Temporal and spatial variations of greenhouse gas fluxes from a tidal mangrove wetland in Southeast China

Abstract

Tidal mangrove wetlands are a source of methane (CH4) and nitrous oxide (N2O); but considering the high productivity of mangroves, they represent a significant sink for carbon dioxide (CO2). An exotic plant Spartina alterniflora has invaded east China over the last few decades, threatening these coastal mangrove ecosystems. However, the atmospheric gas fluxes in mangroves are poorly characterized and the impact of biological invasion on greenhouse gas (GHG) fluxes in the wetland remains unclear. In this study, the temporal and spatial dynamics of key GHG fluxes (CO2, CH4, and N2O) at an unvegetated mudflat, cordgrass (S. alterniflora), and mangrove (Kandelia obovata) sites along an estuary of the Jiulong River in Southeast China were investigated over a 2-year period. The CO2 and CH4 fluxes demonstrated a seasonal and vegetation-dependent variation while N2O fluxes showed no such dependent pattern. Air temperature was the main factor influencing CO2 and CH4 fluxes. Cumulative global warming potential (GWP) ranked in the order of mangrove > cordgrass > mudflat and summer > spring > autumn > winter. Moreover, CH4 accounted for the largest proportion (68%) of GWP, indicating its dominant contribution to the warming potential in mangroves. Notwithstanding the lack of information on plant coverage, cordgrass invasion exhibited a minor influence on GHG emissions. These findings support the notion that mangrove forests are net accumulation sites for GHGs. As vegetation showed considerable effects on fluxes, more information about the significance of vegetation type with a special emphasis on the effects of invasive plants is crucial.

Diurnal and Seasonal Variation of CO2 and CH4 Fluxes in Tomago Wetland

“…High temperatures in summer are favourable for physiological processes in soil microbial processes, and plant respiration. This effect of temperature is supported with the research by Pulliam (1993) and Wang et al, (2016), from which they found that high temperatures promote the oxidative breakdown of organic matter and plant tissue (root and shoot) respiration. In a related study, it was found that wetlands act as sources of CO 2 if climate, hydrologic conditions and soil temperatures enhance oxidation of organic matter and root respiration (Altor & Mitsch, 2008).…”

A synthesis of methane emissions from shallow vegetated coastal ecosystems

“…Vegetated habitats typically have higher sediment OM concentrations compared to sediments without vegetation (e.g., Banerjee et al, 2018; Marinho, Campos, Guimarães, & Esteves, 2012; Yuan et al, 2015). Generally, there is a reported increase in CH 4 emissions in vegetated compared to nonvegetated areas (e.g., Bahlmann et al, 2015; Wang et al, 2016). When plants are photosynthesizing, they deposit labile OM into the sediment around their roots or rhizosphere (Blaabjerg & Finster, 1998; Holmer, Andersen, Nielsen, & Boschker, 2001), thereby providing a substrate to stimulate CH 4 production (Bridgham et al, 2013).…”

Specific impacts of beech and Norway spruce on the structure and diversity of the rhizosphere and soil microbial communities

“…Although the impact of plant species on soil microbial communities is widely documented16710262841, few studies have been performed on tree-associated microbial communities. However, such surveys are essential because by modifying the soil chemistry (pH, nitrogen and cations availability) and microbial biomass and activity, trees have a long-term impact on the environment compared to plants with a shorter lifetime82742.…”