Soil CO 2 emission from an arable soil was measured by closed chamber method to quantify year round soil flux and to develop an equation to predict flux using soil temperature, dissolved organic carbon(DOC) and soil...Soil CO 2 emission from an arable soil was measured by closed chamber method to quantify year round soil flux and to develop an equation to predict flux using soil temperature, dissolved organic carbon(DOC) and soil moisture content. Soil CO 2 flux, soil temperature, DOC and soil moisture content were determined on selected days during the experiment from August 1999 to July 2000, at the Ecological Station of Red Soil, the Chinese Academy of Sciences, in a subtropical region of China. Soil CO 2 fluxes were generally higher in summer and autumn than in winter and spring, and had a seasonal pattern more similar to soil temperature and DOC than soil moisture. The estimation was 2 23 kgCO 2/(m 2·a) for average annual soil CO 2 flux. Regressed separately, the reasons for soil flux variability were 86 6% from soil temperature, 58 8% from DOC, and 26 3% from soil moisture, respectively. Regressed jointly, a multiple equation was developed by the above three variables that explained approximately 85 2% of the flux variance, however by stepwise regression, soil temperature was the dominant affecting soil flux. Based on the exponential equation developed from soil temperature, the predicted annual flux was 2 49 kgCO 2/(m 2·a), and essentially equal to the measured one. It is suggested the exponential relationship between soil flux and soil temperature could be used for accurately predicting soil CO 2 flux from arable soil in subtropical regions of China.展开更多
As an important component of ecosystem carbon(C) budgets, soil carbon dioxide(CO2) flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence showing that the abiot...As an important component of ecosystem carbon(C) budgets, soil carbon dioxide(CO2) flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence showing that the abiotic component can be important in total soil CO2 flux(R(total)), its relative importance has never been systematically assessed. In this study, after comparative measurements of CO2 fluxes on sterilized and natural soils, the R(total) was partitioned into biotic flux(R(biotic)) and abiotic flux(R(abiotic)) across a broad range of land-cover types(including eight sampling sites: cotton field, hops field, halophyte garden, alkaline land, reservoir edge, native saline desert, dune crest and interdune lowland) in Gurbantunggut Desert, Xinjiang, China. The relative contribution of R(abiotic) to R(total), as well as the temperature dependency and predominant factors for R(total), R(biotic) and R(abiotic), were analyzed. Results showed that R(abiotic) always contributed to R(total) for all of the eight sampling sites, but the degree or magnitude of contribution varied greatly. Specifically, the ratio of R(abiotic) to R(total) was very low in cotton field and hops field and very high in alkaline land and dune crest. Statistically, the ratio of R(abiotic) to R(total) logarithmically increased with decreasing R(biotic), suggesting that R(abiotic) strongly affected R(total) when R(biotic) was low. This pattern confirms that soil CO2 flux is predominated by biotic processes in most soils, but abiotic processes can also be dominant when biotic processes are weak. On a diurnal basis, R(abiotic) cannot result in net gain or net loss of CO2, but its effect on transient CO2 flux was significant. Temperature dependency of R(total) varied among the eight sampling sites and was determined by the predominant processes(abiotic or biotic) of CO2 flux. Specifically, R(biotic) was driven by soil temperature while R(abiotic) was regulated by the change in soil temperature(ΔT). Namely, declining temperature(ΔT0) resulted in positive R(abiotic)(i.e., CO2 released from soil). Without recognition of R(abiotic), R(biotic) would be overestimated for the daytime and underestimated for the nighttime. Although R(abiotic) may not change the sum or the net value of daily soil CO2 exchange and may not directly constitute a C sink, it can significantly alter the transient apparent soil CO2 flux, either in magnitude or in temperature dependency. Thus, recognizing the fact that abiotic component in R(total) exists widely in soils has widespread consequences for the understanding of C cycling.展开更多
High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technol...High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic car-bon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm-2 to 30.75×104 kg C hm-2 in the alpine meadow eco-systems,with an average of 26.86×104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1,with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%―81.23% of total CO2 emitted from or-ganic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming,the storage,volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed,which needs further research.展开更多
In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geop...In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.展开更多
Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materia...Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materials(SCMs)to stabilize DMS under ambient and carbon dioxide(CO_(2))curing conditions.Several proprietary experimental tests were conducted to investigate the stabilized DMS.Furthermore,the carbonation-induced mineralogical,thermal,and microstructural properties change of the samples were explored.The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement(0.7-2.1 MPa)for pavement and building foundations.Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag(GGBS)altered the engineering properties and particle packing of the stabilized soils,thus influencing their performances.Biochar increased the porosity of the samples,facilitating higher CO_(2) uptake and improved ductility,while GGBS decreased porosity and increased the dry density of the samples,resulting in higher strength.The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples.Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration.Moreover,incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems.The biochar mixes demonstrated lower toxicity and energy consumption.Ultimately,the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO_(2) in soils through mineral carbonation,potentially reducing environmental pollution while meeting urbanization needs.展开更多
