Greenhouse gas emissions in natural and managed peatlands of America: Case studies along a latitudinal gradient

The production of beef and milk has a significant impact on climate change, as these activities are responsible for a large proportion of the greenhouse gases emitted in agriculture. We used the static closed chamber technique to measure the rate of CH4-C, N2O-N and CO2-C emissions from pastures (102 days) and bovine excretions (27 days) in an intensive pasture monoculture (PM) and an intensive silvopastoral system (ISS) in the Cauca Valley of Colombia. Mean soil CO2-C (mg m2 h−1), CH4-C and N2O-N emissions (μg m−2 h−1) were 236.7 versus 113.4; 46.7 versus 1.01 and 344.7 versus 40.1 for the PM and ISS, respectively. The accumulated flows for PM and ISS during the evaluation period were 751.6 and 424.3; 4.39 and − 0.41; and 12.75 and 1.55 (kg ha−1) for CO2-C, CH4-C and N2O-N, respectively. Regarding manure, the PM had lower CO2-C and CH4-C emissions (498.6 vs. 981.2 mg m−2 h−1, and 1.9 vs. 4.7 μg m2 h−1; p > 0.05), and higher N2O-N emissions (2967.3 vs. 1179.8 μg m−2 h−1; p = 0.02) than the ISS, respectively. For the urine patches, the ISS emitted only 47.9, 2.2 and 11.6% of the CO2-C, CH4-C and N2O-N emissions observed in the PM, respectively. Moreover, comparing both systems with a forest, CH4-C and N2O-N emissions from the ISS were not different (p > 0.05), but the PM presented higher emissions for the three gases (p < 0.0001). The emissions reported in the present study differ from the emission factors suggested by the IPCC and other authors for manure and urine. PM presented higher N losses than the ISS from both manure (1.77 vs. 1.37%) and urine (3.47 vs. 0.3%) (p < 0.05). The ISS might contribute to the reduction of GHG emissions from grasslands in contrast to traditional grazing systems, despite the high stocking rates and legume densities, producing emissions similar to those of a forest.

Effect of broiler litter stockpiling methods on ammonia and greenhouse gas emissions

Several climate change scenarios have predicted that heavy precipitation could result in prolonged flooding (PF) and flooding–drying (FD) of soils under agriculture. The influence of PF and FD on soil greenhouse gas (GHG) fluxes and ammonium‑nitrogen (NH4+-N) and nitrate‑nitrogen (NO3−-N) dynamics of arable and grassland soils, the dominant land-use types in the UK, remain unclear. A two-month soil incubation experiment was conducted to determine the impact of PF and FD on soil N dynamics and GHG fluxes from arable and grassland soils. Arable soil emitted more N2O-N when soil moisture exceeded 100% water-holding capacity (WHC) compared to grassland soil under PF. Grassland soils exhibited increased N2O-N emissions than arable soils when soil moisture was lower than 100% WHC under FD. When soil moisture exceeded 100% WHC, the available NO3−-N in the soil contributed 58% of N2O-N emissions potentially by denitrification from grassland. When soil moisture was lower than 100% WHC, soil NH4+-N and NO3−-N contributed 71% of N2O-N emissions, which suggests coupling of nitrification-denitrification processes in driving high emissions from grassland soils. The N2O-N and CO2-C emissions increased with the incubation time under FD. Moreover, FD significantly increased N2O-N, CO2-C, and CH4-C emissions in grassland soil by 0.93, 2.15, and 37.29 times more than arable soil, respectively. These findings points to important tipping points in the source strengths of GHG fluxes from the two land use types differently. Future land use changes should consider the contribution of the changing dynamics of GHG fluxes in light of climate extremes and its implications for net zero greenhouse gas emission ambitions.

Agroecosystems in arid and semi-arid regions face growing risks of climate extremes and soil degradation. The addition of exogenous carbon can restore degraded soils by adding soil organic carbon, but its effects on greenhouse gas (GHG) emissions and global warming mitigation remain elusive. This study evaluated emissions of three major GHGs-nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4)-following soil amendment with biochar, compost, and a biochar + compost (BC) mixture. Biochar application reduced cumulative N2O-N and CH4-C emissions by 52% and 16%, respectively. Soil CH4-C emissions were generally negative, being lowest with biochar and highest with compost. During the crop season, average CO2-C and N2O-C emissions were 75% and 45% greater, respectively, while CH4-C was 66% less compared to the no-crop season. Increasing soil moisture content increased N2O-N emissions (R2 = 0.39), while soil temperature influenced CH4-C emissions (R2 = 0.37). Among amendments, biochar-treated soil had the lowest cumulative N2O-N and CH4-C emissions, reducing net global warming potential (GWP) by 43% and 30%, respectively, compared to compost-treated soil and control (CTRL). Biochar amendment can be a climate-smart strategy for semi-arid regions as it improves soil health and mitigates GWP by reducing N2O and CH4 emissions.

