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
Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and est...Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems （a Picea asperata plantation and a natural forest）. Mean winter soil CO2 effluxes were 1.08 μmol m-2 s-1 in the plantation and 1.16 μmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing sea- son was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration toannual soil efflux were 15.4 % tor the plantation and 16.5R for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforesta- tion （natural coniferous forests were deforested and refor- ested with P. asperata plantation） may reduce soil respiration by reducing soil carbon substrate availability and input.展开更多
Most soil respiration measurements are conducted during the growing season.In tundra and boreal forest ecosystems,cumulative,non-growing season soil CO2 fluxes are reported to be a significant component of these syst...Most soil respiration measurements are conducted during the growing season.In tundra and boreal forest ecosystems,cumulative,non-growing season soil CO2 fluxes are reported to be a significant component of these systems＇ annual carbon budgets.However,little information exists on soil CO2 efflux during the non-growing season from alpine ecosystems.Therefore,comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of estimating ecosystem carbon budgets,as well as predicting the response of soil CO2 efflux to climate changes.In this study,we measured soil CO2 efflux and its spatial and temporal changes for different altitudes during the non-growing season in an alpine meadow located in the Qilian Mountains,Northwest China.Field experiments on the soil CO2 efflux of alpine meadow from the Qilian Mountains were conducted along an elevation gradient from October 2010 to April 2011.We measured the soil CO2 efflux,and analyzed the effects of soil water content and soil temperature on this measure.The results show that soil CO2 efflux gradually decreased along the elevation gradient during the non-growing season.The daily variation of soil CO2 efflux appeared as a single-peak curve.The soil CO2 efflux was low at night,with the lowest value occurring between 02：00-06：00.Then,values started to rise rapidly between 07：00-08：30,and then descend again between 16：00-18：30.The peak soil CO2 efflux appeared from 11：00 to 16：00.The soil CO2 efflux values gradually decreased from October to February of the next year and started to increase in March.Non-growing season Q10 （the multiplier to the respiration rate for a 10℃ increase in temperature） was increased with raising altitude and average Q10 of the Qilian Mountains was generally higher than the average growing season Q10 of the Heihe River Basin.Seasonally,non-growing season soil CO2 efflux was relatively high in October and early spring and low in the winter.The soil CO2 efflux was positively correlated with soil temperature and soil water content.Our results indicate that in alpine ecosystems,soil CO2 efflux continues throughout the non-growing season,and soil respiration is an important component of annual soil CO2 efflux.展开更多
Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux(Fc).However,both the overall contribution of abiotic CO2 exchange and its drivers remain unknown.He...Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux(Fc).However,both the overall contribution of abiotic CO2 exchange and its drivers remain unknown.Here we analyzed the environmental variables suggested as possible drivers by previous studies and constructed a function of these variables to model the contribution of abiotic exchange to Fc in alkaline soils of arid areas.An automated flux system was employed to measure Fc in the Manas River Basin of Xinjiang Uygur autonomous region,China.Soil pH,soil temperature at 0–5 cm(Ts),soil volumetric water content at 0–5 cm(θs)and air temperature at10 cm above the soil surface(Tas)were simultaneously analyzed.Results highlight reduced sensitivity of Fc to Ts and good prediction of Fc by the model Fc=R10Q10(Tas–10)/10+r7q7(pH–7)+λTas+μθs+e which represents Fc as a sum of biotic and abiotic components.This presents an approximate method to quantify the contribution of soil abiotic CO2 exchange to Fc in alkaline soils of arid areas.展开更多
Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October ...Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007.Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber.The mean soil CO2 efflux in the stand was 2.71 μmol/(m2·s) during the growing season and 1.38 μmol/(m2·s) in the nongrowing season.The seasonal maximum (end of May through early June) andminimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s),respectively.The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent),with theminimum appearing around 05:00 and the maximum around 15:00.Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213).When all variables were considered simultaneously,only soil temperature (R2=0.378),soil moisture (R2=0.147),and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux.Stand volumes were not correlated with soil CO2 efflux on our sites.展开更多
