股票市场和债券市场变量之间的溢出效应是近来金融学研究的一个重要课题。本文实证研究了我国股票市场和债券市场流动性之间的溢出效应,提供了我国股票和债券市场流动性一体化的证据。研究发现:首先,我国股票市场和债券市场流动性之间...股票市场和债券市场变量之间的溢出效应是近来金融学研究的一个重要课题。本文实证研究了我国股票市场和债券市场流动性之间的溢出效应,提供了我国股票和债券市场流动性一体化的证据。研究发现:首先,我国股票市场和债券市场流动性之间存在显著领先滞后关系并互为因果关系,符合"flight to liquidity";其次,宏观环境的变化对两个市场的流动性会产生显著的影响;更为重要的是,宏观环境对市场流动性的影响很大程度上是通过另一市场的传导而间接的发生作用。展开更多
There is limited information on carbon sequestration efficiency(CSE)of soil aggregates in upland and paddy soils under long-term fertilization regimes.In a red soil region of southern China,an upland soil experiment s...There is limited information on carbon sequestration efficiency(CSE)of soil aggregates in upland and paddy soils under long-term fertilization regimes.In a red soil region of southern China,an upland soil experiment started in 1986 and a paddy soil experiment commenced in 1981.These experiments were conducted using different fertilization treatments.After 30 years,soil organic carbon(SOC)content and stock of different aggregate components were analyzed.The results showed that the SOC contents and stocks in upland soil were lower than in paddy soil.In both upland and paddy soils,the SOC contents and stocks of all aggregate components in NPKM(combined treatment with chemical nitrogen(N),phosphorus(P),potassium(K)fertilizers and manure)were the highest among all treatments.Compared with CK(no fertilizer),SOC content of all aggregate components in NPKM was increased by 13.21–63.11%and 19.13–73.33%in upland and paddy soils,respectively.Meanwhile,the change rates in SOC stock of all aggregate components in upland soil were lower than in paddy soil,although the change rate of SOC stock of all aggregate components in NPKM was higher than in other treatments.Furthermore,a linear equation could fit the relationships between carbon(C)input and change rate of SOC stock(P<0.05).Results indicated that the sum of CSE from all aggregate components in upland soil(16.02%)was higher than that of paddy soil(15.12%)in the same climatic condition and from the same parent material.However,the CSEs from all aggregates were higher than that of bulk soil,although the result from bulk soil also showed that the CSE of upland soil was higher than that of paddy soil.展开更多
采用BIOME-BGC模型对广东鹤山的马占相思（Acacia mangium）人工林生态系统1985-2100年间的碳格局及其动态变化进行了模拟。结果表明，马占相思生物量在前12a增长较快，之后增长缓慢，最终达到300t hm^-2；预计2100年马占相思生物量在...采用BIOME-BGC模型对广东鹤山的马占相思（Acacia mangium）人工林生态系统1985-2100年间的碳格局及其动态变化进行了模拟。结果表明，马占相思生物量在前12a增长较快，之后增长缓慢，最终达到300t hm^-2；预计2100年马占相思生物量在于、根、叶中的分配分别为73.91％、21.74％和4.35％。马占相思人工林的碳贮量在前12a增长较快，之后增长缓慢并最终维持在325t C hm^-2左右，在造林初始阶段主要分布于土壤中，之后在植被、土壤和凋落物3大碳库中的分配分别为43.08％、52.30％和4.62％；马占相思净初级生产力（NPP）在4-12a较大，最大可达11t C hm^-2，之后下降至3-6t C hm^-2；马占相思叶面积指数（LAX）前3a增长迅速，5a达到7.84，之后下降，约为2.7-5.0；LAJ与NPP的回归分析结果显示LAI可能是限制马占相思林NPP增长的主要因子。模拟结果还显示马占相思林前期生长迅速，但随后生长缓慢，叶生物量还出现负增长现象。因此，我国南亚热带地区在以马占相思作为先锋树种进行地带性森林植被恢复时，可在12a后进行林分改造。展开更多
Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In ...Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In this study,carbon(C),nitrogen(N),and phosphorus(P)concentrations were evaluated in plant tissues(trees,shrubs,and herbs),litter,and soil of young(≤40-year-old),middle-aged(41–60-year-old),near-mature(61–80-year-old),and mature(81–120-year-old)Quercus secondary forests on the Loess Plateau,China.Vegetation composition,plant biomass,and C stock were determined to illustrate their interaction with stoichiometry.Only tree biomass C signifi cantly increased with stand development.Leaf N and trunk P concentrationsgenerally increased,but branch P decreased with growth stage.Fine roots had the highest C and P concentrations at the middle-aged stage.In contrast,shrubs,herbs,litter,and soil C:N:P stoichiometry did not change signifi cantly during stand development.Leaf N and P were positively correlated with soil C,N,P,and their ratios.However,there was no signifi cant correlation between litter and leaves in terms of C:N:P stoichiometry.A redundancy analysis showed that soil N best explained leaf N and P variance,and tree biomass and C stock were related to biotic factors such as tree age and shrub biomass.Hierarchical partitioning analysis indicated that,compared with soil or litter variables,stand age only accounted for a relatively small proportion of leaf C,N,and P variation.Thus,secondary Quercus ecosystems might have inherent ability to maintain sensitive responses of metabolically active organs to environmental factors during stand aging.The results of this work help to elucidate the biogeochemical cycling of secondary forest ecosystems in tree development,provide novel insights into the adaptation strategies of plants in diff erent organs and growth stages,and could be used to guide fertilization programs and optimize forest structure.展开更多
