Abstract: Soil respiration rate of winter wheat was measured by using a LI-6400 portable photosynthesis system and a LI-6400-09 soil CO2 flux chamber at the Yucheng Comprehensive Experimental Station of the Chinese Academy of Sciences during the main growing season in 2008. The root biomass extrapolation method (RBE) and root exclusion method (RE) were adopted to estimate the contribution of root respiration to the total soil respiration respectively. The results showed that each of the different components of soil respiration had a clear seasonal variation,and the relationship explained 44% of the seasonal variation in soil respiration due to the variation in root biomass. There was a significant exponential correlation between soil respiration and the soil temperature at 5-10cm soil depth. The Q10 of 3 different components of the soil respiration was with 1.4-1.6. The contribution of root respiration to total soil respiration was estimated in the range from 18% to 54.3% with mean value at 32% by using RBE method,while it was from 32.6% to 58.1% with mean value at 44.6% by using RE method which was lower than by RBE method. The trend of seasonal variation of root respiration was the same by two methods and the peak value was at the flowering period of winter wheat. The contribution of root respiration to total soil respiration of winter wheat had a range from 32% to 45% integrated by two methods.

Key words: Root respiration, Root respiration, Total soil respiration, Root biomass, Q10, Winter wheat