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Predicting carbon storage of mixed broadleaf forests based on the finite mixture model incorporating stand factors,site quality,and aridity index

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Forest Ecosystems 2024年第3期11卷 276-286页

作者： Yanlin Wang Dongzhi Wang Dongyan Zhang Qiang Liu Yongning Li college of Forestry Hebei Agricultural UniversityBaoding071001China college of economics and management Hebei Agricultural UniversityBaoding071001China

The diameter distribution function(DDF)is a crucial tool for accurately predicting stand carbon storage(CS).The current key issue,however,is how to construct a high-precision DDF based on stand factors,site quality,and aridity index to predict stand CS in multi-species mixed forests with complex structures.This study used data from70 survey plots for mixed broadleaf Populus davidiana and Betula platyphylla forests in the Mulan Rangeland State Forest,Hebei Province,China,to construct the DDF based on maximum likelihood estimation and finite mixture model(FMM).Ordinary least squares(OLS),linear seemingly unrelated regression(LSUR),and back propagation neural network(BPNN)were used to investigate the influences of stand factors,site quality,and aridity index on the shape and scale parameters of DDF and predicted stand CS of mixed broadleaf forests.The results showed that FMM accurately described the stand-level diameter distribution of the mixed P.davidiana and B.platyphylla forests;whereas the Weibull function constructed by MLE was more accurate in describing species-level diameter distribution.The combined variable of quadratic mean diameter(Dq),stand basal area(BA),and site quality improved the accuracy of the shape parameter models of FMM;the combined variable of Dq,BA,and De Martonne aridity index improved the accuracy of the scale parameter models.Compared to OLS and LSUR,the BPNN had higher accuracy in the re-parameterization process of FMM.OLS,LSUR,and BPNN overestimated the CS of P.davidiana but underestimated the CS of B.platyphylla in the large diameter classes(DBH≥18 cm).BPNN accurately estimated stand-and species-level CS,but it was more suitable for estimating stand-level CS compared to species-level CS,thereby providing a scientific basis for the optimization of stand structure and assessment of carbon sequestration capacity in mixed broadleaf forests.

关键词： Weibull function Finite mixture model Linear seemingly unrelated regression Back propagation neural network Carbon storage

The multiple roles of crop structural change in productivity,nutrition and environment in China:A decomposition analysis

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Journal of Integrative Agriculture 2024年第5期23卷 1763-1773页

作者： Xiangyang Zhang Yumei Zhang Shenggen Fan college of economics and management China Agricultural UniversityBejing 100083China Academy of Global Food economics and Policy China Agricultural UniversityBejing 100083China

China's crop structure has undergone significant changes in the last two decades since 2000,with an increase in the share of cereals,vegetables,and fruit,squeezing out other crops.As a result,land productivity,nutrient supply,and carbon emissions have changed.How to reallocate limited farmland among crops to achieve the multiple goals of agrifood systems becomes an important issue.This study explores the sources of land productivity and nutrition supply growth and carbon emissions reduction,and identifies the multiple roles of crop structural change from 2003 to 2020 based on a decomposition analysis.The results reveal that the growth within crops is still the primary driver in land productivity and nutrition supply and the reduction in carbon emissions.However,structural change also plays various roles at different periods.From 2003 to 2010,crop structural change increased the total calorie supply but lowered land productivity and contributed at least 70%of the total growth of carbon emissions.The crop structure was relatively stable,and their effects were modest from 2010 to 2015.From 2015 to 2020,the crop structural change began to play a greater role and generate synergistic effects in improving land productivity,micronutrient supply,and reducing carbon emissions,contributing to approximately a quarter of the growth of land productivity and 30%of total carbon emissions reduction.These results suggest that strategies for crop structural change should comprehensively consider its multiple impacts,aiming to achieve co-benefits while minimizing trade-offs.

关键词： crop structural change land productivity nutrition carbon emissions

Repositioning fertilizer manufacturing subsidies for improving food security and reducing greenhouse gas emissions in China

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Journal of Integrative Agriculture 2024年第2期23卷 430-443页

作者： Zongyi Wu Xiaolong Feng Yumei Zhang Shenggen Fan Academy of Global Food economics and Policy China Agricultural UniversityBeijing 100083China college of economics and management China Agricultural UniversityBeijing 100083China

China removed fertilizer manufacturing subsidies from 2015 to 2018 to bolster market-oriented reforms and foster environmentally sustainable practices.However,the impact of this policy reform on food security and the environment remains inadequately evaluated.Moreover,although green and low-carbon technologies offer environmental advantages,their widespread adoption is hindered by prohibitively high costs.This study analyzes the impact of removing fertilizer manufacturing subsidies and explores the potential feasibility of redirecting fertilizer manufacturing subsidies to invest in the diffusion of these technologies.Utilizing the China agricultural University Agri-food Systems model,we analyzed the potential for achieving mutually beneficial outcomes regarding food security and environmental sustainability.The findings indicate that removing fertilizer manufacturing subsidies has reduced greenhouse gas(GHG)emissions from agricultural activities by 3.88 million metric tons,with minimal impact on food production.Redirecting fertilizer manufacturing subsidies to invest in green and low-carbon technologies,including slow and controlled-release fertilizer,organic-inorganic compound fertilizers,and machine deep placement of fertilizer,emerges as a strategy to concurrently curtail GHG emissions,ensure food security,and secure robust economic returns.Finally,we propose a comprehensive set of government interventions,including subsidies,field guidance,and improved extension systems,to promote the widespread adoption of these technologies.

