Biochar amendments increase soil organic carbon storage and decrease global warming potentials of soil CH4 and N2O under N addition in a subtropical Moso bamboo plantation

Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate the promoting effects of N input on GHG emissions in forest soils. Here, we quantify the separate and combined effects of biochar amendment(0, 20, and 40 t·ha) and N addition(0, 30, 60, and 90 kg N·ha·yr) on soil GHG fluxes in a long-term field experiment at a Moso bamboo(Phyllostachys edulis) plantation.Results: Low and moderate N inputs(≤60 kg N·ha·yr) significantly increase mean annual soil carbon dioxide(CO) and nitrous oxide(NO) emissions by 17.0%–25.4% and 29.8%–31.2%, respectively, while decreasing methane(CH) uptake by 12.4%–15.9%, leading to increases in the global warming potential(GWP) of soil CHand NO fluxes by 32.4%–44.0%. Moreover, N addition reduces soil organic carbon(C;SOC) storage by 0.2%–6.5%. Compared to the control treatment, biochar amendment increases mean annual soil CO2emissions, CHuptake, and SOC storage by 18.4%–25.4%, 7.6%–15.8%, and 7.1%–13.4%, respectively, while decreasing NO emissions by 17.6%–19.2%, leading to a GWP decrease of 18.4%–21.4%. Biochar amendments significantly enhance the promoting effects of N addition on soil COemissions, while substantially offsetting the promotion of N2O emissions, inhibition of CHuptake, and decreased SOC storage, resulting in a GWP decrease of 9.1%–30.3%.Additionally, soil COand CHfluxes are significantly and positively correlated with soil microbial biomass C(MBC) and pH. Meanwhile, NO emissions have a significant and positive correlation with soil MBC and a negative correlation with pH.Conclusions: Biochar amendment can increase SOC storage and offset the enhanced GWP mediated by elevated N deposition and is, thus, a potential strategy for increasing soil C sinks and decreasing GWPs of soil CHand NO under increasing atmospheric N deposition in Moso bamboo plantations.

Etching characteristics of thin SiON films using a liquefied perfluorocarbon precursor of C_6F_(12)O with a low global warming potential

Perfluorocarbon gas is widely used in the semiconductor industry.However,perfluorocarbon has a negative effect on the global environment owing to its high global warming potential(GWP) value.An alternative solution is essential.Therefore,we evaluated the possibility of replacing conventional perfluorocarbon etching gases such as CHF_3 with C_6F_(12)O,which has a low GWP and is in a liquid state at room temperature.In this study,silicon oxynitride(SiON) films were plasma-etched using inductively coupled CF4+C_6F_(12)O+O_2 mixed plasmas.Subsequently,the etching characteristics of the film,such as etching rate,etching profile,selectivity over Si,and photoresist,were investigated.A double Langmuir probe was used and optical emission spectroscopy was performed for plasma diagnostics.In addition,a contact angle goniometer and x-ray photoelectron spectroscope were used to confirm the change in the surface properties of the etched SiON film surface.Consequently,the etching characteristics of the C_6F_(12)O mixed plasma exhibited a lower etching rate,higher SiON/Si selectivity,lower plasma damage,and more vertical etched profiles than the conventional CHF_3 mixed plasma.In addition,the C_6F_(12)O gas can be recovered in the liquid state,thereby decreasing global warming.These results confirmed that the C_6F_(12)O precursor can sufficiently replace the conventional etching gas.

