Long-term continuous cropping of soybean （Glycine max）, spring wheat （Triticum aesativum） and maize （Zea mays） is widely practiced by local farmers in northeast China. A field experiment （started in 1991） was ...Long-term continuous cropping of soybean （Glycine max）, spring wheat （Triticum aesativum） and maize （Zea mays） is widely practiced by local farmers in northeast China. A field experiment （started in 1991） was used to investigate the differences in soil carbon dioxide （CO2） emissions under continuous cropping of the three major crops and to evaluate the relationships between CO2 fluxes and soil temperature and moisture for Mollisols in northeast China. Soil CO2 emissions were measured using a closed-chamber method during the growing season in 2011. No remarkable differences in soil organic carbon were found among the cropping systems （P〉0.05）. However, significant differences in CO2 emissions from soils were observed among the three cropping systems （P〈0.05）. Over the course of the entire growing season, cumulative soil CO2 emissions under different cropping systems were in the following order： continuous maize （（829±10） g CO2 m2）〉continuous wheat （（629±22） g CO2 m^2）〉continuous soybean （（474±30） g CO2 m-2）. Soil temperature explained 42-65% of the seasonal variations in soil CO2 flux, with a Q10 between 1.63 and 2.31; water-filled pore space explained 25-47% of the seasonal variations in soil CO2 flux. A multiple regression model including both soil temperature （T, ~C） and water-filled pore space （W, %）, log（]）=a＋bT log（W）, was established, accounting for 51-66% of the seasonal variations in soil CO2 flux. The results suggest that soil CO2 emissions and their Q10 values under a continuous cropping system largely depend on crop types in Mollisols of Northeast China.展开更多
The formation and turnover of macroaggregates are critical processes influencing the dynamics and stabilization of soil organic carbon(SOC).Soil aggregate size distribution is directly related to the makeup and activi...The formation and turnover of macroaggregates are critical processes influencing the dynamics and stabilization of soil organic carbon(SOC).Soil aggregate size distribution is directly related to the makeup and activity of microbial communities.We incubated soils managed for>30 years as restored grassland(GL),farmland(FL)and bare fallow(BF)for 60 days using both intact and reduced aggregate size distributions(intact aggregate distribution(IAD)<6 mm;reduced aggregate distribution(RAD)<1 mm),in treatments with added glucose,alanine or inorganic N,to reveal activity and microbial community structure as a function of aggregate size and makeup.Over a 60-day incubation period,the highest phospholipid fatty acid(PLFA)abundance was on day 7 for bacteria and fungi,on day 15 for actinomycete.The majority of the variation in enzymatic activities was likely related to PLFA abundance.GL had higher microbial abundance and enzyme activity.Mechanically reducing macroaggregates(>0.25 mm)by 34.7%in GL soil with no substrate additions increased the abundance of PLFAs(average increase of 15.7%)and activities of β-glucosidase(increase of 17.4%)and N-acetyl-β-glucosaminidase(increase of 7.6%).The addition of C substrates increased PLFA abundance in FL and BF by averages of 18.8 and 33.4%,respectively,but not in GL soil.The results show that the effect of habitat destruction on microorganisms depends on the soil aggregates,due to a release of bioavailable C,and the addition of substrates for soils with limited nutrient availability.The protection of SOC is promoted by larger size soil aggregate structures that are important to different aggregate size classes in affecting soil C stabilization and microbial community structure and activity.展开更多
基金supported by the Key Research Program of the Chinese Academy of Sciences (KZZD-EW-TZ-16-02)the Foundation for Young Talents of the Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences (DLSYQ13001)the National Natural Science Foundation of China (41101283)
文摘Long-term continuous cropping of soybean （Glycine max）, spring wheat （Triticum aesativum） and maize （Zea mays） is widely practiced by local farmers in northeast China. A field experiment （started in 1991） was used to investigate the differences in soil carbon dioxide （CO2） emissions under continuous cropping of the three major crops and to evaluate the relationships between CO2 fluxes and soil temperature and moisture for Mollisols in northeast China. Soil CO2 emissions were measured using a closed-chamber method during the growing season in 2011. No remarkable differences in soil organic carbon were found among the cropping systems （P〉0.05）. However, significant differences in CO2 emissions from soils were observed among the three cropping systems （P〈0.05）. Over the course of the entire growing season, cumulative soil CO2 emissions under different cropping systems were in the following order： continuous maize （（829±10） g CO2 m2）〉continuous wheat （（629±22） g CO2 m^2）〉continuous soybean （（474±30） g CO2 m-2）. Soil temperature explained 42-65% of the seasonal variations in soil CO2 flux, with a Q10 between 1.63 and 2.31; water-filled pore space explained 25-47% of the seasonal variations in soil CO2 flux. A multiple regression model including both soil temperature （T, ~C） and water-filled pore space （W, %）, log（]）=a＋bT log（W）, was established, accounting for 51-66% of the seasonal variations in soil CO2 flux. The results suggest that soil CO2 emissions and their Q10 values under a continuous cropping system largely depend on crop types in Mollisols of Northeast China.
基金funded by the National Key Research and Development Program of China (2016YFD0300806-1, 2016YFD0200309-6 and 2017YFD0300605-3)the National Natural Science Foundation of China (41771327 and 41571219)the Young Scientists’ Group of North Institute of Geography and Agroecology, Chinese Academy of Sciences (DLSXZ1605)
文摘The formation and turnover of macroaggregates are critical processes influencing the dynamics and stabilization of soil organic carbon(SOC).Soil aggregate size distribution is directly related to the makeup and activity of microbial communities.We incubated soils managed for>30 years as restored grassland(GL),farmland(FL)and bare fallow(BF)for 60 days using both intact and reduced aggregate size distributions(intact aggregate distribution(IAD)<6 mm;reduced aggregate distribution(RAD)<1 mm),in treatments with added glucose,alanine or inorganic N,to reveal activity and microbial community structure as a function of aggregate size and makeup.Over a 60-day incubation period,the highest phospholipid fatty acid(PLFA)abundance was on day 7 for bacteria and fungi,on day 15 for actinomycete.The majority of the variation in enzymatic activities was likely related to PLFA abundance.GL had higher microbial abundance and enzyme activity.Mechanically reducing macroaggregates(>0.25 mm)by 34.7%in GL soil with no substrate additions increased the abundance of PLFAs(average increase of 15.7%)and activities of β-glucosidase(increase of 17.4%)and N-acetyl-β-glucosaminidase(increase of 7.6%).The addition of C substrates increased PLFA abundance in FL and BF by averages of 18.8 and 33.4%,respectively,but not in GL soil.The results show that the effect of habitat destruction on microorganisms depends on the soil aggregates,due to a release of bioavailable C,and the addition of substrates for soils with limited nutrient availability.The protection of SOC is promoted by larger size soil aggregate structures that are important to different aggregate size classes in affecting soil C stabilization and microbial community structure and activity.
