Aims Elevated nitrogen(N)deposition in tropical regions may accelerate ecosystem phosphorus(P)limitation.However,it is not explicitly addressed that how changes in soil N and P availability affect foliar nutrients and...Aims Elevated nitrogen(N)deposition in tropical regions may accelerate ecosystem phosphorus(P)limitation.However,it is not explicitly addressed that how changes in soil N and P availability affect foliar nutrients and photosynthesis of plants in tropical forests.In this study,we examined the effects of N and P additions on foliar nutrients and net photosynthesis of two dominant understory species,Randia can-thioides(R.canthioides)and Cryptocarya concinna(C.concinna)in an N-saturated old-growth tropical forest(>400-year-old)in south-ern China.Methods A full factorial NP addition experiment(2×2)was established in 2007 and continued through August 2010.Four treatments,including control,N addition(150 kg N ha^(−1) year^(−1)),P addi-tion(150 kg P ha^(−1) year^(−1))and NP addition(150 kg N ha^(−1) year^(−1) plus 150 kg P ha^(−1) year^(−1))were set up in this experiment.Photosynthetic traits maximum photosynthetic CO_(2) assimilation(Amax),stomatal conductance(gs),leaf transpiration(E),light satu-rating point,concentrations of chlorophyll a/b and foliar nutri-ents(N and P)of the two species were measured with standard methods.Important Findings Three years of N addition had no significant effects on any measured photosynthetic parameter of either species.However,N addition significantly elevated foliar N and P concentrations of one species(R.canthioides),resulting in lower photosynthetic nitrogen use effi-ciency(PNUE).N treatments decreased foliar P concentration of the other(C.concinna),resulting in increased photosynthetic phos-phorus use efficiency,which was potentially related to N-induced P shortage.In contrast,positive effects of P treatments on gs of R.can-thioides,Amax and chlorophyll a+b of C.concinna were observed.P treatments also elevated foliar P and PNUE of both species,imply-ing P induced more efficient use of N.Our results suggested a more important role of P than N on influencing photosynthetic traits of these two understory species.Alleviation of P shortage through P addition may enhance photosynthetic performances of some under-story species in N-rich tropical forests.展开更多
Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the emerging hydrogen economy. Complex nitrate wastewater with a wide pH range calls for flexible catalysts with h...Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the emerging hydrogen economy. Complex nitrate wastewater with a wide pH range calls for flexible catalysts with high selectivity. A high Faradaic efficiency(FE) of NH3 cannot be obtained under strong acid or alkaline conditions due to the uncontrollable adsorption energy and coverage of hydrogen species(H*) on active sites. This article describes the design and fabrication of a copper-palladium(Cu-Pd) alloy nanocrystal catalyst that inhibits H2 and nitrite generation in electrolytes with different nitrate concentrations and varied pH. The interfacial sites of Cu-Pd alloys could enhance the adsorption energy and coverage of H* while increasing the reaction rate constant of NO_(2)*-to-NO*, which achieves a rapid conversion of NO_(2)* along with a decreased FE of NO_(2)-. Under ambient conditions, optimal FE(NH3) is close to 100% at a wide pH range, with the solar-to-chemical conversion efficiency approaching 4.29%. The combination of thermodynamics and kinetics investigations would offer new insights into the reduction mechanism of NO_(2)* for further development of nitrate reduction.展开更多
基金National Natural Science Foundation of China(41273143)National Key Basic Research 973 Program(2010CB833502)Knowledge Innovation Program of the Chinese Academy of Sciences(KSCX2-EW-J-28).
文摘Aims Elevated nitrogen(N)deposition in tropical regions may accelerate ecosystem phosphorus(P)limitation.However,it is not explicitly addressed that how changes in soil N and P availability affect foliar nutrients and photosynthesis of plants in tropical forests.In this study,we examined the effects of N and P additions on foliar nutrients and net photosynthesis of two dominant understory species,Randia can-thioides(R.canthioides)and Cryptocarya concinna(C.concinna)in an N-saturated old-growth tropical forest(>400-year-old)in south-ern China.Methods A full factorial NP addition experiment(2×2)was established in 2007 and continued through August 2010.Four treatments,including control,N addition(150 kg N ha^(−1) year^(−1)),P addi-tion(150 kg P ha^(−1) year^(−1))and NP addition(150 kg N ha^(−1) year^(−1) plus 150 kg P ha^(−1) year^(−1))were set up in this experiment.Photosynthetic traits maximum photosynthetic CO_(2) assimilation(Amax),stomatal conductance(gs),leaf transpiration(E),light satu-rating point,concentrations of chlorophyll a/b and foliar nutri-ents(N and P)of the two species were measured with standard methods.Important Findings Three years of N addition had no significant effects on any measured photosynthetic parameter of either species.However,N addition significantly elevated foliar N and P concentrations of one species(R.canthioides),resulting in lower photosynthetic nitrogen use effi-ciency(PNUE).N treatments decreased foliar P concentration of the other(C.concinna),resulting in increased photosynthetic phos-phorus use efficiency,which was potentially related to N-induced P shortage.In contrast,positive effects of P treatments on gs of R.can-thioides,Amax and chlorophyll a+b of C.concinna were observed.P treatments also elevated foliar P and PNUE of both species,imply-ing P induced more efficient use of N.Our results suggested a more important role of P than N on influencing photosynthetic traits of these two understory species.Alleviation of P shortage through P addition may enhance photosynthetic performances of some under-story species in N-rich tropical forests.
基金supported by the National Key R&D Program of China(2021YFA1500804)the National Natural Science Foundation of China(22121004,51861125104)+1 种基金the Natural Science Foundation of Tianjin City(18JCJQJC47500)Haihe Laboratory of Sustainable Chemical Transformations,the Program of Introducing Talents of Discipline to Universities(BP0618007)and the Xplorer Prize.
文摘Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the emerging hydrogen economy. Complex nitrate wastewater with a wide pH range calls for flexible catalysts with high selectivity. A high Faradaic efficiency(FE) of NH3 cannot be obtained under strong acid or alkaline conditions due to the uncontrollable adsorption energy and coverage of hydrogen species(H*) on active sites. This article describes the design and fabrication of a copper-palladium(Cu-Pd) alloy nanocrystal catalyst that inhibits H2 and nitrite generation in electrolytes with different nitrate concentrations and varied pH. The interfacial sites of Cu-Pd alloys could enhance the adsorption energy and coverage of H* while increasing the reaction rate constant of NO_(2)*-to-NO*, which achieves a rapid conversion of NO_(2)* along with a decreased FE of NO_(2)-. Under ambient conditions, optimal FE(NH3) is close to 100% at a wide pH range, with the solar-to-chemical conversion efficiency approaching 4.29%. The combination of thermodynamics and kinetics investigations would offer new insights into the reduction mechanism of NO_(2)* for further development of nitrate reduction.