Negligible Warming Caused by Nord Stream Methane Leaks

Unanticipated sabotage of two underwater pipelines in the Baltic Sea(Nord Stream 1 and 2)happened on 26September 2022.Massive quantities of natural gas,primarily methane,were released into the atmosphere,which lasted for about one week.As a more powerful greenhouse gas than CO_(2),the potential climatic impact of methane is a global concern.Using multiple methods and datasets,a recent study reported a relatively accurate magnitude of the leaked methane at 0.22±0.03 million tons(Mt),which was lower than the initial estimate in the immediate aftermath of the event.Under an energy conservation framework used in IPCC AR6,we derived a negligible increase in global surface air temperature of 1.8×10^(-5)℃ in a 20-year time horizon caused by the methane leaks with an upper limit of 0.25 Mt.Although the resultant warming from this methane leak incident was minor,future carbon release from additional Earth system feedbacks,such as thawing permafrost,and its impact on the methane mitigation pathways of the Paris Agreement,warrants investigation.

Material flow analysis and global warming potential assessment of an industrial insect-based bioconversion plant using housefly larvae

The significant increase in the demand for biomass waste treatment after garbage classification has led to housefly larvae treatment becoming an attractive treatment option.It can provide a source of protein while treating biomass waste,which means that nutrients can be returned to the natural food chain.However,the performance of this technology in terms of its environmental impacts is still unclear,particularly with regards to global warming potential(GWP).This study used a life cycle assessment(LCA)approach to assess a housefly larvae treatment plant with a treatment capacity of 50 tons of biomass waste per day.The LCA results showed that the 95% confidence intervals for the GWP in summer and winter were determined to be 24.46-32.81 kg CO_(2) equivalent(CO_(2)-eq)/ton biomass waste and5.37-10.08 kg CO_(2)-eq/ton biomass waste,respectively.The greater GWP value in summer is due to the longer ventilation time and higher ventilation intensity in summer,which consumes more power.The main GWP contributions are from(1)electricity needs(accounting for 78.6% of emissions in summer and 70.2%in winter)and(2)product substitution by mature housefly larvae and compost(both summer and winter accounting for 96.8% of carbon reduction).

Radiative forcing and global warming potential of perfluorocarbons and sulfur hexafluoride

We developed two radiation parameterizations with different resolutions （17-band and 998-band） for perfluorocarbons （PFCs） and sulfur hexafluoride （SF6） using the updated High-resolution Transmission Molecular Absorption （HITRAN） 2004 database and the correlated k-distribution method. We analyzed the impacts of the two radiation schemes on heating rates. Then we studied their instantaneous radiative efficiency, stratospheric adjusted radiative efficiency, global warming potential （GWP）, and global temperature potential （GTP）, for both clear- and all-sky conditions using a high-resolution radiation scheme. We found that the stratosphere-adjusted radiative efficiencies of C2F6, CF4, and SF6 for the whole sky were 0.346, 0.098, and 0.680 W m^-2 ppbv^-1, respectively. Radiative forcing from the industrial revolution to 2005 was 0.001, 0.007, and 0.004 W m^-2, respectively; and was predicted to rise to 0.008, 0.036, and 0.037 W m^-2, respectively, by 2100, according to emission scenarios provided by the IPCC. The GWPs of C2F6, CF4, and SF6 are 17035, 7597, and 31298, respectively, for a time horizon of 100 years relative to CO2. Their GTPs of pulse and sustained emissions, GTPv and GTPs, are 22468, 10052, and 40935 and 16498, 7355, and 30341, respectively, for a 100-year time horizon.

Methane and Nitrous Oxide Emissions from Three Paddy Rice Based Cultivation Systems in Southwest China

