The terrestrial ecosystem may be either a source or a sink of CH_4 in rice paddies, depending, to a great extent, on the change of ecosystem types and land use patterns. CH_4 emission fluxes from paddy fields under 4 ...The terrestrial ecosystem may be either a source or a sink of CH_4 in rice paddies, depending, to a great extent, on the change of ecosystem types and land use patterns. CH_4 emission fluxes from paddy fields under 4 cultivation patterns (conventional plain culture of rice(T1), no-tillage and ridge culture of rice(T2), no-tillage and ridge culture of rice and wheat (T3), and rice-wheat rotation(T4)) were measured with the closed chamber technique in 1996 and 1998 in Chongqing, China. The results showed that differences existed in CH_4 emission from paddy fields under these land management practices. In 1996 and 1998, CH_4 emission was 71 48% and 78 82%(T2), 65 93% and 57 18%(T3), and 61 53% and 34 22%(T4) of that in T1 during the rice growing season. During the non-rice growing season, CH_4 emission from rice fields was 76 23% in T2 and 38 69% in T1 The accumulated annual CH_4 emission in T2, T3 and T4 in 1996 decreased by 33 53%, 63 30% and 65 73%, respectively, as compared with that in T1 In 1998, the accumulated annual CH_4 emission in T1, T2, T3 and T4 was 116 96 g/m^2, 68 44 g/m^2, 19 70 g/m^2 and 11 80 g/m^2, respectively. Changes in soil physical and chemical properties, in thermal and moisture conditions in the soil and in rice plant growth induced by different land use patterns were the dominant causes for the difference in CH_4 emission observed. The relative contribution of various influencing factors to CH_4 emission from paddy fields differed significantly under different land use patterns. However, the general trend was that chlorophyll content in rice leaves, air temperature and temperature at the 5 cm soil layer play a major role in CH_4 emission from paddy fields and the effects of illumination, relative humidity and water layer depth in the paddy field and CH_4 concentration in the crop canopy were relatively non-significant. Such conservative land use patterns as no-tillage and ridge culture of rice with or without rotation with wheat are thought to be beneficial to reducing CH_4 emission from paddy fields and are, therefore, recommended as a significant solution to the problems of global(climatic) change.展开更多
Using the closed chamber technique, the in situ measurements of N2O and CH4 fluxes was conducted in a broad-leaved Korean pine mixed forest ecosystem in Changbai Mountain, China. from June 1994 to october 1995. The re...Using the closed chamber technique, the in situ measurements of N2O and CH4 fluxes was conducted in a broad-leaved Korean pine mixed forest ecosystem in Changbai Mountain, China. from June 1994 to october 1995. The relationships between fluxes (N2O and CH4) and some major environmental factors (temperature, soil water content and soil availabIe nitrogen) were studied. A significant positive correlation between Nzo emission and air/soil temperature was observed, but no significant correIation was found between N2O emission and soil water content (SWC). This result showed that temperature was an important controlling factor of N2O flux. There was a significant correlation between CH4 uptake and SWC, but no significant correlation was found between CH4 uptake and temperature. This suggested SWC was an important factor controlling CH4 uptake. The very significant negative correlation between logarithmic N2O flux and soil nitrate concentration, significant negative correlation between CH4 flux and soil ammonium content were also found.展开更多
Developed regions of the world represent a major atmospheric methane(CH_4) source,but these regional emissions remain poorly constrained.The Yangtze River Delta(YRD) region of China is densely populated(about 16% of C...Developed regions of the world represent a major atmospheric methane(CH_4) source,but these regional emissions remain poorly constrained.The Yangtze River Delta(YRD) region of China is densely populated(about 16% of China's total population) and consists of large anthropogenic and natural CH_4 sources.Here,atmospheric CH_4 concentrations measured at a 70-m tall tower in the YRD are combined with a scale factor Bayesian inverse(SFBI) modeling approach to constrain seasonal variations in CH_4 emissions.Results indicate that in 2018 agricultural soils(AGS,rice production) were the main driver of seasonal variability in atmospheric CH_4 concentration.There was an underestimation of emissions from AGS in the a priori inventories(EDGAR—Emissions Database for Global Atmospheric Research v432 or v50),especially during the growing seasons.Posteriori CH_4 emissions from AGS accounted for 39%(4.58 Tg,EDGAR v432) to 47%(5.21 Tg,EDGAR v50) of the total CH_4 emissions.The posteriori natural emissions(including wetlands and water bodies) were1.21 Tg and 1.06 Tg,accounting for 10.1%(EDGAR v432) and 9.5%(EDGAR v50) of total emissions in the YRD in2018.Results show that the dominant factor for seasonal variations in atmospheric concentration in the YRD was AGS,followed by natural sources.In summer,AGS contributed 42%(EDGAR v432) to 64%(EDGAR v50) of the CH_4 concentration enhancement while natural sources only contributed about 10%(EDGAR v50) to 15%(EDGAR v432).In addition,the newer version of the EDGAR product(EDGAR v50) provided more reasonable seasonal distribution of CH_4 emissions from rice cultivation than the old version(EDGAR v432).展开更多
Soil samples were taken from depth of 0-12cm in the virgin broad- leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L-1 and 200 μL·L-1 CH4 and N2O concentration were supplied for a...Soil samples were taken from depth of 0-12cm in the virgin broad- leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L-1 and 200 μL·L-1 CH4 and N2O concentration were supplied for analysis. Laboratory study on CH4 oxidation and N2O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N2O. Air-dried soil sample could not oxidize atmospheric methane, but could produCt N2O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L-1. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N2O emissions within 2 hours. There were curvilinear correlations between N2O emission and temperature (r2=0.706, p <0.05), and between N2O emission andtwater content (r2=0.2968. p <0.05). These suggested temperature and water content were important factors controlling N2O emission. The correlation between CH4 oxidization and temperature was also found while CH4 was supplied 200 μL·L-1 (r2 =0.3573, p<0.05). Temperature was an important f8Ctor controlling CH4 oxidation. However, when 20 μL·L-1 CH4 was supplied, there was no correlation among CH4 oxidization, N2O emission, temperature and water content.展开更多