Lunan stone forest is a kind of typical karst in China, which is mainly developed under red soil. In the winter of 1999, three study sites were chosen in stone forest national park according to veget...Lunan stone forest is a kind of typical karst in China, which is mainly developed under red soil. In the winter of 1999, three study sites were chosen in stone forest national park according to vegetation cover, geomorphologic location and soil types. CO 2 concentration was measured with Gastec pump at different depths of soil (20, 40, 60 cm) and at the same time soil samples were gathered and soil properties such as soil moisture, pH, soil organic content were analyzed and the total number of viable microbes were counted in laboratory. In the study, dependent variable was chosen as the mean soil log (PCO 2 ), and soil properties were chosen as the independent variables. Multiple stepwise regression analysis showed that the total amount of microbes and soil moisture are the best indicators of the CO 2 production, with the equation LOG(PCO 2 ) = - 0.039(TNM) - 0.056(Mo) + 1.215 accounting for 86% of the variation of the soil CO 2 concentration, where TNM is the total number of microbes in the soil and Mo is the moisture of soil sample.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
From the middle of 19 century, mountain glacier recession occurs widely and Hailuogou glacier does so on a great scale. There is a primary vegetation succession series on the shrinking glacial area. The enhancement of...From the middle of 19 century, mountain glacier recession occurs widely and Hailuogou glacier does so on a great scale. There is a primary vegetation succession series on the shrinking glacial area. The enhancement of greenhouse gases result in the climate warming. Glacier recession is a response to the global climate warming. Determination on soil respiration plays an important role in the research on the global carbon cycling, which is one key problem for the global climate change studies. The observed values differ in different sites or with different measuring methods or by distinct observers, which add up one indefinite factor to the study on the global carbon balance. There exist different base courses at one same climatic district on the glacier shrinking area in Hailuogou, Gongga Mountain.Comparing the characteristic of different soil CO 2 emissions through the synchronous observation by the analyze ways of on\|the\|spot infrared CO 2(CI\|301) and chromatographic mainframe(HP5890A),and with the achievements of the study on the glacial recession area and vegetation succession, we established a series of soil CO 2 emission flux that can be a reference to emend the determination of soil CO 2 emission on different regions of the globe and that can be a useful parameter for modeling the global carbon cycling . Vegetation succession in the more than 2000m long glacial recession area is serially divided into 6 phases :①exposed shrinking area phase,②herbs phase,③shrubs phase,④deciduous and broad\|leaved mixed forest phase⑤coniferous and broad\|leaved mixed forest phase,⑥coniferous forest phase. Based on the two\|year’s measurement, the series of the mean intensity of soil respiration was arranged: 0, 1 960, 1 136, 2 080, 3 688 and 4 706μmol CO\-2/(m\+2·s); the series of the flux of soil CO\-2 emission was arranged: 0, 74 510, 43 185, 79 071, 140 200 and 178 890kg CO\-2/(hm\+2·d), respectively.Among the effect factors of soil respiration, temperature is the main one. All kinds of temperature influence soil respiration during the 6 succession phases.. The 2nd phase is influenced by atmospheric temperature, the 3rd and 4th phase by near\|surface temperature, the 5th and 6th phases by 5～10cm soil temperature.展开更多
Soil CO<sub>2</sub> efflux is an ongoing process of respiration from soil;plant parts/ microbes below the ground to the atmosphere which is known for faster cycling of carbon sources. A large portion of ca...Soil CO<sub>2</sub> efflux is an ongoing process of respiration from soil;plant parts/ microbes below the ground to the atmosphere which is known for faster cycling of carbon sources. A large portion of carbon sequestered and fixed by forests is returned to the atmosphere through soil CO<sub>2</sub> efflux and multiple controlling parameters mainly temperature, precipitation, and growth factors interact with the soil CO<sub>2</sub> efflux variation. This study assessed the soil CO<sub>2</sub> efflux every month for consecutive 2-years (August 2015 to July 2017) by using the closed chamber method to determine the role of ecological parameters that govern the soil CO<sub>2</sub> efflux and its temporal modification in a sub-tropical mixed forest of central region in Nepal. The results of this study manifested that soil CO<sub>2</sub> efflux accounted 63.2% (y = 31.96e<sup>0.128x</sup>), 71.3% (y = 44.77e<sup>0.123x</sup>) and 64.5% (y = 44.11e<sup>0.117x</sup>) variations