Grassland is the largest terrestrial ecosystem in China. It is of great significance to measure accurately the soil respiration of different grassland types for the contribution evaluation of the Chinese terrestrial e...Grassland is the largest terrestrial ecosystem in China. It is of great significance to measure accurately the soil respiration of different grassland types for the contribution evaluation of the Chinese terrestrial ecosystem’s carbon emission to the atmospheric CO2 concentration. A three-year (2005-2007) field experiment was carried out on three steppes of Stipa L. in the Xilin River Basin, Inner Mongolia, China, using a static opaque chamber technique. The seasonal and interannual variations of soil respiration rates were analyzed, and the annual total soil respiration of the three steppes was estimated. The numerical models between soil respiration and water-heat factors were established respectively. Similar seasonal dynamic and high annual and interannual variations of soil respiration were found in all of the three steppes. In the growing season, the fluctuation of soil respiration was particularly evident. The coefficients of variation (CVs) for soil respiration in different growing seasons ranged from 54% to 93%, and the annual CVs were all above 115%. The interannual CV of soil respiration progressively decreased in the order of Stipa grandis (S. grandis) steppe 】 Stipa baicalensis (S. baicalensis) steppe 】 Stipa krylovii (S. krylovii) steppe. The annual total soil respiration for the S. baicalensis steppe was 223.62?299.24 gC m-2 a-1, 150.62-226.99 gC m-2 a-1 for the S. grandis steppe, and 111.31–131.55 gC m-2 a-1 for the S. krylovii steppe, which were consistent with the precipitation gradient. The variation in the best fitting temperature factor explained the 63.5%, 73.0%, and 73.2% change in soil respiration in the three steppes at an annual time scale, and the corresponding Q10 values were 2.16, 2.98, and 2.40, respectively. Moreover, the Q10 values that were calculated by soil temperature at different depths all expressed a 10 cm 】 5 cm 】 surface in the three sampling sites. In the growing season, the soil respiration rates were related mostly to the surface soil moisture, and the 95.2%, 97.4%, and 93.2% variations in soil respiration in the three steppes were explained by the change in soil moisture at a depth of 0-10 cm, respectively.展开更多
Cultivation is one of the most important human activities affecting the grassland ecosystem besides grazing, but its impacts on soil total organic carbon （C）, especially on the liable organic C fractions have not be...Cultivation is one of the most important human activities affecting the grassland ecosystem besides grazing, but its impacts on soil total organic carbon （C）, especially on the liable organic C fractions have not been fully understood yet. In this paper, the role of cropping in soil organic C pool of different fractions was investigated in a meadow steppe region in Inner Mongolia of China, and the relationships between different C fractions were also discussed. The results indicated that the concentrations of different C fractions at steppe and cultivated land all decreased progressively with soil depth. After the conversion from steppe to spring wheat field for 36 years, total organic carbon （TOC） concentration at the 0 to 100 cm soil depth has decreased by 12.3% to 28.2%, and TOC of the surface soil horizon, especially those of 0-30 cm decreased more significantly （p〈0.01）. The dissolved organic carbon （DOC） and microbial biomass carbon （MBC） at the depth of 0-40 cm were found to have decreased by 66.7% to 77.1% and 36.5% to 42.4%, respectively. In the S.baicalensis steppe, the ratios of soil DOC to TOC varied between 0.52% and 0.60%, and those in the spring wheat field were only in the range of 0.18%-0.20%. The microbial quotients （qMBs） in the spring wheat field, varying from 1.11% to 1.40%, were also lower than those in the S. baicalensis steppe, which were in the range of 1.50%-1.63%. The change of DOC was much more sensitive to cultivation disturbance. Soil TOC, DOC, and MBC were significantly positive correlated with each other in the S. baicalensis steppe, but in the spring wheat field, the correlativity between DOC and TOC and that between DOC and MBC did not reach the significance level of 0.05.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 40730105, 40673067, and 40973057)National Key Technology Research and Development Program (Grant No. 2007BAC03A11)
文摘Grassland is the largest terrestrial ecosystem in China. It is of great significance to measure accurately the soil respiration of different grassland types for the contribution evaluation of the Chinese terrestrial ecosystem’s carbon emission to the atmospheric CO2 concentration. A three-year (2005-2007) field experiment was carried out on three steppes of Stipa L. in the Xilin River Basin, Inner Mongolia, China, using a static opaque chamber technique. The seasonal and interannual variations of soil respiration rates were analyzed, and the annual total soil respiration of the three steppes was estimated. The numerical models between soil respiration and water-heat factors were established respectively. Similar seasonal dynamic and high annual and interannual variations of soil respiration were found in all of the three steppes. In the growing season, the fluctuation of soil respiration was particularly evident. The coefficients of variation (CVs) for soil respiration in different growing seasons ranged from 54% to 93%, and the annual CVs were all above 115%. The interannual CV of soil respiration progressively decreased in the order of Stipa grandis (S. grandis) steppe 】 Stipa baicalensis (S. baicalensis) steppe 】 Stipa krylovii (S. krylovii) steppe. The annual total soil respiration for the S. baicalensis steppe was 223.62?299.24 gC m-2 a-1, 150.62-226.99 gC m-2 a-1 for the S. grandis steppe, and 111.31–131.55 gC m-2 a-1 for the S. krylovii steppe, which were consistent with the precipitation gradient. The variation in the best fitting temperature factor explained the 63.5%, 73.0%, and 73.2% change in soil respiration in the three steppes at an annual time scale, and the corresponding Q10 values were 2.16, 2.98, and 2.40, respectively. Moreover, the Q10 values that were calculated by soil temperature at different depths all expressed a 10 cm 】 5 cm 】 surface in the three sampling sites. In the growing season, the soil respiration rates were related mostly to the surface soil moisture, and the 95.2%, 97.4%, and 93.2% variations in soil respiration in the three steppes were explained by the change in soil moisture at a depth of 0-10 cm, respectively.
基金National Natural Science foundation of China, No.40730105 No.40973057+1 种基金 No.41073061 Knowledge In novation Program of the Chinese Academy of Sciences, No.KZCX2-EW-302
文摘Cultivation is one of the most important human activities affecting the grassland ecosystem besides grazing, but its impacts on soil total organic carbon （C）, especially on the liable organic C fractions have not been fully understood yet. In this paper, the role of cropping in soil organic C pool of different fractions was investigated in a meadow steppe region in Inner Mongolia of China, and the relationships between different C fractions were also discussed. The results indicated that the concentrations of different C fractions at steppe and cultivated land all decreased progressively with soil depth. After the conversion from steppe to spring wheat field for 36 years, total organic carbon （TOC） concentration at the 0 to 100 cm soil depth has decreased by 12.3% to 28.2%, and TOC of the surface soil horizon, especially those of 0-30 cm decreased more significantly （p〈0.01）. The dissolved organic carbon （DOC） and microbial biomass carbon （MBC） at the depth of 0-40 cm were found to have decreased by 66.7% to 77.1% and 36.5% to 42.4%, respectively. In the S.baicalensis steppe, the ratios of soil DOC to TOC varied between 0.52% and 0.60%, and those in the spring wheat field were only in the range of 0.18%-0.20%. The microbial quotients （qMBs） in the spring wheat field, varying from 1.11% to 1.40%, were also lower than those in the S. baicalensis steppe, which were in the range of 1.50%-1.63%. The change of DOC was much more sensitive to cultivation disturbance. Soil TOC, DOC, and MBC were significantly positive correlated with each other in the S. baicalensis steppe, but in the spring wheat field, the correlativity between DOC and TOC and that between DOC and MBC did not reach the significance level of 0.05.