Little has been done in measurement and research of the flux of CH4 emission from paddy fields in Changchun area, Jilin Province, China before 1994. So the purpose of the study is to offer available regional data of C...Little has been done in measurement and research of the flux of CH4 emission from paddy fields in Changchun area, Jilin Province, China before 1994. So the purpose of the study is to offer available regional data of CH4 emission flux and to discuss the factors which affect CH4 emission from paddy fields. Experimental paddy fields are chosen using TM pictures respectively in Xinlicheng (43° 49′ N, 125° 20′ E) of the Yitong River’s and in Wanchang (43° 44′ 10″ N, 125° 53′ 11″ E) of the Yinma River’s alluvial plain. The fluxes of CH4 emission from paddy fields are measured by the method of static chamber in Changchun area in 3 consecutive years. The research results show that the peak of CH4 emission from paddy fields occurs during the booting stage. The mean fluxes of CH4 emission are 7.056 mg/(m2· h) and 0.489 mg/(m2· h) in the paddy fields of flood and discontinuous irrigation respectively. The contrastive study holds that climate condition, the way of water management and fertilizer variation have significant influence on fluxes of CH4 emission from paddy fields. The difference of climatic conditions causes the interannual change of the flux of CH4 emission from paddy fields. In general, the flux of CH4 emission from paddy fields of flood irrigation is greater than that from paddy fields of discontinuous irrigation. To change the way of water management perhaps is an available way to reduce CH4 emission flux from paddy fields.展开更多
Wetland ecosystems are the most important natural methane(CH_(4))sources,whose fluxes periodically fluctuate.Methanogens(methane producers)and methanotrophs(methane consumers)are considered key factors affecting CH_(4...Wetland ecosystems are the most important natural methane(CH_(4))sources,whose fluxes periodically fluctuate.Methanogens(methane producers)and methanotrophs(methane consumers)are considered key factors affecting CH_(4)fluxes in wetlands.However,the symbiotic relationship between methanogens and methanotrophs remains unclear.To help close this research gap,we collected and analyzed samples from four soil depths in the Dajiuhu subalpine peatland in January,April,July,and October 2019 and acquired seasonal methane flux data from an eddy covariance(EC)system,and investigated relationships.A phylogenetic molecular ecological networks(pMENs)analysis was used to identify keystone species and the seasonal variations of the co-occurrence patterns of methanogenic and methanotrophic communities.The results indicate that the seasonal variations of the interactions between methanogenic and methanotrophic communities contributed to CH_(4)emissions in wetlands.The keystone species discerned by the network analysis also showed their importance in mediating CH_(4)fluxes.Methane(CH_(4))emissions in wetlands were lowest in spring;during this period,the most complex interactions between microbes were observed,with intense competition among methanogens while methanotrophs demonstrated better cooperation.Reverse patterns manifested themselves in summer when the highest CH_(4)flux was observed.Methanoregula formicica was negatively correlated with CH_(4)fluxes and occupied the largest ecological niches in the spring network.In contrast,both Methanocella arvoryzae and Methylocystaceae demonstrated positive correlations with CH_(4)fluxes and were better adapted to the microbial community in the summer.In addition,soil temperature and nitrogen were regarded as significant environmental factors to CH_(4)fluxes.This study was successful in explaining the seasonal patterns and microbial driving mechanisms of CH_(4)emissions in wetlands.展开更多
Biochar amendment is generally recognized as an effective mitigation option of methane(CH_(4))emissions from rice cultivation.Although its mitigation mechanisms are not well understood,the potential relevance of surfa...Biochar amendment is generally recognized as an effective mitigation option of methane(CH_(4))emissions from rice cultivation.Although its mitigation mechanisms are not well understood,the potential relevance of surface area and porosity of biochar has been discussed.This study aimed to evaluate the application of different biochar particle sizes on CH_(4) production,oxidation,and emissions from rice cultivation in a clay loam soil,based on the assumption that porosity and surface area of biochar are directly related to its mitigation effects.Rice was grown under greenhouse conditions for two growing seasons,either with 0.5–2 mm(small,SB)or with 2–4 mm(large,LB)biochar.The results show that both sizes of biochar increased soil pH and redox potential(Eh)during rice growth.Soil dissolved organic carbon(DOC),nitrate(NO^(−)_(3)),and sulfate(SO^(2−)_(4))also increased under both biochar amendments,but size effects were not observed.SB and LB suppressed the abundance of CH_(4) producers(methanogens)but stimulated the abundance of CH_(4) consumers(methanotrophs).The increase of soil Eh and electron acceptors(NO^(−)_(3)and SO^(2−)_(4))indicated the increase in soil oxidation capacity is a barrier to CH_(4) production by methanogens in both biochar treatments.Laboratory incubation experiments showed that CH_(4) production activity was significantly(p≤0.05)reduced by 18.5%using SB and by 11.3%using LB compared to the control.In contrast,the stimulation of methanotrophs promoted greater CH_(4) oxidation activity by 15.0%in SB and 18.7%in LB compared to the control.It shows that CH_(4) production was reduced more by larger surface area biochar(SB),while a greater increase in CH_(4) oxidation was found using larger pore volume biochar(LB).The effects on CH_(4) production were more pronounced than those on CH_(4) oxidation,resulting in a greater reduction of cumulative CH_(4) emissions by SB than LB(by 26.6%and 19.9%compared to control,respectively).展开更多
Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions ...Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions on soil CH_(4) flux in tropical rainforests are still poorly understood.From January 2015 to December 2018,a field experiment was conducted in a primary tropical montane rainforest(PTMR)and a secondary tropical montane rainforest(STMR)in southern China to quantify the impact of N additions at four levels(N0:0 kg N⋅ha^(-1)⋅year^(-1);N25:25 kg N⋅ha^(-1)⋅year^(-1);N50:50 kg N⋅ha^(-1)⋅year^(-1);N100:100 kg N⋅ha^(-1)⋅year^(-1)on soil CH_(4) flux.Results:Four years of measurements showed clear seasonal variations in CH_(4) flux in all treatment plots for both forest types(PTMR and STMR),with lower rates of soil CH_(4) uptake during the wet season and higher rates of soil CH_(4) uptake during the dry season.Soil CH_(4) uptake rates were significantly and negatively correlated with both soil temperature and soil moisture for both forest types.Annual CH_(4) uptake for the N0 plots from the PTMR and STMR soils were2.20 and1.98 kg N⋅ha^(-1)⋅year^(-1),respectively.At the PTMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 19%,29%,and 36%for the N25,N50,and N100 treatments,respectively.At the STMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 15%,18%,and 38%for the N25,N50,and N100 treatments,respectively.High level N addition had a stronger inhibitory impact on soil CH_(4) uptake than did the low level N addition.Conclusion:Our data suggest that soil CH_(4) uptake in tropical rainforests is sensitive to N deposition.If atmospheric N deposition continues to increase in the future,the soil CH_(4) sink strength of tropical rainforests may weaken further.展开更多
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...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.展开更多
Rice(Oryza sativa L.)paddies are increasingly threatened by cadmium(Cd)pollution,and potentially serve as CH_(4)emitters to the atmosphere.Remediation agents widely mitigate Cd pollution in paddy soil,however,we know ...Rice(Oryza sativa L.)paddies are increasingly threatened by cadmium(Cd)pollution,and potentially serve as CH_(4)emitters to the atmosphere.Remediation agents widely mitigate Cd pollution in paddy soil,however,we know little about their regulations on CH_(4)emission.Here,via adding biochar(B),sulfhydryl-modified palygorskite(SMP),and selenium foliar fertilizer(SFF),we conducted a pot experiment to investigate soil and rice Cd contents together with in-situ CH_(4)f luxes.Compared to CK,the addition of SMP,SFF,and B-SMP reduced Cd in brown rice by 25%to 50%,25%,and 50%to 75%,respectively.Agents 7%B,7%B-0.01%SMP,and SFF reduced CH_(4)emissions by 8.46%,5.30%,and 4.11%,respectively.CH_(4)emission increased gradually along the growing season,with the cumulative CH_(4)fluxes ranging between 338.82 and 619.13 kg hm^(-2).Our results highlight that mixed 7%B-0.01%SMP and SFF showed collaborative eff ects on Cd remediation and CH_(4)emission.This study reveals the feasibility of reducing Cd pollution and CH_(4)emission in karst rice paddies,which hopes to supplement the knowledge of collaborative controls on soil remediation and carbon emission.展开更多
To understand the CH_(4) flux variations and their climatic drivers in the rice-wheat agroecosystem in the Huai River Basin of China,the CH_(4) flux was observed by using open-path eddy covariance at a typical rice-wh...To understand the CH_(4) flux variations and their climatic drivers in the rice-wheat agroecosystem in the Huai River Basin of China,the CH_(4) flux was observed by using open-path eddy covariance at a typical rice-wheat rotation system in Anhui Province,China from November 2019 to October 2021.The variations and their drivers were then analyzed with the Akaike information criterion method.CH_(4) flux showed distinct diurnal variations with single peaks during 9:00-13:00 local time.The highest peak was 2.15μg m^(-2)s^(-1)which occurred at 11:00 in the vegetative growth stage in the rice growing season(RGS).CH_(4) flux also showed significant seasonal variations.The average CH_(4)flux in the vegetative growth stage in the RGS(193.8±74.2 mg m^(-2)d^(-1))was the highest among all growth stages.The annual total CH_(4) flux in the non-rice growing season(3.2 g m^(-2))was relatively small compared to that in the RGS(23.9 g m^(-2)).CH_(4) flux increased significantly with increase in air temperature,soil temperature,and soil water content in both the RGS and the non-RGS,while it decreased significantly with increase in vapor pressure deficit in the RGS.This study provided a comprehensive understanding of the CH_(4) flux and its drivers in the rice-wheat rotation agroecosystem in the Huai River Basin of China.In addition,our findings will be helpful for the validation and adjustment of the CH_(4) models in this region.展开更多
A simulation model developed by the authors (Huang et al., 1999) was validated against independent field measurements of methane emission from rice paddy soils in Texas of USA, Tuzu Of China and Vercelli of Italy.A si...A simulation model developed by the authors (Huang et al., 1999) was validated against independent field measurements of methane emission from rice paddy soils in Texas of USA, Tuzu Of China and Vercelli of Italy.A simplified version of the simulation model was further validated against methane emission measurements from various regions of the world, including italy, China, Indonesia, Philippines and the United States. Model validation suggested that the seasonal variation of methane emission was mainly regulated by rice growth and development and that methane emission could be predicted from rice net productivity, cultivar character, soil texture and temperature, and organic matter amendments. Model simulations in general agreed with the observations. The comparison between computed and measured methane emission resulted in correlation coefficients r2 values from 0.450 to 0.952, significant at 0.01-0.001 probability level.On the basis of available information on rice cultivated area, growth duration, grain yield, soil texture and temperature, methane emission from rice paddy soils of China's Mainland was estimated for 28 rice cultivated provinces/municipal cities by employing the validated model. The calculated daily methane emission rates, on a provincial scale, ranged from 0.12 to 0.71 g m-2 with an average of 0.26 g m-2. A total amount of 7.92 Tg CH4 per year, ranging from 5.89 to 11.17 Tg year-1, was estimated to be released from Chinese rice paddy soils. Of the total, 45% was emitted from the single-rice growing season, and 19% and 36% were from the early-rice and the late-rice growing seasons, respectively. Approximately 70% of the total was emitted in the region located at latitude between 25°and 32°N. The emissions from rice fields in Sichuan and Hunan provinces were calculated to be 2.34 Tg year-1, accounting for approximately 30% of the total.展开更多
