Abstract: Grassland is the most important and widely spread terrestrial ecosystem. The use patterns and degree of grassland influence grassland's growth and therefore affect the spectrum of the grassland. In this study, hyper-spectral data of temperate steppes in different use patterns and degree are collected from Inner Mongolia in 2011. Spectral characteristics of the data including reflectance, first derivation of reflectance, continuum removed reflectance and vegetation indices are analyzed. The analysis is helpful for the remote sensing classification of temperate steppe and provides a strong support for remote sensing monitoring of grassland degeneration. The analysis result shows that the combination of the spectral reflectance between 750～950 nm, the first derivative reflectance at 730 nm, the red edge slope, NDVI and EVI is able to clearly classify the vegetation types of Setaria italica, Stipa grandis and Leymus chinensis. The red edge slope, NDVI and EVI can differentiate enclosed Stipa grandis and grazed Stipa grandis, and distinguish cut Leymus chinensis from uncut Leymus chinensis respectively. The long-term round enclosing will lead to grassland degeneration. Conservative grazing is useful to keep grassland ecosystem healthy. In temperate steppe of Inner Mongolia, vegetation fraction and aboveground biomass with NDVI has a high correlation, and the R² value is 0.601 and 0.818 which is higher than the R² value of 0.281 and 0.675 in the correlation with EVI, respectively. So NDVI is a better choice than EVI to estimate the grassland biomass or vegetation coverage of the temperate steppe in Inner Mongolia. Estimation of aboveground biomass is more reliable than the estimation of vegetation coverage based on NDVI.

Key words: Temperate steppe, Vegetation spectrum, Spectral characteristics analysis, Use patterns of grassland

摘要： 人类对草地资源的利用方式和利用程度影响着草地的生长发育,进而影响草地的光谱特征。采集不同利用方式下内蒙古锡林郭勒盟温性草原地面高光谱数据并分析其光谱特征,可为温性草原植被类型遥感分类和草地退化遥感监测提供基础数据。结果表明:750～950 nm处反射率、730 nm处反射率的一阶导数、红边斜率、NDVI和EVI等特征值的组合可以将粟(Setaria italica)、大针茅(Stipa grandis)及羊草(Leymus chinensis)植被类型加以区分;且红边斜率、NDVI和EVI等特征值分别能对内蒙古温性草原围封和天然放牧2种利用方式下大针茅植被,以及打草前和打草后的羊草打草地进行区分。在内蒙古温性草原,NDVI与植被覆盖度和地上生物量的相关性较好,线性拟合R²分别为0.601和0.818,优于EVI的0.281和0.675,因此在估算该地区草地生物量和植被盖度时,应选择植被指数NDVI而非EVI,且用NDVI来估算地上生物量的可信度远高于植被盖度。

关键词: 温性草原, 植被光谱, 光谱特征分析, 利用方式