CO 2 is the key gas of the greenhouse ones, the effect of its radiation on temperature ascent is 60% of the total greenhouse gases. The elevating CO 2 concentration influences to a great extent the future climate warm...CO 2 is the key gas of the greenhouse ones, the effect of its radiation on temperature ascent is 60% of the total greenhouse gases. The elevating CO 2 concentration influences to a great extent the future climate warming in a regional or global scale. Forest is the main part of carbon cycling in the land ecosystem.. Monitoring CO 2 absorption and emission in the forest ecosystem play a non\| fungible role in study on the global change. Gongga Mountain is located in the southeast margin of the Tibetan Plateau, and there exist intact vertical vegetation zonality, which is advantageous for measuring soil CO\-2 emission on each vertical forest zonality and researching the ecological factors of soil respiration.The east slope of Gongga Mountain develops 5 natural forest vertical zones from lower to higher altitudes: secondary forest, ever\|greened and deciduous broad\|leaved mixed forest, broad\|leaved and coniferous mixed forest, coniferous forest and alpine shrubs. Based on the two\|year’s measurement, the soil respiration of each forest averaged: 5 488, 6 344, 5 912, 4 176 and 3 864μmol CO 2/(m 2·s); the flux of soil CO 2 emission was arranged: 208 628, 241 169, 224 746, 158 752 and 146 891kg CO 2/(hm 2·d), respectively.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
N2O fluxes as a function of incubation time from soil with different available N contents and pH were determined. Cumulative carbon dioxide （CO2） emissions were measured to indicate soil respiration. A 144-hr incuba...N2O fluxes as a function of incubation time from soil with different available N contents and pH were determined. Cumulative carbon dioxide （CO2） emissions were measured to indicate soil respiration. A 144-hr incubation experiment was conducted in a slightly acidic agricultural soil （PHH2o 5.33） after the pH was adjusted to four different values （3.65, 5.00, 6.90 and 8.55）. The experiments consisted of a control without added N, and with NH^-N and NO^-N fertilization. The results showed that soil pH contributed significantly to N20 flux from the soils. There were higher N20 emissions in the period 0-12 hr in the four pH treatments, especially those enhanced with N- fertilization. The cumulative NEO-N emission reached a maximum at pH 8.55 and was stimulated by NO3-N fertilization （70.4 μg/kg）. The minimum emissions appeared at pH 3.65 and were not stimulated by NO3^--N or NH4^＋-N fertilization. Soil respiration increased significantly due to N-fertilization. Soil respiration increased positively with soil pH （R2 = 0.98, P 〈 0.01）. The lowest CO2-C emission （30.2 mg/kg） was presented in pH 3.65 soils without N-fertilization. The highest CO2-C emissions appeared in the pH 8.55 soils for NH4^＋-N fertilization （199 mg/kg）. These findings suggested that N20 emissions and soil respiration were significantly influenced by low pH, which strongly inhibits soil microbial nitrification and denitrification activities. The content of NO3^--N in soil significantly and positively affected the N2O emissions through denitrification.展开更多
With global climate change, soil drying-rewetting(DRW) events have intensified and occurred frequently on the Loess Plateau of China. However, the extent to which the DRW cycles with different wetting intensities and ...With global climate change, soil drying-rewetting(DRW) events have intensified and occurred frequently on the Loess Plateau of China. However, the extent to which the DRW cycles with different wetting intensities and cycle numbers alter microbial community and respiration is barely understood. Here,indoor DRW one and four cycles treatments were implemented on soil samples obtained from the Loess Plateau, involving increase of soil moisture from10% water-holding capacity(WHC) to 60% and 90% WHC(i.e., 10%–60% and 10%–90% WHC, respectively). Constant soil moistures of 10%, 60%,and 90% WHC were used as the controls. The results showed