Increased precipitation during the vegetation periods was observed in and further predicted for Inner Mongolia. The changes in the associated soil moisture may affect the biosphere-atmosphere exchange of greenhouse ga...Increased precipitation during the vegetation periods was observed in and further predicted for Inner Mongolia. The changes in the associated soil moisture may affect the biosphere-atmosphere exchange of greenhouse gases. Therefore, we set up an irrigation experiment with one watered (W) and one unwatered plot (UW) at a winter-grazed Leymus chinensis-steppe site in the Xilin River catchment, Inner Mongolia. UW only received the natural precipitation of 2005 (129 mm), whereas W was additionally watered after the precipitation data of 1998 (in total 427 mm). In the 3-hour resolution, we determined nitrous oxide (N20), methane (CH4) and carbon dioxide (CO2) fluxes at both plots between May and September 2005, using a fully automated, chamber-based measuring system. N20 fluxes in the steppe were very low, with mean emissions (±s.e.) of 0.9-4-0.5 and 0.7-4-0.5 μg N m^-2 h^-1 at W and UW, respectively. The steppe soil always served as a CH4 sink, with mean fluxes of -24.1-4-3.9 and -31.1-4- 5.3 μg C m^-2 h^-1 at W and UW. Nighttime mean CO2 emissions were 82.6±8.7 and 26.3±1.7 mg C m^-2 h^-1 at W and UW, respectively, coinciding with an almost doubled aboveground plant biomass at W. Our results indicate that the ecosystem CO2 respiration responded sensitively to increased water input during the vegetation period, whereas the effects on CH4 and N2O fluxes were weak, most likely due to the high evapotranspiration and the lack of substrate for N2O producing processes. Based on our results, we hypothesize that with the gradual increase of summertime precipitation in Inner Mongolia, ecosystem CO2 respiration will be enhanced and CH4 uptake by the steppe soils will be lightly inhibited.展开更多
亚热带蔬菜地是氧化亚氮(N_2O)的重要排放源,本研究首次采用基于闭路量子级联激光吸收光谱仪的涡动相关(QCLAS-EC)法观测亚热带蔬菜地秋冬季非施肥阶段的N_2O排放通量,以评估QCLAS-EC法测量亚热带蔬菜地N_2O通量的适用性。结果表明,QCLA...亚热带蔬菜地是氧化亚氮(N_2O)的重要排放源,本研究首次采用基于闭路量子级联激光吸收光谱仪的涡动相关(QCLAS-EC)法观测亚热带蔬菜地秋冬季非施肥阶段的N_2O排放通量,以评估QCLAS-EC法测量亚热带蔬菜地N_2O通量的适用性。结果表明,QCLAS-EC观测系统在野外条件下能长期稳定运行,可观测到N_2O排放的季节变化趋势,其检测限为18.5μg N m^(-2) h^(-1)(95%置信水平),试验期间获得的97.5%的N_2O通量大于此检测限,表明QCLAS-EC观测系统可有效并准确测量亚热带蔬菜地的N_2O排放通量,仪器本身的灵敏度不是通量检测的限制因素。展开更多
Soil nitrogen mineralization(Nmin)is a key process that converts organic N into mineral N that controls soil N availability to plants.However,regional assessments of soil Nmin in cropland and its affecting factors are...Soil nitrogen mineralization(Nmin)is a key process that converts organic N into mineral N that controls soil N availability to plants.However,regional assessments of soil Nmin in cropland and its affecting factors are lacking,especially in relation to variation in elevation.In this study,a 4-week incubation experiment was implemented to measure net soil Nmin rate,gross nitrification(Nit)rate and corresponding soil abiotic properties in five field soils(A-C,maize;D,flue-cured tobacco;and E,vegetables;with elevation decreasing from A to E)from different altitudes in a typical intensive agricultural area in Dali City,Yunnan Province,China.The results showed that soil Nmin rate ranged from 0.10 to 0.17 mg·kg^(-1)·d^(-1)N,with the highest value observed in field E,followed by fields D,C,B,and A,which indicated that soil Nmin and Nit rates varied between fields,decreasing with elevation.The soil Nit rate ranged from 434.2 to 827.1μg·kg^(-1)·h^(-1)N,with the highest value determined in field D,followed by those in fields E,C,B,and A.The rates of soil Nmin and Nit were positively correlated with several key soil parameters,including total soil N,dissolved organic carbon and dissolved inorganic N across all fields,which indicated that soil variables regulated soil Nmin and Nit in cropland fields.In addition,a strong positive relationship was observed between soil Nmin and Nit.These findings provide a greater understanding of the response of soil Nmin among cropland fields related to spatial variation.It is suggested that the soil Nmin from cropland should be considered in the evaluation of the N transformations at the regional scale.展开更多