in soil temperature with significantly (p < 0.05) exponential positive relation in the year 2015/2016, 2016/2017 and the two years when merged. And the temperature sensitivity value (Q<sub>10</sub>) of the soil CO<sub>2</sub> efflux was 3.6, 3.4, and 3.2, respectively. Soil water content also expressed significantly (p < 0.05) positive exponential effect on soil CO<sub>2</sub> efflux and accounted 62.0% (y = 138.3e<sup>0.057x</sup>), 46.1% (y = 88.42e<sup>0.052x</sup>) and 40.5% (y = 133.1e<sup>0.0447x</sup>) in its variability in different years and the merged years. Evident variations of soil CO<sub>2</sub> efflux, soil temperature, soil water content, and litter were observed in the forest seasonally and inter-annually. Two years mean total annual soil CO<sub>2</sub> efflux of the forest was estimated at 904.76 g C·m<sup>-2</sup>·y<sup>-1</sup>. The study revealed that sub-tropical forests could be more influenced by precipitation regimes in progressing warm climates i.e. vulnerable to climate change, illustrating the comprehensive dynamics of the representative forest carbon cycle in the tropical region.展开更多
Wetland is considered as a special ecosystem which has some functions in the earth.Wetland’s carbon cycle is very important for global climate changes. The research on wetland soil CO-2 flux is a key of wetland carbo...Wetland is considered as a special ecosystem which has some functions in the earth.Wetland’s carbon cycle is very important for global climate changes. The research on wetland soil CO-2 flux is a key of wetland carbon cycle. This paper analysed observation methods and influential factors of wetland soil CO-2 flux, introduced wetland soil CO-2 flux model, and discussed research emphases and direction on wetland soil CO-2 flux.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(31200474,31270552)the National Key Technologies R&D in China(2011BAC09B05)Postdoctoral Science Foundation of China(2013M540714 and 2014T70880)
文摘Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems （a Picea asperata plantation and a natural forest）. Mean winter soil CO2 effluxes were 1.08 μmol m-2 s-1 in the plantation and 1.16 μmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing sea- son was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration toannual soil efflux were 15.4 % tor the plantation and 16.5R for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforesta- tion （natural coniferous forests were deforested and refor- ested with P. asperata plantation） may reduce soil respiration by reducing soil carbon substrate availability and input.
基金funded by the National Natural Science Foundation of China(31270482,41101026,91025002)the Natural Science Foundation of Gansu Province(1107RJZA089)+1 种基金the West Light Foundation of the Chinese Academy of Sciencesthe National Key Technology R & D Program(2012BAC08B05)
文摘Most soil respiration measurements are conducted during the growing season.In tundra and boreal forest ecosystems,cumulative,non-growing season soil CO2 fluxes are reported to be a significant component of these systems＇ annual carbon budgets.However,little information exists on soil CO2 efflux during the non-growing season from alpine ecosystems.Therefore,comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of estimating ecosystem carbon budgets,as well as predicting the response of soil CO2 efflux to climate changes.In this study,we measured soil CO2 efflux and its spatial and temporal changes for different altitudes during the non-growing season in an alpine meadow located in the Qilian Mountains,Northwest China.Field experiments on the soil CO2 efflux of alpine meadow from the Qilian Mountains were conducted along an elevation gradient from October 2010 to April 2011.We measured the soil CO2 efflux,and analyzed the effects of soil water content and soil temperature on this measure.The results show that soil CO2 efflux gradually decreased along the elevation gradient during the non-growing season.The daily variation of soil CO2 efflux appeared as a single-peak curve.The soil CO2 efflux was low at night,with the lowest value occurring between 02：00-06：00.Then,values started to rise rapidly between 07：00-08：30,and then descend again between 16：00-18：30.The peak soil CO2 efflux appeared from 11：00 to 16：00.The soil CO2 efflux values gradually decreased from October to February of the next year and started to increase in March.Non-growing season Q10 （the multiplier to the respiration rate for a 10℃ increase in temperature） was increased with raising altitude and average Q10 of the Qilian Mountains was generally higher than the average growing season Q10 of the Heihe River Basin.Seasonally,non-growing season soil CO2 efflux was relatively high in October and early spring and low in the winter.The soil CO2 efflux was positively correlated with soil temperature and soil water content.Our results indicate that in alpine ecosystems,soil CO2 efflux continues throughout the non-growing season,and soil respiration is an important component of annual soil CO2 efflux.
