Warming effects on the flux of CH4 from peatland mesocosms are regulated by plant species composition: Richness and functional types

Rainstorm and strong wind weathers largely increase greenhouse gases flux in shallow ponds

Shallow-water ponds represent the hotspots of greenhouse gas (GHG) emissions. Most current studies focus on the temporal dynamics for GHGs in water, with little consideration given to the effects of weather changes. In this study, we measured and compared the concentrations and fluxes of CO2, CH4, and N2O from a pond in Northeast China under different meteorological conditions. Results showed that the rates of CO2, CH4, and N2O emissions from pond into the atmosphere during strong winds were 85.85 ± 7.55 mmol m-2 d-1, 22.05 ± 6.80 mmol m-2 d-1, and 10.87 ± 0.72 μmol m-2 d-1, respectively, significantly higher than those measured during non-rain weather. Among which, over 88 % of CH4 emissions were contributed by ebullition. Meanwhile, the CO2 and N2O flux were also significantly higher during heavy rainfall, reaching 100.05 ± 19.76 mmol m-2 d-1 and 5.90 ± 1.03 μmol m-2 d-1, respectively. Strong winds and precipitation induced sediment disturbances, high gas transport coefficients, reduced photosynthesis and oxygen greatly promoted the GHGs escape evasion. Wind speed, air pressure, solar radiation, and dissolved oxygen in water were important influencing factors. Our results emphasize the importance of capturing short-term weather disturbance events, especially rainstorm and strong winds, to accurately assess the annual GHG budget from these shallow water ecosystems.

A comprehensive review on methane's dual role: effects in climate change and potential as a carbon-neutral energy source

The unprecedented population and anthropogenic activity rise have challenged the future look up for shifts in global temperature and climate patterns. Anthropogenic activities such as land fillings, building dams, wetlands converting to lands, combustion of biomass, deforestation, mining, and the gas and coal industries have directly or indirectly increased catastrophic methane (CH4) emissions at an alarming rate. Methane is 25 times more potent trapping heat when compared to carbon dioxide (CO2) in the atmosphere. A rise in atmospheric methane, on a 20-year time scale, has an impact of 80 times greater than that of CO2. With increased population growth, waste generation is rising and is predicted to reach 6 Mt by 2025. CH4 emitted from landfills is a significant source that accounts for 40% of overall global methane emissions. Various mitigation and emissions reduction strategies could significantly reduce the global CH4 burden at a cost comparable to the parallel and necessary CO2 reduction measures, reversing the CH4 burden to pathways that achieve the goals of the Paris Agreement. CH4 mitigation directly benefits climate change, has collateral impacts on the economy, human health, and agriculture, and considerably supports CO2 mitigation. Utilizing the CO2 from the environment, methanogens produce methane and lower their carbon footprint. NGOs and the general public should act on time to overcome atmospheric methane emissions by utilizing the raw source for producing carbon-neutral fuel. However, more research potential is required for green energy production and to consider investigating the untapped potential of methanogens for dependable energy generation.

Warming-induced vapor pressure deficit suppression of vegetation growth diminished in northern peatlands

Recent studies have reported worldwide vegetation suppression in response to increasing atmospheric vapor pressure deficit (VPD). Here, we integrate multisource datasets to show that increasing VPD caused by warming alone does not suppress vegetation growth in northern peatlands. A site-level manipulation experiment and a multiple-site synthesis find a neutral impact of rising VPD on vegetation growth; regional analysis manifests a strong declining gradient of VPD suppression impacts from sparsely distributed peatland to densely distributed peatland. The major mechanism adopted by plants in response to rising VPD is the "open" water-use strategy, where stomatal regulation is relaxed to maximize carbon uptake. These unique surface characteristics evolve in the wet soil‒air environment in the northern peatlands. The neutral VPD impacts observed in northern peatlands contrast with the vegetation suppression reported in global nonpeatland areas under rising VPD caused by concurrent warming and decreasing relative humidity, suggesting model improvement for representing VPD impacts in northern peatlands remains necessary.

Does genotypic diversity of Hydrocotyle vulgaris affect CO2 and CH4 fluxes?

Biodiversity plays important roles in ecosystem functions and genetic diversity is a key component of biodiversity. While effects of genetic diversity on ecosystem functions have been extensively documented, no study has tested how genetic diversity of plants influences greenhouse gas fluxes from plant-soil systems. We assembled experimental populations consisting of 1, 4 or 8 genotypes of the clonal plant Hydrocotyle vulgaris in microcosms, and measured fluxes of CO2 and CH4 from the microcosms. The fluxes of CO2 and CO2 equivalent from the microcosms with the 1-genotype populations of H. vulgaris were significantly lower than those with the 4- and 8-genotype populations, and such an effect increased significantly with increasing the growth period. The cumulative CO2 flux was significantly negatively related to the growth of the H. vulgaris populations. However, genotypic diversity did not significantly affect the flux of CH4. We conclude that genotypic diversity of plant populations can influence CO2 flux from plant-soil systems. The findings highlight the importance of genetic diversity in regulating greenhouse gas fluxes.

