Competitive effect, but not competitive response, varies along a climatic gradient depending on tree species identity

Background: Understanding the role of species identity in interactions among individuals is crucial for assessing the productivity and stability of mixed forests over time. However, there is limited knowledge concerning the variation in competitive effect and response of different species along climatic gradients. In this study, we investigated the importance of climate, tree size, and competition on the growth of three tree species: spruce(Picea abies), fir(Abies alba), and beech(Fagus sylvatica), and examined their competitive response and effect along a climatic gradient.Methods: We selected 39 plots distributed across the European mountains with records of the position and growth of 5,759 individuals. For each target species, models relating tree growth to tree size, climate and competition were proposed. Competition was modelled using a neighbourhood competition index that considered the effects of inter-and intraspecific competition on target trees. Competitive responses and effects were related to climate.Likelihood methods and information theory were used to select the best model.Results: Our findings revealed that competition had a greater impact on target species growth than tree size or climate. Climate did influence the competitive effects of neighbouring species, but it did not affect the target species? response to competition. The strength of competitive effects varied along the gradient, contingent on the identity of the interacting species. When the target species exhibited an intermediate competitive effect relative to neighbouring species, both higher inter-than intraspecific competitive effects and competition reduction occurred along the gradient. Notably, species competitive effects were most pronounced when the target species' growth was at its peak and weakest when growing conditions were far from their maximum.Conclusions: Climate modulates the effects of competition from neighbouring trees on the target tree and not the susceptibility of the target tree to competition. The modelling approach should be useful in future research to expand our knowledge of how competition modulates forest communities across environmental gradients.

Competition effects in an afrotemperate forest

Background： Information about competition responses is mainly available for monospecific stands or mixed stands with a small number of species. Studies on complex multi-species and highly structured forest ecosystems are scarce. Accordingly, the objective of this study was to quantify competition effects and analyse competition responses in a species-diverse afrotemperate forest in South Africa, based on an observational study with mapped tree positions and long-term diameter increment records. Methods： The sensitivity to competition was analysed for individual species and involved the calculation of the slope of the linear relation between the value of a competition index （CI） and diameter growth as a measure of sensitivity. In a next step different competition indices were combined and tree diameters were grouped in three classes as surrogates for canopy status and ontogenetic stage. Results： Five competition indices were found to be effective in showing sensitivity to competition for a number of canopy and sub-canopy species. Significant linear regressions were fitted for 18 of a total of 25 species. Species reactions varied significantly in their sensitivity to the different CIs. The indices were classified as belonging to two groups, those that responded more to local crowding and those that are more sensitive to overtopping, which revealed species-specific sensitivities to both factors. The analysis based on diameter classes revealed that species clearly changed their sensitivity to crowding or overtopping depending on diameter. Canopy and sub-canopy species showed distinct differences in their reactions. Conclusions： The application of multiple CIs brought novel insights relating to the dynamics of afrotemperate forests. The response patterns to different competition indices that focus on crowding and overtopping are varied and tree diameter dependent, indicating that oversimplified assumptions are not warranted in the interpretation of Cl- growth relations.

Effect of UV-B irradiation on interspecific competition between Ulva pertusa and Grateloupia filicina

We report the effect of UVoB irradiation （9.6 kJ m-2 day^-） on interspecific competition between two species of macroalgae, Ulva pertusa （U） and Grateloupiafilicina （G）, in co-culture. Growth of U. pertusa and G. filicina was inhibited by UV-B irradiation in mono-culture and specific growth rate （μ） declined as a result. Interspecific competition between U. pertusa and G filicina was closely related to the initial weights when co-cultured. When initial ratios of U. pertusa （U） to G filicina （G） were U：G=I.2：I and 1：1, U. pertusa was the dominant algae. When the initial U：G ratio was 1：1.2, G. filicina was competitively dominant in the earlier stage, but U. pertusa grew faster, superseding G. filicina in the later stage. At initial ration U：G = 1：1.4, G. filicina was predominant. Under UV-B irradiation, the competitive ability of G filicina was weakened and the interspecific competitive balance favored U. pertusa, which suggests that G. filicina was more sensitive to UV-B irradiation. We also probed the potential allelopathic effects between the two species, which led to mutual growth inhibition.

