Some Pasture Changes in the Eastern Steppe of Mongolia

Significant vegetation changes have been recorded in Mongolian steppe types such as Speargrass-Cleistogenes, Cleistogenes-Forbs and Filifolim sibiricum-Speargrass and these changes have been attributed to climate factors rather than human activity. Species dominance in those pasture types exhibited change that was linearly related to the degradation ratio. For example, Speargrass, which is a dominant species in the steppe and is seen as a preferred species for building sustainable grasslands, is slowly losing dominance in the eastern steppe grassland type due to heavy degradation and is replaced by a range of sedges. During the years of this study (2000 to 2008), records from the nearby weather stations of Matad, Choibalsan and Dashbalvar showed a warming and drying trend with a 2-4oC increase in mean annual temperatures, an increase in maximum and minimum temperature extremes, and delays of rains during the summer growth season. Pasture type changes included: shift in species dominance from healthy grassland to degraded plots (low, medium and heavy) as indicated by changes in species diversity, species frequency, decreased land cover, canopy cover, basal cover, plant height and biomass. Vegetation changes or degradation is most pronounced around settlements (2-3 km radius), but degradation is less severe with increasing distance from the settlements. This study defines the measurement criteria most suited to detecting degradation in the Eastern Steppe grasslands.