Effects of warming and litter positions on litter decomposition in a boreal peatland

Litter decomposition is an important source of carbon accumulation in the permafrost peatlands. Climate warming has led to shrub expansions and accelerated litter mixing with soils and fluctuations in the water table. However, little is known about how changes in the position of the litter will affect litter decomposition under climate warming. To reveal the mechanisms of response of the location of litter in the soil and climate warming to litter decomposition in permafrost peatlands. Here, we selected the evergreen shrub, Chamaedaphne calyculata, and the deciduous shrub, Vaccinium uliginosum, from the permafrost peatlands of the Greater Hing’an Mountains, China. The leaf litter was placed on the soil surface (no-mixing) and mixed with the soil (soil-litter mixing), and then it was incubated for 124 days at 15°C (control) and 20°C (warming). Our results showed that warming significantly increased the CO2 emission rates of C. calyculata and V. uliginosum by 19.9 and 17.4%, respectively. When compared to no-mixing, the CO2 emission rates were reduced (not significantly) by 1.5 (C. calyculata) and increased 13.6% (V. uliginosum) with soil-litter mixing. Interestingly, soil-litter mixing suppressed the positive effect of warming on the CO2 emission rates relative to no-mixing, and the suppressing effects in the V. uliginosum subplot were stronger than those in the C. calyculata subplot. Specifically, warming significantly increased the CO2 emissions of C. calyculata by 27.4% under no-mixing but the increase decreased to 13.1% under soil-litter mixing. Similarly, warming induced significant increases in the CO2 emissions of V. uliginosum, with an increase of 38.8% under no-mixing but non-significant increases (1.9%) were observed under soil-litter mixing. The combination of the enzyme activities of β-1,4-glucosidase, β-1,4-xylosidase and β-D-1,4-cellobiosidase and laccase and phenolics explained more than 60.0% of the variability in the CO2 emissions of C. calyculata and V. uliginosum, respectively. Our study highlights the importance of litter positions in mediating the responses of litter decomposition to climate warming and shrub expansions in the northern peatlands.

Response of Carbon Emissions and the Bacterial Community to Freeze-Thaw Cycles in a Permafrost-Affected Forest-Wetland Ecotone in Northeast China

Climate warming can affect freeze–thaw cycle (FTCs) patterns in northern high-latitude regions and may affect permafrost carbon emissions. The response of carbon release and microbial communities to FTCs has not been well characterized. Here, we conducted laboratory incubation experiments to investigate the relationships among carbon emissions, bacterial community, and soil variables in a permafrost-affected forest–wetland ecotone in Northeast China. The emission rates of CO₂ and CH₄ increased during the FTCs. FTC amplitude, FTC frequency, and patch type had significant effects on carbon emissions. FTCs increased the contents of soil DOC, NH₄⁺-N, and NO₃⁻-N but reduced bacterial alpha diversity. CO₂ emissions were mainly affected by bacterial alpha diversity and composition, and the inorganic nitrogen content was the important factor affecting CH₄ emissions. Our findings indicated that FTCs could significantly regulate CO₂ and CH₄ emissions by reducing bacterial community diversity and increasing the concentration of available soil substrates. Our findings shed new light on the microorganism-substrate mechanisms regulating the response patterns of the soil carbon cycle to FTCs in permafrost regions.

Impact of climate change-induced alterations in peatland vegetation phenology and composition on carbon balance

Global climate is changing faster than humankind has ever experienced. Model-based predictions of future climate are becoming more complex and precise, but they still lack crucial information about the reaction of some important ecosystems, such as peatlands. Peatlands belong to one of the largest carbon stores on the Earth. They are mostly distributed in high latitudes, where the temperature rises faster than in the other parts of the planet. Warmer climate and changes in precipitation patterns cause changes in the composition and phenology of peatland vegetation. Peat mosses are becoming less abundant, vascular plants cover is increasing, and the vegetation season and phenophases of vascular plants start sooner. The alterations in vegetation cause changes in the carbon assimilation and release of greenhouse gases. Therefore, this article reviews the impact of climate change-induced alterations in peatland vegetation phenology and composition on future climate and the uncertainties that need to be addressed for more accurate climate prediction.