To understand methane （CH4） and nitrous oxide （N2O） emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years （from late 2002 to early 2005） in three rice-based cultivation systems, which are a permanently flooded rice field cultivated with a single time and followed by a non-rice season （PF）, a rice-wheat rotation system （RW） and a rice-rapeseed rotation system （RR） in a hilly area in Southwest China. The results showed that the total CH4 emissions from PF were 646.3±52.1 and 215.0±45.4 kg CH4 hm^-2 during the rice-growing period and non-rice period, respectively. Both values were much lower than many previous reports from similar regions in Southwest China. The CH4 emissions in the rice-growing season were more intensive in PF, as compared to RW and RR. Only 33% of the total annual CH4 emission in PF occurred in the non-rice season, though the duration of this season is two times longer than the rice season. The annual mean N2O flux in PF was 4.5±0.6 kg N2O hm^-2 yr^-1. The N2O emission in the rice-growing season was also more intensive than in the non-rice season, with only 16% of the total annual emission occurring in the non-rice season. The amounts of N2O emission in PF were ignorable compared to the CH4 emission in terms of the global warming potential （GWP）. Changing PF to RW or RR not only eliminated CH4 emissions in the non-rice season, but also substantially reduced the CH4 emission during the following rice-growing period （ca. 58%, P〈0.05）. However, this change in cultivation system substantially increased N2O emissions, especially in the non-rice season, by a factor of 3.7 to 4.5. On the 100-year horizon, the integrated GWP of total annual CH4 and N2O emissions satisfies PF〉〉RR≈RW. The GWP of PF is higher than that of RW and RR by a factor of 2.6 and 2.7, respectively. Of the total GWP of CH4 and N2O emissions, CH4 emission contributed to 93%, 65% and 59% in PF, RW and RR, respectively. These results suggest that changing PF to RW and RR can substantially reduce not only CH4 emission but also the total GWP of the CH4 and N2O emissions.

The effects of nitrogen fertilizer application on methane and nitrous oxide emission/uptake in Chinese croplands

The application of nitrogen（N） fertilizer to increase crop yields has a significant influence on soil methane（CH_4） and nitrous oxide（N_2O） emission/uptake.A meta-analysis was carried out on the effect of N application on（i） CH_4 emissions in rice paddies,（ii） CH_4 uptake in upland fields and（iii） N_2O emissions.The responses of CH_4 emissions to N application in rice paddies were highly variable and overall no effects were found.CH_4 emissions were stimulated at low N application rates（〈100 kg N ha^（-1）） but inhibited at high N rates（〉200 kg N ha^（-1）） as compared to no N fertilizer（control）.The response of CH_4 uptake to N application in upland fields was 15%lower than control,with a mean CH_4 uptake factor of-0.001 kg CH_4-C kg^（-1） N.The mean N_2O emission factors were 1.00 and 0.94%for maize（Zea mays） and wheat（Triticum aestivum）,respectively,but significantly lower for the rice（Oryza sativa）（0.51%）.Compared with controls,N addition overall increased global warming potential of CH_4 and N_2O emissions by 78%.Our result revealed that response of CH_4 emission to N input might depend on the CH_4concentration in rice paddy.The critical factors that affected CH_4 uptake and N_2O emission were N fertilizer application rate and the controls of CH_4 uptake and N_2O emission.The influences of application times,cropping systems and measurement frequency should all be considered when assessing CH_4 and N_2O emissions/uptake induced by N fertilizer.

Thermodynamic Performance and Flammability Studies of Hydrocarbon Based Low Global Warming Potential Refrigerant Mixtures

This paper presents a theoretical method to calculate the minimum inerting concentration(MIC)of binary and ternary blends(refrigerants)that are used in small refrigeration systems.MIC is the concentration of the dilutant which makes the flammable mixture into just non-flammable(at non-zero quenching potential).In this study,the refrigerant safety parameters such as flammability,Global Warming Potential(GWP)and performance(COP)are analyzed for twelve binary and thirteen ternary blends containing one flammable and two nonflammable(dilutant)components.Flammability investigation was carried out with the hydrocarbon refrigerants R290,R600,R600a each mixed with dilutants R227ea,R125,R245fa,R13I1 and R134a at different concentrations respectively.Two methods,thermal balance method(TBM)and modified thermal balanced method(MTBM),are used to estimate the MIC(which decides the flammable zone).Thirteen ternary blends were identified based on the MIC values estimated using MTBM.In the case of ternary blends,it was observed that the non-flammable zone is high for the compositions of the Mixture G,Mixture H and Mixture I.It was also estimated that the COPs of the proposed mixtures M22,M24,M25 and M27 are 4%greater than the COP of R134a(for the same operating conditions).Further,it was also understood that the corresponding GWP value is reduced by 90%to 97%for the mixtures(M21,M22,M24,M25 and M27)when compared to R134a(GWP=1300).Therefore,out of the thirteen proposed ternary mixtures(M15 to M27),the mixtures(M21,M22,M24,M25 and M27)are safe in terms of flammability,GWP and possess reasonable COP which can be a potential alternative refrigerant mixture to R134a in small refrigeration systems.

