| CO2 flux data obtained by eddy covariance theory was analyzed at Xilamuren desert steppe in June to December 2019.The aims were to investigate daily and seasonal variation of CO2 flux,the factors influencing the CO2 flux,the charcteristic of grassland as carbon source or sink,and provide a basis for the characteristics of carbon cycle in the region,combined with biomass and meteorological data.The main results were shown as follows:1.The variation of CO2 flux showed out a U-shaped curve in the daytime.Within typical day,the ecosystem began to absorb CO2 after one hour at the daytime,and the ability to absorb CO2 continuously strengthened.The absorbing ability weaken and the value of CO2 flux increased until about 15:00.CO2 flux at night from June to September decreased after the peak value presented between 20:00 and 22:30.2.As time gose on,total CO2 flux in the daytime continuously decreased and reached the minimum value with-9.55gCO2m-2 at August,then increased.The variation of total CO2 flux at night was just opposite to it in the daytime,and the maximum value was 6.03gCO2m-2 in August.3.In the whole growing season,the daily CO2 flux were negative value,the grassland was carbon sink.The daily CO2 flux were positive values from mid-October to December,and the grassland was carbon source.The obseavation was 214 days,the grassland represented as carbon sink with 141.15gCO2/m2 during this study.4.CO2 flux was negatively related to temperature,latent heat flux sensible heat flux and vapor pressure deficit(p<0.01)during the growing and non-growing season,positively related to Relative humidity(p<0.01),and negatively related to aboveground biomass(p<0.01),while not significant correlation with surface litter.5.The footprint source area were 10?248m,11?262m,12?206m,13?277m,10-295m,12?167m and 12?138m,respectively in June to December.The main wind direction was 180°-270° during the study period,which affects the footprint source. |
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