基金supported by the National Basic Research Program of China(2009CB825105)
文摘Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux(Fc).However,both the overall contribution of abiotic CO2 exchange and its drivers remain unknown.Here we analyzed the environmental variables suggested as possible drivers by previous studies and constructed a function of these variables to model the contribution of abiotic exchange to Fc in alkaline soils of arid areas.An automated flux system was employed to measure Fc in the Manas River Basin of Xinjiang Uygur autonomous region,China.Soil pH,soil temperature at 0–5 cm(Ts),soil volumetric water content at 0–5 cm(θs)and air temperature at10 cm above the soil surface(Tas)were simultaneously analyzed.Results highlight reduced sensitivity of Fc to Ts and good prediction of Fc by the model Fc=R10Q10(Tas–10)/10+r7q7(pH–7)+λTas+μθs+e which represents Fc as a sum of biotic and abiotic components.This presents an approximate method to quantify the contribution of soil abiotic CO2 exchange to Fc in alkaline soils of arid areas.
基金supported by National Natural Science Foundation of China (40801001,40671010,40701054)National Key Technologies R&D Program of China during the 11th Five-Year Plan Period (2007BAD46B01)
文摘Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007.Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber.The mean soil CO2 efflux in the stand was 2.71 μmol/(m2·s) during the growing season and 1.38 μmol/(m2·s) in the nongrowing season.The seasonal maximum (end of May through early June) andminimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s),respectively.The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent),with theminimum appearing around 05:00 and the maximum around 15:00.Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213).When all variables were considered simultaneously,only soil temperature (R2=0.378),soil moisture (R2=0.147),and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux.Stand volumes were not correlated with soil CO2 efflux on our sites.
基金National Natural Science Foundation of China No.40071017+2 种基金 No.90202017 The Shilin Research Foundation of China No.199903
文摘Lunan stone forest is a kind of typical karst in China, which is mainly developed under red soil. In the winter of 1999, three study sites were chosen in stone forest national park according to vegetation cover, geomorphologic location and soil types. CO 2 concentration was measured with Gastec pump at different depths of soil (20, 40, 60 cm) and at the same time soil samples were gathered and soil properties such as soil moisture, pH, soil organic content were analyzed and the total number of viable microbes were counted in laboratory. In the study, dependent variable was chosen as the mean soil log (PCO 2 ), and soil properties were chosen as the independent variables. Multiple stepwise regression analysis showed that the total amount of microbes and soil moisture are the best indicators of the CO 2 production, with the equation LOG(PCO 2 ) = - 0.039(TNM) - 0.056(Mo) + 1.215 accounting for 86% of the variation of the soil CO 2 concentration, where TNM is the total number of microbes in the soil and Mo is the moisture of soil sample.