that bacterial diversity and richness decreased and those of fungi remained unchanged under DRW treatments compared to the controls. Under all moisture levels, Actinobacteriota and Ascomycota were the most dominant bacterial and fungal phyla,respectively. The bacterial network was more complex than that of fungi, indicating that bacteria had a greater potential for interaction and niche sharing under DRW treatments. The pulse of respiration rate declined as the DRW cycle increased under 10%–60% WHC, but remained similar for different cycles under 10%–90% WHC. Moreover, the DRW treatments reduced the overall carbon loss, and the direct carbon release under 10%–60% WHC was larger than that under 10%–90% WHC. The cumulative CO_(2) emissions after four DRW cycles were significantly positively correlated with microbial biomass carbon and negatively correlated with fungal richness(Chao 1).展开更多
Aims Soil CO_(2) emission from steppes is affected by soil properties and vegetation in different successional stages.Primary and secondary succession of plants frequently occurred at the meadow steppe in Songnen Plai...Aims Soil CO_(2) emission from steppes is affected by soil properties and vegetation in different successional stages.Primary and secondary succession of plants frequently occurred at the meadow steppe in Songnen Plain,Northeast China,which indicates the large uncer-tainty associated with CO_(2) emission in this environment.This study aims to investigate the temporal variations of soil respiration(Rs)and the effect of plant succession on cumulative soil CO_(2) emission during the growing season.Methods Using a LI-6400 soil CO_(2) flux system,Rs of five vegetation types which represented different stages of plant succession in meadow steppes of Songnen Plain,China,was investigated during the grow-ing seasons of 2011 and 2012.Important Findings Soil temperature(Ts)was the dominant controlling factor of Rs,which could explain~64%of the change in CO_(2) fluxes.The Q10 values of Rs were ranged from 2.0 to 6.7,showing a decreasing trend with the plant successional stages.The cumulative CO_(2) emis-sion increased with the degree of vegetation succession and it aver-aged to 316±6 g C m^(−2)(ranges:74.8±6.7 to 516.5±11.4 g C m^(−2))during the growing season.The magnitude of soil CO_(2) emission during the growing season was positively correlated with above-ground plant biomass,soil organic carbon content and mean soil water content,while negatively linked to mean Ts,pH,electrical conductivity and exchangeable sodium percentages.The results implied that soil CO_(2) emission increased with the development of plant communities toward more advanced stages.Our findings pro-vided valuable information for understanding the variations of CO_(2) emission in the process of vegetation succession.展开更多
全球变暖已经成为不争的事实,陆地生态系统碳循环的研究受到了各界广泛关注,是当前全球变化研究中的重点。土壤CO_(2)排放是陆地生态系统与大气间二氧化碳交换的最大通量之一,当前陆地生态系统中土壤CO_(2)排放如何响应全球气候变暖及...全球变暖已经成为不争的事实,陆地生态系统碳循环的研究受到了各界广泛关注,是当前全球变化研究中的重点。土壤CO_(2)排放是陆地生态系统与大气间二氧化碳交换的最大通量之一,当前陆地生态系统中土壤CO_(2)排放如何响应全球气候变暖及其影响因素仍不清楚,限制了对土壤碳循环过程及影响机制的深入认识。旨在明确全球变暖背景下陆地生态系统中土壤CO_(2)排放格局及影响因素。基于Web of Science、PubMed和中国知网等中英文期刊数据库,充分收集全球范围内的相关野外试验文献81篇,提取出65个研究位置和213组相关研究数据,采用Meta分析方法探讨陆地生态系统土壤CO_(2)排放对增温的响应特征,分析其与海拔、气候、土壤含水量、容重(BD)、pH、全氮(TN)和土壤有机碳(SOC)的相关关系。结果表明:陆地生态系统中土壤CO_(2)排放对增温整体有显著的正向响应,在农、林、草生态系统中,增温使土壤CO_(2)排放分别显著增加13.1%、18.0%、5.9%(P<0.05),森林生态系统对增温响应的正效应最强烈;增温能在短时期内促进土壤呼吸,但随着增温持续时间增加,土壤呼吸对温度的敏感性会降低,对温度变化产生适应性,从而使其对增温的响应能力减弱;响应特征受到环境因子、土壤特性以及其他试验条件等的影响,绝大多数条件下对增温表现出显著的正响应特征,不同影响因子之间共同作用、相互影响。增温通常能够改变植物生物量、土壤养分含量及微生物数量和活性,从而影响到植被根际呼吸和土壤呼吸速率。相关分析表明,海拔对土壤CO_(2)排放有显著负向影响,而年均气温、年均降水量、土壤含水量和仪器嵌入土壤深度则对土壤CO_(2)排放产生显著正向影响。这些结果对于理解全球土壤CO_(2)排放的时空变化格局有重要意义,也为准确评价全球变暖背景下土壤碳汇功能及其持续性提供理论依据。展开更多
