Chin J Plant Ecol ›› 2006, Vol. 30 ›› Issue (3): 432-440.DOI: 10.17521/cjpe.2006.0058

Special Issue: 碳水能量通量

• Original article • Previous Articles     Next Articles

EMISSIONS OF CH<sub>4</sub> AND N<sub>2</sub>O FROM A WETLAND IN THE SANJIANG PLAIN

YANG Ji-Song1,2(), LIU Jing-Shuang1, WANG Jin-Da1, YU Jun-Bao1, SUN Zhi-Gao1,2, LI Xin-Hua1,2   

  1. 1Northeast Institute of Geography and Agricultural Ecology, Chinese Academy of Sciences, Changchun 130012, China
    2Graduate School of Chinese Academy of Sciences, Beijing 100039, China
  • Accepted:2005-09-08 Published:2006-05-30

Abstract:

In order to understand more about mechanisms of and factors that influence CH4 and N2O production in wetlands, fluxes of CH4 and N2O were measured using static-chamber and gas-chromatography methods in a marsh wetland, located at the Honghe Farm in eastern part of Heilongjiang Province, China (47°35'17.8″ N, 133°37'48.4″ E), from June to September,2003. Three plant communities, Carex pseudocuraica, Carex lasiocarpa and Deyeuxia angustifolia, were selected to measure fluxes of CH4 and N2O to contrast the variance of the emission rates of both greenhouse gases in these different plant zones. Air temperature and soil temperature at 5 cm depth, soil redox potential (0-100 cm), and standing water depth at each site also were measured to determine the main factors that control CH4 and N2O emissions within and among plant zones.

The wetland was a source of both CH4 and N2O during the growing season and emissions showed conspicuous temporal and spatial variations. Similar temporal variations of CH4 and N2O fluxes were observed in the C. pseudocuraica and C. lasiocarpa sites. Emission rates of CH4 were higher in July and August while emissions of N2O were higher in July and September. However, the highest emissions of CH4 and N2O in the C. angustifolia site occurred about one month earlier than in the C. pseudocuraica and C. lasiocarpa sites. The highest CH4 emissions observed in the wetland were in the C. pseudocuraica site on July 19 with a rate of 696.24 mg·m-2·d-1, and the highest N2O emissions were in the D. angustifolia site on June 12 with a rate of 2.53 mg·m-2·d-1. The average CH4 flux from the C. pseudocuraica site was 273.6 mg·m-2·d-1, the highest among the three sites over the growing season but was not significantly different from 259.2 mg·m-2·d-1 of the C. lasiocarpa site. However, both were significantly higher than the 38.16 mg·m-2·d-1 measured in the D. angustifolia site (p<0.000 1). These results showed that average CH4 fluxes in submerged wetlands were higher than in seasonal wetlands. N2O fluxes from the C. pseudocuraica, C. lasiocarpa and D. angustifolia sites were not significantly different (p=0.967) with an average flux of 0.969, 0.932 and 0.983 mg·m-2·d-1, respectively, suggesting that submerged and seasonal wetlands had similar rates of N2O emissions.

Air temperature, soil temperature, soil redox potential and standing water depth were important factors influencing emission rates of CH4 and N2O from the wetlands. Relationship analysis showed that CH4 fluxes were correlated weakly with air temperature and soil temperature at 5 cm depth within a site (0.201<r<0.560) but not correlated with standing water depth ((0.100<r<0.176). Strong correlations were found between N2O fluxes and standing water depth (r1=-0.701; r2=-0.528), but no correlation between N2O fluxes and air temperature and soil temperature at 5 cm depth in the C. pseudocuraica and C. lasiocarpa sites (-0.089<r<0.211) was found. However, in theD. angustifolia site, there were no correlations between N2O fluxes and the three factors (r<0.344). These results indicated that temperature was more important in influencing CH4 emissions in the seasonal and submerged wetlands whereas standing water depth was more important in influencing N2O emissions in the submerged wetlands. Furthermore, standing water table was the main control of the difference in CH4 emissions among plant zones. However, there appeared to be similar rates of N2O emissions among plant zones in the wetlands with strongly anaerobic conditions.

Key words: CH4, N2O, Growing seasons, Plant zones, Wetland, Sanjiang Plain