With an understanding of the processes of methane production, oxidation and emission, a semi-empirical model, focused on the contributions of rice plants to the processes and also the influence of environmental factor...With an understanding of the processes of methane production, oxidation and emission, a semi-empirical model, focused on the contributions of rice plants to the processes and also the influence of environmental factors, was developed to predict methane emission from rice paddy soils. In the present model, the amount of methane transported from the soil to the atmosphere was determined by the rates of CH4 production and an emitted fraction. The rates of CH4 production in irrigated rice soils were computed from the availability of methanogenic substrates that are primarily derived from rice plaaes and added organic matter and the influence of soil texture, soil redox potential and temperature. The fraction of methane emitted was assumed to be modulated by the rice plants and declines with rice growth and development. TO make it applicable to a wider area with limited data sets, a simplified version of the model was also derived to predict methane emission in a more practical manner.展开更多
The areal extent of cold freshwater wetlands on the Tibetan Plateau is estimated to be 0.133×10 6 km 2, suggesting a significant methane potential. Methane fluxes from wet alpine meadows, peatlands, Hippuris vulg...The areal extent of cold freshwater wetlands on the Tibetan Plateau is estimated to be 0.133×10 6 km 2, suggesting a significant methane potential. Methane fluxes from wet alpine meadows, peatlands, Hippuris vulgaris mires and secondary marshes were 43.18,12.96,-0.28 and 45.90 mg·m -2 ·d -1 , respectively, based on the transection studies at the Huashixia Permafrost Station from July to August 1996. Average CH 4 flux in the thaw season was extrapolated to be 5.68 g·m -2 according to the areal percentage of wetland areas in the Huashixia region. CH 4 fluxes at four fixed sites, representative of similar ecosystems, ranged from -19.384 to 347.15 mg·m -2 ·d -1 , and the average CH 4 fluxes varied from 6.54 to 71.97 mg·m -2 ·d -1 at each site from April to September 1997. CH 4 emissions at each site during the entire thaw season was estimated from 1.21 to 10.65 g·m -2 , displaying strong spatial variations. Seasonal variations of CH 4 fluxes were also observed at the four sites. It is found that CH 4 bursted in the early thaw season, and increased afterwards with rising soil temperatures. Episodic fluxes were observed in summer, which influenced the average CH 4 flux considerably. Annual CH 4 emissions from cold wetlands on the plateau were estimated at about 0.7～0.9 Tg based on the distribution of wetlands, representative CH 4 fluxes, and number of thaw days. The centers of CH 4 releasing are located in the sources of the Yangtze and Yellow Rivers, and Zoige Peatlands.展开更多
Climate change may badly affect the availability of water and soil nutrients to rice plant. Research experiments were conducted at the Environmental Science Departmental field, Bangladesh Agricultural University, Myme...Climate change may badly affect the availability of water and soil nutrients to rice plant. Research experiments were conducted at the Environmental Science Departmental field, Bangladesh Agricultural University, Mymensingh during July 2017 to June 2019, to find out the suitable combination of biochar with inorganic fertilizers for minimizing seasonal yield scaled CH<sub>4</sub> emissions, reducing global warming potentials (GWPs) and sustainable rice farming under feasible irrigation practices. There were ten experimental treatments with different combinations of inorganic NPKS fertilizers and biochar (15 - 30 t/ha) under conventional flooding (CF) and alternate wetting-drying irrigations (AWDI). This study revealed that NPKS fertilization (50% of the recommended doze) with 15 t/ha biochar amendments under AWD irrigation maximized rice yield 6750 kg/ha and 4380 kg/ha in dry boro and wet aman seasons respectively, while the lowest rice yield 1850 kg/ha and 1550 kg/ha were recorded in continuously irrigated control treatment (T<sub>1</sub>) during the dry and wet seasons respectively. Seasonal cumulative CH<sub>4</sub> emission, yield scaled CH<sub>4 </sub>emission and GWPs were suppressed significantly with biochar amendments 15 - 30 t/ha under both conventional and AWDI irrigation systems during the wet and dry seasons of rice cultivation. Significant interactions were observed among biochar amendments and irrigation practices during the dry boro rice cultivation. Dry seasonal cumulative CH<sub>4</sub> emissions were decreased by 14.7%, 18.9% and 24.8% with biochar amendments at 15 t/ha, 20 t/ha and 30 t/ha respectively under conventional irrigation;while cumulative CH<sub>4</sub> emissions were reduced by 10.6%, 26% and 41.6% respectively, under AWDI system. Finally, total global warming potentials (GWPs) were decreased by 6% - 15%, 13% - 30% with biochar amendments under conventional and AWDI irrigations respectively, in wet season;while global warming potentials (GWPs) also decreased by 14% - 25%, 11% - 42% with biochar amendments under conventional and AWDI irrigations, respectively, in the dry boro season. Biochar amendments increased water productivity index to some extent, but AWD irrigations significantly increased water productivity over the conventional irrigation in both wet and dry seasons. After experimental period, it was found that soil porosity, redox status, soil organic carbon (SOC) as well as overall soil properties were improved significantly with biochar amendments and AWD irrigations. Conclusively, biochar amendments @15 - 20 t/ha with half of the recommended inorganic (NPKS) fertilizers under alternate wetting-drying irrigations revealed an environment friendly integrated package approach to reduce seasonal cumulative CH<sub>4</sub> emissions as well as GWPs, while improving rice rhizosphere environment and rice productivity to meet the national food security.展开更多