【目的】明确不同土地利用方式土壤氧化亚氮(N_(2)O)排放系数的差异并评估区域N_(2)O排放,为评估南方红壤丘陵区N_(2)O排放清单提供基础数据和参考依据。【方法】选择南方红壤丘陵区4种常见的土地利用方式(油茶林、旱地农田、稻田和松...【目的】明确不同土地利用方式土壤氧化亚氮(N_(2)O)排放系数的差异并评估区域N_(2)O排放,为评估南方红壤丘陵区N_(2)O排放清单提供基础数据和参考依据。【方法】选择南方红壤丘陵区4种常见的土地利用方式(油茶林、旱地农田、稻田和松林),通过分析土壤不施肥与施氮肥时N_(2)O排放速率和排放量的差异,计算排放系数,并用^(15)N同位素标记方法探究硝化作用和反硝化作用对土壤排放N_(2)O的相对贡献。【结果】不同土地利用方式土壤理化性质差异明显,稻田全氮含量最高(2.22 g/kg),显著高于其他3种土地利用方式土壤(P<0.05,下同)。土壤不施肥时,N_(2)O排放速率在0~227.80μg/(kg·h),施氮量为200 kg N/ha时,N_(2)O排放速率在0~4213.27μg/(kg·h)。4种土地利用方式的土壤N_(2)O排放系数均随土壤孔隙含水量(WPFS)增加而增加,WPFS为75%时,稻田、旱地农田、油茶林和松林土壤N_(2)O排放系数分别为2.47%、0.39%、2.31%和0.91%。4种土地利用方式土壤N_(2)O排放系数主要受全氮含量影响,N_(2)O累积排放量均与潜在反硝化潜势呈显著正相关,除稻田外,其他3种土地利用方式土壤N_(2)O累积排放量也与潜在硝化势呈显著正相关,以NO_(3)^(-)-N为底物的反硝化作用对N_(2)O排放的相对贡献平均大于90.00%,远高于硝化作用。【结论】南方红壤丘陵区土壤以NO_(3)^(-)-N为底物的反硝化作用主导N_(2)O排放,施用氨基氮肥可能有效减少氮肥N_(2)O排放损失,为国家执行碳中和政策提供理论依据。展开更多
Seasonal metrics and environmental responses to forestry soil surface CO_(2)emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatog...Seasonal metrics and environmental responses to forestry soil surface CO_(2)emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatograph techniques among three types of lower subtropical forests.Results showed that annual CO_(2)effluxes(S+L)reached 3942.20,3422.36 and 2163.02 CO_(2)g·m-2·a-1,respectively in the monsoon evergreen broadleaf forest,mixed broadleaf-coniferous forest and coniferous forest.All the three types of forests revealed the same characteristics of seasonal changes with the CO_(2)effluxes peaking throughout June to August.During this peaking period,the effluxes were 35.9%,38.1%and 40.2%of the total annual effluxes,respectively.The CO_(2)emission process responding to the environmental factors displayed significantly different patterns in forestry soils of the three types of forests.The coniferous forest(CF)was more sensitive to temperature than the other two types.The Q10 values were higher,along with greater seasonal variations of the CO_(2)efflux,indicating that the structurally unique forestry ecosystem has disadvantage against interferences.All the three types of forestry CO_(2)effluxes showed significant correlation with the soil temperature(Ts),soil water content(Ms)and air pressure(Pa).However,stepwise regression analysis indicated no significant correlation between air pressure and the soil CO_(2)efflux.With an empirical model to measure soil temperature and water content in 5 cm beneath the soil surface,the CO_(2)effluxes accounting for 75.7%,77.8%and 86.5%of the efflux variability respectively in soils of BF,MF and PF were calculated.This model can be better used to evaluate the CO2 emission of soils under water stress and arid or semi-arid conditions.展开更多
Intensification of grazed grasslands following conversion from dryland to irrigated farming has the potential to alter ecosystem carbon(C)cycling and affect components of carbon dioxide(CO_(2))exchange that could lead...Intensification of grazed grasslands following conversion from dryland to irrigated farming has the potential to alter ecosystem carbon(C)cycling and affect components of carbon dioxide(CO_(2))exchange that could lead to either net accumulation or loss of soil C.While there are many studies on the effect of water availability on biomass production and soil C stocks,much less is known about the effect of the frequency of water inputs on the components of CO_(2)exchange.We grew Bermuda grass(Cynodon dactylon L.)in mesocosms under irrigation frequencies of every day(I_(1) treatment,30 d),every two days(I_(2) treatment,12 d),every three days(I_(3) treatment,30 d),and every six days(I_(6) treatment,18 d,after I_(2) treatment).Rates of CO_(2)exchange for estimating net ecosystem CO_(2)exchange(F_(N)),ecosystem respiration(R_(E)),and soil respiration(R_(S))were measured,and gross C uptake by plants(F_(G))and respiration from leaves(R_(L))were calculated during two periods,1–12 and 13–30 d,of the 30-d experiment.During the first 12 d,there were no significant differences in cumulative F_(N)(mean±standard deviation,61±30 g C m^(-2),n=4).During the subsequent 18 d,cumulative F_(N) decreased with decreasing irrigation frequency and increasing cumulative soil water deficit(W),with values of 70±22,60±16,and 18±12 g C m^(-2) for the I_(1),I_(3),and I_(6) treatments,respectively.There were similar decreases in F_(G),R_(E),and R_(L) with increasing W,but differences in R_(S) were not significant.Use of the C_(4) grass growing in a C_(3)-derived soil enabled partitioning of R_(S) into its autotrophic(R_(A))and