利用2001-2010年的空间分辨率为1km的MODIS-NDVI数据,以蒙古国为研究区域,利用最大值合成法、均值法与差值法、一元线性回归等方法,分析了不同季节下植被覆盖的年内变化、年际变化与波动趋势、空间变化特征。结果表明:MODIS-NDVI对植被的生长变化具有较高的敏感度,可有效应用于植被生态的评估和监测;蒙古国植被季相变化明显,夏秋季植被生长旺盛;近10年里,春季的植被以波动退化为主要趋势,夏季保持稳定,秋、冬季则在波动中趋向改善;前5年的植被变化幅度较小,后5年的植被变化幅度显著,总体上改善幅度略大于退化幅度;蒙古国的植被覆盖在近10年里,呈现出总体保持稳定、局部轻微改善的趋势;从空间上分布看,稳定区分布广泛,改善区主要分布在东部,退化区主要分布在中部。根据以上研究结论,可以看出:蒙古国近几年的植被覆盖变化趋于平缓,并在东部地区呈现轻微的改善趋势,说明该国东部地区加强防治措施初见成效。但与此同时,蒙古国的中部地区出现植被略微退化的趋势,也应引起我国生态环境防治方面的关注。

The change of Normalized Difference Vegetation Index (NDVI) can reveal the evolvement of environment. Long-term quantitative analysis of vegetal distribution and change can illustrate the reason of environment change, and has become a research focus in recent years. In this paper, we made Mongolia as the study area, analyzed the annual and interannual changes, fluctuation degree and the spatial trend of vegetation distribution by 1 km MODIS-NDVI from 2001 to 2010. The MVC method, average value method, difference value method and linear regression method were used to analyze the annual and interannual changes. The results were: 1) MODIS-NDVI was highly sensitive to growth and change of plants, so it could be effectively applied to evaluate and monitor vegetation ecology; 2) Seasonal change of NDVI was remarkable in Mongolia, NDVI was abundant during summer and autumn, while was poor during winter and spring; 3) In recent ten years, the peak values of vegetation coverage occurred at the year of 2008 in spring, got into valley values in 2010, presented a retrograde tendency on the whole. The summer vegetation coverage and winter vegetation coverage changed slightly, in general the growth of plants was a little better in summer during the past decade, but was gradually reducing in winter. In autumn, the fluctuation of vegetation growth was wider, but still kept a increasing trend in general; 4) As for interannual change, the fluctuating range of NDVI variation was relatively wider from 2006 to 2010, the NDVI degradation was popular in spring and the NDVI coverage was increased during other seasons, and the extent of improvement was slightly higher than the extent of degradation; 5) According to the NDVI trend of Mongolia during 2001-2010, the vegetation area which kept a relatively steady state was 72.40% in spring, 70.30% in summer, 84.01% in autumn and 77.53% in winter, indicating that the NDVI coverage of Mongolia showed a overall stable, locally lightly improved trend in the past ten years; And 6) from the spacial distribution, the stable region was widely distributed on a national scale, the improved region was mainly distributed in the eastern part of the country and the degraded NDVI coverage was mainly distributed in the central region.