关键词： food security fertilizer manufacturing subsidies agri-food systems greenhouse gas emissions

Shikimic acid accelerates phase change and flowering in Chinese jujube

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Horticultural Plant Journal 2024年第2期10卷 413-424页

作者： Xianwei Meng Zhiguo Liu Li Dai Weiqiang Zhao Jiurui Wang Lili Wang Yuanpei Cui Ying Li Yinshan Cui Yao Zhang Luyao Wang Fengjiao Yu Jin Zhao Mengjun Liu Research Center of Chinese Jujube Hebei Agricultural UniversityBaodingHebei 071000China college of Horticulture Hebei Agricultural UniversityBaodingHebei 071000China college of Life Science Hebei Agricultural UniversityBaodingHebei 071000China college of Forestry Hebei Agricultural UniversityBaodingHebei 071000China eCollege of Economics and ManagementHebei Agricultural UniversityBaodingHebei 071000China college of economics and management Hebei Agricultural University

The juvenile-to-adult phase change with first flowering as the indicator plays a crucial role in the lifecycle of fruit trees. However, the molecular mechanisms underlying phase change in fruit trees remain largely unknown. Shikimic acid (ShA) pathway is a main metabolic pathway closely related to the synthesis of hormones and many important secondary metabolites participating in plant phase change. So,whether ShA regulates phase change in plants is worth clarifying. Here, the distinct morphological characteristics and the underlying mechanisms of phase change in jujube (Ziziphus jujuba Mill.), an important fruit tree native to China with nutritious fruit and outstanding tolerance abiotic stresses, were clarified. A combined transcriptome and metabolome analysis found that ShA is positively involved in jujube(Yuhong’×Xing 16’) phase change. The genes in the upstream of ShA synthesis pathway (ZjDAHPS, ZjDHQS and ZjSDH), the contents of ShA and the downstream secondary metabolites like phenols were significantly upregulated in the phase change period. Further, the treatment of spraying exogenous ShA verified that ShA at a very low concentration (60 mg·L^(-1)) can substantially speed up the phase change and flowering of jujube and other tested plants including Arabidopsis, tomato and wheat. The exogenous ShA (60 mg·L^(-1)) treatment in jujube seedlings could increase the accumulation of endogenous ShA, enhance leaf photosynthesis and the synthesis of phenols especially flavonoids and phenolic acids, and promote the expression of genes (ZjCOs, ZjNFYs and ZjPHYs) involved in flowering pathway. Basing on above results, we put forward a propose for the underlying mechanism of ShA regulating phase change, and a hypothesis that ShA could be considered a phytohormone-like substance because it is endogenous, ubiquitous, movable and highly efficient at very low concentrations. This study highlights the critical role of ShA in plant phase change and its phytohormone-like properties.

关键词： Ziziphus jujuba Mill. Phase change Flowering Shikimic acid Transcriptome Metabolome

Transforming agri-food systems for multiple wins in nutrition,inclusion and environment

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Journal of Integrative Agriculture 2024年第2期23卷 355-358页

作者： Shenggen Fan Qiran Zhao Jingjing Wang Academy of Global Food economics and Policy/college of economics and management China Agricultural UniversityBeijing 100083China

The call for agri-food system transformation is urgent in many global development agendas(UN 2023).Food systems have contributed to economic prosperity and feeding the world,but they are also associated with numerous challenges,including climate change,continued hunger,poor diets and malnutrition,and increasing disparities(Webb et al.2020;Fanzo et al.2021).

关键词： continued nutrition urgent

The impact of Internet access on household dietary quality:Evidence from rural China

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Journal of Integrative Agriculture 2024年第2期23卷 374-383页

作者： Yi Cui Qiran Zhao Thomas Glauben Wei Si college of economics and management China Agricultural UniversityBeijing 100083China Academy of Global Food economics and Policy China Agricultural UniversityBeijing 100083China Leibniz Institute of agricultural Development in Transition Economies(IAMO) Halle(Saale)06120Germany

Over the past few decades,the Internet has rapidly diffused across China.The spread of the Internet has had a profound economic and social impact on Chinese rural areas.Existing research shows that Internet access significantly impacts agricultural production and improves smallholder farmers’income.Beyond these,the Internet can affect other dimensions of social welfare.However,research about the impact of Internet access on dietary quality in rural China remains scarce.This study utilizes multi-period panel data from Fixed Observation Point in rural China from 2009 to 2015 to estimate the impact of Internet access on dietary quality and food consumption of rural households and conducts a causal analysis.Regression models with time and household fixed effects allow robust estimation while reducing potential issues of unobserved heterogeneity.The estimates show that Internet access has significantly increased rural household dietary quality(measured by the Chinese Diet Balance Index).Further research finds that Internet access has increased the consumption of animal products,such as aquatic and dairy products.We also examine the underlying *** access improves dietary quality and food consumption mainly through increasing household income and food expenditure.These results encourage the promotion of Internet access as a valuable tool for nutritional improvements,especially in rural areas.