heterotrophic(R_(H))components using a^(13)C natural abundance isotopic technique at the end of the experiment when differences in cumulative W between the treatments were the greatest.The values of R_(H) and its percentage contributions to R_(S)(43%±8%,42%±8%,and 8%±5%for the I_(1),I_(3),and I_(6) treatments,respectively)suggested that R_(H) remained unaffected across a wide range of W and then decreased under extreme W.There were no significant differences in aboveground biomass between the treatments.Nitrous oxide(N_(2)O)emission was measured to determine if there was a trade-off effect between irrigation frequency and increasing W on net greenhouse gas emission,but no significant differences were found between the treatments.These findings suggest that over short periods in well-drained soil,irrigation frequency could be managed to manipulate soil water deficit in order to reduce net belowground respiratory C losses,particularly those from the microbial decomposition of soil organic matter,with no significant effect on biomass production and N_(2)O emission.展开更多
文摘CO 2 is the key gas of the greenhouse ones, the effect of its radiation on temperature ascent is 60% of the total greenhouse gases. The elevating CO 2 concentration influences to a great extent the future climate warming in a regional or global scale. Forest is the main part of carbon cycling in the land ecosystem.. Monitoring CO 2 absorption and emission in the forest ecosystem play a non\| fungible role in study on the global change. Gongga Mountain is located in the southeast margin of the Tibetan Plateau, and there exist intact vertical vegetation zonality, which is advantageous for measuring soil CO\-2 emission on each vertical forest zonality and researching the ecological factors of soil respiration.The east slope of Gongga Mountain develops 5 natural forest vertical zones from lower to higher altitudes: secondary forest, ever\|greened and deciduous broad\|leaved mixed forest, broad\|leaved and coniferous mixed forest, coniferous forest and alpine shrubs. Based on the two\|year’s measurement, the soil respiration of each forest averaged: 5 488, 6 344, 5 912, 4 176 and 3 864μmol CO 2/(m 2·s); the flux of soil CO 2 emission was arranged: 208 628, 241 169, 224 746, 158 752 and 146 891kg CO 2/(hm 2·d), respectively.
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.
基金supported by the National Natural Science Foundation of China (No. 40971145,40601045)the Open Foundation from State Key Laboratory of Soil and Sustainable Agriculture (No. 0812000050)the Chinese Scholarship Council
文摘N2O fluxes as a function of incubation time from soil with different available N contents and pH were determined. Cumulative carbon dioxide （CO2） emissions were measured to indicate soil respiration. A 144-hr incubation experiment was conducted in a slightly acidic agricultural soil （PHH2o 5.33） after the pH was adjusted to four different values （3.65, 5.00, 6.90 and 8.55）. The experiments consisted of a control without added N, and with NH^-N and NO^-N fertilization. The results showed that soil pH contributed significantly to N20 flux from the soils. There were higher N20 emissions in the period 0-12 hr in the four pH treatments, especially those enhanced with N- fertilization. The cumulative NEO-N emission reached a maximum at pH 8.55 and was stimulated by NO3-N fertilization （70.4 μg/kg）. The minimum emissions appeared at pH 3.65 and were not stimulated by NO3^--N or NH4^＋-N fertilization. Soil respiration increased significantly due to N-fertilization. Soil respiration increased positively with soil pH （R2 = 0.98, P 〈 0.01）. The lowest CO2-C emission （30.2 mg/kg） was presented in pH 3.65 soils without N-fertilization. The highest CO2-C emissions appeared in the pH 8.55 soils for NH4^＋-N fertilization （199 mg/kg）. These findings suggested that N20 emissions and soil respiration were significantly influenced by low pH, which strongly inhibits soil microbial nitrification and denitrification activities. The content of NO3^--N in soil significantly and positively affected the N2O emissions through denitrification.
