The Spatial and Temporal Variation Characteristics of CH<sub>4</sub> and CO<sub>2</sub> Emission Flux under Different Land Use Types in the Yellow River Delta Wetland

Abstract

The Yellow River Delta Wetland is one of the youngest wetlands, and also the most complete, extensive wetlands in China. The wetland in this delta is ecologically important due to their hydrologic attributes and their roles as ecotones between terrestrial and aquatic ecosystems. In the study, the spatial and temporal variation characteristics of CH4 and CO2 emission flux under five kinds of land use types in the wetland were investigated. The results indicated that the greenhouse gas emission flux, especially the CO2 and CH4, showed distinctly spatial and temporal variation under different land use types in the wetland. In the spring, the emission flux of CO2 was higher than that of CO2 in the autumn, and appeared negative in HW3 and HW4 in the autumn. CH4 emission flux of HW4 and HW5 was negative in the spring and autumn, which indicated that the CH4 emission process was net absorption. Among the five kinds of land use types, the CO2 emission flux of HW4 discharged the largest emission flux reaching 29.3 mg•m −2 •h −1 , but the CH4 emission flux of HW2 discharged the largest emission flux reaching 0.15 mg•m −2 •h −1 . From the estuary to the inland, the emission flux of CO2 was decreased at first and then appeared increasing trend, but the emission flux of CH4 was contrary to CO2.

Inter-Annual Variability of Area-Scaled Gaseous Carbon Emissions from Wetland Soils in the Liaohe Delta, China

“…Similar trends were reported from the nearby Yellow River Delta, where complete reversals of CO 2 and CH 4 fluxes from soil uptake to efflux were documented for some wetland types (e.g., P . australis ) among years [ 36 ], although the reasons were not discussed. Indeed, we can conclude that GHG assessments across multiple years are critical for determining mass C fluxes from wetlands.…”

“…australis wetlands both typically serve as sinks for CO 2 , but emit CH 4 [ 24 – 25 , 32 ], while this course is less clear for S . salsa marshes [ 33 – 36 ].…”

“…Much uncertainty arises when measuring soil CO 2 and CH 4 fluxes infrequently or in singular years [ 26 , 34 – 35 ], if the goal of such assessment is to upscale to larger areas and over multiple years. Inter-annual and seasonal variations in soil CO 2 and CH 4 fluxes are large in coastal wetlands of Northeast China [ 36 – 38 ]. Indeed, we recognized this in a previous study [ 38 ], which focused on linking environmental variables (e.g., salinity, soil temperature, water table depth, plant biomass) from a single year to emissions of CO 2 and CH 4 from P .…”