The main purpose of this study was to explore the dynamic changes of greenhouse gas（GHG）from grasslands under different degradation levels during the growing seasons of Inner Mongolia, China.Grassland degradation is...The main purpose of this study was to explore the dynamic changes of greenhouse gas（GHG）from grasslands under different degradation levels during the growing seasons of Inner Mongolia, China.Grassland degradation is associated with the dynamics of GHG fluxes, e.g., CO2, CH4 and N2O fluxes. As one of the global ecological environmental problems, grassland degradation has changed the vegetation productivity as well as the accumulation and decomposition rates of soil organic matter and thus will influence the carbon and nitrogen cycles of ecosystems, which will affect the GHG fluxes between grassland ecosystems and the atmosphere. Therefore, it is necessary to explore how the exchanges of CO2,CH4 and N2O fluxes between soil and atmosphere are influenced by the grassland degradation. We measured the fluxes of CO2, CH4 and N2O in lightly degraded, moderately degraded and severely degraded grasslands in Inner Mongolia of China during the growing seasons from July to September in 2013 and 2014. The typical semi-arid grassland of Inner Mongolia plays a role as the source of atmospheric CO2 and N2O and the sink for CH4. Compared with CO2 fluxes, N2O and CH4 fluxes were relatively low. The exchange of CO2, N2O and CH4 fluxes between the grassland soil and the atmosphere may exclusively depend on the net exchange rate of CO2 in semi-arid grasslands. The greenhouse gases showed a clear seasonal pattern, with the CO2 fluxes of –33.63–386.36 mg/（m·h）, CH4 uptake fluxes of 0.113–0.023 mg/（m·h） and N2O fluxes of –1.68–19.90 μg/（m·h）. Grassland degradation significantly influenced CH4 uptake but had no significant influence on CO2 and N2O emissions. Soil moisture and temperature were positively correlated with CO2 emissions but had no significant effect on N2O fluxes.Soil moisture may be the primary driving factor for CH4 uptake. The research results can be in help to better understand the impact of grassland degradation on the ecological environment.展开更多
Using stat ic chamber technique, fluxes of CO 2 , CH 4 and N 2 O were measured in the alpine grassland area from July 2000 to July 2001, d eterminations of mean fluxes showed that CO 2 and N 2 O were gene rally releas...Using stat ic chamber technique, fluxes of CO 2 , CH 4 and N 2 O were measured in the alpine grassland area from July 2000 to July 2001, d eterminations of mean fluxes showed that CO 2 and N 2 O were gene rally released from the soil, while the alpine grassland accounted for a weak CH 4 sink. Fluxes of CO 2 , CH 4 and N 2 O ranged widely. The highest CO 2 emission occurred in August, whereas a lmost 90% of the whole year emission occurred in the growing season. But the variations of CH 4 and N 2 O fluxes did not show any clear patterns over the one-year-experim ent. During a daily variation, the maximum CO 2 emission occurred at 16:00, and then decreased to the minimum emi ssion in the early morning. Daily pattern analyses indicated that the variation in CO 2 fluxes was positively related to air temperatures (R 2 =0.73) and soil temperatures at a depth of 5 cm (R 2 =0.86), whereas daily variations in CH 4 and N 2 O fluxes were poorly explained by soil temperatures and climatic va riables. CO 2 emissions in this area were much lower than other grasslands in plain areas .展开更多
Using the static opaque chamber method, the soil respiration rates （SR） were measured through the continuous experiments in situ in semiarid Stipa grandis steppe in Xilin River Basin of Inner Mongolia, China from Ju...Using the static opaque chamber method, the soil respiration rates （SR） were measured through the continuous experiments in situ in semiarid Stipa grandis steppe in Xilin River Basin of Inner Mongolia, China from June 2001 to June 2003, in parallel, the difference between the SR and the ecosystem respiration rates （TER） were compared. The results indicated that the seasonal variations of the SR and TER were obvious with higher emissions in growing season and a relatively low efflux level in non-growing season, furthermore, the negative effluxes were found in the observation site in winter; the annual CO2 efflux of total ecosystem ranged from 160.5 gC/（m^2·a） to 162.8 gC/（m^2·a） and that of soil ranged from 118.7 gC/（m^2·a） to 152.3 gC/（m^2·a）. The annual SR accounted for about 74.0% to 93.5% of the annual TER, but the results of Analysis of Variance （ANOVA） indicated that the difference between the annual average TER and SR did not reach the significance level of 0.05. The TER was under similar environmental controls as SR, in growing seasons of drought years, the variations of soil moisture at 0-10 cm and 10-20 cm depth could account for 79,1% 95.6% of the changes of the SR and TER, but in non-growing season, more than 75% of the variations of the SR and TER could be explained by the changes of the ground temperature of soil surface layers.展开更多