To accurately evaluate the carbon sequestration potential and better elucidate the relationship between the carbon cycle and regional climate change, using eddy covariance system, we conducted a long-term measurement ...To accurately evaluate the carbon sequestration potential and better elucidate the relationship between the carbon cycle and regional climate change, using eddy covariance system, we conducted a long-term measurement of CO 2 fluxes in the rain-fed winter wheat field of the Chinese Loess Plateau. The results showed that the annual net ecosystem CO 2 exchange (NEE) was (-71.6±5.7) and (-65.3±5.3) g C m-2 y-1 for 2008-2009 and 2009-2010 crop years, respectively, suggesting that the agro-ecosystem was a carbon sink (117.4-126.2 g C m-2 yr-1). However, after considering the harvested grain, the agro- ecosystem turned into a moderate carbon source. The variations in NEE and ecosystem respiration (R eco ) were sensitive to changes in soil water content (SWC). When SWC ranged form 0.15 to 0.21 m3 m-3, we found a highly significant relationship between NEE and photosynthetically active radiation (PAR), and a highly significant relationship between R eco and soil temperature (T s ). However, the highly significant relationships were not observed when SWC was outside the range of 0.15-0.21 m3 m-3. Further, in spring, the R eco instantly responded to a rapid increase in SWC after effective rainfall events, which could induce 2 to 4-fold increase in daily R eco , whereas the R eco was also inhibited by heavy summer rainfall when soils were saturated. Accumulated R eco in summer fallow period decreased carbon fixed in growing season by 16- 25%, indicating that the period imposed negative impacts on annual carbon sequestration.展开更多
Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November),for three years,in a total of 11 upland crop fields in central Hokkaido...Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November),for three years,in a total of 11 upland crop fields in central Hokkaido,Japan.The annual mean N2O fluxes ranged from 2.95 to 164.17 μgN/(m2·h),with the lowest observed in a grassland and the highest in an onion field.The instantaneous N2O fluxes showed a large temporal variation with peak emissions generally occurring following fertilization and heavy rainfall eve...展开更多
Long-term continuous cropping of soybean (Glycine max), spring wheat (Triticum aesativum) and maize (Zea mays) is widely practiced by local farmers in northeast China. A field experiment (started in 1991) was ...Long-term continuous cropping of soybean (Glycine max), spring wheat (Triticum aesativum) and maize (Zea mays) is widely practiced by local farmers in northeast China. A field experiment (started in 1991) was used to investigate the differences in soil carbon dioxide (CO2) emissions under continuous cropping of the three major crops and to evaluate the relationships between CO2 fluxes and soil temperature and moisture for Mollisols in northeast China. Soil CO2 emissions were measured using a closed-chamber method during the growing season in 2011. No remarkable differences in soil organic carbon were found among the cropping systems (P〉0.05). However, significant differences in CO2 emissions from soils were observed among the three cropping systems (P〈0.05). Over the course of the entire growing season, cumulative soil CO2 emissions under different cropping systems were in the following order: continuous maize ((829±10) g CO2 m2)〉continuous wheat ((629±22) g CO2 m^2)〉continuous soybean ((474±30) g CO2 m-2). Soil temperature explained 42-65% of the seasonal variations in soil CO2 flux, with a Q10 between 1.63 and 2.31; water-filled pore space explained 25-47% of the seasonal variations in soil CO2 flux. A multiple regression model including both soil temperature (T, ~C) and water-filled pore space (W, %), log(])=a+bT log(W), was established, accounting for 51-66% of the seasonal variations in soil CO2 flux. The results suggest that soil CO2 emissions and their Q10 values under a continuous cropping system largely depend on crop types in Mollisols of Northeast China.展开更多
Municipal solid waste landfills emit nitrous oxide (N2O) gas. Assuming that the soil cover is the primary N2O source from landfills, this study tested, during a four-year project, the hypothesis that the proper use ...Municipal solid waste landfills emit nitrous oxide (N2O) gas. Assuming that the soil cover is the primary N2O source from landfills, this study tested, during a four-year project, the hypothesis that the proper use of chosen soils with fine texture minimizes N2O emissions. A full-scale sanitary landfill, a full-scale bioreactor landfill and a cell planted with Nerium indicum or Festuca arundinacea Schreb, at the Hangzhou Tianziling landfill in Hangzhou City were the test sites. The N2O emission rates from all test sites were considerably lower than those reported in the published reports. Specifically, the N2O emission rate was dependent on soil water content and nitrate concentrations in the cover soil. The effects of leachate recirculation and irrigation were minimal. Properly chosen cover soils applied to the landfills reduced N2O flux.展开更多