The urban regeneration lies on closed loops of energy,materials,information.The aim of case study is to evaluate and support policies of urban regeneration.The topic of the study is the control of waste flow made by t...The urban regeneration lies on closed loops of energy,materials,information.The aim of case study is to evaluate and support policies of urban regeneration.The topic of the study is the control of waste flow made by the C&D(construction&demolition)activities involving the urban district.Each building produces a continuous flow of wastes during its predicted service life.This flow is mainly due to small building sites that generate small amount of wastes.In this way the collection,recycle and reuse material can be less accurate.In a regeneration perspective the reused and/or recycled part must be maximized.The study develops a GIS(geographic information system)based model for the assessment of the maintenance workloads of wastes produced.Coming from the data available by the public authorities and the survey on sites,the research group has carried out evaluation of the amount of wastes for building envelope,interior refurbishment of apartments,roads and parking lots.The output is a raw estimation of the C&D wastes by the maintenance and refurbishment of an urban district in Turin based on real evaluation of works needed.展开更多
文摘股票市场和债券市场变量之间的溢出效应是近来金融学研究的一个重要课题。本文实证研究了我国股票市场和债券市场流动性之间的溢出效应,提供了我国股票和债券市场流动性一体化的证据。研究发现:首先,我国股票市场和债券市场流动性之间存在显著领先滞后关系并互为因果关系,符合"flight to liquidity";其次,宏观环境的变化对两个市场的流动性会产生显著的影响;更为重要的是,宏观环境对市场流动性的影响很大程度上是通过另一市场的传导而间接的发生作用。
基金supported by the National Key Research and Development Program of China (2016YFD0200101 and 2016YFD0300901)the National Natural Science Foundation of China (41671301 and 41371293)the Innovation Plan of Scientific and Research in Modern Agriculture, Jiangxi Province, China (JXXTCX2015003-005)
文摘There is limited information on carbon sequestration efficiency(CSE)of soil aggregates in upland and paddy soils under long-term fertilization regimes.In a red soil region of southern China,an upland soil experiment started in 1986 and a paddy soil experiment commenced in 1981.These experiments were conducted using different fertilization treatments.After 30 years,soil organic carbon(SOC)content and stock of different aggregate components were analyzed.The results showed that the SOC contents and stocks in upland soil were lower than in paddy soil.In both upland and paddy soils,the SOC contents and stocks of all aggregate components in NPKM(combined treatment with chemical nitrogen(N),phosphorus(P),potassium(K)fertilizers and manure)were the highest among all treatments.Compared with CK(no fertilizer),SOC content of all aggregate components in NPKM was increased by 13.21–63.11%and 19.13–73.33%in upland and paddy soils,respectively.Meanwhile,the change rates in SOC stock of all aggregate components in upland soil were lower than in paddy soil,although the change rate of SOC stock of all aggregate components in NPKM was higher than in other treatments.Furthermore,a linear equation could fit the relationships between carbon(C)input and change rate of SOC stock(P<0.05).Results indicated that the sum of CSE from all aggregate components in upland soil(16.02%)was higher than that of paddy soil(15.12%)in the same climatic condition and from the same parent material.However,the CSEs from all aggregates were higher than that of bulk soil,although the result from bulk soil also showed that the CSE of upland soil was higher than that of paddy soil.
