Preliminary studies on nitrous oxide emissions from the ornithogenic soils on Xi-sha atoll, South China Sea

Article type: Research Article

Authors: ZHU, Ren-bin | SUN, Li-guang | ZHAO, San-ping | XIE, Zhou-qing | LIU, Xiao-dong | YIN, Xue-bin

Affiliations: Institute of Polar Environment, University of Science and Technology of China, Hefei 230026, China

Note: [] Corresponding author. E-mail: [email protected]

Abstract: 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·h) on Dong lsland and 3.2 to 20.4 μg/(m^2·h) on Yongxing lsland 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 ws 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 lsland 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 lsland, 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.

Keywords: South China Sea, ornithogenic soil, nitrous oxide, Xi-sha atoll, emission

Journal: Journal of Environmental Sciences, vol. 17, no. 4, pp. 551-556, 2005