Safe and economical disposal of paper mill sludge is a key consideration for forest products industry. A study was conducted to examine the effects of amendments of sludge and nutrients on soil surface CO2 flux (Rs)...Safe and economical disposal of paper mill sludge is a key consideration for forest products industry. A study was conducted to examine the effects of amendments of sludge and nutrients on soil surface CO2 flux (Rs) in northern hardwood forests and to quantify the relationship among Rs, soil temperature, and moisture in these stands. The experiment was a randomized complete block design that included sludge-amended, fertilized, and control treatments in sugar maple (Acer saccharum Marsh) dominated hardwood forests in the Upper Peninsula of Michigan, USA. Results showed that Rs was positively correlated to soil temperature (R^2 = 0.80, p 〈 0.001), but was poorly correlated to soil moisture. Soil moisture positively affected the Rs only in the sludge-amended treatment. The Rs was significantly greater in the sludge-amended treatment than in the fertilized (p = 0.033) and the control (p = 0.048) treatments. The maximum Rs in the sludge-amended treatment was 8.8 μmol CO2 · m^ 2. s^-1, 91% and 126% greater than those in the fertilized (4.6 μmol CO2 · m^-2· s^-1) and control (3.9 μmol CO2· m^- 2· s^-1) treatments, respectively. The Rs did not differ significantly between the fertilized and control treatments. The difference in Rs between sludge-amended and the other treatments decreased with time following treatment.展开更多
The soil CO2 evolution rate was measured in a virpin Korean pine forest. The results in June showed that the lowest value of evolution rate was 220 mg /(m2·h) and appeared at 6:00 a.m. The highest value was 460 m...The soil CO2 evolution rate was measured in a virpin Korean pine forest. The results in June showed that the lowest value of evolution rate was 220 mg /(m2·h) and appeared at 6:00 a.m. The highest value was 460 mg /(m2·h) at 18:00. The rates of CO2 evolution were related with soil temperature. On the basis of the constructed regression equation and the monthly average values of temperature, the magnitude of CO2 evolution from Korean pine forest soil was 10.4 t /hm2 during a growing season.展开更多
The United States continues to be the largest corn producer in the world. How to maximize corn yield and at the same time reduce greenhouse gas emissions, is becoming a challenging effort for growers and researchers. ...The United States continues to be the largest corn producer in the world. How to maximize corn yield and at the same time reduce greenhouse gas emissions, is becoming a challenging effort for growers and researchers. As a result, our understanding of the responses of soil CO2 and CH4 fluxes to agricultural practices in cornfields is still limited. We conducted a 3-yr cornfield experiment to study the responses of soil CO2 and CH4 fluxes to various agricultural practices in middle Tennessee. The agricultural practices included no-tillage + regular applications of urea ammonium nitrate (NT-URAN);no-tillage + regular applications of URAN + denitrification inhibitor (NT-inhi- bitor);no-tillage + regular applications of URAN + biochar (NT-biochar);no-tillage + 20% applications of URAN + chicken litter (NT-litter);no-tillage + split applications of URAN (NT-split);and conventional tillage + regular applications of URAN as a control (CT-URAN). A randomized complete block design was used with six replications. The same amount of fertilizer equivalent to 217 kg·N·ha-1 was applied to all of the experimental plots. The results showed that improved fertilizer and soil management, except the NT-biochar treatment significantly increased soil CO2 flux as compared to the conventional tillage (CT-URAN, 487.05 mg CO2 m-2·h-1). Soil CO2 flux increased exponentially with soil temperature (T 2 flux tended to be positively related to corn yield and/or soil moisture. Soil CH4 flux increased linearly with soil moisture in all treatments. Improved fertilizer and soil management did not alter soil CH4 flux, but significantly affected its moisture sensitivity. Our results indicated that agricultural practices enhancing corn yield may also result in a net increase in carbon emissions from soil, hence reducing the potential of carbon sequestration in croplands.展开更多
We investigated the effects of land-use changes on soil carbon storage and soil CO2 flux by comparing soils from mature cloud forest and 31-year-old secondary forest, both in the Santa Elena Forest Reserve, a municipa...We investigated the effects of land-use changes on soil carbon storage and soil CO2 flux by comparing soils from mature cloud forest and 31-year-old secondary forest, both in the Santa Elena Forest Reserve, a municipallyowned reserve at an elevation of 1600 to 1700 m near the town of Monteverde, and a clear-cut pasture near the reserve. Soils in the mature forest exhibit only weak horizonation but typically thick A horizons;they also consistently yield the highest carbon contents in the upper 30 cm. Soil CO2 flux was the highest in these soils, but also displayed the highest spatial variability. Secondary forest soils contain substantially less soil carbon than mature forest soils, but more than pasture soils. CO2 flux in the secondary forest soils was more similar to that of the mature forest, but displayed lower spatial variability. The pasture soils contain less soil carbon and produced lower CO2 flux levels than either of the forest soils. The pasture soils typically contain a well-defined coarse sandy layer 10 to 20 cm below the surface that we interpret as a sediment layer deposited across much of the landscape following a widespread erosion event, likely a consequence of the clear-cutting. Soil nitrogen concentrations are more than an order of magnitude lower than soil carbon concentrations, and display no trends between the different landscapes examined. Our preliminary results suggest that reforestation does restore soil carbon to clear-cut landscapes, but returning soil carbon levels to pre-land use levels occurs at a time scale of centuries, rather than decades.展开更多