Biochar application has the potential to improve soil fertility and increase soil carbon stock, especially in tropical regions. Information on the temperature sensitivity of carbon dioxide(CO2) evolution from biochar-...Biochar application has the potential to improve soil fertility and increase soil carbon stock, especially in tropical regions. Information on the temperature sensitivity of carbon dioxide(CO2) evolution from biochar-amended soils at very high temperatures, as observed for tropical surface soils, is limited but urgently needed for the development of region-specific biochar management targeted to optimize biochar effects on soil functions. Here, we investigated the temperature sensitivity of soil respiration to the addition of different rates of Miscanthus biochar(0, 6.25, 12.5, and 25 Mg ha-1) in two types of soils with contrasting textures. Biochar-amended soil treatments and their controls were incubated at constant temperatures of 20, 30, and 40℃. Overall, our results show that: i) considering data from all treatments and temperatures, the addition of biochar decreased soil CO2 emissions when compared to untreated soils;ii) CO2 emissions from biochar-amended soils had a higher temperature sensitivity than those from biochar-free soils;iii) the temperature sensitivity of soil respiration in sandy soils was higher than that in clay soils;and iv) for clay soils, relative increases in soil CO2 emissions from biochar-amended soils were higher when the temperature increased from 30 to 40℃, while for sandy soils, the highest temperature responses of soil respiration were observed when increasing the temperature from 20 to 30℃. Together, these findings suggest a significantly reduced potential to increase soil organic carbon stocks when Miscanthus biochar is applied to tropical soils at high surface temperatures, which could be counteracted by the soil-and weather-specific timing of biochar application.展开更多
基金the German Research Foundation (DFG, Research UnitNo. 536, "Matter fluxes in grasslands of Inner Mongo-lia as influenced by stocking rate", MAGIM) (BU 1173/6-2)the National Natural Science Foundation of China(NSFC) (Grant Nos. 40425010, 40331014)
文摘Increased precipitation during the vegetation periods was observed in and further predicted for Inner Mongolia. The changes in the associated soil moisture may affect the biosphere-atmosphere exchange of greenhouse gases. Therefore, we set up an irrigation experiment with one watered (W) and one unwatered plot (UW) at a winter-grazed Leymus chinensis-steppe site in the Xilin River catchment, Inner Mongolia. UW only received the natural precipitation of 2005 (129 mm), whereas W was additionally watered after the precipitation data of 1998 (in total 427 mm). In the 3-hour resolution, we determined nitrous oxide (N20), methane (CH4) and carbon dioxide (CO2) fluxes at both plots between May and September 2005, using a fully automated, chamber-based measuring system. N20 fluxes in the steppe were very low, with mean emissions (±s.e.) of 0.9-4-0.5 and 0.7-4-0.5 μg N m^-2 h^-1 at W and UW, respectively. The steppe soil always served as a CH4 sink, with mean fluxes of -24.1-4-3.9 and -31.1-4- 5.3 μg C m^-2 h^-1 at W and UW. Nighttime mean CO2 emissions were 82.6±8.7 and 26.3±1.7 mg C m^-2 h^-1 at W and UW, respectively, coinciding with an almost doubled aboveground plant biomass at W. Our results indicate that the ecosystem CO2 respiration responded sensitively to increased water input during the vegetation period, whereas the effects on CH4 and N2O fluxes were weak, most likely due to the high evapotranspiration and the lack of substrate for N2O producing processes. Based on our results, we hypothesize that with the gradual increase of summertime precipitation in Inner Mongolia, ecosystem CO2 respiration will be enhanced and CH4 uptake by the steppe soils will be lightly inhibited.
