The vertical distribution and exchange mechanisms of soil organic and inorganic carbon(SOC,SIC)play an important role in assessing carbon(C)cycling and budgets.However,the impact of land use through time for deep soil...The vertical distribution and exchange mechanisms of soil organic and inorganic carbon(SOC,SIC)play an important role in assessing carbon(C)cycling and budgets.However,the impact of land use through time for deep soil C(below 100 cm)is not well known.To investigate deep C storage under different land uses and evaluate how it changes with time,we collected soil samples to a depth of 500 cm in a soil profile in the Gutun watershed on the Chinese Loess Plateau(CLP);and determined SOC,SIC,and bulk density.The magnitude of SOC stocks in the 0-500 cm depth range fell into the following ranking:shrubland(17.2 kg m-2)>grassland(16.3 kg m-2)>forestland(15.2 kg m-2)>cropland(14.1 kg m 2)>gully land(6.4 kg m 2).The ranking for SIC stocks were:grassland(104.1 kg m^2)>forestland(96.2 kg m^2)>shrubland(90.6 kg m-2)>cropland(82.4 kg m 2)>gully land(50.3 kg m-2).Respective SOC and SIC stocks were at least 1.6-and 2.1-fold higher within the 100-500 cm depth range,as compared to the 0-100 cm depth range.Overall SOC and SIC stocks decreased significantly from the 5th to the 15th year of cultivation in croplands,and generally increased up to the 70th year.Both SOC and SIC stocks showed a turning point at 15 years cultivation,which should be considered when evaluating soil C sequestration.Estimates of C stocks greatly depends on soil sampling depth,and understanding the influences of land use and time will improve soil productivity and conservation in regions with deep soils.展开更多
To meet the measurement demands on small-mass radiocarbon （carbon content at 10.6 g level） which are becoming increasingly significant, Xi＇an-AMS has made improvements to the existing method of sample loading and h...To meet the measurement demands on small-mass radiocarbon （carbon content at 10.6 g level） which are becoming increasingly significant, Xi＇an-AMS has made improvements to the existing method of sample loading and has upgraded the Cs sputter ion source from the original SO-110 model. In order to study the feasibility of small-mass samples in Xi＇an-AMS and evaluate the radiocarbon sample preparation ability using existing routine systems of H2/Fe and Zn/Fe, the small-mass samples prepared by four different methods are tested. They are the mass division method, mass dilution method, H2/Fe reduction method and Zn/Fe reduction method. The results show that carbon mass above 25 μg can be prepared using the existing Zn/Fe system, but no less than 100 μg is required using the existing H2/Fe system, which can be improved. This indicates Xi＇an-AMS are now able to analyze small-mass radiocarbon samples.展开更多
基金The Strategic Priority Research Program of the Chinese Academy of Sciences,NO.XDB 40000000National Natural Science Foundation of China,No.41730108,No.41773141,No.41573136,No.41991252National Research Program for Key Issues in Air Pollution Control,No.DQGGO 105-02。
文摘The vertical distribution and exchange mechanisms of soil organic and inorganic carbon(SOC,SIC)play an important role in assessing carbon(C)cycling and budgets.However,the impact of land use through time for deep soil C(below 100 cm)is not well known.To investigate deep C storage under different land uses and evaluate how it changes with time,we collected soil samples to a depth of 500 cm in a soil profile in the Gutun watershed on the Chinese Loess Plateau(CLP);and determined SOC,SIC,and bulk density.The magnitude of SOC stocks in the 0-500 cm depth range fell into the following ranking:shrubland(17.2 kg m-2)>grassland(16.3 kg m-2)>forestland(15.2 kg m-2)>cropland(14.1 kg m 2)>gully land(6.4 kg m 2).The ranking for SIC stocks were:grassland(104.1 kg m^2)>forestland(96.2 kg m^2)>shrubland(90.6 kg m-2)>cropland(82.4 kg m 2)>gully land(50.3 kg m-2).Respective SOC and SIC stocks were at least 1.6-and 2.1-fold higher within the 100-500 cm depth range,as compared to the 0-100 cm depth range.Overall SOC and SIC stocks decreased significantly from the 5th to the 15th year of cultivation in croplands,and generally increased up to the 70th year.Both SOC and SIC stocks showed a turning point at 15 years cultivation,which should be considered when evaluating soil C sequestration.Estimates of C stocks greatly depends on soil sampling depth,and understanding the influences of land use and time will improve soil productivity and conservation in regions with deep soils.
基金Supported by National Natural Science Foundation of China(11205161,41290254)
文摘To meet the measurement demands on small-mass radiocarbon （carbon content at 10.6 g level） which are becoming increasingly significant, Xi＇an-AMS has made improvements to the existing method of sample loading and has upgraded the Cs sputter ion source from the original SO-110 model. In order to study the feasibility of small-mass samples in Xi＇an-AMS and evaluate the radiocarbon sample preparation ability using existing routine systems of H2/Fe and Zn/Fe, the small-mass samples prepared by four different methods are tested. They are the mass division method, mass dilution method, H2/Fe reduction method and Zn/Fe reduction method. The results show that carbon mass above 25 μg can be prepared using the existing Zn/Fe system, but no less than 100 μg is required using the existing H2/Fe system, which can be improved. This indicates Xi＇an-AMS are now able to analyze small-mass radiocarbon samples.