Carbon dioxide(CO_(2))emissions from aquatic ecosystems are an important component of the karst carbon cycle process and also a key indicator for assessing the effect of karst carbon sinks.This paper reviewed the CO_(...Carbon dioxide(CO_(2))emissions from aquatic ecosystems are an important component of the karst carbon cycle process and also a key indicator for assessing the effect of karst carbon sinks.This paper reviewed the CO_(2)partial pressure(pCO_(2))and its diffusion flux(FCO_(2))in karst surface aquatic ecosystems,mainly rivers,lakes,and reservoirs,and their influencing factors summarized the methods for monitoring CO_(2)emissions in karst aquatic ecosystems and discussed their adaptation conditions in karst areas.The pCO_(2)and FCO_(2)decreased in the order of rivers>reservoirs>lakes,and the values in karst lakes were eventually significantly lower than those in global lakes.The pCO_(2)and FCO_(2)of karst aquatic ecosystems had patterns of variation with diurnal,seasonal,water depth and hydrological cycles,and spatial and temporal hetero-geneity.The sources of CO_(2)in karst waters are influenced by both internal and external sources,and the key spatial and temporal factors affecting the CO_(2)emissions from karst rivers,lakes,and reservoirs were determined in terms of physicochemical indicators,biological factors,and bio-genic elements;additionally,the process of human activity interference on CO_(2)emissions was discussed.Finally,a conceptual model illustrating the impacts of urban devel-opment,agriculture,mining,and dam construction on the CO_(2)emissions at the karst surface aquatic ecosystem is presented.Meanwhile,based on the disadvantages existing in current research,we proposed several important research fields related to CO_(2)emissions from karst surface aquatic ecosystems.展开更多
CO_(2)capture and storage(CCS)has the risk of CO_(2)leakage,and this leakage always increases soil CO_(2)concentration,and the long-term CO_(2)stress damages crop production in farmland.Using maize,the growth characte...CO_(2)capture and storage(CCS)has the risk of CO_(2)leakage,and this leakage always increases soil CO_(2)concentration,and the long-term CO_(2)stress damages crop production in farmland.Using maize,the growth characteristics,such as plant height and yield,and physiological indexes(osmoregulation substances and antioxidant enzymes)were explored under different simulative CO_(2)leakage conditions.Further,the relationship between maize physiological indexes and soil CO_(2)concentration was analyzed,showing that soil CO_(2)stress inhibited maize growth to a certain extent,resulting in shorter plants,thinner stems and lower kernel yield.With an increase in soil CO_(2)concentration,the contents of malondialdehyde,soluble sugar and soluble protein in maize leaves increased;with continuing stress,the increase rate of malondialdehyde was greatly augmented,whereas the increase rates of soluble sugar and soluble protein decreased.With extended CO_(2)stress,the activity of the enzyme superoxide dismutase(SOD)increased continuously,while the activities of catalase and peroxidase first increased and then decreased.Superoxide dismutase activity was closely correlated with soil CO_(2)concentration(r=0.762),and responded quickly to the change of soil CO_(2)concentration(R~2=0.9951).Therefore,SOD plays an important role in maize resistance to soil CO_(2)stress.This study will help further understanding of the mechanism of maize tolerance to soil CO_(2)stress,providing a theoretical basis for agricultural production in CCS project areas.展开更多
Mangrove forests are under the stress of sea level rise(SLR)which would affect mangrove soil biogeochemistry.Mangrove soils are important sources of soil-atmosphere greenhouse gas(GHG)emissions,including carbon dioxid...Mangrove forests are under the stress of sea level rise(SLR)which would affect mangrove soil biogeochemistry.Mangrove soils are important sources of soil-atmosphere greenhouse gas(GHG)emissions,including carbon dioxide(CO_(2)),methane(CH_(4))and nitrous oxide(N_(2)O).Understanding how SLR influences GHG emissions is critical for evaluating mangrove blue carbon capability.In this study,potential effects of SLR on the GHG emissions were quantified through static closed chamber technique among three sites under different intertidal elevations,representing tidal flooding situation of SLR values of 0 cm,40 cm and 80 cm,respectively.Compared with Site SLR 0 cm,annual CO_(2) and N_(2)O fluxes decreased by approximately 75.0%and 27.3%due to higher soil water content,lower salinity and soil nutrient environments at Site SLR 80 cm.However,CH_(4) fluxes increased by approximately 13.7%at Site SLR 40 cm and 8.8%at Site SLR 80 cm because of lower salinity,higher soil water content and soil pH.CO_(2)-equivalent fluxes were 396.61 g/(m^(2)·a),1423.29 g/(m^(2)·a)and 1420.21 g/(m^(2)·a)at Sites SLR 80 cm,SLR 40 cm and SLR 0 cm,respectively.From Site SLR 0 cm to Site SLR 80 cm,contribution rate of N_(2)O and CH_(4) increased by approximately 7.42%and 3.02%,while contribution rate of CO_(2) decreased by approximately 10.44%.The results indicated that warming potential of trace CH_(4) and N_(2)O was non-negligible with SLR.Potential effects of SLR on the mangrove blue carbon capability should warrant attention due to changes of all three greenhouse gas fluxes with SLR.展开更多
文摘Soil CO 2 emission from an arable soil was measured by closed chamber method to quantify year round soil flux and to develop an equation to predict flux using soil temperature, dissolved organic carbon(DOC) and soil moisture content. Soil CO 2 flux, soil temperature, DOC and soil moisture content were determined on selected days during the experiment from August 1999 to July 2000, at the Ecological Station of Red Soil, the Chinese Academy of Sciences, in a subtropical region of China. Soil CO 2 fluxes were generally higher in summer and autumn than in winter and spring, and had a seasonal pattern more similar to soil temperature and DOC than soil moisture. The estimation was 2 23 kgCO 2/(m 2·a) for average annual soil CO 2 flux. Regressed separately, the reasons for soil flux variability were 86 6% from soil temperature, 58 8% from DOC, and 26 3% from soil moisture, respectively. Regressed jointly, a multiple equation was developed by the above three variables that explained approximately 85 2% of the flux variance, however by stepwise regression, soil temperature was the dominant affecting soil flux. Based on the exponential equation developed from soil temperature, the predicted annual flux was 2 49 kgCO 2/(m 2·a), and essentially equal to the measured one. It is suggested the exponential relationship between soil flux and soil temperature could be used for accurately predicting soil CO 2 flux from arable soil in subtropical regions of China.