Grazing alters sandy soil greenhouse gas emissions in a sand-binding area of the Hobq Desert,China

Deserts are sensitive to environmental changes caused by human interference and are prone to degradation.Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand.However,the effects of grazing,which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification,on the greenhouse gas(GHG)fluxes from soils remain unknown.Herein,we investigated GHG fluxes in the Hobq Desert,Inner Mongolia Autonomous Region of China,at the mobile(desertified),fixed(vegetated),and grazed(re-desertified)sites from January 2018 to December 2019.We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential(GWP).CO_(2)was emitted at an average rate of 4.2,3.7,and 1.1 mmol/(m^(2)•h)and N_(2)O was emitted at an average rate of 0.19,0.15,and 0.09μmol/(m^(2)•h)at the grazed,fixed,and mobile sites,respectively.Mean CH_(4) consumption was as follows:fixed site(2.9μmol/(m^(2)•h))>grazed site(2.7μmol/(m^(2)•h))>mobile site(1.1μmol/(m^(2)•h)).GHG fluxes varied seasonally,and soil temperature(10 cm)and soil water content(30 cm)were the key micrometeorological factors affecting the fluxes.The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO_(2)and N_(2)O emissions and decreased CH_(4) absorption.Grazing also significantly increased the GWP of the soil(P<0.05).This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage.These findings could be used to formulate informed policies on the management and utilization of desert ecosystems.

Development of High Efficiency Swing Compressor for R32 Refrigerant

In the age of global warming, energy saving features and overall reduction of environmental impact are critical components that must be addressed when developing new HVAC （heating ventilation and air conditioning） units. We chose R32 refrigerant, with its lower LCCP （life cycle climate performance） as a more sustainable choice than R410A. However, R32 has its drawbacks. Due to its smaller molecular weight, internal leakage loss is higher for R32. Moreover, high discharge gas temperature decreases the reliability of the compressor, and makes a large overheating loss increase. In this study, we will describe the technologies （reducing the piston pressurizing force, heat-insulating structure, optimizing the port diameter） that were developed to overcome these drawbacks. We will also oresent the performance and reliability of the newly develoned high efficiency swing, comnressor series for R32 refrigerant.

Energy return on investment, energy payback time, and greenhouse gas emissions of coal seam gas(CSG) production in China: a case of the Fanzhuang CSG project

The studies and development of coal seam gas（CSG） have been conducted for more than 30 years in China, but few of China＇s CSG projects have achieved large-scale commercial success; faced with the boom of shale gas, some investors are beginning to lose patience and confidence in CSG. China currently faces the following question： Should the government continue to vigorously support the development of the CSG industry？ To provide a reference for policy makers and investors, this paper calculates the EROI_（stnd）[a standardized energy return on investment（EROI） method], EROI_（ide）（the maximum theoretical EROI）, EROI_（3,i）（EROI considering the energy investment in transport）, and EROI_（3,1＋e）（EROI with environmental inputs） of a single vertical CSG well in the Fanzhuang CSG project in the Qinshui Basin. The energy payback time（EPT） and the greenhouse gas（GHG） emissions of the CSG systems are also calculated. The results show that over a 15-year lifetime, EROI_（stnd）, EROI_（ide）, EROI_（3,1）, and EROI_（3,1＋e）are expected to deliver EROIs of approximately11：1, 20：1, 7：1, and 6：1, respectively. The EPT within different boundaries is no more than 2 years, and the life-cycle GHG emissions are approximately 18.8 million kg CO_2 equivalent. The relatively high EROI and short EPT indicate that the government should take more positive measures to promote the development of the CSG industry.

