锡林郭勒草原植被覆盖度时空动态与影响因素分析

Dynamics of Fractional Vegetation Cover and Its Influence Factors in Xilingol Steppe

以MODIS地表辐射率数据对内蒙古自治区锡林郭勒草地进行研究,分析了2001—2013年生长季(4—10月份)草甸草原、典型草原、沙地草原和荒漠草原4种草地类型植被覆盖度(fv)的时空变化特征,用变异系数(C_v)衡量各类草原f_v的变化程度,并结合气象和放牧数据分析气候变化和人类活动(放牧)对草地f_v的影响。结果表明,在不同年份各类型草原f_v均表现为由东向西递减的规律,同类型草原年际间fv呈不显著波动变化。研究区多年f_v的Cv结果表明有78.66%地区属脆弱和很脆弱水平,其中典型草原和沙地草原属脆弱级别,而荒漠草原属很脆弱级别,只有草甸草原属稳定级别。降水量对f_v的影响较大,呈显著正相关关系;而温度对fv的影响较小,呈不显著负相关关系;牲畜养殖数量对f_v影响较大,锡林郭勒盟草原的适宜综合牲畜养殖数量为39只/km^2(以标准羊计)。

The fractional vegetation cover （fv） is one of the important indicators to reflect the health of grassland ecosystem. However, fv is influenced by both natural factors such as temperature and precipitation, and human activities such as grazing. The fv estimated by MODIS surface reflectance product （MOD09） was used to analyze the grassland variation in Xilingol steppe. There are four different types grassland in Xilingol steppe, which are temperate meadow, typical steppe, sand steppe and desert steppe. The temporal and spatial variations of those four different types grassland were analyzed in growth seasons （April to October） from 2001 to 2013 by fo. The coefficient of variation （Cv） was used to indicate the changing degree of fv during the study period. Moreover, the climate and livestock data were combined to analyze the effects of climate change and human activities on grassland variations. The results indicated that the spatial distributions of fv in different years were similar, which were decreased from east to west. However, the interannual variations of the same type of grassland had no significant fluctuations. The yearly Cv variations indicated that 78.66% of the study area was in fragile and very fragile level. The typical steppe and sand steppe were in fragile level, and the desert steppe was in very fragile level, but the temperate meadow was in stabile level. The effect of precipitation on fv was positive and in very significant level. On the contrary, the influence of temperature on fv was negative and not significant. The livestock number had significant effect on fv, and the suitable livestock number should be 39 standard sheeps/km^2 in Xilingol steppe.