Methane flux from the ornithogenic soils was preliminarily measured by closed chamber method on Xi-sha atoll, South China Sea during March 10 to April 11, 2003 for the first time. The CH4 flux ranged from - 226.7 μg/...Methane flux from the ornithogenic soils was preliminarily measured by closed chamber method on Xi-sha atoll, South China Sea during March 10 to April 11, 2003 for the first time. The CH4 flux ranged from - 226.7 μg/（m^2 ·h） to 226.3 μg/（m^· h） at the observation sites on Dong Island. High atmospheric CH4 consumption was observed from the ornithogenic soils on sunny days. CH4 uptake rates showed the highest value after the midday and they had a strong positive correlation with soil temperatures. Under the same weather conditions, the CH4 fluxes were also observed from the intact and disturbed soils on Yongxing Island. Results showed that the intact soils with natural vegetation also showed high atmospheric CH4 consumption and the average flux was - 141.8 μg/（ m^2· h）. However, disturbed soils via anthropogenic reclamation showed CH4 emissions and the average flux was 441 .7 μg/（ m^2· h）. Therefore land use changes may have an important effect on the CH4 fluxes from the tropical ornithogenic soils. In addition, different observation sites show a high spatial variation in CH4 fluxes. The wetland in salt marsh showed the CH4 emission on Dong Island, and the dry soil sites all showed high atmospheric CH4 consumption, suggesting that CH4 fluxes were predominantly controlled by soil water regime. The effects of soil chemical properties on CH4 fluxes were also analyzed and discussed in this paper.展开更多
The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N_2O fluxes from the ornithogenic soils ranged f...The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N_2O fluxes from the ornithogenic soils ranged from 1 8 to 40 3 μg/(m^2\5h) on Dong Island and 3 2 to 20 4 μg/(m^2·h) on Yongxing Island and their flux averaged 11 0 μg/(m^2·h) and 8 3 μg/(m^2·h), respectively. N_2O fluxes from two wetland sites in salt marsh of Dong Island were approximately one order of magnitude lower than those from the ornithogenic soils and averaged 2 1 μg/(m^2·h) and 2 4 μg/(m^2·h). The diurnal variation cycle in the fluxes was obtained at the observation sites; the N_2O flux increased with the increase in soil temperature. The sudden increase in soil moisture greatly stimulated N_2O emission from the ornithogenic soils on Dong Island due to the heavy rainfall. The undisturbed soils showed the lower N_2O fluxes and the average was 4 8 μg/(m^2·h) and the soils via the reclamation showed the higher N_2O fluxes and the average was 16 6 μg/(m^2·h) on Yongxing Island, suggesting that the changes of land use have an important effect on N_2O fluxes from the ornithogenic soils. In addition, the N_2O fluxes at the different sites showed high spatial variations. The fluxes were positively correlated with the concentrations of NO^-_3, PO~ 3- _4 and Mn in the soils. The negative correlation between the fluxes and total S concentration in the ornithogenic soils was also found for the first time. Coastal soils or sediments constitute an important source of global atmospheric N_2O and the increases in nitrogen loading from seabird guanos will lead to significant increases in the flux of this atmospherically active gas.展开更多
基金The Key Project of National Natural Science Foundationof China(No.40231002) ,the National Natural Science Foundationof China(No.40406001) andthe Specialized Research Fundfor the Doctoral Programof Higher Education(No.20030358002)
文摘Methane flux from the ornithogenic soils was preliminarily measured by closed chamber method on Xi-sha atoll, South China Sea during March 10 to April 11, 2003 for the first time. The CH4 flux ranged from - 226.7 μg/（m^2 ·h） to 226.3 μg/（m^· h） at the observation sites on Dong Island. High atmospheric CH4 consumption was observed from the ornithogenic soils on sunny days. CH4 uptake rates showed the highest value after the midday and they had a strong positive correlation with soil temperatures. Under the same weather conditions, the CH4 fluxes were also observed from the intact and disturbed soils on Yongxing Island. Results showed that the intact soils with natural vegetation also showed high atmospheric CH4 consumption and the average flux was - 141.8 μg/（ m^2· h）. However, disturbed soils via anthropogenic reclamation showed CH4 emissions and the average flux was 441 .7 μg/（ m^2· h）. Therefore land use changes may have an important effect on the CH4 fluxes from the tropical ornithogenic soils. In addition, different observation sites show a high spatial variation in CH4 fluxes. The wetland in salt marsh showed the CH4 emission on Dong Island, and the dry soil sites all showed high atmospheric CH4 consumption, suggesting that CH4 fluxes were predominantly controlled by soil water regime. The effects of soil chemical properties on CH4 fluxes were also analyzed and discussed in this paper.
文摘The preliminary measurements of nitrous oxide fluxes from the ornithogenic soils on tropical Xi-sha atoll were made using a closed chamber technique for the first time. N_2O fluxes from the ornithogenic soils ranged from 1 8 to 40 3 μg/(m^2\5h) on Dong Island and 3 2 to 20 4 μg/(m^2·h) on Yongxing Island and their flux averaged 11 0 μg/(m^2·h) and 8 3 μg/(m^2·h), respectively. N_2O fluxes from two wetland sites in salt marsh of Dong Island were approximately one order of magnitude lower than those from the ornithogenic soils and averaged 2 1 μg/(m^2·h) and 2 4 μg/(m^2·h). The diurnal variation cycle in the fluxes was obtained at the observation sites; the N_2O flux increased with the increase in soil temperature. The sudden increase in soil moisture greatly stimulated N_2O emission from the ornithogenic soils on Dong Island due to the heavy rainfall. The undisturbed soils showed the lower N_2O fluxes and the average was 4 8 μg/(m^2·h) and the soils via the reclamation showed the higher N_2O fluxes and the average was 16 6 μg/(m^2·h) on Yongxing Island, suggesting that the changes of land use have an important effect on N_2O fluxes from the ornithogenic soils. In addition, the N_2O fluxes at the different sites showed high spatial variations. The fluxes were positively correlated with the concentrations of NO^-_3, PO~ 3- _4 and Mn in the soils. The negative correlation between the fluxes and total S concentration in the ornithogenic soils was also found for the first time. Coastal soils or sediments constitute an important source of global atmospheric N_2O and the increases in nitrogen loading from seabird guanos will lead to significant increases in the flux of this atmospherically active gas.
