GEOGRAPHICAL RESEARCH ›› 2010, Vol. 29 ›› Issue (5): 935-946.doi: 10.11821/yj2010050018

• Environment and Ecology • Previous Articles     Next Articles

Characteristics and influencing factors of CO2, CH4 and N2O emissions from Chongming eastern tidal flat wetland

WANG Qing1,2, LIU Min2, HOU Li-jun3, CHENG Shu-bo2,4   

  1. 1. Department of Geography, Anhui Normal University, Wuhu 241000, Anhui, China;
    2. Department of Geography, Key laboratory of Geo-information of the Ministry of Education, East China Normal University, Shanghai 200062, China;
    3. State Key Laboratory of Estuarine and Coastal Research, Shanghai 200062, China;
    4. Department of Environmental Geosciences Center for Earth Sciences, Vienna University, Althanstrasse 14, 1090 Vienna, Austria
  • Received:2009-05-16 Revised:2009-09-26 Online:2010-05-20 Published:2010-05-20

Abstract:

The temporal and spatial variations and effect factors of greenhouse gases (CO2, CH4 and N2O) emission from Chongming eastern tidal flat, the typical and most important wetland of the Yangtze estuary, have been studied on three time scales, i.e. seasonally, diurnally and tidally, and at four sampling areas, i.e. reclaimed wetland, high tidal flat, middle tidal flat and low tidal flat. On the scale of growing season, all of the gases emitted significantly from wetland. Diurnal fluxes of CO2 and CH4 were less than nocturnal ones, and N2O flux peak was found in the afternoon. In the early stage of the exposure after tide ebbed, CH4 and N2O emitted from sediments, while CO2 was absorbed by sediments. The spatial variation of greenhouse gases was related to water gradient along the direction from land to sea. CH4 emission from high tidal flat was significantly higher than that from reclaimed wetland and from middle tidal flat, and a slight consumption was observed at low tidal flat. N2O emitted only at reclaimed wetland and consumed at other sampling sites. CO2 showed a significant emission from the planted sites and a slight consumption at low tidal flat. Both air temperature and soil temperature exerted influence on gases emission, with plants as intermediary. Tide-caused "immergence-exposure" change in sediment proved to be indispensable to gases emission from tidal wetlands. Physic-chemical characteristics of soil, such as organic carbon, ammonium, sulfate and redox potential, had profound effects on gases emission. Cutting of plants led to consequent additional emission. Land use change caused change of gases emission: as high tidal flat was converted into reclaimed wetland, flux of CH4 decreased and fluxes of N2O and CO2 increased. The estimated emissions in growing season from the Chongming eastern tidal flat wetland were 5.1×107 g CH4, 1.0×105 g N2O and 1.7×1011 g CO2, respectively.

Key words: carbon dioxide, methane, nitrous oxide, greenhouse gas emission, coastal wetland, Yangtze estuary