文摘采用BIOME-BGC模型对广东鹤山的马占相思（Acacia mangium）人工林生态系统1985-2100年间的碳格局及其动态变化进行了模拟。结果表明，马占相思生物量在前12a增长较快，之后增长缓慢，最终达到300t hm^-2；预计2100年马占相思生物量在于、根、叶中的分配分别为73.91％、21.74％和4.35％。马占相思人工林的碳贮量在前12a增长较快，之后增长缓慢并最终维持在325t C hm^-2左右，在造林初始阶段主要分布于土壤中，之后在植被、土壤和凋落物3大碳库中的分配分别为43.08％、52.30％和4.62％；马占相思净初级生产力（NPP）在4-12a较大，最大可达11t C hm^-2，之后下降至3-6t C hm^-2；马占相思叶面积指数（LAX）前3a增长迅速，5a达到7.84，之后下降，约为2.7-5.0；LAJ与NPP的回归分析结果显示LAI可能是限制马占相思林NPP增长的主要因子。模拟结果还显示马占相思林前期生长迅速，但随后生长缓慢，叶生物量还出现负增长现象。因此，我国南亚热带地区在以马占相思作为先锋树种进行地带性森林植被恢复时，可在12a后进行林分改造。
基金supported by the National Nature Science Foundation of China(No.41977418 and 42130717)National Key R&D Program of China(2016YFC0501703 and 2017YFC0504605)CAS“Light of West China”Program(XAB201702).
文摘Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In this study,carbon(C),nitrogen(N),and phosphorus(P)concentrations were evaluated in plant tissues(trees,shrubs,and herbs),litter,and soil of young(≤40-year-old),middle-aged(41–60-year-old),near-mature(61–80-year-old),and mature(81–120-year-old)Quercus secondary forests on the Loess Plateau,China.Vegetation composition,plant biomass,and C stock were determined to illustrate their interaction with stoichiometry.Only tree biomass C signifi cantly increased with stand development.Leaf N and trunk P concentrationsgenerally increased,but branch P decreased with growth stage.Fine roots had the highest C and P concentrations at the middle-aged stage.In contrast,shrubs,herbs,litter,and soil C:N:P stoichiometry did not change signifi cantly during stand development.Leaf N and P were positively correlated with soil C,N,P,and their ratios.However,there was no signifi cant correlation between litter and leaves in terms of C:N:P stoichiometry.A redundancy analysis showed that soil N best explained leaf N and P variance,and tree biomass and C stock were related to biotic factors such as tree age and shrub biomass.Hierarchical partitioning analysis indicated that,compared with soil or litter variables,stand age only accounted for a relatively small proportion of leaf C,N,and P variation.Thus,secondary Quercus ecosystems might have inherent ability to maintain sensitive responses of metabolically active organs to environmental factors during stand aging.The results of this work help to elucidate the biogeochemical cycling of secondary forest ecosystems in tree development,provide novel insights into the adaptation strategies of plants in diff erent organs and growth stages,and could be used to guide fertilization programs and optimize forest structure.
文摘The urban regeneration lies on closed loops of energy,materials,information.The aim of case study is to evaluate and support policies of urban regeneration.The topic of the study is the control of waste flow made by the C&D(construction&demolition)activities involving the urban district.Each building produces a continuous flow of wastes during its predicted service life.This flow is mainly due to small building sites that generate small amount of wastes.In this way the collection,recycle and reuse material can be less accurate.In a regeneration perspective the reused and/or recycled part must be maximized.The study develops a GIS(geographic information system)based model for the assessment of the maintenance workloads of wastes produced.Coming from the data available by the public authorities and the survey on sites,the research group has carried out evaluation of the amount of wastes for building envelope,interior refurbishment of apartments,roads and parking lots.The output is a raw estimation of the C&D wastes by the maintenance and refurbishment of an urban district in Turin based on real evaluation of works needed.