基金supported from the Ministry of Science and Technology of China[grant number 2012CB417106]the Chinese Academy of Sciences[grant number XDA05020100]+1 种基金the German Science Foundation[contract number BU1173/12-1]the National Natural Science Foundation of China[grant numbers41405137 and 41321064]
文摘亚热带蔬菜地是氧化亚氮(N_2O)的重要排放源,本研究首次采用基于闭路量子级联激光吸收光谱仪的涡动相关(QCLAS-EC)法观测亚热带蔬菜地秋冬季非施肥阶段的N_2O排放通量,以评估QCLAS-EC法测量亚热带蔬菜地N_2O通量的适用性。结果表明,QCLAS-EC观测系统在野外条件下能长期稳定运行,可观测到N_2O排放的季节变化趋势,其检测限为18.5μg N m^(-2) h^(-1)(95%置信水平),试验期间获得的97.5%的N_2O通量大于此检测限,表明QCLAS-EC观测系统可有效并准确测量亚热带蔬菜地的N_2O排放通量,仪器本身的灵敏度不是通量检测的限制因素。
基金founded by China Postdoctoral Science Foundation(2021M703131)National Key Research and Development Program(2019YFD1100503).
文摘Soil nitrogen mineralization(Nmin)is a key process that converts organic N into mineral N that controls soil N availability to plants.However,regional assessments of soil Nmin in cropland and its affecting factors are lacking,especially in relation to variation in elevation.In this study,a 4-week incubation experiment was implemented to measure net soil Nmin rate,gross nitrification(Nit)rate and corresponding soil abiotic properties in five field soils(A-C,maize;D,flue-cured tobacco;and E,vegetables;with elevation decreasing from A to E)from different altitudes in a typical intensive agricultural area in Dali City,Yunnan Province,China.The results showed that soil Nmin rate ranged from 0.10 to 0.17 mg·kg^(-1)·d^(-1)N,with the highest value observed in field E,followed by fields D,C,B,and A,which indicated that soil Nmin and Nit rates varied between fields,decreasing with elevation.The soil Nit rate ranged from 434.2 to 827.1μg·kg^(-1)·h^(-1)N,with the highest value determined in field D,followed by those in fields E,C,B,and A.The rates of soil Nmin and Nit were positively correlated with several key soil parameters,including total soil N,dissolved organic carbon and dissolved inorganic N across all fields,which indicated that soil variables regulated soil Nmin and Nit in cropland fields.In addition,a strong positive relationship was observed between soil Nmin and Nit.These findings provide a greater understanding of the response of soil Nmin among cropland fields related to spatial variation.It is suggested that the soil Nmin from cropland should be considered in the evaluation of the N transformations at the regional scale.
基金We acknowledge the National Council for Scientific and Technological Development(CNPq)of Brazil(No.404150/2013-6)for financing this research.T.F.Rittl is grateful to the São Paulo Research Foundation(FAPESP)of Brazil for supporting her postdoctoral scholarship(No.2015/10108-9)and L.Canisares thanks to CNPq for her undergraduate scientific scholarship.
文摘Biochar application has the potential to improve soil fertility and increase soil carbon stock, especially in tropical regions. Information on the temperature sensitivity of carbon dioxide(CO2) evolution from biochar-amended soils at very high temperatures, as observed for tropical surface soils, is limited but urgently needed for the development of region-specific biochar management targeted to optimize biochar effects on soil functions. Here, we investigated the temperature sensitivity of soil respiration to the addition of different rates of Miscanthus biochar(0, 6.25, 12.5, and 25 Mg ha-1) in two types of soils with contrasting textures. Biochar-amended soil treatments and their controls were incubated at constant temperatures of 20, 30, and 40℃. Overall, our results show that: i) considering data from all treatments and temperatures, the addition of biochar decreased soil CO2 emissions when compared to untreated soils;ii) CO2 emissions from biochar-amended soils had a higher temperature sensitivity than those from biochar-free soils;iii) the temperature sensitivity of soil respiration in sandy soils was higher than that in clay soils;and iv) for clay soils, relative increases in soil CO2 emissions from biochar-amended soils were higher when the temperature increased from 30 to 40℃, while for sandy soils, the highest temperature responses of soil respiration were observed when increasing the temperature from 20 to 30℃. Together, these findings suggest a significantly reduced potential to increase soil organic carbon stocks when Miscanthus biochar is applied to tropical soils at high surface temperatures, which could be counteracted by the soil-and weather-specific timing of biochar application.