Impacts of Basic Seedling on Yield-Scaled Greenhouse Gas Emissions from Rice Fields in China

Many researches showed a comprehensive assessment of the cropping practice effect on greenhouse gas （GHG） emissions per unit yield （yield-scaled） rather than per the land area （area-scaled）, and it was noteworthy that cropping practices decided to increase or decrease grain yield, and reduce or promote greenhouse gas emissions. In this study, a meta-analysis was conducted to quantify the effects of rice basic seedlings （BS） on the global warming potential （GWP） of GHG emissions at the yield-scale in China. The results suggested that significant difference was observed in yield-scaled GWP of BS. The lowest yield-scaled GWP occurred at 80-100 BS （415.65 kg CO2 equiv/mg）. The yield-scaled GHG emission from high to low was that of the hybrid rice varieties （1 028.86 kg CO2 equiv/mg）, the conventional rice varieties （634.15 kg CO2 equiv/mg） and the super rice varieties （576.57 kg CO2 equiv/mg）. Consequently, the model of conventional rice varieties and super rice varieties at 80-100 BS could be a scientifc method of matching inthe rice cropping system. A further assessment of rice density and variety impacts on GHG emissions at yield-scale was urgently needed to develop, so as to achieve win-win policies of rice production for higher yield with lower emissions.

Shares Differences of Greenhouse Gas Emissions Calculated with GTP and GWP for Major Countries

The global warming potential (GWP) and global temperature potential (GTP) are two common metrics to calculate the CO2 equivalent of greenhouse gases (GHGs). If the country's GHG emissions are calculated with GTP instead of GWP, the shares of the EU, USA, Japan, Canada and South Africa rise in the period 1990-2005, and those of Brazil, Australia, China, India, Mexico and Russia decrease. From 2015 to 2030, the projected shares of the EU, USA, Japan and China will increase, but those of Russia, Canada, Australia, India, Mexico and Brazil will decrease. The reduced shares of Brazil and Australia and increased share of the EU might be one of the important reasons that Brazil and Australia suggested to adopt GTP instead of GWP as early as possible, but the EU opposed it.

Mountain Wood vs. Lowland Wood Harvesting Methods： An Ecological Case Study

Are Austrian mountain wood harvesting techniques more ecological than techniques applied in the lowlands of southern Germany？ For this comparative study, the authors selected the area of Lower Bavaria for lowland wood, as a great deal of wood is imported from this region to western Austria. At first, the felling area is described for both regions, from forest site to sawmill. Thereby, the authors create mean values related to timber harvesting and transportation, which are applicable to the whole of western Austria and Lower Bavaria, southern Germany. Secondly, the eco-balance of mountain and lowland wood is established. It is based on the following impact categories： global warming potential, acidification potential, eutrophication potential, ozone depletion potential and non-renewable primary energy. The environmental impact is more expressive if the results are applied to a specific construction part （i.e., glued laminated timber-ceiling）. Our research study showed the eco-balance of western Austrian mountain wood is more favourable than the environmental impact of harvesting lowland wood in southern Germany.