Enhancing selectivity in acidic CO_(2) electrolysis:Cation effects and catalyst innovation

The electrochemical reduction of CO_(2)(eCO_(2)R)under ambient conditions is crucial for reducing carbon emissions and achieving carbon neutrality.Despite progress with alkaline and neutral electrolytes,their efficiency is limited by(bi)carbonates formation.Acidic media have emerged as a solution,addressing the(bi)carbonates challenge but introducing the issue of the hydrogen evolu-tion reaction(HER),which reduces CO_(2) conversion efficiency in acidic environments.This review focuses on enhancing the selectivity of acidic CO_(2) electrolysis.It commences with an overview of the latest advancements in acidic CO_(2) electrolysis,focusing on product selectivity and electrocatalytic activity enhancements.It then delves into the critical factors shaping selectivity in acidic CO_(2) electrolysis,with a special emphasis on the influence of cations and catalyst design.Finally,the research challenges and personal perspectives of acidic CO_(2) electrolysis are suggested.

Effect of Soil Fertility and Planting Density on the Partitioning of the Above-Ground Biomass of Eucalyptus in a Plantation (Pointe-Noire, Republic of Congo)

Afforestation and reforestation are useful approaches to improve carbon sequestration. With the advent of forest plantations, growing environment conditions have become increasingly restrictive for light, soil nutrients, and interactions between trees to acquire available resources. Tree biomass data are essential for understanding the forest carbon cycle and plant adaptations to the environment. The distribution of tree biomass depends on the sum of multiple stand conditions. The data are from a dedicated experiment with two very contrasting areas of fertility, and two planting densities, including a high density at planting in order to achieve thinning. The plant material consists of the high-performance clones of Eucalyptus urophylla × E. grandis and the reference clone E. PF1. We hypothesize that the distribution of biomass changes as the intensity of competition changes and that this is accelerated by the fertility of the sites in time. The results indicate that fertilization, planting density and clones have an impact on biomass partitioning.

China's Low Export Markups Puzzle: Competition Effect and Selection Effect

Based on China's industrial enterprises-customs matched data, this paper utilizes two-tier stochastic frontier analysis method to estimate and verify the extent to which selection effect and competition effect influence exporting firms' markup. Our findings suggest that the interaction between selection effect and competition effect ultimately causes actual firm markup to be higher than the baseline markup by 7.11%. Exporting firms' actual markup is higher than the baseline markup by different degrees. In terms of the decomposition of selection effect, TFP explains for 28.05% of selection effect, and nonproductivity factors explain for the rest 71.95%. By controlling for the type of firms' export,the export-productivity paradox only exists for processing trade firms, which shows that with increasing trade facilitation, the policy incentives to encourage firms to export are major contributors to the low export markups.

Impact of coupling coordination development of port and city environments on urban economic competitiveness:Evidence from the coastal port cities in eastern China

Promoting the coupling coordination development of port and its hinterland city environments is an important way to improve urban economic competitiveness.Based on relevant data of 13 coastal port cities in eastern China from 2000 to 2018,this study explores the coupling coordination development of port and city environments and its impact on urban economic competitiveness by constructing the coupling coordination degree model and the panel threshold model.The research results show that:(1)In terms of the coupling coordination development of port and city environments,most coastal ports and their hinterland cities are in a state of moderate or serious disorder.Overall,the degree of coupling coordination of port and city environments needs to be further improved;(2)The coupling coordination degree of port and city environments has a significant impact on urban economic competitiveness,and this effect gradually increases with the development of the ports and the urban economy.Among the variables that impact the urban economic competitiveness,fixed assets investment and foreign trade are significant factors that can enhance urban economic competitiveness.(3)At present,there is a“U-shaped”relationship between the coupling coordination degree of port-city environments and the urban economic competitiveness.This relationship lies on the right side of the inflection point of the“U-shaped”curve.Therefore,following the concept of assigning priority to ecological development,expanding fixed assets investment and actively developing foreign trade can further enhance the urban economic competitiveness.