文摘The terrestrial ecosystem may be either a source or a sink of CH_4 in rice paddies, depending, to a great extent, on the change of ecosystem types and land use patterns. CH_4 emission fluxes from paddy fields under 4 cultivation patterns (conventional plain culture of rice(T1), no-tillage and ridge culture of rice(T2), no-tillage and ridge culture of rice and wheat (T3), and rice-wheat rotation(T4)) were measured with the closed chamber technique in 1996 and 1998 in Chongqing, China. The results showed that differences existed in CH_4 emission from paddy fields under these land management practices. In 1996 and 1998, CH_4 emission was 71 48% and 78 82%(T2), 65 93% and 57 18%(T3), and 61 53% and 34 22%(T4) of that in T1 during the rice growing season. During the non-rice growing season, CH_4 emission from rice fields was 76 23% in T2 and 38 69% in T1 The accumulated annual CH_4 emission in T2, T3 and T4 in 1996 decreased by 33 53%, 63 30% and 65 73%, respectively, as compared with that in T1 In 1998, the accumulated annual CH_4 emission in T1, T2, T3 and T4 was 116 96 g/m^2, 68 44 g/m^2, 19 70 g/m^2 and 11 80 g/m^2, respectively. Changes in soil physical and chemical properties, in thermal and moisture conditions in the soil and in rice plant growth induced by different land use patterns were the dominant causes for the difference in CH_4 emission observed. The relative contribution of various influencing factors to CH_4 emission from paddy fields differed significantly under different land use patterns. However, the general trend was that chlorophyll content in rice leaves, air temperature and temperature at the 5 cm soil layer play a major role in CH_4 emission from paddy fields and the effects of illumination, relative humidity and water layer depth in the paddy field and CH_4 concentration in the crop canopy were relatively non-significant. Such conservative land use patterns as no-tillage and ridge culture of rice with or without rotation with wheat are thought to be beneficial to reducing CH_4 emission from paddy fields and are, therefore, recommended as a significant solution to the problems of global(climatic) change.
文摘Using the closed chamber technique, the in situ measurements of N2O and CH4 fluxes was conducted in a broad-leaved Korean pine mixed forest ecosystem in Changbai Mountain, China. from June 1994 to october 1995. The relationships between fluxes (N2O and CH4) and some major environmental factors (temperature, soil water content and soil availabIe nitrogen) were studied. A significant positive correlation between Nzo emission and air/soil temperature was observed, but no significant correIation was found between N2O emission and soil water content (SWC). This result showed that temperature was an important controlling factor of N2O flux. There was a significant correlation between CH4 uptake and SWC, but no significant correlation was found between CH4 uptake and temperature. This suggested SWC was an important factor controlling CH4 uptake. The very significant negative correlation between logarithmic N2O flux and soil nitrate concentration, significant negative correlation between CH4 flux and soil ammonium content were also found.
基金supported by the National Key R&D Program of China (Grant Nos.2020YFA0607501 and 2019YFA0607202 to WX)the Natural Science Foundation of Jiangsu Province (Grant No.BK20200802 to CH)the Key Laboratory of Meteorology and Ecological Environment of Hebei Province (Grant No.Z201901H to WX)。
文摘Developed regions of the world represent a major atmospheric methane(CH_4) source,but these regional emissions remain poorly constrained.The Yangtze River Delta(YRD) region of China is densely populated(about 16% of China's total population) and consists of large anthropogenic and natural CH_4 sources.Here,atmospheric CH_4 concentrations measured at a 70-m tall tower in the YRD are combined with a scale factor Bayesian inverse(SFBI) modeling approach to constrain seasonal variations in CH_4 emissions.Results indicate that in 2018 agricultural soils(AGS,rice production) were the main driver of seasonal variability in atmospheric CH_4 concentration.There was an underestimation of emissions from AGS in the a priori inventories(EDGAR—Emissions Database for Global Atmospheric Research v432 or v50),especially during the growing seasons.Posteriori CH_4 emissions from AGS accounted for 39%(4.58 Tg,EDGAR v432) to 47%(5.21 Tg,EDGAR v50) of the total CH_4 emissions.The posteriori natural emissions(including wetlands and water bodies) were1.21 Tg and 1.06 Tg,accounting for 10.1%(EDGAR v432) and 9.5%(EDGAR v50) of total emissions in the YRD in2018.Results show that the dominant factor for seasonal variations in atmospheric concentration in the YRD was AGS,followed by natural sources.In summer,AGS contributed 42%(EDGAR v432) to 64%(EDGAR v50) of the CH_4 concentration enhancement while natural sources only contributed about 10%(EDGAR v50) to 15%(EDGAR v432).In addition,the newer version of the EDGAR product(EDGAR v50) provided more reasonable seasonal distribution of CH_4 emissions from rice cultivation than the old version(EDGAR v432).
文摘Soil samples were taken from depth of 0-12cm in the virgin broad- leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L-1 and 200 μL·L-1 CH4 and N2O concentration were supplied for analysis. Laboratory study on CH4 oxidation and N2O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N2O. Air-dried soil sample could not oxidize atmospheric methane, but could produCt N2O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L-1. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N2O emissions within 2 hours. There were curvilinear correlations between N2O emission and temperature (r2=0.706, p <0.05), and between N2O emission andtwater content (r2=0.2968. p <0.05). These suggested temperature and water content were important factors controlling N2O emission. The correlation between CH4 oxidization and temperature was also found while CH4 was supplied 200 μL·L-1 (r2 =0.3573, p<0.05). Temperature was an important f8Ctor controlling CH4 oxidation. However, when 20 μL·L-1 CH4 was supplied, there was no correlation among CH4 oxidization, N2O emission, temperature and water content.