基金supported by the Provincial Natural Science Foundation of Hunan, China (No. 2020JJ4429)the Open Fund of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau of China (No. A314021402-202101)the Hundred-Talent Project of Chinese Academy of Sciences (No. A315021407).
文摘With global climate change, soil drying-rewetting(DRW) events have intensified and occurred frequently on the Loess Plateau of China. However, the extent to which the DRW cycles with different wetting intensities and cycle numbers alter microbial community and respiration is barely understood. Here,indoor DRW one and four cycles treatments were implemented on soil samples obtained from the Loess Plateau, involving increase of soil moisture from10% water-holding capacity(WHC) to 60% and 90% WHC(i.e., 10%–60% and 10%–90% WHC, respectively). Constant soil moistures of 10%, 60%,and 90% WHC were used as the controls. The results showed that bacterial diversity and richness decreased and those of fungi remained unchanged under DRW treatments compared to the controls. Under all moisture levels, Actinobacteriota and Ascomycota were the most dominant bacterial and fungal phyla,respectively. The bacterial network was more complex than that of fungi, indicating that bacteria had a greater potential for interaction and niche sharing under DRW treatments. The pulse of respiration rate declined as the DRW cycle increased under 10%–60% WHC, but remained similar for different cycles under 10%–90% WHC. Moreover, the DRW treatments reduced the overall carbon loss, and the direct carbon release under 10%–60% WHC was larger than that under 10%–90% WHC. The cumulative CO_(2) emissions after four DRW cycles were significantly positively correlated with microbial biomass carbon and negatively correlated with fungal richness(Chao 1).
基金National Natural Science Foundation of China(31100403,41101207)Special Fund for Agro-scientific Research in the Public Interest,China(201303095-8).
文摘Aims Soil CO_(2) emission from steppes is affected by soil properties and vegetation in different successional stages.Primary and secondary succession of plants frequently occurred at the meadow steppe in Songnen Plain,Northeast China,which indicates the large uncer-tainty associated with CO_(2) emission in this environment.This study aims to investigate the temporal variations of soil respiration(Rs)and the effect of plant succession on cumulative soil CO_(2) emission during the growing season.Methods Using a LI-6400 soil CO_(2) flux system,Rs of five vegetation types which represented different stages of plant succession in meadow steppes of Songnen Plain,China,was investigated during the grow-ing seasons of 2011 and 2012.Important Findings Soil temperature(Ts)was the dominant controlling factor of Rs,which could explain~64%of the change in CO_(2) fluxes.The Q10 values of Rs were ranged from 2.0 to 6.7,showing a decreasing trend with the plant successional stages.The cumulative CO_(2) emis-sion increased with the degree of vegetation succession and it aver-aged to 316±6 g C m^(−2)(ranges:74.8±6.7 to 516.5±11.4 g C m^(−2))during the growing season.The magnitude of soil CO_(2) emission during the growing season was positively correlated with above-ground plant biomass,soil organic carbon content and mean soil water content,while negatively linked to mean Ts,pH,electrical conductivity and exchangeable sodium percentages.The results implied that soil CO_(2) emission increased with the development of plant communities toward more advanced stages.Our findings pro-vided valuable information for understanding the variations of CO_(2) emission in the process of vegetation succession.
