The dynamics of calcium(Ca)and magnesium(Mg)in the forest floor and topsoil caused by anthropogenic and natural processes continue to be a concern in temperate forests.However,the impacts of abiotic and biotic variabl...The dynamics of calcium(Ca)and magnesium(Mg)in the forest floor and topsoil caused by anthropogenic and natural processes continue to be a concern in temperate forests.However,the impacts of abiotic and biotic variables as well as their interactions remain unclear,especially in areas undergoing long-term forest restoration.In this study,Ca and Mg concentrations in the forest floor and topsoil from 239 forest plots across the Loess Plateau were measured,and the effects of forest types,climate,soil properties,stand characteristics and nitrogen deposition were explored.The results showed significantly higher Ca concentrations in the forest floor(20.68±8.04 mg/g)than in the topsoil(13.28±12.83 mg/g),whereas Mg exhibited the inverse pattern(3.64±1.09 and 10.11±2.51 mg/g,respectively).The effect of forest types was only significant on forest floor Ca,and Ca concentrations were higher in broadleaf and mixed forests than in coniferous forests.Overall,Ca and Mg concentrations in forest floor and topsoil increased with latitudes while decreased with elevations,and the significance of the trends varied among forest types.Forest floor Ca and Mg were mainly influenced by environmental variables aboveground,i.e.,basal area(BA)and mean annual precipitation(MAP),respectively;topsoil Ca and Mg were more affected by soil properties(soil C/N and pH,respectively).Those suggested a depletion of Ca belowground was associated with forest growth and enriched soil nitrogen,and the leaching of mobile Mg was correlated with rainfall and soil acidification.Besides,the impact of environmental variables on Ca-Mg balance(Ca/Mg ratio)belowground was primarily through the regulation of Ca.Elucidating the influence of environmental variables will improve our ability to predict future changes in base cations and thus forest soil health in the greening vegetated Loess Plateau.展开更多
Conventional electrocatalytic urea synthesis via CO_(2)+N_(2) or CO_(2)+NO_(3)^(-)coelectrolysis generally suffers from poor reactants coactivation,low C-N coupling efficiency,and serious competing reactions.To overco...Conventional electrocatalytic urea synthesis via CO_(2)+N_(2) or CO_(2)+NO_(3)^(-)coelectrolysis generally suffers from poor reactants coactivation,low C-N coupling efficiency,and serious competing reactions.To overcome these limitations,we implement HCOOH+NO_(3)^(-)coelectrolysis to urea using a Fe-Pd dual-atom catalyst(Fe_(1)Pd_(1)-DAC).Operando spectroscopic measurements and theoretical computations collectively reveal that Pd_(1) selectively dehydrogenates HCOOH to^(*)COOH,while Fe_(1) selectively activates NO_(3)^(-)to^(*)NH_(2).Specifically,the spatial proximity and electrophilic-nucleophilic synergy of^(*)COOH and^(*)NH_(2) enable the high C-N coupling efficiency and well-suppressed competing reactions.Consequently,Fe_(1)Pd_(1)-DAC assembled in a flow cell delivers the unprecedented urea yield rate up to 448.1 mmol h^(-1) g^(-1) and Faradaic efficiency of 78.3%at an industrial-level current density of-215 mA cm^(-2),far outperforming those obtained from CO_(2)+N_(2) or CO_(2)+NO_(3) coelectrolysis.Further techno-economic analysis demonstrates Fe_(1)Pd_(1)-DAC as a promising catalyst for economically feasible urea production via HCOOH+NO_(3)^(-)coelectrolysis.展开更多
基金supported by the National Natural Science Foundation of China(42401054)Natural Science Foundation of Hebei Province(D2024205019)Science and Technology Project of Hebei Education Department(BJ2025014).
文摘The dynamics of calcium(Ca)and magnesium(Mg)in the forest floor and topsoil caused by anthropogenic and natural processes continue to be a concern in temperate forests.However,the impacts of abiotic and biotic variables as well as their interactions remain unclear,especially in areas undergoing long-term forest restoration.In this study,Ca and Mg concentrations in the forest floor and topsoil from 239 forest plots across the Loess Plateau were measured,and the effects of forest types,climate,soil properties,stand characteristics and nitrogen deposition were explored.The results showed significantly higher Ca concentrations in the forest floor(20.68±8.04 mg/g)than in the topsoil(13.28±12.83 mg/g),whereas Mg exhibited the inverse pattern(3.64±1.09 and 10.11±2.51 mg/g,respectively).The effect of forest types was only significant on forest floor Ca,and Ca concentrations were higher in broadleaf and mixed forests than in coniferous forests.Overall,Ca and Mg concentrations in forest floor and topsoil increased with latitudes while decreased with elevations,and the significance of the trends varied among forest types.Forest floor Ca and Mg were mainly influenced by environmental variables aboveground,i.e.,basal area(BA)and mean annual precipitation(MAP),respectively;topsoil Ca and Mg were more affected by soil properties(soil C/N and pH,respectively).Those suggested a depletion of Ca belowground was associated with forest growth and enriched soil nitrogen,and the leaching of mobile Mg was correlated with rainfall and soil acidification.Besides,the impact of environmental variables on Ca-Mg balance(Ca/Mg ratio)belowground was primarily through the regulation of Ca.Elucidating the influence of environmental variables will improve our ability to predict future changes in base cations and thus forest soil health in the greening vegetated Loess Plateau.
基金supported by the National Natural Science Foundation of China(52561042)the Industrial Support Plan Project of Gansu Provincial Education Department(2024CYZC-22)。
文摘Conventional electrocatalytic urea synthesis via CO_(2)+N_(2) or CO_(2)+NO_(3)^(-)coelectrolysis generally suffers from poor reactants coactivation,low C-N coupling efficiency,and serious competing reactions.To overcome these limitations,we implement HCOOH+NO_(3)^(-)coelectrolysis to urea using a Fe-Pd dual-atom catalyst(Fe_(1)Pd_(1)-DAC).Operando spectroscopic measurements and theoretical computations collectively reveal that Pd_(1) selectively dehydrogenates HCOOH to^(*)COOH,while Fe_(1) selectively activates NO_(3)^(-)to^(*)NH_(2).Specifically,the spatial proximity and electrophilic-nucleophilic synergy of^(*)COOH and^(*)NH_(2) enable the high C-N coupling efficiency and well-suppressed competing reactions.Consequently,Fe_(1)Pd_(1)-DAC assembled in a flow cell delivers the unprecedented urea yield rate up to 448.1 mmol h^(-1) g^(-1) and Faradaic efficiency of 78.3%at an industrial-level current density of-215 mA cm^(-2),far outperforming those obtained from CO_(2)+N_(2) or CO_(2)+NO_(3) coelectrolysis.Further techno-economic analysis demonstrates Fe_(1)Pd_(1)-DAC as a promising catalyst for economically feasible urea production via HCOOH+NO_(3)^(-)coelectrolysis.
