Abstract
Forested coastal wetlands are globally important systems sequestering carbon and intercepting nitrogen pollution from nutrient-rich river systems. Coastal wetlands that have suffered extensive disturbance are the target of comprehensive restoration efforts. Accurate assessment of restoration success requires detailed mechanistic understanding of wetland soil biogeochemical functioning across restoration chrono-sequences, which remains poorly understood for these sparsely investigated systems. This study investigated denitrification and greenhouse gas fluxes in mangrove and Melaleuca forest soils of Vietnam, using the 15N-Gas flux method. Denitrification-derived N2O was significantly higher from Melaleuca than mangrove forest soils, despite higher potential rates of total denitrification in the mangrove forest soils (8.1 ng N g-1 h-1) than the Melaleuca soils (6.8 ng N g-1 h-1). Potential N2O and CO2 emissions were significantly higher from the Melaleuca soils than from the mangrove soils. Disturbance and subsequent recovery had no significant effect on N biogeochemistry except with respect to the denitrification product ratio in the mangrove sites, which was highest from the youngest mangrove site. Potential CO2 and CH4 fluxes were significantly affected by restoration in the mangrove soils. The lowest potential CO2 emissions were observed in the mid-age plantation and potential CH4 fluxes decreased in the older forests. The mangrove system, therefore, may remove excess N and improve water quality with low greenhouse gas emissions, whereas in Melaleucas, increased N2O and CO2 emissions also occur. These emissions are likely balanced by higher carbon stocks observed in the Melaleuca soils. These mechanistic insights highlight the importance of ecosystem restoration for pollution attenuation and reduction of greenhouse gas emissions from coastal wetlands. Restoration efforts should continue to focus on increasing wetland area and function, which will benefit local communities with improved water quality and potential for income generation under future carbon trading.
Highlights
Forested coastal wetlands provide globally important ecosystem services including carbon and nitrogen (N) sequestration and removal of N to the atmosphere (Adame et al, 2019a; Barbier, 2019; Chmura et al, 2003; Krauss et al, 2018)
Potential fluxes of denitrification-derived 15N-N2 were highest from mangrove soils and this difference was significant (p-value = 0.02, Wilcoxon, Fig. 3c)
When normalised to soil carbon, potential denitrification-driven 15N-N2O fluxes were highest from mangrove soils and this difference was significant (p-value
Summary
Forested coastal wetlands provide globally important ecosystem services including carbon and nitrogen (N) sequestration and removal of N to the atmosphere (Adame et al, 2019a; Barbier, 2019; Chmura et al, 2003; Krauss et al, 2018). Soil biogeochemical processes in forested coastal wetlands influence N and carbon cycling, which may produce or consume greenhouse gases (GHGs: CO2, CH4 and N2O) and remove N from the system (Adame et al, 2019b; Bartlett and Harriss, 1993; Kreuzwieser et al, 2003; Reddy and DeLaune, 2008). Rates of nitrification from mangrove systems have been observed between 0 and 0.82 mg m-2 h-1 or 0.6 to 57.1 ng N g-1 h-1 (Alongi et al, 2002; Xiao et al, 2018)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