We describe the last glaciation climatic history Marine Isotope Stage(MIS, 2-4) from 66.7 ka to 14.5 ka in Hexigten, northeast Inner Mongolia, North China. The climate of the region experienced frequent and significan...We describe the last glaciation climatic history Marine Isotope Stage(MIS, 2-4) from 66.7 ka to 14.5 ka in Hexigten, northeast Inner Mongolia, North China. The climate of the region experienced frequent and significant fluctuations between dry-cold and less dry-cold during the late MIS4. The climate was generally warm and humid during early MIS3(MIS3 c) and late MIS3(MIS3 a), whereas it was cold and dry in middle MIS3(MIS3 b) and during MIS2. In this study, the cold and dry conditions were correlated with a stronger East Asian winter monsoon and strong dune activity; whereas, warm and humid conditions were related to a stronger East Asian summer monsoon(EASM) and weak dune activity. This study establishes six distinct dry and cold intervals during the last glacial period(66.7-14.5 ka) based on optically stimulated luminescence data, multi-proxies record(magnetic susceptibility, grain size analysis, Rb/Sr, SiO2/TiO2) and chemical index of alteration(CIA). The last glacial period may be correlated with Heinrich events 1 to 6 which were further confirmed by comparison with the Hulu cave stalagmites and Greenland ice core records. It is concluded that the study area was substantially affected by the EASM, as compared with the loess-desert transition zone of the Chinese Loess Plateau, especially in MIS3 c and suggested that the East Asian monsoon played a pivotal role in the last glacial period climate and dune activity.展开更多
Methane （OH4）, carbon dioxide （CO2） and nitrous oxide （N2O） are known to be major greenhouse gases that contribute to global warming. To identify the flux dynamics of these greenhouse gases is, therefore, of gre...Methane （OH4）, carbon dioxide （CO2） and nitrous oxide （N2O） are known to be major greenhouse gases that contribute to global warming. To identify the flux dynamics of these greenhouse gases is, therefore, of great significance. In this paper, we conducted a comparative study on an alpine grassland and alpine wetland at the Bayinbuluk Grassland Eco-system Research Station, Chinese Academy of Sciences. By using opaque, static, manual stainless steel chambers and gas chromatography, we measured the fluxes of CH4, N2O and CO2 from the grassland and wetland through an in situ monitoring study from May 2010 to October 2012. The mean flux rates of CH4, N2O and CO2 for the experimental alpine wetland in the growing season （from May to October） were estimated at 322.4 μg/（m2.h）, 16.7 μg/（m2.h） and 76.7 mg/（m2.h）, respectively; and the values for the alpine grassland were -88.2 μg/（m2.h）, 12.7 μg/（m2.h）, 57.3 mg/（m2.h）, respectively. The gas fluxes showed large seasonal and annual variations, suggesting weak fluxes in the non-growing season. The relationships between these gas fluxes and environmental factors were analyzed for the two alpine ecosystems. The results showed that air temperature, precipitation, soil temperature and soil moisture can greatly influence the fluxes of CH4, N2O and CO2, but the alpine grassland and alpine wetland showed different feedback mechanisms under the same climate and environmental conditions.展开更多
The mechanisms underlying the response of soil respiration(Rs) to nitrogen(N) addition remain to be explored in semiarid ecosystems. This study was conducted to determine the effect of N addition on soil microbial com...The mechanisms underlying the response of soil respiration(Rs) to nitrogen(N) addition remain to be explored in semiarid ecosystems. This study was conducted to determine the effect of N addition on soil microbial composition, Rs and the temperature sensitivity of Rs(Q10). The N addition experiment was carried out in a semiarid grassland in China, with N fertilizer application rates of 0, 2, 4, 8, 16, or 32 gN m-2yr-1. Microbial phospholipid fatty acids(PLFAs), Rs and Q10 were measured, and their relationships with soil properties were determined for three growing seasons. The results showed that N addition significantly increased the content of soil dissolved organic carbon(DOC) and inorganic nitrogen(IN), and decreased soil p H. With respect to soil microbes, N addition reduced soil PLFAs, reduced the fungi to bacteria ratio(F:B) and increased the gram-positive bacteria to gram-negative bacteria ratio(G+:G–). Rs under the N2, N4, N8, N16 and N32 treatments decreased by 2.58%, 14.86%, 22.62%, 23.97% and 19.87%, respectively, compared to the N0(control) treatment. The results of structural equation models showed that N addition reduced Rs by lowering soil PLFAs and altering the microbial composition. However, N addition had no significant effect on either Q10, soil total organic carbon(TOC) or total nitrogen(TN), indicating that N addition alleviated soil carbon loss and was unlikely to change the potential for a bigger loss under global warming.展开更多
