Agricultural ecosystems play a pivotal role in global carbon(C)sequestration efforts.Microbial C use efficiency(CUE)serves as a comprehensive metric that reflects the balance between microbial contributions to the acc...Agricultural ecosystems play a pivotal role in global carbon(C)sequestration efforts.Microbial C use efficiency(CUE)serves as a comprehensive metric that reflects the balance between microbial contributions to the accumulation and decomposition of soil organic C.However,the overall distribution patterns and underlying drivers of microbial CUE at the national scale remain unclear.Herein,data from 209 paired samples from 55 studies were analyzed to assess the distribution patterns and influencing factors of microbial CUE based on enzyme stoichiometry(CUE_(ST))in agricultural ecosystems across China.Results revealed that farmlands exhibited the highest CUE_(ST)value(mean=0.51),exceeding those of grasslands(0.46)and forests(0.44).Contrasting patterns of CUE_(ST)regulation were observed across land-use types,with farmlands showing significant(P<0.001)positive relationships of CUE_(ST)with phosphorus vs.nitrogen(N/P)limitation index,while grasslands and forests demonstrated inverse(P<0.05)relationships of CUE_(ST)with C limitation index.Nutrient stoichiometry emerged as the dominant driver of CUE_(ST),with enzyme ratios and mean annual precipitation playing secondary roles.Moreover,land management practices,including fertilization,grazing,and tillage,as well as land-use transition,significantly influenced microbial CUE_(ST)by potentially altering nutrient availability and soil properties;notably,water addition in grasslands had particularly positive effects.These findings provide a critical foundation for harnessing microbial CUE in agriculture and may inform scalable strategies to enhance soil C sequestration and climate-smart land management.展开更多
A grain-based distinct element model featuring three-dimensional （3D） Voronoi tessellations （randompoly-crystals） is proposed for simulation of crack damage development in brittle rocks. The grainboundaries in pol...A grain-based distinct element model featuring three-dimensional （3D） Voronoi tessellations （randompoly-crystals） is proposed for simulation of crack damage development in brittle rocks. The grainboundaries in poly-crystal structure produced by Voronoi tessellations can represent flaws in intact rockand allow for numerical replication of crack damage progression through initiation and propagation ofmicro-fractures along grain boundaries. The Voronoi modelling scheme has been used widely in the pastfor brittle fracture simulation of rock materials. However the difficulty of generating 3D Voronoi modelshas limited its application to two-dimensional （2D） codes. The proposed approach is implemented inNeper, an open-source engine for generation of 3D Voronoi grains, to generate block geometry files thatcan be read directly into 3DEC. A series of Unconfined Compressive Strength （UCS） tests are simulated in3DEC to verify the proposed methodology for 3D simulation of brittle fractures and to investigate therelationship between each micro-parameter and the model＇s macro-response. The possibility of numericalreplication of the classical U-shape strength curve for anisotropic rocks is also investigated innumerical UCS tests by using complex-shaped （elongated） grains that are cemented to one another alongtheir adjoining sides. A micro-parameter calibration procedure is established for 3D Voronoi models foraccurate replication of the mechanical behaviour of isotropic and anisotropic （containing a fabric） rocks. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.42225706,42377297,42407408,42177283)the Fundamental Research Funds for the Central Universities of China(No.2662023PY010)the support from the Postdoctoral Fellowship Program of the China Postdoctoral Science Foundation(No.GZB20230246)。
文摘Agricultural ecosystems play a pivotal role in global carbon(C)sequestration efforts.Microbial C use efficiency(CUE)serves as a comprehensive metric that reflects the balance between microbial contributions to the accumulation and decomposition of soil organic C.However,the overall distribution patterns and underlying drivers of microbial CUE at the national scale remain unclear.Herein,data from 209 paired samples from 55 studies were analyzed to assess the distribution patterns and influencing factors of microbial CUE based on enzyme stoichiometry(CUE_(ST))in agricultural ecosystems across China.Results revealed that farmlands exhibited the highest CUE_(ST)value(mean=0.51),exceeding those of grasslands(0.46)and forests(0.44).Contrasting patterns of CUE_(ST)regulation were observed across land-use types,with farmlands showing significant(P<0.001)positive relationships of CUE_(ST)with phosphorus vs.nitrogen(N/P)limitation index,while grasslands and forests demonstrated inverse(P<0.05)relationships of CUE_(ST)with C limitation index.Nutrient stoichiometry emerged as the dominant driver of CUE_(ST),with enzyme ratios and mean annual precipitation playing secondary roles.Moreover,land management practices,including fertilization,grazing,and tillage,as well as land-use transition,significantly influenced microbial CUE_(ST)by potentially altering nutrient availability and soil properties;notably,water addition in grasslands had particularly positive effects.These findings provide a critical foundation for harnessing microbial CUE in agriculture and may inform scalable strategies to enhance soil C sequestration and climate-smart land management.
文摘A grain-based distinct element model featuring three-dimensional （3D） Voronoi tessellations （randompoly-crystals） is proposed for simulation of crack damage development in brittle rocks. The grainboundaries in poly-crystal structure produced by Voronoi tessellations can represent flaws in intact rockand allow for numerical replication of crack damage progression through initiation and propagation ofmicro-fractures along grain boundaries. The Voronoi modelling scheme has been used widely in the pastfor brittle fracture simulation of rock materials. However the difficulty of generating 3D Voronoi modelshas limited its application to two-dimensional （2D） codes. The proposed approach is implemented inNeper, an open-source engine for generation of 3D Voronoi grains, to generate block geometry files thatcan be read directly into 3DEC. A series of Unconfined Compressive Strength （UCS） tests are simulated in3DEC to verify the proposed methodology for 3D simulation of brittle fractures and to investigate therelationship between each micro-parameter and the model＇s macro-response. The possibility of numericalreplication of the classical U-shape strength curve for anisotropic rocks is also investigated innumerical UCS tests by using complex-shaped （elongated） grains that are cemented to one another alongtheir adjoining sides. A micro-parameter calibration procedure is established for 3D Voronoi models foraccurate replication of the mechanical behaviour of isotropic and anisotropic （containing a fabric） rocks. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