关键词： dietary quality fixed effect model Internet access rural China

Does Green Food Certification promote agri-food export quality?Evidence from China

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Journal of Integrative Agriculture 2024年第3期23卷 1061-1074页

作者： Ping Wei Hongman Liu Chaokai Xu Shibin Wen college of economics and management China Agricultural UniversityBeijing 100083China School of Public Affairs Zhejiang UniversityHangzhou 310058China

The construction of a food certification system plays a vital role in upgrading export quality, which previous studies have largely overlooked. We match China's industry-level data of Green Food Certification with its HS6-digit export data of agri-food products to quantify the impact of Green Food Certification on export quality. We identify the significant and positive effect of Green Food Certification on export quality. The 2SLS estimation based on instrumental variables and a range of robustness checks confirm the validity and robustness of the benchmark conclusions. Further analysis discloses that Green Food Certification improves export quality by raising agricultural production efficiency and brand premiums. Heterogeneity analysis shows that the effect of Green Food Certification varies across regions, notably improving the quality of agri-food products exported to developed regions and regions with high levels of import supervision. Furthermore, among various product types, Green Food Certification significantly improves the export quality of primary products and products vulnerable to non-tariff measures. The above findings could guide the future development of agri-food quality certification systems, potentially leading to a transformation and promotion of the agri-food trade.

关键词： Green Food Certification agri-food products green transformation export quality food labeling

Will the State-owned Capital Transfer Policy Enhance the Sustainability of the Urban Employee Basic Pension Insurance Fund in China?

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China & World Economy 2024年第3期32卷 98-129页

作者： Jia Wang Huan Liu Mei Li Han Li School of economics Xiamen UniversityChina School of economics and management Nanjing Agricultural UniversityChina School of economics and management Wuhan UniversityChina

To analyze the efect of the state-owned capital transfer policy on the sustainability of China's urban employee basic pension insurance fund(CUEBPIF),this study develops an actuarial model for pension insurance.The results reveal the following:(i)Without policy intervention,the CUEBPIF would face a deficit in 2027 and a cumulative shortfall of RMB207.44 trillion by 2050,and the proportion of fiscal subsidies for the CUEBPIF in the total fiscal expenditure would increase to 12.86 percent in 2050.(i)Based on a delayed retirement policy,the transfer of 10 percent of state-owned capital can delay the onset of the fund deficit by 6 years,and the accumulated shortfall in 2050 would fall to RMB39.42 trillion,and the proportion of fiscal subsidies would decrease by I1.77 percentage points.(ii)The state-owned capital transfer policy can improve the sustainability of the CUEBPIF and reduce the burden of enterprise social security contributions when the transfer ratio increases to 20 percent.

关键词： burden of enterprise social security contributions delayed retirement policy state-owned capital transfer policy sustainability of basic pension insurance fund

Downstream Competition and Upstream Innovation:Theory and Evidence from China

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China Finance and Economic Review 2024年第1期13卷 67-87页

作者： Jing Dai Guanchun Liu Ziqi Ye Haiou Mao Yongwei Ye School of Finance Hubei University of Economics Lingnan college Sun Yatsen University School of Business Administration Zhongnan University of Economics and Law college of economics and management Huazhong Agricultural University School of Public economics and management Shanghai University of Finance and Economics

Competition is the catalyst of corporate innovation,which is the foundation of a country's core competitiveness.From the view of vertical industrial chain,this paper examines how downstream competition affects upstream firms'innovation output.Given innovation helps reduce the production cost of each product,increasing demand of intermediate products caused by downstream competition enhances the marginal revenue of upstream firms'innovation,thus leading to an innovation incentive effect.To identify causality,we utilize China's WTO accession,a quasinatural experiment,to calculate downstream competition combined with import tariff reduction and input-output table,and then run a difference-in-difference regression.Using the data of Annual Survey of Industrial Firms and State Intellectual Property Office,our results find that downstream competition has a significantly positive impact on upstream firms'innovation,and this effect is more pronounced in firms with less industry competition,greater initial innovation capacity and weaker financial constraints.Moreover,the number of firms,the degree of industry competition and the scale of intermediate products in the downstream sector increase,confirming the market size channel.In sum,our findings document that downstream competition can motivate upstream firms to innovate through vertical industrial chain,providing some useful insights for China to build a fair market competition environment and promote innovation-driven growth regime.

关键词： downstream competition upstream firms'innovation vertical industrial chain market size effect