套耕作及城镇化等人类活动则是导致具有相似气候条件的内蒙古与蒙古国植被覆盖变化区域差异的原因。

Impact of Climate Change and Human Activities on Vegetation Coverage in the Mongolian Plateau

Global climate change and Global Change and Terrestrial Ecosystems (GCTE) are currently the hot and difficult topics in researching global change. Climate change impacts significantly the global ecosystems, and it has become as an important issue to ascertain the interaction between climate change and ecosystems at different scales and reveal the responses of ecosystems to climate change. Based on GIMMS Normalized Difference Vegetation Index (NDVI) data in the Mongolian Plateau during the period from 1981 to 2006, the spatial and temporal variations of vegetation coverage were studied, and the factors affecting the change of vegetation coverage were analyzed from the perspectives of climate change and human activities. Vegetation coverage in the Mongolian Plateau was generally improved in a fluctuation way during the period of 1981-2006, and the improvement included the following phases: ① Relatively stable phase during the period of 1981-1988; ② Persistently increasing phase during the period of 1989-1993; ③ Relatively low phase during the period of 1994-1998; and ④ Persistently increasing phase during the period of 1999-2006. There was an obvious zonal spatial and temporal distribution of annual maximum NDVI in the Mongolian Plateau during the period of 1981-2006, and the NDVI change trend was different from different land use types: The vegetation in forest area with high NDVI value was in degeneration, there was a significant negative correlation between temperature and precipitation, and the area with vegetation regeneration was much smaller than that with vegetation degeneration. The vegetation coverage in farmland with relatively low NDVI value was in a significant increase trend, there was a significant increase trend of both temperature and precipitation, the NDVI value was obviously increased under the dramatic effect of human activities, and the area with vegetation regeneration in farmland and grasslands were much larger than that with vegetation degeneration.