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From the middle of 19 century, mountain glacier recession occurs widely and Hailuogou glacier does so on a great scale. There is a primary vegetation succession series on the shrinking glacial area. The enhancement of greenhouse gases result in the climate warming. Glacier recession is a response to the global climate warming. Determination on soil respiration plays an important role in the research on the global carbon cycling, which is one key problem for the global climate change studies. The observed values differ in different sites or with different measuring methods or by distinct observers, which add up one indefinite factor to the study on the global carbon balance. There exist different base courses at one same climatic district on the glacier shrinking area in Hailuogou, Gongga Mountain.Comparing the characteristic of different soil CO 2 emissions through the synchronous observation by the analyze ways of on\|the\|spot infrared CO 2(CI\|301) and chromatographic mainframe(HP5890A),and with the achievements of the study on the glacial recession area and vegetation succession, we established a series of soil CO 2 emission flux that can be a reference to emend the determination of soil CO 2 emission on different regions of the globe and that can be a useful parameter for modeling the global carbon cycling . Vegetation succession in the more than 2000m long glacial recession area is serially divided into 6 phases :①exposed shrinking area phase,②herbs phase,③shrubs phase,④deciduous and broad\|leaved mixed forest phase⑤coniferous and broad\|leaved mixed forest phase,⑥coniferous forest phase. Based on the two\|year’s measurement, the series of the mean intensity of soil respiration was arranged: 0, 1 960, 1 136, 2 080, 3 688 and 4 706μmol CO\-2/(m\+2·s); the series of the flux of soil CO\-2 emission was arranged: 0, 74 510, 43 185, 79 071, 140 200 and 178 890kg CO\-2/(hm\+2·d), respectively.Among the effect factors of soil respiration, temperature is the main one. All kinds of temperature influence soil respiration during the 6 succession phases.. The 2nd phase is influenced by atmospheric temperature, the 3rd and 4th phase by near\|surface temperature, the 5th and 6th phases by 5～10cm soil temperature.
文摘Soil CO<sub>2</sub> efflux is an ongoing process of respiration from soil;plant parts/ microbes below the ground to the atmosphere which is known for faster cycling of carbon sources. A large portion of carbon sequestered and fixed by forests is returned to the atmosphere through soil CO<sub>2</sub> efflux and multiple controlling parameters mainly temperature, precipitation, and growth factors interact with the soil CO<sub>2</sub> efflux variation. This study assessed the soil CO<sub>2</sub> efflux every month for consecutive 2-years (August 2015 to July 2017) by using the closed chamber method to determine the role of ecological parameters that govern the soil CO<sub>2</sub> efflux and its temporal modification in a sub-tropical mixed forest of central region in Nepal. The results of this study manifested that soil CO<sub>2</sub> efflux accounted 63.2% (y = 31.96e<sup>0.128x</sup>), 71.3% (y = 44.77e<sup>0.123x</sup>) and 64.5% (y = 44.11e<sup>0.117x</sup>) variations in soil temperature with significantly (p < 0.05) exponential positive relation in the year 2015/2016, 2016/2017 and the two years when merged. And the temperature sensitivity value (Q<sub>10</sub>) of the soil CO<sub>2</sub> efflux was 3.6, 3.4, and 3.2, respectively. Soil water content also expressed significantly (p < 0.05) positive exponential effect on soil CO<sub>2</sub> efflux and accounted 62.0% (y = 138.3e<sup>0.057x</sup>), 46.1% (y = 88.42e<sup>0.052x</sup>) and 40.5% (y = 133.1e<sup>0.0447x</sup>) in its variability in different years and the merged years. Evident variations of soil CO<sub>2</sub> efflux, soil temperature, soil water content, and litter were observed in the forest seasonally and inter-annually. Two years mean total annual soil CO<sub>2</sub> efflux of the forest was estimated at 904.76 g C·m<sup>-2</sup>·y<sup>-1</sup>. The study revealed that sub-tropical forests could be more influenced by precipitation regimes in progressing warm climates i.e. vulnerable to climate change, illustrating the comprehensive dynamics of the representative forest carbon cycle in the tropical region.
文摘Wetland is considered as a special ecosystem which has some functions in the earth.Wetland’s carbon cycle is very important for global climate changes. The research on wetland soil CO-2 flux is a key of wetland carbon cycle. This paper analysed observation methods and influential factors of wetland soil CO-2 flux, introduced wetland soil CO-2 flux model, and discussed research emphases and direction on wetland soil CO-2 flux.