基金financially supported by the National Key Basic Research Program of China (2014CB138803,2016YFC0500502)the Natural Science Foundation of China (31570451)the Program for Changjiang Scholars and Innovative Research Team in University (IRT_15R06)
文摘The main purpose of this study was to explore the dynamic changes of greenhouse gas（GHG）from grasslands under different degradation levels during the growing seasons of Inner Mongolia, China.Grassland degradation is associated with the dynamics of GHG fluxes, e.g., CO2, CH4 and N2O fluxes. As one of the global ecological environmental problems, grassland degradation has changed the vegetation productivity as well as the accumulation and decomposition rates of soil organic matter and thus will influence the carbon and nitrogen cycles of ecosystems, which will affect the GHG fluxes between grassland ecosystems and the atmosphere. Therefore, it is necessary to explore how the exchanges of CO2,CH4 and N2O fluxes between soil and atmosphere are influenced by the grassland degradation. We measured the fluxes of CO2, CH4 and N2O in lightly degraded, moderately degraded and severely degraded grasslands in Inner Mongolia of China during the growing seasons from July to September in 2013 and 2014. The typical semi-arid grassland of Inner Mongolia plays a role as the source of atmospheric CO2 and N2O and the sink for CH4. Compared with CO2 fluxes, N2O and CH4 fluxes were relatively low. The exchange of CO2, N2O and CH4 fluxes between the grassland soil and the atmosphere may exclusively depend on the net exchange rate of CO2 in semi-arid grasslands. The greenhouse gases showed a clear seasonal pattern, with the CO2 fluxes of –33.63–386.36 mg/（m·h）, CH4 uptake fluxes of 0.113–0.023 mg/（m·h） and N2O fluxes of –1.68–19.90 μg/（m·h）. Grassland degradation significantly influenced CH4 uptake but had no significant influence on CO2 and N2O emissions. Soil moisture and temperature were positively correlated with CO2 emissions but had no significant effect on N2O fluxes.Soil moisture may be the primary driving factor for CH4 uptake. The research results can be in help to better understand the impact of grassland degradation on the ecological environment.
基金National Key Project for Basic Research,No.G1998040800
文摘Using stat ic chamber technique, fluxes of CO 2 , CH 4 and N 2 O were measured in the alpine grassland area from July 2000 to July 2001, d eterminations of mean fluxes showed that CO 2 and N 2 O were gene rally released from the soil, while the alpine grassland accounted for a weak CH 4 sink. Fluxes of CO 2 , CH 4 and N 2 O ranged widely. The highest CO 2 emission occurred in August, whereas a lmost 90% of the whole year emission occurred in the growing season. But the variations of CH 4 and N 2 O fluxes did not show any clear patterns over the one-year-experim ent. During a daily variation, the maximum CO 2 emission occurred at 16:00, and then decreased to the minimum emi ssion in the early morning. Daily pattern analyses indicated that the variation in CO 2 fluxes was positively related to air temperatures (R 2 =0.73) and soil temperatures at a depth of 5 cm (R 2 =0.86), whereas daily variations in CH 4 and N 2 O fluxes were poorly explained by soil temperatures and climatic va riables. CO 2 emissions in this area were much lower than other grasslands in plain areas .
基金The State Key Basic Research Development and Planning Project (No. 2002CB412503) the Knowledge Innovation Program of theChinese Academy of Sciences (No. KZCX1-SW-01-04) the Knowledge Innovation Project of the Institute of Geographic Sciences and NaturalResources Research, Chinese Academy of Sciences(No. CXIOG-E01-03-01) and the National Natural Science Foundation of China(No. 40501072)
文摘Using the static opaque chamber method, the soil respiration rates （SR） were measured through the continuous experiments in situ in semiarid Stipa grandis steppe in Xilin River Basin of Inner Mongolia, China from June 2001 to June 2003, in parallel, the difference between the SR and the ecosystem respiration rates （TER） were compared. The results indicated that the seasonal variations of the SR and TER were obvious with higher emissions in growing season and a relatively low efflux level in non-growing season, furthermore, the negative effluxes were found in the observation site in winter; the annual CO2 efflux of total ecosystem ranged from 160.5 gC/（m^2·a） to 162.8 gC/（m^2·a） and that of soil ranged from 118.7 gC/（m^2·a） to 152.3 gC/（m^2·a）. The annual SR accounted for about 74.0% to 93.5% of the annual TER, but the results of Analysis of Variance （ANOVA） indicated that the difference between the annual average TER and SR did not reach the significance level of 0.05. The TER was under similar environmental controls as SR, in growing seasons of drought years, the variations of soil moisture at 0-10 cm and 10-20 cm depth could account for 79,1% 95.6% of the changes of the SR and TER, but in non-growing season, more than 75% of the variations of the SR and TER could be explained by the changes of the ground temperature of soil surface layers.
