关键词: 养分添加, 内蒙古温带草地, 地上生物量, 地下生物量, 根冠比

Abstract: In order to compare the response of community biomass to nutrient additions among different grassland ecosystems, the authors established nutrient addition experiments on three grassland ecosystems along the climate gradient, including meadow steppe, typical steppe and desert steppe in Inner Mongolia. On the basis of the threeyear experiment, the impacts of different nutrients (N, P) on different nutrient gradient (N: 10, 5 and 2.5 g/m2; P: 10 g/m2) on above- and belowground biomass of these grassland ecosystems was analyzed. The results show that nitrogen leads to a significant increase in the aboveground biomass of grassland in Inner Mongolia by 27% to 53.3%, an average increase of 37.8%. In addition, the response of biomass to N addition increases with the N gradients. Belowground biomass has a less response to fertilization than aboveground biomass. There is an average of 10.2% increase in the total biomass of grassland community in response to N addition. Biomass responds to P addition less deeply than N addition. Furthermore, the response of biomass to nutrient addition varies among three grassland ecosystems. In arid desert steppe, community biomass is more sensitive to N limitation than the typical steppe and meadow steppe. N addition reduces belowground biomass and R/S ratio in meadow steppe and desert steppe, whereas promotes the values in typical steppe. In contrast, nutrient additions have relatively less and insignificant impacts on the root distribution of temperate grasses. These observations indicate that nutrient addition has different effects on community biomass under different environmental conditions, which means it is necessary to consider the changed response of different grassland ecosystems to nutrient addition in the carbon cycle models budget and grassland management.

Key words: fertilization, Inner Mongolia grassland, aboveground biomass, belowground biomass, R/S ratio