Greenhouse Gas Emission from Inland Open Water Bodies and Their Estimation Process—An Emerging Issue in the Era of Climate Change

The persistent rise in concentrations of greenhouse gases (GHGs) in the earth’s atmosphere is responsible for global warming and climate change. Besides the known source of GHGs emissions like energy, industry, and agriculture, intrinsic emissions from natural inland water bodies like wetland, rivers, reservoirs, estuaries, etc. have also been identified as other hotspots of GHGs emission and gaining the attention of the scientific communities in recent times. Inland fisheries in India are threatened by climate changes such as a change in temperature, precipitation, droughts, storm, sea-level rise, saltwater intrusion, floods that affect mostly the production, productivity and ultimately affect the fishers’ livelihood. There are, however, different mitigation and adaptation strategies to cope with the effects of climate change. Carbon sequestration and other related management interventions are one of the options available minimizing GHGs emissions from inland open waters, particularly the wetlands and coastal mangroves which are well known worldwide for their significant role in the storage of carbon. Assessment of C efflux from exposed sediments in dry streams, reservoirs, lakes, rivers, and ponds into the atmosphere can be considered imperative for a better understanding of their role as a C-sink or as a C-source to the atmosphere.

Global warming potential analysis of bio‑jet fuel based on life cycle assessment

Due to the large amount of greenhouse gas(GHG)emissions and the high dependence on fossil energy,the aviation industry has attracted a lot of attention for emission reduction and sustainable development.Biomass is a green and sustainable renewable resource,and its chemical conversion to produce bio-jet fuel is considered to be an effective way to replace fossil jet fuel and achieve emission reduction.In this study,the cradle-to-grave life cycle analysis is conducted for three bio-jet fuel conversion pathways,including biomass aqueous phase reforming(APR),hydrogenated esters and fatty acids(HEFA),and hydrothermal liquefaction(HTL).Compared with fossil jet fuels,the three bio-jet fuels have a great advantage on global warming potential(GWP),contributing 29.2,43.6 and 51.2 g CO_(2)-eq/MJ respectively.In general,as a relatively new bio-jet fuel conversion technology,the technology of aqueous phase reforming has minimal environmental impact.If the barriers of raw material availability and economy could be broken down,bio-jet fuel will have great development potential in replacing fossil jet fuel and realizing sustainable development.

ENVIRONMENTAL IMPACT ASSESSMENT OF LIGHT-FRAME AND TIMBER FRAME STRUCTURES

The objective of this study was to analyze the environmental performance of different wood structural assemblies for residential buildings.Two structural systems(a traditional timber frame and a light-frame)were compared together with alternate material options for each system.Environmental impacts were determined using the Athena Impact Estimator for Buildings software.Design alterations for generalization were made to an existing timber frame(TF)structure used as the basis of this analysis,and an equivalent light-frame(LF)structure was designed based on the International Residential Code(IRC).Environmental impacts observed include total energy consumption,fossil fuel consumption,global warming potential(GWP),and wood fiber use.All analyses were considered cradle-to-gate,including the manufacturing and construction life-cycle stages.Results show how GWP is linked to both fossil fuel consumption and wood fiber use,and how ultimate environmental impact is driven by energy source.Environmental impacts of structures are driven by material choice,and levels of carbon stored in structural wood serve to decrease GWP.Of the structural assemblies analyzed,the most traditional TF structure outperformed all other options in almost every measure.

Global methane and nitrous oxide emissions from terrestrial ecosystems due to multiple environmental changes

Greenhouse gas(GHG)-induced climate change is among the most pressing sustainability challenges facing humanity today,posing serious risks for ecosystem health.Methane(CH_(4))and nitrous oxide(N_(2)O)are the two most important GHGs after carbon dioxide(CO_(2)),but their regional and global budgets are not well known.In this study,we applied a process-based coupled biogeochemical model to concurrently estimate the magnitude and spatial and temporal patterns of CH_(4)and N_(2)O fluxes as driven by multiple environmental changes,including climate variability,rising atmospheric CO_(2),increasing nitrogen deposition,tropospheric ozone pollution,land use change,and nitrogen fertilizer use.The estimated CH_(4)and N_(2)O emissions from global land ecosystems during 1981-2010 were 144.39±12.90 Tg C/yr(mean 62 SE;1 Tg=1012 g)and 12.52±0.74 Tg N/yr,respectively.Our simulations indicated a significant(P,0.01)annually increasing trend for CH_(4)(0.43±0.06 Tg C/yr)and N_(2)O(0.14±0.02 Tg N/yr)in the study period.CH_(4)and N_(2)O emissions increased significantly in most climatic zones and continents,especially in the tropical regions and Asia.The most rapid increase in CH_(4)emission was found in natural wetlands and rice fields due to increased rice cultivation area and climate warming.N_(2)O emission increased substantially in all the biome types and the largest increase occurred in upland crops due to increasing air temperature and nitrogen fertilizer use.Clearly,the three major GHGs(CH_(4),N_(2)O,and CO_(2))should be simultaneously considered when evaluating if a policy is effective to mitigate climate change.