基金Under the auspices of Jilin Commttee of Science and Technology (grant 963416- 1), and Changchun Jingyuetan Remote Sensing Test
文摘Little has been done in measurement and research of the flux of CH4 emission from paddy fields in Changchun area, Jilin Province, China before 1994. So the purpose of the study is to offer available regional data of CH4 emission flux and to discuss the factors which affect CH4 emission from paddy fields. Experimental paddy fields are chosen using TM pictures respectively in Xinlicheng (43° 49′ N, 125° 20′ E) of the Yitong River’s and in Wanchang (43° 44′ 10″ N, 125° 53′ 11″ E) of the Yinma River’s alluvial plain. The fluxes of CH4 emission from paddy fields are measured by the method of static chamber in Changchun area in 3 consecutive years. The research results show that the peak of CH4 emission from paddy fields occurs during the booting stage. The mean fluxes of CH4 emission are 7.056 mg/(m2· h) and 0.489 mg/(m2· h) in the paddy fields of flood and discontinuous irrigation respectively. The contrastive study holds that climate condition, the way of water management and fertilizer variation have significant influence on fluxes of CH4 emission from paddy fields. The difference of climatic conditions causes the interannual change of the flux of CH4 emission from paddy fields. In general, the flux of CH4 emission from paddy fields of flood irrigation is greater than that from paddy fields of discontinuous irrigation. To change the way of water management perhaps is an available way to reduce CH4 emission flux from paddy fields.
基金supported by the National Science Foundation of China(Grant No.31971490).
文摘Wetland ecosystems are the most important natural methane(CH_(4))sources,whose fluxes periodically fluctuate.Methanogens(methane producers)and methanotrophs(methane consumers)are considered key factors affecting CH_(4)fluxes in wetlands.However,the symbiotic relationship between methanogens and methanotrophs remains unclear.To help close this research gap,we collected and analyzed samples from four soil depths in the Dajiuhu subalpine peatland in January,April,July,and October 2019 and acquired seasonal methane flux data from an eddy covariance(EC)system,and investigated relationships.A phylogenetic molecular ecological networks(pMENs)analysis was used to identify keystone species and the seasonal variations of the co-occurrence patterns of methanogenic and methanotrophic communities.The results indicate that the seasonal variations of the interactions between methanogenic and methanotrophic communities contributed to CH_(4)emissions in wetlands.The keystone species discerned by the network analysis also showed their importance in mediating CH_(4)fluxes.Methane(CH_(4))emissions in wetlands were lowest in spring;during this period,the most complex interactions between microbes were observed,with intense competition among methanogens while methanotrophs demonstrated better cooperation.Reverse patterns manifested themselves in summer when the highest CH_(4)flux was observed.Methanoregula formicica was negatively correlated with CH_(4)fluxes and occupied the largest ecological niches in the spring network.In contrast,both Methanocella arvoryzae and Methylocystaceae demonstrated positive correlations with CH_(4)fluxes and were better adapted to the microbial community in the summer.In addition,soil temperature and nitrogen were regarded as significant environmental factors to CH_(4)fluxes.This study was successful in explaining the seasonal patterns and microbial driving mechanisms of CH_(4)emissions in wetlands.
基金This study was funded by the Thailand Research Fund(TRF)through the International Research Network Program(IRN)(IRN57W0001,IRN5701PHDW06)the Joint Graduate School of Energy and Environment(JGSEE)at King Mongkut’s University of Technology Thonburi,and the Center of Excellence on Energy Technology and Environment(CEE),PERDO,Ministry of Higher Education,Science,Research and Innovation.
文摘Biochar amendment is generally recognized as an effective mitigation option of methane(CH_(4))emissions from rice cultivation.Although its mitigation mechanisms are not well understood,the potential relevance of surface area and porosity of biochar has been discussed.This study aimed to evaluate the application of different biochar particle sizes on CH_(4) production,oxidation,and emissions from rice cultivation in a clay loam soil,based on the assumption that porosity and surface area of biochar are directly related to its mitigation effects.Rice was grown under greenhouse conditions for two growing seasons,either with 0.5–2 mm(small,SB)or with 2–4 mm(large,LB)biochar.The results show that both sizes of biochar increased soil pH and redox potential(Eh)during rice growth.Soil dissolved organic carbon(DOC),nitrate(NO^(−)_(3)),and sulfate(SO^(2−)_(4))also increased under both biochar amendments,but size effects were not observed.SB and LB suppressed the abundance of CH_(4) producers(methanogens)but stimulated the abundance of CH_(4) consumers(methanotrophs).The increase of soil Eh and electron acceptors(NO^(−)_(3)and SO^(2−)_(4))indicated the increase in soil oxidation capacity is a barrier to CH_(4) production by methanogens in both biochar treatments.Laboratory incubation experiments showed that CH_(4) production activity was significantly(p≤0.05)reduced by 18.5%using SB and by 11.3%using LB compared to the control.In contrast,the stimulation of methanotrophs promoted greater CH_(4) oxidation activity by 15.0%in SB and 18.7%in LB compared to the control.It shows that CH_(4) production was reduced more by larger surface area biochar(SB),while a greater increase in CH_(4) oxidation was found using larger pore volume biochar(LB).The effects on CH_(4) production were more pronounced than those on CH_(4) oxidation,resulting in a greater reduction of cumulative CH_(4) emissions by SB than LB(by 26.6%and 19.9%compared to control,respectively).
基金funded by the National Key R&D Program of China(No.2016YFC0500203)a Natural Sciences and Engineering Research Council of Canada Discovery Grant.