Abstract&amp;#160;&amp;#160;&amp;#160; Under the predicted climate change scenarios, heavy precipitation could result in prolonged flooding (PF) and flooding-drying (FD) of soils in agriculture. The influence of PF and FD on soil greenhouse gas fluxes and nitrogen (N) dynamics of arable and grassland soils, which are the dominant land use types in UK soil, is still unclear. Two months of soil incubation experiments were conducted to find out the impact of PF and FD on soil nitrogen dynamics and greenhouse gas fluxes from arable and grassland soil. The result showed the developed ion selective electrodes (ISE) sensor was working to measure NH4+ in the first 5 days of real-life application under both grassland and arable soil. There were less N2O-N emissions in grassland and arable soil when soil moisture was higher than 100% water-holding capacity (WHC). Arable soil had more N2O-N emissions when soil moisture was higher than 100% WHC compared to grassland soil due to a low pH. Grassland soil had more N2O-N emissions when soil moisture was lower than 100% WHC compare to arable soil due to a high carbon and nitrogen source. When soil moisture was greater than 100% WHC, the available NO3--N in the soil controlled N2O-N emissions of grassland more effectively. The N2O-N emissions of grassland soil were more controlled by soil stable NH4+-N and NO3--N when soil moisture was lower than 100% WHC. The emissions of N2O-N and CO2-C were increased with the time of FD. FD significantly increased N2O-N, CO2-C, and CH4-C emissions in grassland soil compared to arable soil by 0.93, 2.15, and 37.29 times, respectively. Converting arable land use to grassland could increase the greenhouse gas (GHG) emissions under climate change (heavy rain). Further research needs to be done to find out how to reduce the GHG emissions under climate change after transfer arable to grassland.

Nutrient retention, availability and greenhouse gas emissions from biochar-fertilized Chernozems

Biosolid stockpiles are a significant point source for greenhouse gas emissions

Spring thawing can affect the soil carbon and nitrogen cycling processes and lead to changes in the emissions of greenhouse gases. The temporal variations and impact factors of soil GHGs fluxes were measured in Phragmites australis and Carex appendiculata with the static chamber from the end of March to the end of May in 2018 in riparian wetlands of Xilin River, which is typical inland river meandering through steppe region in Inner Mongolia, China. The results showed that soil CH4 and N2O emissions of the P. australis were significantly higher than those of the Carex appendiculata, whereas CO2 emissions were no significant difference. The responses of soil GHG fluxes to soil environmental factors in P. australis and Carex appendiculata differed. In the P. australis community, soil CO2 and CH4 emissions were influenced jointly by mainly the soil temperature and microbial biomass nitrogen, whereas soil N2O emission was mainly affected by the soil temperature. The dominant controlling factor for CO2 and N2O was soil temperature in the Carex appendiculata, whereas CH4 was mainly regulated by soil water content. The global warming potential of P. australis was significantly higher than that of Carex appendiculata. Those findings highlight the difference in soil greenhouse gas fluxes in different plant communities and the importance of CH4 and N2O emissions during the spring thaw, which contributes to predicting the riparian wetland soil greenhouse gases and their global warming potential under global climate changes.

Greenhouse gas emission in constructed wetlands for wastewater treatment: A review