文摘全球变暖已经成为不争的事实,陆地生态系统碳循环的研究受到了各界广泛关注,是当前全球变化研究中的重点。土壤CO_(2)排放是陆地生态系统与大气间二氧化碳交换的最大通量之一,当前陆地生态系统中土壤CO_(2)排放如何响应全球气候变暖及其影响因素仍不清楚,限制了对土壤碳循环过程及影响机制的深入认识。旨在明确全球变暖背景下陆地生态系统中土壤CO_(2)排放格局及影响因素。基于Web of Science、PubMed和中国知网等中英文期刊数据库,充分收集全球范围内的相关野外试验文献81篇,提取出65个研究位置和213组相关研究数据,采用Meta分析方法探讨陆地生态系统土壤CO_(2)排放对增温的响应特征,分析其与海拔、气候、土壤含水量、容重(BD)、pH、全氮(TN)和土壤有机碳(SOC)的相关关系。结果表明:陆地生态系统中土壤CO_(2)排放对增温整体有显著的正向响应,在农、林、草生态系统中,增温使土壤CO_(2)排放分别显著增加13.1%、18.0%、5.9%(P<0.05),森林生态系统对增温响应的正效应最强烈;增温能在短时期内促进土壤呼吸,但随着增温持续时间增加,土壤呼吸对温度的敏感性会降低,对温度变化产生适应性,从而使其对增温的响应能力减弱;响应特征受到环境因子、土壤特性以及其他试验条件等的影响,绝大多数条件下对增温表现出显著的正响应特征,不同影响因子之间共同作用、相互影响。增温通常能够改变植物生物量、土壤养分含量及微生物数量和活性,从而影响到植被根际呼吸和土壤呼吸速率。相关分析表明,海拔对土壤CO_(2)排放有显著负向影响,而年均气温、年均降水量、土壤含水量和仪器嵌入土壤深度则对土壤CO_(2)排放产生显著正向影响。这些结果对于理解全球土壤CO_(2)排放的时空变化格局有重要意义,也为准确评价全球变暖背景下土壤碳汇功能及其持续性提供理论依据。
文摘【目的】明确不同土地利用方式土壤氧化亚氮(N_(2)O)排放系数的差异并评估区域N_(2)O排放,为评估南方红壤丘陵区N_(2)O排放清单提供基础数据和参考依据。【方法】选择南方红壤丘陵区4种常见的土地利用方式(油茶林、旱地农田、稻田和松林),通过分析土壤不施肥与施氮肥时N_(2)O排放速率和排放量的差异,计算排放系数,并用^(15)N同位素标记方法探究硝化作用和反硝化作用对土壤排放N_(2)O的相对贡献。【结果】不同土地利用方式土壤理化性质差异明显,稻田全氮含量最高(2.22 g/kg),显著高于其他3种土地利用方式土壤(P<0.05,下同)。土壤不施肥时,N_(2)O排放速率在0~227.80μg/(kg·h),施氮量为200 kg N/ha时,N_(2)O排放速率在0~4213.27μg/(kg·h)。4种土地利用方式的土壤N_(2)O排放系数均随土壤孔隙含水量(WPFS)增加而增加,WPFS为75%时,稻田、旱地农田、油茶林和松林土壤N_(2)O排放系数分别为2.47%、0.39%、2.31%和0.91%。4种土地利用方式土壤N_(2)O排放系数主要受全氮含量影响,N_(2)O累积排放量均与潜在反硝化潜势呈显著正相关,除稻田外,其他3种土地利用方式土壤N_(2)O累积排放量也与潜在硝化势呈显著正相关,以NO_(3)^(-)-N为底物的反硝化作用对N_(2)O排放的相对贡献平均大于90.00%,远高于硝化作用。【结论】南方红壤丘陵区土壤以NO_(3)^(-)-N为底物的反硝化作用主导N_(2)O排放,施用氨基氮肥可能有效减少氮肥N_(2)O排放损失,为国家执行碳中和政策提供理论依据。
基金This work was supported by the Na-tional Natural Science Foundation of China(Grant No.30570350)the Knowledge Innovation Program of Chinese Academy of Sciences(Grant Nos.KZCX1-SW-01 and KSCX2-SW-120)+1 种基金the Ministry of Science and Technol-ogy of China(Grant No.2002CB412501)This research was assisted by Mr.Liu Guangren,Drs.Wang Yinghong and Sun Yang from CERN's Atmosphere Center.Thanks are also due to the following people who participated in the field work:Chu Guowei,Wang Xu,Ouyang Xuejun,Xu Guo-liang,Kuang Yuanwen,Luo Yan,Yin Guangcai,Guan Lili,Liu Yan,Meng Ze and Mo Dingsheng.