基金supported by the National Natural Science Foundation of China (41301279, 41201041)the International Science & Technology Cooperation Program of China (2010DFA92720)the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX2-YW-T09)
文摘As an important component of ecosystem carbon(C) budgets, soil carbon dioxide(CO2) flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence showing that the abiotic component can be important in total soil CO2 flux(R(total)), its relative importance has never been systematically assessed. In this study, after comparative measurements of CO2 fluxes on sterilized and natural soils, the R(total) was partitioned into biotic flux(R(biotic)) and abiotic flux(R(abiotic)) across a broad range of land-cover types(including eight sampling sites: cotton field, hops field, halophyte garden, alkaline land, reservoir edge, native saline desert, dune crest and interdune lowland) in Gurbantunggut Desert, Xinjiang, China. The relative contribution of R(abiotic) to R(total), as well as the temperature dependency and predominant factors for R(total), R(biotic) and R(abiotic), were analyzed. Results showed that R(abiotic) always contributed to R(total) for all of the eight sampling sites, but the degree or magnitude of contribution varied greatly. Specifically, the ratio of R(abiotic) to R(total) was very low in cotton field and hops field and very high in alkaline land and dune crest. Statistically, the ratio of R(abiotic) to R(total) logarithmically increased with decreasing R(biotic), suggesting that R(abiotic) strongly affected R(total) when R(biotic) was low. This pattern confirms that soil CO2 flux is predominated by biotic processes in most soils, but abiotic processes can also be dominant when biotic processes are weak. On a diurnal basis, R(abiotic) cannot result in net gain or net loss of CO2, but its effect on transient CO2 flux was significant. Temperature dependency of R(total) varied among the eight sampling sites and was determined by the predominant processes(abiotic or biotic) of CO2 flux. Specifically, R(biotic) was driven by soil temperature while R(abiotic) was regulated by the change in soil temperature(ΔT). Namely, declining temperature(ΔT0) resulted in positive R(abiotic)(i.e., CO2 released from soil). Without recognition of R(abiotic), R(biotic) would be overestimated for the daytime and underestimated for the nighttime. Although R(abiotic) may not change the sum or the net value of daily soil CO2 exchange and may not directly constitute a C sink, it can significantly alter the transient apparent soil CO2 flux, either in magnitude or in temperature dependency. Thus, recognizing the fact that abiotic component in R(total) exists widely in soils has widespread consequences for the understanding of C cycling.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40231015, 40471120 and 40473002)the Guangdong Provincial Natural Science Foundation of China (Grant No. 06300102)
文摘High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic car-bon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm-2 to 30.75×104 kg C hm-2 in the alpine meadow eco-systems,with an average of 26.86×104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1,with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%―81.23% of total CO2 emitted from or-ganic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming,the storage,volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed,which needs further research.
基金This study was supported by MatSoil Company(Grant No.04G/2022)This research was funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie(Grant No.778120).
文摘In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.
基金This work was supported by the Creative Groups of Natural Science Foundation of Hubei Province(Grant No.2021CFA030).Onyekwena Chikezie Chimere is an awardee for the ANSO Scholarship 2020-PhD.Ishrat Hameed Alvi is a recipient of the 2021 PhD ANSO Scholarship.
文摘Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materials(SCMs)to stabilize DMS under ambient and carbon dioxide(CO_(2))curing conditions.Several proprietary experimental tests were conducted to investigate the stabilized DMS.Furthermore,the carbonation-induced mineralogical,thermal,and microstructural properties change of the samples were explored.The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement(0.7-2.1 MPa)for pavement and building foundations.Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag(GGBS)altered the engineering properties and particle packing of the stabilized soils,thus influencing their performances.Biochar increased the porosity of the samples,facilitating higher CO_(2) uptake and improved ductility,while GGBS decreased porosity and increased the dry density of the samples,resulting in higher strength.The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples.Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration.Moreover,incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems.The biochar mixes demonstrated lower toxicity and energy consumption.Ultimately,the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO_(2) in soils through mineral carbonation,potentially reducing environmental pollution while meeting urbanization needs.