There is a lack of information regarding carbon dioxide (CO), methane (CH), and nitrous oxide (NO) emissions from pasture soils and the effects of grazing. The objective of this study was to quantify greenhouse gas (GHG) fluxes from pasture soils grazed with cow-calf pairs managed with different stocking rates and densities. The central hypothesis was that irrigated low-density stocking systems (SysB) would result in greater GHG emissions from pasture soils than nonirrigated high-density stocking systems (SysA) and grazing-exclusion (GRE) pasture sites. The nonirrigated high-density stocking systems consisted of 120 cow-calf pairs rotating on a total of 120 ha (stocking rate 1 cow/ha, stocking density 112,000 kg BW/ha, rest period of 60 to 90 d). The irrigated low-density stocking systems consisted of 64 cow-calf pairs rotating on a total of 26 ha of pasture (stocking rate 2.5 cows/ha, stocking density 32,700 kg BW/ha, rest period of 18 to 30 d). Both systems consisted of mixed cool-season grass-legume pastures. Static chambers were randomly placed for collection of CO, CH, and NO samples. Soil temperature (ST), ambient temperature (temperature inside the chamber; AT), and soil water content (WC) were monitored and considered explanatory variables for GHG emissions. GHG fluxes were monitored for 3 yr (2011 to 2013) at the beginning (P1) and at the end (P2) of the grazing season, always postgrazing. Paddock was the experimental unit (3 pseudoreplicates per treatment), and chambers (30 chambers per paddock) were considered multiple measurements of each experimental unit. A completely randomized design considered the term year × period as a repeated measure and chamber nested within paddock and treatment as the random term. Generally, SysB had greater CO emissions than SysA and GRE pasture sites across years and periods ( < 0.01). Soil temperature, AT, and WC had effects on CO emissions. Methane and NO emissions were observed from pasture sites of the 3 systems, but the effect of grazing was not constantly significant for CH and NO emissions. In addition, ST, AT, and WC did not conclusively explain CH and NO emissions. No clear trade-offs between GHG were observed; generally, GHG emissions increased from 2011 to 2013, which was likely associated with weather conditions, such as higher daily temperature and precipitation events. The central hypothesis that SysB would result in greater GHG emissions from pasture soils than SysA and GRE was not confirmed.

Rivers play an important role in greenhouse gas emissions. Over the past decade, because of global urbanization trends, rapid land use changes have led to changes in river ecosystems that have had a stimulating effect on the greenhouse gas production and emissions. Presently, there is an urgent need for assessments of the greenhouse gas concentrations and emissions in watersheds. Therefore, this study was designed to evaluate river-based greenhouse gas emissions and their spatial-temporal features as well as possible impact factors in a rapidly urbanizing area. The specific objectives were to investigate how river greenhouse gas concentrations and emission fluxes are responding to urbanization in the Liangtan River, which is not only the largest sub-basin but also the most polluted one in Chongqing City. The thin layer diffusion model method was used to monitor year-round concentrations of pCO2, CH4, and N2O in September and December 2014, and March and June 2015. The pCO2 range was (23.38±34.89)-(1395.33±55.45) Pa, and the concentration ranges of CH4 and N2O were (65.09±28.09)-(6021.36±94.36) nmol·L-1 and (29.47±5.16)-(510.28±18.34) nmol·L-1, respectively. The emission fluxes of CO2, CH4, and N2O, which were calculated based on the method of wind speed model estimations, were -6.1-786.9, 0.31-27.62, and 0.06-1.08 mmol·(m2·d)-1, respectively. Moreover, the CO2 and CH4 emissions displayed significant spatial differences, and these were roughly consistent with the pollution load gradient. The greenhouse gas concentrations and fluxes of trunk streams increased and then decreased from upstream to downstream, and the highest value was detected at the middle reaches where the urbanization rate is higher than in other areas and the river is seriously polluted. As for branches, the greenhouse gas concentrations and fluxes increased significantly from the upstream agricultural areas to the downstream urban areas. The CO2 fluxes followed a seasonal pattern, with the highest CO2 emission values observed in autumn, then successively winter, summer, and spring. The CH4 fluxes were the highest in spring and the lowest in summer, while N2O flux seasonal patterns were not significant. Because of the high carbon and nitrogen loads in the basin, the CO2 products and emissions were not restricted by biogenic elements, but levels were found to be related to important biological metabolic factors such as the water temperature, pH, DO, and chlorophyll a. The carbon, nitrogen, and phosphorus content of the water combined with sewage input influenced the CH4 products and emissions. Meanwhile, N2O production and emissions were mainly found to be driven by urban sewage discharge with high N2O concentrations. Rapid urbanization accelerated greenhouse gas emissions from the urban rivers, so that in the urban reaches, CO2/CH4 fluxes were twice those of the non-urban reaches, and all over the basin N2O fluxes were at a high level. These findings illustrate how river basin urbanization can change aquatic environments and aggravate allochthonous pollution inputs such as carbon, nitrogen, and phosphorus, which in turn can dramatically stimulate river-based greenhouse gas production and emissions; meanwhile, spatial and temporal differences in greenhouse gas emissions in rivers can lead to the formation of emission hotspots.

