Abstract: Desert steppe is one of the major community types of Inner Mongolia grassland, which becomes sensitive in response to climate change. CENTURY model applicability was tested using 50-year climate data, recent 5-year soil investigation information, and 7-year quadrat data on-ecological meteorological observation experimental station of Siziwang County. The correlations of aboveground net primary production (ANPP) simulation values and 26 meteorological factors in the past 50 years were analyzed. Based on the output data of climate emissions scenarios of SRES B2, A2 and A1B from the regional climate system of PRECIS, possible variation trends of ANPP were analyzed under three kinds of climate scenarios over the future 50 years in the study area. The results showed that CENTURY model can successfully simulate the seasonal dynamics and interannual variability in Siziwang County desert steppe. The correlation of monthly aboveground biomass between the simulated and observed values was good in growing season (R²=0.66, P<0.01). Increased air temperature, slightly increased precipitation, and increased ANPP were found in Siziwang County desert steppe in the past 50 years. With changes of temperature and precipitation, simulated ANPP presented obvious change patterns. Correlation analysis showed that ANPP was significantly positively correlated with precipitation, negatively correlated with annual extreme maximum temperature and annual evaporation, and not remarkably correlated with the other meteorological factors. Under the climate scenarios of SRES B2, A2 and A1B, the mean maximum temperature, minimum temperature and precipitation were all of increasing trends. The overall increasing trend of ANPP was evident though its inter-annual fluctuation was stronger. The increases of future ANPP under the three scenarios were 2.55%, 4.19% and 9.44% over the baseline period, respectively. Under the three climate scenarios, impact of climate change on ANPP would be positive in Siziwang County desert steppe in future. This research realized the application of CENTURY model on desert steppe in Inner Mongolia, and made up the lack of unrealizable dynamical evaluation and estimation for grassland productivity due to the shortage of continuous long-term field experiment data and the heterogeneity of ecosystem.

Key words: ammonia volatilization, Eichhornia crassipes, nitrogen loss, nitrogen preserving agent, high temperature composting