title: Contrasting ecosystem CO2fluxes of inland and coastal wetlands: a meta-analysis of eddy covariance data.
abstract: Wetlands play an important role in regulating the atmospheric carbon dioxide (CO2) concentrations and thus affecting the climate. However, there is still lack of quantitative evaluation of such a role across different wetland types, especially at the global scale. Here, we conducted a meta-analysis to compare ecosystem CO2fluxes among various types of wetlands using a global database compiled from the literature. This database consists of 143 site-years of eddy covariance data from 22 inland wetland and 21 coastal wetland sites across the globe. Coastal wetlands had higher annual gross primary productivity (GPP), ecosystem respiration (Re), and net ecosystem productivity (NEP) than inland wetlands. On a per unit area basis, coastal wetlands provided large CO2sinks, while inland wetlands provided small CO2sinks or were nearly CO2neutral. The annual CO2sink strength was 93.15 and 208.37 g C m-2for inland and coastal wetlands, respectively. Annual CO2fluxes were mainly regulated by mean annual temperature (MAT) and mean annual precipitation (MAP). For coastal and inland wetlands combined, MAT and MAP explained 71%, 54%, and 57% of the variations in GPP, Re, and NEP, respectively. The CO2fluxes of wetlands were also related to leaf area index (LAI). The CO2fluxes also varied with water table depth (WTD), although the effects of WTD were not statistically significant. NEP was jointly determined by GPP and Refor both inland and coastal wetlands. However, the NEP/Reand NEP/GPP ratios exhibited little variability for inland wetlands and decreased for coastal wetlands with increasing latitude. The contrasting of CO2fluxes between inland and coastal wetlands globally can improve our understanding of the roles of wetlands in the global C cycle. Our results also have implications for informing wetland management and climate change policymaking, for example, the efforts being made by international organizations and enterprises to restore coastal wetlands for enhancing blue carbon sinks.
authors.affiliation: National Marine Environmental Monitoring Center, State Oceanic Administration, Dalian, 116023, China.
authors.forename: Weizhi
authors.initials: W
authors.lastname: Lu
authors.affiliation: Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, 03824, USA.
authors.forename: Jingfeng
authors.initials: J
authors.lastname: Xiao
authors.affiliation: Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, Tsinghua University, Beijing, 100084, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.affiliation: National Marine Environmental Monitoring Center, State Oceanic Administration, Dalian, 116023, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: National Marine Environmental Monitoring Center, State Oceanic Administration, Dalian, 116023, China.
authors.forename: Chang'an
authors.initials: C
authors.lastname: Liu
authors.affiliation: Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, Tsinghua University, Beijing, 100084, China.|Division of Ocean Science and Technology, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Lin
mesh_terms: D002245:Carbon Dioxide; D002980:Climate; D057231:Climate Change; D017753:Ecosystem; D053833:Wetlands
chemical_list: D002245:Carbon Dioxide
keywords: carbon budget; cross-site synthesis; ecosystem respiration; gross primary productivity; mangroves; marshes; net ecosystem productivity