Abstract: Methane flux from the omithogenic 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 CH_4 flux ranged from
−226.7μg/(m^2·h) to
226.3μg/(m_2·h) at the observation sites on Dong
Island. High atmospheric CH_4 consumption was observed from
the ornithogenic soils on sunny days. CH_4 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
CH_4 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 CH_4 consumption and
the average flux was −141.8μg/(m^2·h).
However, disturbed soils via anthropogenic reclamation showed
CH_4 emissions and the average flux was
441.7μg/(m_2·h). Therefore land use changes may
have an important effect on the CH_4 fluxes from the
tropical ornithogenic soils. In addition, different observation sites show a
high spatial variation in CH_4 fluxes. The wetland in salt
marsh showed the CH_4 emission on Dong Island, and the dry
soil sites all showed high atmospheric CH_4 consumption,
suggesting that CH_4 fluxes were predominantly controlled by
soil water regime. The effects of soil chemical properties on
CH_4 fluxes were also analyzed and discussed in this
paper.
Keywords: methane, flux, South China Sea, omithogenic soil, Xi-sha atoll