基金supported by the Research Fund for Hexigten Global Geopark(Grant No.62932014004)Specialized Fund for Fundamental Research Program of China University of Geosciences,Beijing(Grant No.2011YYL016)+1 种基金the Specialized Fund for Public Welfare Industry,Ministry of Land and Resources of China(Grant No.201211077-3)the Specialized Research Fund for the Doctoral Program of Higher Education of China(for PhD supervisors,Grant No.20110022110005)
文摘We describe the last glaciation climatic history Marine Isotope Stage(MIS, 2-4) from 66.7 ka to 14.5 ka in Hexigten, northeast Inner Mongolia, North China. The climate of the region experienced frequent and significant fluctuations between dry-cold and less dry-cold during the late MIS4. The climate was generally warm and humid during early MIS3(MIS3 c) and late MIS3(MIS3 a), whereas it was cold and dry in middle MIS3(MIS3 b) and during MIS2. In this study, the cold and dry conditions were correlated with a stronger East Asian winter monsoon and strong dune activity; whereas, warm and humid conditions were related to a stronger East Asian summer monsoon(EASM) and weak dune activity. This study establishes six distinct dry and cold intervals during the last glacial period(66.7-14.5 ka) based on optically stimulated luminescence data, multi-proxies record(magnetic susceptibility, grain size analysis, Rb/Sr, SiO2/TiO2) and chemical index of alteration(CIA). The last glacial period may be correlated with Heinrich events 1 to 6 which were further confirmed by comparison with the Hulu cave stalagmites and Greenland ice core records. It is concluded that the study area was substantially affected by the EASM, as compared with the loess-desert transition zone of the Chinese Loess Plateau, especially in MIS3 c and suggested that the East Asian monsoon played a pivotal role in the last glacial period climate and dune activity.
基金funded by the National Basic Research Program of China (2009CB825103)the National Natural Science Foundation of China (41340041)the West Light Foundation of the Chinese Academy of Sciences (XBBS201206)
文摘Methane （OH4）, carbon dioxide （CO2） and nitrous oxide （N2O） are known to be major greenhouse gases that contribute to global warming. To identify the flux dynamics of these greenhouse gases is, therefore, of great significance. In this paper, we conducted a comparative study on an alpine grassland and alpine wetland at the Bayinbuluk Grassland Eco-system Research Station, Chinese Academy of Sciences. By using opaque, static, manual stainless steel chambers and gas chromatography, we measured the fluxes of CH4, N2O and CO2 from the grassland and wetland through an in situ monitoring study from May 2010 to October 2012. The mean flux rates of CH4, N2O and CO2 for the experimental alpine wetland in the growing season （from May to October） were estimated at 322.4 μg/（m2.h）, 16.7 μg/（m2.h） and 76.7 mg/（m2.h）, respectively; and the values for the alpine grassland were -88.2 μg/（m2.h）, 12.7 μg/（m2.h）, 57.3 mg/（m2.h）, respectively. The gas fluxes showed large seasonal and annual variations, suggesting weak fluxes in the non-growing season. The relationships between these gas fluxes and environmental factors were analyzed for the two alpine ecosystems. The results showed that air temperature, precipitation, soil temperature and soil moisture can greatly influence the fluxes of CH4, N2O and CO2, but the alpine grassland and alpine wetland showed different feedback mechanisms under the same climate and environmental conditions.
基金The National Natural Science Foundation of China(31770519)The National Key Research and Development Program of China(2017YFC0503805).
文摘The mechanisms underlying the response of soil respiration(Rs) to nitrogen(N) addition remain to be explored in semiarid ecosystems. This study was conducted to determine the effect of N addition on soil microbial composition, Rs and the temperature sensitivity of Rs(Q10). The N addition experiment was carried out in a semiarid grassland in China, with N fertilizer application rates of 0, 2, 4, 8, 16, or 32 gN m-2yr-1. Microbial phospholipid fatty acids(PLFAs), Rs and Q10 were measured, and their relationships with soil properties were determined for three growing seasons. The results showed that N addition significantly increased the content of soil dissolved organic carbon(DOC) and inorganic nitrogen(IN), and decreased soil p H. With respect to soil microbes, N addition reduced soil PLFAs, reduced the fungi to bacteria ratio(F:B) and increased the gram-positive bacteria to gram-negative bacteria ratio(G+:G–). Rs under the N2, N4, N8, N16 and N32 treatments decreased by 2.58%, 14.86%, 22.62%, 23.97% and 19.87%, respectively, compared to the N0(control) treatment. The results of structural equation models showed that N addition reduced Rs by lowering soil PLFAs and altering the microbial composition. However, N addition had no significant effect on either Q10, soil total organic carbon(TOC) or total nitrogen(TN), indicating that N addition alleviated soil carbon loss and was unlikely to change the potential for a bigger loss under global warming.