文摘Seasonal metrics and environmental responses to forestry soil surface CO_(2)emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatograph techniques among three types of lower subtropical forests.Results showed that annual CO_(2)effluxes(S+L)reached 3942.20,3422.36 and 2163.02 CO_(2)g·m-2·a-1,respectively in the monsoon evergreen broadleaf forest,mixed broadleaf-coniferous forest and coniferous forest.All the three types of forests revealed the same characteristics of seasonal changes with the CO_(2)effluxes peaking throughout June to August.During this peaking period,the effluxes were 35.9%,38.1%and 40.2%of the total annual effluxes,respectively.The CO_(2)emission process responding to the environmental factors displayed significantly different patterns in forestry soils of the three types of forests.The coniferous forest(CF)was more sensitive to temperature than the other two types.The Q10 values were higher,along with greater seasonal variations of the CO_(2)efflux,indicating that the structurally unique forestry ecosystem has disadvantage against interferences.All the three types of forestry CO_(2)effluxes showed significant correlation with the soil temperature(Ts),soil water content(Ms)and air pressure(Pa).However,stepwise regression analysis indicated no significant correlation between air pressure and the soil CO_(2)efflux.With an empirical model to measure soil temperature and water content in 5 cm beneath the soil surface,the CO_(2)effluxes accounting for 75.7%,77.8%and 86.5%of the efflux variability respectively in soils of BF,MF and PF were calculated.This model can be better used to evaluate the CO2 emission of soils under water stress and arid or semi-arid conditions.
基金funded by the New Zealand Agricultural Greenhouse Gas Research Centre(NZAGRC)National Natural Science Foundation of China(No.32101431)。
文摘Intensification of grazed grasslands following conversion from dryland to irrigated farming has the potential to alter ecosystem carbon(C)cycling and affect components of carbon dioxide(CO_(2))exchange that could lead to either net accumulation or loss of soil C.While there are many studies on the effect of water availability on biomass production and soil C stocks,much less is known about the effect of the frequency of water inputs on the components of CO_(2)exchange.We grew Bermuda grass(Cynodon dactylon L.)in mesocosms under irrigation frequencies of every day(I_(1) treatment,30 d),every two days(I_(2) treatment,12 d),every three days(I_(3) treatment,30 d),and every six days(I_(6) treatment,18 d,after I_(2) treatment).Rates of CO_(2)exchange for estimating net ecosystem CO_(2)exchange(F_(N)),ecosystem respiration(R_(E)),and soil respiration(R_(S))were measured,and gross C uptake by plants(F_(G))and respiration from leaves(R_(L))were calculated during two periods,1–12 and 13–30 d,of the 30-d experiment.During the first 12 d,there were no significant differences in cumulative F_(N)(mean±standard deviation,61±30 g C m^(-2),n=4).During the subsequent 18 d,cumulative F_(N) decreased with decreasing irrigation frequency and increasing cumulative soil water deficit(W),with values of 70±22,60±16,and 18±12 g C m^(-2) for the I_(1),I_(3),and I_(6) treatments,respectively.There were similar decreases in F_(G),R_(E),and R_(L) with increasing W,but differences in R_(S) were not significant.Use of the C_(4) grass growing in a C_(3)-derived soil enabled partitioning of R_(S) into its autotrophic(R_(A))and heterotrophic(R_(H))components using a^(13)C natural abundance isotopic technique at the end of the experiment when differences in cumulative W between the treatments were the greatest.The values of R_(H) and its percentage contributions to R_(S)(43%±8%,42%±8%,and 8%±5%for the I_(1),I_(3),and I_(6) treatments,respectively)suggested that R_(H) remained unaffected across a wide range of W and then decreased under extreme W.There were no significant differences in aboveground biomass between the treatments.Nitrous oxide(N_(2)O)emission was measured to determine if there was a trade-off effect between irrigation frequency and increasing W on net greenhouse gas emission,but no significant differences were found between the treatments.These findings suggest that over short periods in well-drained soil,irrigation frequency could be managed to manipulate soil water deficit in order to reduce net belowground respiratory C losses,particularly those from the microbial decomposition of soil organic matter,with no significant effect on biomass production and N_(2)O emission.
