Boron isotopic compositions in marine planktonic foraminifers can record changes in seawater pH and hence provide a new tool to reconstruct the changes of paleo-atmospheric PCO2.Here a comparative study was done on bo...Boron isotopic compositions in marine planktonic foraminifers can record changes in seawater pH and hence provide a new tool to reconstruct the changes of paleo-atmospheric PCO2.Here a comparative study was done on boron isotopes and trace element abundances of planktonic foraminifers,Globigerinoides sacculifer and Globigerinoides ruber from three tropical ODP sites,Site 806B,Site 664C and Site 999A.It is demonstrated here that G.ruber is a better species to be used for downcore boron isotope analyses on glacial-interglacial scales,particularly since G.sacculifer is prone to dissolution causing unexpectedly light boron isotopes during glacial times.It has been shown that the trace elements composition of foraminifers (i.e.,Mg/Ca,U/Ca,B/Ca,and Li/Ca) can reflect the variations of seawater temperature and/or [CO3 2-].However,all of these systems are highly species de-pendent and affected by other vital effects,and it is therefore important to perform necessary calibrations when applying them to the downcore analyses.展开更多
依托FACE(Free air carbon dioxide enrichment)技术平台,采用稳定^(13)C同位索法,通过将C_3作物小麦种植于长期单作玉米的C_4土壤上,研究了大气CO_2浓度升高和不同氮肥水平对水稻-小麦轮作制中冬小麦生长季土壤有机碳更新的影响。结果...依托FACE(Free air carbon dioxide enrichment)技术平台,采用稳定^(13)C同位索法,通过将C_3作物小麦种植于长期单作玉米的C_4土壤上,研究了大气CO_2浓度升高和不同氮肥水平对水稻-小麦轮作制中冬小麦生长季土壤有机碳更新的影响。结果表明,种植一季小麦后土壤有机碳的δ^(13)C值显著降低,小麦生长改变了土壤有机碳的组成,大气CO_2浓度增加促进作物向土壤中输入更多的碳。大气CO_2浓度升高增加了麦田土壤有机碳的更新率,使土壤有机碳的更新率由3.61%(施氮量为150 kg hm^(-2),LN)～4.59%(施氮量为250 kg hm^(-2),HN)提高至6.72%(LN)～8.55%(HN),分别增加72.7%和86.1%。结果表明,大气CO_2浓度升高和提高氮肥用量将加快农田土壤有机碳的更新。展开更多
依托FACE（free air carbon dioxide enrichment）技术平台，利用阻断根法，采用H6400红外气体分析仪（IRGA）-田间原位测定的方法，研究了大气CO2浓度升高和不同氮肥水平对水稻／小麦轮作制中冬小麦旺盛生长期间根际呼吸的影响。结果...依托FACE（free air carbon dioxide enrichment）技术平台，利用阻断根法，采用H6400红外气体分析仪（IRGA）-田间原位测定的方法，研究了大气CO2浓度升高和不同氮肥水平对水稻／小麦轮作制中冬小麦旺盛生长期间根际呼吸的影响。结果表明，在整个测定期间，大气CO2浓度升高增强了根际呼吸速率，提高了根际呼吸排放量。在高N和低N处理中，高CO2浓度下的根际呼吸总排放量分别比Ambient极显著增加117．0％和90．8％。根际呼吸速率在孕穗初期达到最大值；使根际呼吸在土壤呼吸中的比重由24．5％（LN）～26．7（HN）提高到39．8％（LN）～47．1％（HN）。CO2浓度升高与氮肥用量对根际呼吸产生交互效应。表明大气CO2浓度升高将加快土壤向大气的CO2排放，结果将有助于评价未来高CO2浓度背景下农田生态系统土壤碳的固定潜力。展开更多
基金funded by ORS fellowship supplemented by he Department of Earth Scieces,University of Bristol to Ni R. Y.National Natural Science Foundation of China (Grant No.40703014)
文摘Boron isotopic compositions in marine planktonic foraminifers can record changes in seawater pH and hence provide a new tool to reconstruct the changes of paleo-atmospheric PCO2.Here a comparative study was done on boron isotopes and trace element abundances of planktonic foraminifers,Globigerinoides sacculifer and Globigerinoides ruber from three tropical ODP sites,Site 806B,Site 664C and Site 999A.It is demonstrated here that G.ruber is a better species to be used for downcore boron isotope analyses on glacial-interglacial scales,particularly since G.sacculifer is prone to dissolution causing unexpectedly light boron isotopes during glacial times.It has been shown that the trace elements composition of foraminifers (i.e.,Mg/Ca,U/Ca,B/Ca,and Li/Ca) can reflect the variations of seawater temperature and/or [CO3 2-].However,all of these systems are highly species de-pendent and affected by other vital effects,and it is therefore important to perform necessary calibrations when applying them to the downcore analyses.
文摘依托FACE(Free air carbon dioxide enrichment)技术平台,采用稳定^(13)C同位索法,通过将C_3作物小麦种植于长期单作玉米的C_4土壤上,研究了大气CO_2浓度升高和不同氮肥水平对水稻-小麦轮作制中冬小麦生长季土壤有机碳更新的影响。结果表明,种植一季小麦后土壤有机碳的δ^(13)C值显著降低,小麦生长改变了土壤有机碳的组成,大气CO_2浓度增加促进作物向土壤中输入更多的碳。大气CO_2浓度升高增加了麦田土壤有机碳的更新率,使土壤有机碳的更新率由3.61%(施氮量为150 kg hm^(-2),LN)～4.59%(施氮量为250 kg hm^(-2),HN)提高至6.72%(LN)～8.55%(HN),分别增加72.7%和86.1%。结果表明,大气CO_2浓度升高和提高氮肥用量将加快农田土壤有机碳的更新。
文摘依托FACE（free air carbon dioxide enrichment）技术平台，利用阻断根法，采用H6400红外气体分析仪（IRGA）-田间原位测定的方法，研究了大气CO2浓度升高和不同氮肥水平对水稻／小麦轮作制中冬小麦旺盛生长期间根际呼吸的影响。结果表明，在整个测定期间，大气CO2浓度升高增强了根际呼吸速率，提高了根际呼吸排放量。在高N和低N处理中，高CO2浓度下的根际呼吸总排放量分别比Ambient极显著增加117．0％和90．8％。根际呼吸速率在孕穗初期达到最大值；使根际呼吸在土壤呼吸中的比重由24．5％（LN）～26．7（HN）提高到39．8％（LN）～47．1％（HN）。CO2浓度升高与氮肥用量对根际呼吸产生交互效应。表明大气CO2浓度升高将加快土壤向大气的CO2排放，结果将有助于评价未来高CO2浓度背景下农田生态系统土壤碳的固定潜力。