文摘Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions on soil CH_(4) flux in tropical rainforests are still poorly understood.From January 2015 to December 2018,a field experiment was conducted in a primary tropical montane rainforest(PTMR)and a secondary tropical montane rainforest(STMR)in southern China to quantify the impact of N additions at four levels(N0:0 kg N⋅ha^(-1)⋅year^(-1);N25:25 kg N⋅ha^(-1)⋅year^(-1);N50:50 kg N⋅ha^(-1)⋅year^(-1);N100:100 kg N⋅ha^(-1)⋅year^(-1)on soil CH_(4) flux.Results:Four years of measurements showed clear seasonal variations in CH_(4) flux in all treatment plots for both forest types(PTMR and STMR),with lower rates of soil CH_(4) uptake during the wet season and higher rates of soil CH_(4) uptake during the dry season.Soil CH_(4) uptake rates were significantly and negatively correlated with both soil temperature and soil moisture for both forest types.Annual CH_(4) uptake for the N0 plots from the PTMR and STMR soils were2.20 and1.98 kg N⋅ha^(-1)⋅year^(-1),respectively.At the PTMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 19%,29%,and 36%for the N25,N50,and N100 treatments,respectively.At the STMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 15%,18%,and 38%for the N25,N50,and N100 treatments,respectively.High level N addition had a stronger inhibitory impact on soil CH_(4) uptake than did the low level N addition.Conclusion:Our data suggest that soil CH_(4) uptake in tropical rainforests is sensitive to N deposition.If atmospheric N deposition continues to increase in the future,the soil CH_(4) sink strength of tropical rainforests may weaken further.
文摘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.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB40020200)the National Natural Science Foundation of China(41663015,42273021)+4 种基金Guizhou Science and Technology Cooperation Basic Project([2020]1Y188)the construction project of Key Laboratory of State Ethnic Aff airs Commission([2020]No 0.91 of DDA office)the Innovation Team Project of Guizhou Higher Education([2022]013)Foundation of Guizhou Minzu University(GZMU[2019]YB11)Thanks to the support of the independent deployment project of the State Key Laboratory of Environmental Geochemistry。
文摘Rice(Oryza sativa L.)paddies are increasingly threatened by cadmium(Cd)pollution,and potentially serve as CH_(4)emitters to the atmosphere.Remediation agents widely mitigate Cd pollution in paddy soil,however,we know little about their regulations on CH_(4)emission.Here,via adding biochar(B),sulfhydryl-modified palygorskite(SMP),and selenium foliar fertilizer(SFF),we conducted a pot experiment to investigate soil and rice Cd contents together with in-situ CH_(4)f luxes.Compared to CK,the addition of SMP,SFF,and B-SMP reduced Cd in brown rice by 25%to 50%,25%,and 50%to 75%,respectively.Agents 7%B,7%B-0.01%SMP,and SFF reduced CH_(4)emissions by 8.46%,5.30%,and 4.11%,respectively.CH_(4)emission increased gradually along the growing season,with the cumulative CH_(4)fluxes ranging between 338.82 and 619.13 kg hm^(-2).Our results highlight that mixed 7%B-0.01%SMP and SFF showed collaborative eff ects on Cd remediation and CH_(4)emission.This study reveals the feasibility of reducing Cd pollution and CH_(4)emission in karst rice paddies,which hopes to supplement the knowledge of collaborative controls on soil remediation and carbon emission.
基金supported by the Natural Science Foundation of Jiangsu Province,China(BK20220017)the Innovation Development Project of China Meteorological Administration(CXFZ2023J073)+1 种基金the Key Research and Development Program of Anhui Province,China(2022M07020003)the Graduate Student Practice and Innovation Program of Jiangsu Province,China(SJCX22_0374)。
文摘To understand the CH_(4) flux variations and their climatic drivers in the rice-wheat agroecosystem in the Huai River Basin of China,the CH_(4) flux was observed by using open-path eddy covariance at a typical rice-wheat rotation system in Anhui Province,China from November 2019 to October 2021.The variations and their drivers were then analyzed with the Akaike information criterion method.CH_(4) flux showed distinct diurnal variations with single peaks during 9:00-13:00 local time.The highest peak was 2.15μg m^(-2)s^(-1)which occurred at 11:00 in the vegetative growth stage in the rice growing season(RGS).CH_(4) flux also showed significant seasonal variations.The average CH_(4)flux in the vegetative growth stage in the RGS(193.8±74.2 mg m^(-2)d^(-1))was the highest among all growth stages.The annual total CH_(4) flux in the non-rice growing season(3.2 g m^(-2))was relatively small compared to that in the RGS(23.9 g m^(-2)).CH_(4) flux increased significantly with increase in air temperature,soil temperature,and soil water content in both the RGS and the non-RGS,while it decreased significantly with increase in vapor pressure deficit in the RGS.This study provided a comprehensive understanding of the CH_(4) flux and its drivers in the rice-wheat rotation agroecosystem in the Huai River Basin of China.In addition,our findings will be helpful for the validation and adjustment of the CH_(4) models in this region.
