Above-ground Biomass and its relationship to soil moisture of Natural Grassland in the Northern Slopes of the Qilian Mountains

Based on the research on the above-ground biomass of natural grassland: alpine pastureland,mountainous meadow,mountainous meadow rangeland,mountainous pastureland,mountainous desert rangeland in the northern slopes of the Mountains Qilian,the results showed that the difference of aboveground biomass among five grassland was significant(P0.05),but the curve of seasonal dynamic of aboveground biomass was single apex type and variation trend were same,and it reached the peak value in August.The above-ground biomass of mountainous meadow(100.24 g/m2) is the highest in five vegetation types,and others are in order of mountainous meadow rangeland(71.24 g/m2),mountainous pastureland(70.20 g/m2),alpine pastureland(52.40 g/m2),and mountainous desert rangeland(20.44 g/m2).The result of the Logistic model of above-ground biomass growth curve showed that all grassland types did not reach its maximum the environment can support.The above-ground biomass of different type grassland positively correlated to the accumulated value of precipitation and mean soil moisture.Soil moisture of different soil layers had different impact on the aboveground biomass,but the soil moisture within root distributed soil layers had same impact on aboveground biomass in all grasslands(P0.05).