基金supported by the National Natural Science Foundation of China (31171506 and 31071375)
文摘To accurately evaluate the carbon sequestration potential and better elucidate the relationship between the carbon cycle and regional climate change, using eddy covariance system, we conducted a long-term measurement of CO 2 fluxes in the rain-fed winter wheat field of the Chinese Loess Plateau. The results showed that the annual net ecosystem CO 2 exchange (NEE) was (-71.6±5.7) and (-65.3±5.3) g C m-2 y-1 for 2008-2009 and 2009-2010 crop years, respectively, suggesting that the agro-ecosystem was a carbon sink (117.4-126.2 g C m-2 yr-1). However, after considering the harvested grain, the agro- ecosystem turned into a moderate carbon source. The variations in NEE and ecosystem respiration (R eco ) were sensitive to changes in soil water content (SWC). When SWC ranged form 0.15 to 0.21 m3 m-3, we found a highly significant relationship between NEE and photosynthetically active radiation (PAR), and a highly significant relationship between R eco and soil temperature (T s ). However, the highly significant relationships were not observed when SWC was outside the range of 0.15-0.21 m3 m-3. Further, in spring, the R eco instantly responded to a rapid increase in SWC after effective rainfall events, which could induce 2 to 4-fold increase in daily R eco , whereas the R eco was also inhibited by heavy summer rainfall when soils were saturated. Accumulated R eco in summer fallow period decreased carbon fixed in growing season by 16- 25%, indicating that the period imposed negative impacts on annual carbon sequestration.
基金the Global Environmental Research Program of the Ministry of the Environment of Japan (No.S-2).
文摘Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November),for three years,in a total of 11 upland crop fields in central Hokkaido,Japan.The annual mean N2O fluxes ranged from 2.95 to 164.17 μgN/(m2·h),with the lowest observed in a grassland and the highest in an onion field.The instantaneous N2O fluxes showed a large temporal variation with peak emissions generally occurring following fertilization and heavy rainfall eve...
基金supported by the Key Research Program of the Chinese Academy of Sciences (KZZD-EW-TZ-16-02)the Foundation for Young Talents of the Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences (DLSYQ13001)the National Natural Science Foundation of China (41101283)
文摘Long-term continuous cropping of soybean (Glycine max), spring wheat (Triticum aesativum) and maize (Zea mays) is widely practiced by local farmers in northeast China. A field experiment (started in 1991) was used to investigate the differences in soil carbon dioxide (CO2) emissions under continuous cropping of the three major crops and to evaluate the relationships between CO2 fluxes and soil temperature and moisture for Mollisols in northeast China. Soil CO2 emissions were measured using a closed-chamber method during the growing season in 2011. No remarkable differences in soil organic carbon were found among the cropping systems (P〉0.05). However, significant differences in CO2 emissions from soils were observed among the three cropping systems (P〈0.05). Over the course of the entire growing season, cumulative soil CO2 emissions under different cropping systems were in the following order: continuous maize ((829±10) g CO2 m2)〉continuous wheat ((629±22) g CO2 m^2)〉continuous soybean ((474±30) g CO2 m-2). Soil temperature explained 42-65% of the seasonal variations in soil CO2 flux, with a Q10 between 1.63 and 2.31; water-filled pore space explained 25-47% of the seasonal variations in soil CO2 flux. A multiple regression model including both soil temperature (T, ~C) and water-filled pore space (W, %), log(])=a+bT log(W), was established, accounting for 51-66% of the seasonal variations in soil CO2 flux. The results suggest that soil CO2 emissions and their Q10 values under a continuous cropping system largely depend on crop types in Mollisols of Northeast China.
基金This work was supported by the National Science and Technology Supporting Program of China (No. 2006BAJ04A06, 2006BAC06B05) ;the National Natural Science Foundation of China (No. 50538080).
文摘Municipal solid waste landfills emit nitrous oxide (N2O) gas. Assuming that the soil cover is the primary N2O source from landfills, this study tested, during a four-year project, the hypothesis that the proper use of chosen soils with fine texture minimizes N2O emissions. A full-scale sanitary landfill, a full-scale bioreactor landfill and a cell planted with Nerium indicum or Festuca arundinacea Schreb, at the Hangzhou Tianziling landfill in Hangzhou City were the test sites. The N2O emission rates from all test sites were considerably lower than those reported in the published reports. Specifically, the N2O emission rate was dependent on soil water content and nitrate concentrations in the cover soil. The effects of leachate recirculation and irrigation were minimal. Properly chosen cover soils applied to the landfills reduced N2O flux.
