Effects of semi-lunar tidal cycling on soil CO2 and CH4 emissions: a case study in the Yangtze River estuary, China

• Published in: Wetlands ecology and management 2015-08, Vol.23 (4), p.727-736
• Main Authors: Bu, Nai-Shun, Qu, Jun-Feng, Zhao, Hua, Yan, Qing-Wu, Zhao, Bin, Fan, Jing-Lan, Fang, Chang-Ming, Li, Gang
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; carbon; Carbon cycle; Carbon dioxide; case studies; Conservation Biology/Ecology; Emissions; Environmental Law/Policy/Ecojustice; Estuaries; Freshwater & Marine Ecology; greenhouse gas emissions; Greenhouse gases; Hydrology/Water Resources; Life Sciences; Marine & Freshwater Sciences; Methane; methane production; Methanogenesis; Original Paper; Redox potential; Rivers; salinity; Soil moisture; Soil salinity; soil water; Spring tides; Sulfates; temporal variation; Tidal effects; Tides; Water Quality/Water Pollution; Wetlands
• ISSN: 0923-4861; 1572-9834
• DOI: 10.1007/s11273-015-9415-5

Coastal wetlands, commonly inundated by periodic tides, have been recognized as important sources of greenhouse gases. However, little is known of tidal effects on in situ soil CO₂ and CH₄ emissions in a semi-lunar tidal cycle consisting of neap and spring tide periods (NTP and STP). A field study was conducted in the Yangtze River estuary to investigate temporal variations of soil CO₂ and CH₄ emissions along with the transition from NTP to STP in a semi-lunar tidal cycle. Soil moisture, salinity and sulfate were significantly greater in STP than in NTP, whereas soil redox potential had an opposite pattern because of frequent tidal inundation. Soil CO₂ and CH₄ effluxes decreased significantly in STP, being 29–34 and 28–35 %, respectively, compared with those in NTP. The decrease in soil CO₂ effluxes was likely attributable to two causes, an anaerobic environment inhibiting CO₂ production, and tidal inundation impeding CO₂ diffusion from the soil into the atmosphere. The inhibition of methanogenesis by increased soil salinity and sulfate was likely the primary reason of the decrease in CH₄ effluxes during STP. Our results suggest that the effects of semi-lunar tidal cycling significantly reduce soil carbon emissions, which may be one of the potential mechanisms underlying strong carbon accumulation in wetlands of the Yangtze River estuary.