文摘A simulation model developed by the authors (Huang et al., 1999) was validated against independent field measurements of methane emission from rice paddy soils in Texas of USA, Tuzu Of China and Vercelli of Italy.A simplified version of the simulation model was further validated against methane emission measurements from various regions of the world, including italy, China, Indonesia, Philippines and the United States. Model validation suggested that the seasonal variation of methane emission was mainly regulated by rice growth and development and that methane emission could be predicted from rice net productivity, cultivar character, soil texture and temperature, and organic matter amendments. Model simulations in general agreed with the observations. The comparison between computed and measured methane emission resulted in correlation coefficients r2 values from 0.450 to 0.952, significant at 0.01-0.001 probability level.On the basis of available information on rice cultivated area, growth duration, grain yield, soil texture and temperature, methane emission from rice paddy soils of China's Mainland was estimated for 28 rice cultivated provinces/municipal cities by employing the validated model. The calculated daily methane emission rates, on a provincial scale, ranged from 0.12 to 0.71 g m-2 with an average of 0.26 g m-2. A total amount of 7.92 Tg CH4 per year, ranging from 5.89 to 11.17 Tg year-1, was estimated to be released from Chinese rice paddy soils. Of the total, 45% was emitted from the single-rice growing season, and 19% and 36% were from the early-rice and the late-rice growing seasons, respectively. Approximately 70% of the total was emitted in the region located at latitude between 25°and 32°N. The emissions from rice fields in Sichuan and Hunan provinces were calculated to be 2.34 Tg year-1, accounting for approximately 30% of the total.
文摘With an understanding of the processes of methane production, oxidation and emission, a semi-empirical model, focused on the contributions of rice plants to the processes and also the influence of environmental factors, was developed to predict methane emission from rice paddy soils. In the present model, the amount of methane transported from the soil to the atmosphere was determined by the rates of CH4 production and an emitted fraction. The rates of CH4 production in irrigated rice soils were computed from the availability of methanogenic substrates that are primarily derived from rice plaaes and added organic matter and the influence of soil texture, soil redox potential and temperature. The fraction of methane emitted was assumed to be modulated by the rice plants and declines with rice growth and development. TO make it applicable to a wider area with limited data sets, a simplified version of the model was also derived to predict methane emission in a more practical manner.
文摘The areal extent of cold freshwater wetlands on the Tibetan Plateau is estimated to be 0.133×10 6 km 2, suggesting a significant methane potential. Methane fluxes from wet alpine meadows, peatlands, Hippuris vulgaris mires and secondary marshes were 43.18,12.96,-0.28 and 45.90 mg·m -2 ·d -1 , respectively, based on the transection studies at the Huashixia Permafrost Station from July to August 1996. Average CH 4 flux in the thaw season was extrapolated to be 5.68 g·m -2 according to the areal percentage of wetland areas in the Huashixia region. CH 4 fluxes at four fixed sites, representative of similar ecosystems, ranged from -19.384 to 347.15 mg·m -2 ·d -1 , and the average CH 4 fluxes varied from 6.54 to 71.97 mg·m -2 ·d -1 at each site from April to September 1997. CH 4 emissions at each site during the entire thaw season was estimated from 1.21 to 10.65 g·m -2 , displaying strong spatial variations. Seasonal variations of CH 4 fluxes were also observed at the four sites. It is found that CH 4 bursted in the early thaw season, and increased afterwards with rising soil temperatures. Episodic fluxes were observed in summer, which influenced the average CH 4 flux considerably. Annual CH 4 emissions from cold wetlands on the plateau were estimated at about 0.7～0.9 Tg based on the distribution of wetlands, representative CH 4 fluxes, and number of thaw days. The centers of CH 4 releasing are located in the sources of the Yangtze and Yellow Rivers, and Zoige Peatlands.
文摘Climate change may badly affect the availability of water and soil nutrients to rice plant. Research experiments were conducted at the Environmental Science Departmental field, Bangladesh Agricultural University, Mymensingh during July 2017 to June 2019, to find out the suitable combination of biochar with inorganic fertilizers for minimizing seasonal yield scaled CH<sub>4</sub> emissions, reducing global warming potentials (GWPs) and sustainable rice farming under feasible irrigation practices. There were ten experimental treatments with different combinations of inorganic NPKS fertilizers and biochar (15 - 30 t/ha) under conventional flooding (CF) and alternate wetting-drying irrigations (AWDI). This study revealed that NPKS fertilization (50% of the recommended doze) with 15 t/ha biochar amendments under AWD irrigation maximized rice yield 6750 kg/ha and 4380 kg/ha in dry boro and wet aman seasons respectively, while the lowest rice yield 1850 kg/ha and 1550 kg/ha were recorded in continuously irrigated control treatment (T<sub>1</sub>) during the dry and wet seasons respectively. Seasonal cumulative CH<sub>4</sub> emission, yield scaled CH<sub>4 </sub>emission and GWPs were suppressed significantly with biochar amendments 15 - 30 t/ha under both conventional and AWDI irrigation systems during the wet and dry seasons of rice cultivation. Significant interactions were observed among biochar amendments and irrigation practices during the dry boro rice cultivation. Dry seasonal cumulative CH<sub>4</sub> emissions were decreased by 14.7%, 18.9% and 24.8% with biochar amendments at 15 t/ha, 20 t/ha and 30 t/ha respectively under conventional irrigation;while cumulative CH<sub>4</sub> emissions were reduced by 10.6%, 26% and 41.6% respectively, under AWDI system. Finally, total global warming potentials (GWPs) were decreased by 6% - 15%, 13% - 30% with biochar amendments under conventional and AWDI irrigations respectively, in wet season;while global warming potentials (GWPs) also decreased by 14% - 25%, 11% - 42% with biochar amendments under conventional and AWDI irrigations, respectively, in the dry boro season. Biochar amendments increased water productivity index to some extent, but AWD irrigations significantly increased water productivity over the conventional irrigation in both wet and dry seasons. After experimental period, it was found that soil porosity, redox status, soil organic carbon (SOC) as well as overall soil properties were improved significantly with biochar amendments and AWD irrigations. Conclusively, biochar amendments @15 - 20 t/ha with half of the recommended inorganic (NPKS) fertilizers under alternate wetting-drying irrigations revealed an environment friendly integrated package approach to reduce seasonal cumulative CH<sub>4</sub> emissions as well as GWPs, while improving rice rhizosphere environment and rice productivity to meet the national food security.