基金The research was funded by a NCASI grant to S.T. Gower. Wang CK was supported by Innovated Talent Program of Northeast Forestry University (2004-07)
文摘Safe and economical disposal of paper mill sludge is a key consideration for forest products industry. A study was conducted to examine the effects of amendments of sludge and nutrients on soil surface CO2 flux (Rs) in northern hardwood forests and to quantify the relationship among Rs, soil temperature, and moisture in these stands. The experiment was a randomized complete block design that included sludge-amended, fertilized, and control treatments in sugar maple (Acer saccharum Marsh) dominated hardwood forests in the Upper Peninsula of Michigan, USA. Results showed that Rs was positively correlated to soil temperature (R^2 = 0.80, p 〈 0.001), but was poorly correlated to soil moisture. Soil moisture positively affected the Rs only in the sludge-amended treatment. The Rs was significantly greater in the sludge-amended treatment than in the fertilized (p = 0.033) and the control (p = 0.048) treatments. The maximum Rs in the sludge-amended treatment was 8.8 μmol CO2 · m^ 2. s^-1, 91% and 126% greater than those in the fertilized (4.6 μmol CO2 · m^-2· s^-1) and control (3.9 μmol CO2· m^- 2· s^-1) treatments, respectively. The Rs did not differ significantly between the fertilized and control treatments. The difference in Rs between sludge-amended and the other treatments decreased with time following treatment.
文摘The soil CO2 evolution rate was measured in a virpin Korean pine forest. The results in June showed that the lowest value of evolution rate was 220 mg /(m2·h) and appeared at 6:00 a.m. The highest value was 460 mg /(m2·h) at 18:00. The rates of CO2 evolution were related with soil temperature. On the basis of the constructed regression equation and the monthly average values of temperature, the magnitude of CO2 evolution from Korean pine forest soil was 10.4 t /hm2 during a growing season.
文摘The United States continues to be the largest corn producer in the world. How to maximize corn yield and at the same time reduce greenhouse gas emissions, is becoming a challenging effort for growers and researchers. As a result, our understanding of the responses of soil CO2 and CH4 fluxes to agricultural practices in cornfields is still limited. We conducted a 3-yr cornfield experiment to study the responses of soil CO2 and CH4 fluxes to various agricultural practices in middle Tennessee. The agricultural practices included no-tillage + regular applications of urea ammonium nitrate (NT-URAN);no-tillage + regular applications of URAN + denitrification inhibitor (NT-inhi- bitor);no-tillage + regular applications of URAN + biochar (NT-biochar);no-tillage + 20% applications of URAN + chicken litter (NT-litter);no-tillage + split applications of URAN (NT-split);and conventional tillage + regular applications of URAN as a control (CT-URAN). A randomized complete block design was used with six replications. The same amount of fertilizer equivalent to 217 kg·N·ha-1 was applied to all of the experimental plots. The results showed that improved fertilizer and soil management, except the NT-biochar treatment significantly increased soil CO2 flux as compared to the conventional tillage (CT-URAN, 487.05 mg CO2 m-2·h-1). Soil CO2 flux increased exponentially with soil temperature (T 2 flux tended to be positively related to corn yield and/or soil moisture. Soil CH4 flux increased linearly with soil moisture in all treatments. Improved fertilizer and soil management did not alter soil CH4 flux, but significantly affected its moisture sensitivity. Our results indicated that agricultural practices enhancing corn yield may also result in a net increase in carbon emissions from soil, hence reducing the potential of carbon sequestration in croplands.
文摘We investigated the effects of land-use changes on soil carbon storage and soil CO2 flux by comparing soils from mature cloud forest and 31-year-old secondary forest, both in the Santa Elena Forest Reserve, a municipallyowned reserve at an elevation of 1600 to 1700 m near the town of Monteverde, and a clear-cut pasture near the reserve. Soils in the mature forest exhibit only weak horizonation but typically thick A horizons;they also consistently yield the highest carbon contents in the upper 30 cm. Soil CO2 flux was the highest in these soils, but also displayed the highest spatial variability. Secondary forest soils contain substantially less soil carbon than mature forest soils, but more than pasture soils. CO2 flux in the secondary forest soils was more similar to that of the mature forest, but displayed lower spatial variability. The pasture soils contain less soil carbon and produced lower CO2 flux levels than either of the forest soils. The pasture soils typically contain a well-defined coarse sandy layer 10 to 20 cm below the surface that we interpret as a sediment layer deposited across much of the landscape following a widespread erosion event, likely a consequence of the clear-cutting. Soil nitrogen concentrations are more than an order of magnitude lower than soil carbon concentrations, and display no trends between the different landscapes examined. Our preliminary results suggest that reforestation does restore soil carbon to clear-cut landscapes, but returning soil carbon levels to pre-land use levels occurs at a time scale of centuries, rather than decades.
基金supported by the National Natural Science Foundation of China(42163003)the Project of Talent Base in Guizhou Province(No.RCJD2018-21).