Greenhouse gas emissions studies commonly focus on temperate and subtropical regions. As a result, greenhouse gas emissions from agricultural soils in tropical areas are often neglected. Therefore, greenhouse gas fluxes in a Hainan paddy field under different fertilization regimes were studied. This research provides an accurate assessment of CH4 and N2O emissions from paddy fields in China and sound mitigation measures. Through static chamber/gas chromatography techniques, CH4 and N2O emissions, global warming potential (GWP), and greenhouse gas emissions intensity (GHGI) in late rice season under five fertilizer treatments were measured. The treatments included:control (CK), conventional treatment (CON), optimized fertilization treatment (YH), optimized fertilization combined with controlled slow-release fertilizer treatment (ZHY1), optimized fertilization combined with controlled slow-release fertilizer and organic fertilizer treatment (ZHY2). The results showed that the cumulative CH4 emissions in the CK, CON, YH1, ZYH1, and ZYH2 treatments were 175.70, 60.30, 63.00, 62.80, and 56.60kg·hm-2, and the cumulative N2O emissions were 0.78, 3.40, 1.03, 1.44, and 0.44kg·hm-2, respectively. Correlation analysis showed that soil temperature and Eh were the main factors driving CH4 emission. Compared with CK, CON, YH, and ZYH1, the yield of rice in ZYH2 treatment increased by 29.69%, 11.81%, 6.74%, and 10.36%, respectively. While GWP of ZYH2 decreased by 64.80%, 43.23%, 12.93%, and 15.15%, and GHGI decreased by 76.49%, 52.52%, 20.54%, and 23.87%, respectively. Therefore, in terms of yield and greenhouse gas emissions, optimal fertilization combined with sheep manure and slow release fertilizer treatment (ZYH2) is feasible in this region.

CO2 and N2O emissions in a soil chronosequence at a glacier retreat zone in Maritime Antarctica

IntroductionThe changes in grassland management and grassland types are strongly linked with dynamics in soil physico-chemical properties and vegetation attributes, with important implications for carbon/nitrogen cycling and greenhouse gas (GHG) fluxes. However, the seasonal variations of GHG emissions from sheepfolds, and the underlying biotic and abiotic drivers affecting GHG exchanges across different steppe and management types remain largely unclear.MethodsTaking the Inner Mongolian grassland as a model system, we measured the fluxes of CO2, CH4 and N2O, as well as soil and vegetation variables, in three contrasting grassland management areas (grazing, sheepfold, enclosure) and in three representative (wet typical, dry typical, desert) grassland ecosystems in July, September and November 2016.ResultsOur results showed that: (1) GHG fluxes were mostly higher in the plant growing season (July and September) than in the nongrowing season (November); sheepfold area had significantly higher GHG emissions (in July and mean over the season) than enclosed and grazing areas, with the effects being most pronounced in dry typical steppe. (2) The high GHG emissions in dry typical steppe were closely associated with the interactions among favorable soil temperature and moisture, high total organic carbon (TOC) content, and high aboveground biomass. The important predictors for CO2 emission were soil TOC and pH, whereas that for CH4 and N2O emissions were soil temperature and moisture content, in sheepfold areas. (3) Three GHG emissions were negatively affected by species richness across all steppe and management types, which might be a consequence of indirect effects through the changes in soil TOC and total nitrogen (TN).DiscussionThese results indicate that sheepfold areas are intensive hotspot sources of GHGs in the steppes, and it is of great importance to help to account GHG emissions and develop mitigation strategies for sheepfold areas for sustainable grassland management in the natural steppe based pastoral production ecosystems.

This study investigates the effect of energy consumption on greenhouse gas (GHG) emissions in 33 African countries from 1995–2017. It contributes to the literature by investigating the effect of disaggregated measures of energy consumption (coal, oil and other liquids, renewable energy, and electricity) on GHG emissions (CO2, N2O, CH4, and total GHG emissions) in Africa and identifies the transmission channels through which energy consumption affects GHG emissions. The system GMM is used in the study as it accounts for possible endogeneity and the potential correlation between the error term and the country fixed effects. The results show that coal consumption significantly increases CO2, CH4, and total GHG emissions and reduces N2O emissions. Oil consumption increases CO2 and total GHG emissions but reduces N2O and CH4 emissions. Renewable energy consumption reduces CO2 and CH4 emissions but increases N2O emissions. Finally, electricity consumption promotes CO2, N2O, CH4 and total GHG emissions in Africa. Further analyses show that foreign trade and economic growth are the channels through which oil consumption increases GHG emissions. The adverse effect of electricity is through urbanization. Renewable consumption could decrease GHG emissions through sustainable urbanization and trade policies. The findings suggest that countries should gradually reduce coal consumption and encourage renewable energy consumption, which has the lowest impact on the environment.