Analysis of niche suitability and spatial difference of grassland ecosystem in Gannan

Based on the historical research results, the mathematical model of niche suitability and evolutional momentum of grassland ecosystem in Gannan was established by means of niche suitability theory. Eight indices were used to measure the niche suitability of the grassland ecosystem and evolutional momentum, including population density, GDP per capita, GDP per capita in the first industry, farmer's annual net income, ratio of grassland degraded at medium level, average biomass, grassland area damaged by rodents, animal production value per unit grassland and stocking rate. The resulted showed that there were big spatial differences of grassland ecosystem niche suitability among different counties and cities in Gannan. The niche suitability could be ranked into 5 levels and their spatial differences were analyzed.