文摘Carbon dioxide(CO_(2))emissions from aquatic ecosystems are an important component of the karst carbon cycle process and also a key indicator for assessing the effect of karst carbon sinks.This paper reviewed the CO_(2)partial pressure(pCO_(2))and its diffusion flux(FCO_(2))in karst surface aquatic ecosystems,mainly rivers,lakes,and reservoirs,and their influencing factors summarized the methods for monitoring CO_(2)emissions in karst aquatic ecosystems and discussed their adaptation conditions in karst areas.The pCO_(2)and FCO_(2)decreased in the order of rivers>reservoirs>lakes,and the values in karst lakes were eventually significantly lower than those in global lakes.The pCO_(2)and FCO_(2)of karst aquatic ecosystems had patterns of variation with diurnal,seasonal,water depth and hydrological cycles,and spatial and temporal hetero-geneity.The sources of CO_(2)in karst waters are influenced by both internal and external sources,and the key spatial and temporal factors affecting the CO_(2)emissions from karst rivers,lakes,and reservoirs were determined in terms of physicochemical indicators,biological factors,and bio-genic elements;additionally,the process of human activity interference on CO_(2)emissions was discussed.Finally,a conceptual model illustrating the impacts of urban devel-opment,agriculture,mining,and dam construction on the CO_(2)emissions at the karst surface aquatic ecosystem is presented.Meanwhile,based on the disadvantages existing in current research,we proposed several important research fields related to CO_(2)emissions from karst surface aquatic ecosystems.
基金supported by the 863 Program Grant of the Ministry of Science and Technology of China(Grant No.2012AA050103)the High-level Talents Scientific Research Start-up Fund Project of Yulin University(Grant No.2023GK13)+5 种基金the Key Industry Innovation Chain Group Project of Shaanxi Province(Grant No.2023-ZDLSF-64)the“New Star of Science and Technology”Talent Program of Yulin(Grant No.CXY-2022-137)the Natural Science Research Project of the Education Department in Shaanxi Province of China(Grant No.22JK0636)the Natural Science Basic Research Program of Shaanxi Province(Grant No.2021JCW-04)Young Talent Fund of Association for Science and Technology in Yulinthe Natural Science Sesearch Program of the Yulin High-tech Zone Science and Technology Bureau。
文摘CO_(2)capture and storage(CCS)has the risk of CO_(2)leakage,and this leakage always increases soil CO_(2)concentration,and the long-term CO_(2)stress damages crop production in farmland.Using maize,the growth characteristics,such as plant height and yield,and physiological indexes(osmoregulation substances and antioxidant enzymes)were explored under different simulative CO_(2)leakage conditions.Further,the relationship between maize physiological indexes and soil CO_(2)concentration was analyzed,showing that soil CO_(2)stress inhibited maize growth to a certain extent,resulting in shorter plants,thinner stems and lower kernel yield.With an increase in soil CO_(2)concentration,the contents of malondialdehyde,soluble sugar and soluble protein in maize leaves increased;with continuing stress,the increase rate of malondialdehyde was greatly augmented,whereas the increase rates of soluble sugar and soluble protein decreased.With extended CO_(2)stress,the activity of the enzyme superoxide dismutase(SOD)increased continuously,while the activities of catalase and peroxidase first increased and then decreased.Superoxide dismutase activity was closely correlated with soil CO_(2)concentration(r=0.762),and responded quickly to the change of soil CO_(2)concentration(R~2=0.9951).Therefore,SOD plays an important role in maize resistance to soil CO_(2)stress.This study will help further understanding of the mechanism of maize tolerance to soil CO_(2)stress,providing a theoretical basis for agricultural production in CCS project areas.
基金The National Natural Science Foundation of China under contract Nos 42076142 and 41776097the Provincial Natural Science Foundation of Fujian under contract No.2020J06030the Fund of Fujian Provincial Key Laboratory of Marine Ecological Conservation and Restoration under contract No.EPR2020003.
文摘Mangrove forests are under the stress of sea level rise(SLR)which would affect mangrove soil biogeochemistry.Mangrove soils are important sources of soil-atmosphere greenhouse gas(GHG)emissions,including carbon dioxide(CO_(2)),methane(CH_(4))and nitrous oxide(N_(2)O).Understanding how SLR influences GHG emissions is critical for evaluating mangrove blue carbon capability.In this study,potential effects of SLR on the GHG emissions were quantified through static closed chamber technique among three sites under different intertidal elevations,representing tidal flooding situation of SLR values of 0 cm,40 cm and 80 cm,respectively.Compared with Site SLR 0 cm,annual CO_(2) and N_(2)O fluxes decreased by approximately 75.0%and 27.3%due to higher soil water content,lower salinity and soil nutrient environments at Site SLR 80 cm.However,CH_(4) fluxes increased by approximately 13.7%at Site SLR 40 cm and 8.8%at Site SLR 80 cm because of lower salinity,higher soil water content and soil pH.CO_(2)-equivalent fluxes were 396.61 g/(m^(2)·a),1423.29 g/(m^(2)·a)and 1420.21 g/(m^(2)·a)at Sites SLR 80 cm,SLR 40 cm and SLR 0 cm,respectively.From Site SLR 0 cm to Site SLR 80 cm,contribution rate of N_(2)O and CH_(4) increased by approximately 7.42%and 3.02%,while contribution rate of CO_(2) decreased by approximately 10.44%.The results indicated that warming potential of trace CH_(4) and N_(2)O was non-negligible with SLR.Potential effects of SLR on the mangrove blue carbon capability should warrant attention due to changes of all three greenhouse gas fluxes with SLR.