Abstract: From July 2008 to May 2009,taking the Xilinguole typical steppe as experimental area of the observation,the spectral reflectance,aboveground biomass of the protected grassland and the free grassland were measured and analyzed.It was showed that enclosure improved grassland plant population structure significantly,increased the biomass of forage grasses.During vigorous growth period(July),enclosure had significant advantage in spectral reflectance characteristics,and could greatly improve the four vegetation indexes.The dead ripe period and the green up period had no obvious effects on spectral reflectance characteristics.

Key words: Typical steppe, Typical steppe, Protected grassland, Free grassland, Spectral reflectance, Vegetation index