Effects of different organic fertilizers on nitrous oxide and methane emissions from double-cropping rice fields

Rice fields are a major source of greenhouse gases,such as nitrous oxide (N_(2)O) and methane (CH_(4)).Organic fertilizers may potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth;however,the simultaneous effects of organic fertilizers on N_(2)O and CH_(4)emissions and crop yield in paddy fields remain poorly understood and quantified.In this study,experimental plots were established in conventional double-cropping paddy fields in the Pearl River Delta,China,including an unfertilized control and five fertilizer treatments with fresh organic fertilizer (FOF),successively composted organic fertilizer (SOF),chemically composted organic fertilizer (COF),COF supplemented with inorganic fertilizer (COIF),and chemical fertilizers (CFs)(TFOF,TSOF,TCOF,TCOIF,and TCF,respectively).Paddy field soils behaved simultaneously as an N_(2)O sink (cumulative N_(2)O emission:-196 to-381 g N ha^(-1)) and as a CH_(4)source (cumulative CH_(4)emission:719 to 2 178 kg ha^(-1)).Compared to CFs,the effects of organic fertilizers on N_(2)O emission were not significant.In contrast,total annual CH_(4)emission increased by 157%,132%,125%,and 37%in TFOF,TCOF,TSOF,and TCOIF,respectively,compared to TCF.In TCOIF,rice yield was maintained,while CH_(4)emission was not significantly increased from the paddy fields characterized by a prolonged flood period.An important next step is to extend these field-based measurements to larger rice cultivation areas to quantify the regional and national-scale impacts on greenhouse gas emissions and to help determine the optimum practice for fertilizer use.

Methane and nitrous oxide emissions in rice-crab culture systems of northeast China

Rice-crab integrated ecosystem has been confirmed to improve the ecological environment and brought greater economic benefits.In order to know greenhouse gases methane(CH_(4))and nitrous oxide(N_(2)O)emissions in ricecrab system,they were quantified from a flooding rice field in northeast China,as affected by integrated ricecrab cultivation.Three treatments with three replications each were given:(1)RC1-rice with crab(megalopa),(2)RC2-rice with crab(juvenile),(3)RM-rice only.Seasonal CH_(4) and N_(2)O fluxes were measured by closed chamber method.Compared with RM treatment,RC1 and RC2 treatments greatly enhanced the cumulative seasonal CH_(4) emissions(by 36.8%and 29.2%,respectively),and reduced the cumulative seasonal N_(2)O emissions(by 28.2%and 19.7%,respectively).Across treatments,CH_(4) represented over 97%of total global warming potential(GWP)and as a result,RC1 and RC2 treatments significantly increased the GWP than RM treatment.Although the GWP was highest in RC1 treatment,it provided highest rice yield(8780 kg/ha)and net ecosystem economic budget(NEEB,23,159 Yuan/ha)over RM(7668 kg/ha,15,130 Yuan/ha)and RC2(8042 kg/ha,18,713 Yuan/ha)treatments.To summarize,cultivation of megalopa in rice field is a better strategy to optimize the economic and environmental benefits in northeast China.