Required width of exit to avoid the faster-is-slower effect in highly competitive evacuation

A group of competitive people escaping through an exit could lead to the formation of a deadlock, which significantly increases the evacuation time. Such a phenomenon is called the faster-is-slower effect（FIS） and it has been experimentally verified in different systems of particles flowing through an opening. In this paper, the numerical simulation based on discrete element method（DEM） is adopted to study a group of highly competitive people through an exit of varying widths. The FIS effect is observed for a narrow exit whilst it is not observed for the exit wide enough to accommodate two people through it side-by-side. Experimental validation of such a phenomenon with humans is difficult due to ethical issues. The mouse is a kind of self-driven and soft-body creature and it exhibits selfish behaviour under stressed conditions.Particles flowing through an opening in different systems, such as pedestrian flow, animal flow, silo flow, etc. have similar characteristics. Therefore, experimental study is conducted by driving mice to escape through an exit of different widths at varying levels of stimulus. The escape time through a narrow exit（i.e., 2 cm） increases obviously with the increase of stimulus level but it is quite opposite to a wider exit（i.e., 4 cm）. The FIS effect is avoided for an exit wide enough to accommodate two mice passing through it side-by-side. The study illustrates that FIF effect could be effectively prevented for an exit when its width is twice the size of particles.

Optimal decision-making considering inter-supply-chain competition and negative-spillover from environmental effort

Focusing on negative-spillover from environmental effort,this paper explores the issues of competition and optimal decision-making based on two competing two-stage manufacturer-dominated supply chains:centralized and decentralized.We develop the Stackelberg competition models according to four identified competition scenarios(pure centralized structure-CC,mixed structure-DC,mixed structure-CD,and pure decentralized structure-DD).By comparing the results of the four scenarios,we find that negative-spillover from environmental effort negatively impacts environmental-effort providers and reduces the optimal profit of the manufacturer who provide the environmental effort,which in turn reduces the profit of the entire supply chain.The inter-supply-chain competition also produces a negative incentive for environmental-effort providers but provides a free riding effect on the non-provider,and this effect increases as competition increases.In terms of network externality,the structural change of a supply chain from centralized to decentralized is altruistic,which generates a double-marginalization(i.e.,the network externality enhances competitor performance).Furthermore,the leader supply chain with a centralized structure is more willing to provide greater environmental effort,whereas when the leader supply chain structure remains unchanged,its environmental effort depends on the negative-spillover effect and the follower supply chain structure.Therefore,excessive supply chain competition should be avoided,and the negative-spillover effect of environmental effort should be reduced to motivate environmental-effort providers to increase their environmental efforts and promote the development of sustainable green supply chains.Future research should examine retailer-dominated supply chain competition and compare the results with the conclusions of this study.

An Evaluation of Network Competitiveness and the Effects of LCCs on South Korea’s Network Connectivity:Using Aviation Market Data

LCCs(low cost carriers)are expanding their routes,which is affecting airport network connectivity.The subsequent increases in market competition and the number of airlines operating in air network routes have made the centrality analysis more significant because it can be used to identify airport network connectivity competitiveness.This study analyzes the network connectivity competitiveness of South Korea among Asian airports using the MIDT(marketing information data transfer)dataset provided by OAG Traffic Analyser,which provides data collected from regional Asian airports since 2011.The network centrality of individual airports is estimated to compare network connectivity competitiveness in Asia.Measures for overall network centrality include degree,closeness and betweenness centrality.This network centrality analysis may be helpful for South Korean airports in identifying their network performance and competitive position in Asia and confirming the effects that LCCs have on airport network connectivity.The results indicate that South Korea’s aviation market needs to expand its network via a strategy that prioritizes the strengthening of airport connectivity and the pursuit of liberalization.In addition,LCC operations will support Korea’s network growth via the various strategies that they employ.Consequently,this in turn will bolster the overall market competitiveness of South Korean airports.

Interspecific Competition and Grain-Hosts Selection of Maize Weevil, <i>Sitophilus zeamais</i>(Motsch.) (Coleoptera;Dryophtoridae) and Larger Grain Borer, <i>Prostephanus truncatus</i>(Horn) (Coleoptera;Bostrichidae)

Laboratory interspecific competition and grain-hosts selection experiments involving maize weevil (MW), Sitophilus zeamais (Motsch.) and larger grain borer (LGB), Prostephanus truncatus (Horn) were performed under ambient temperature and relative humidity (25°C - 35°C and 70% - 80% relative humidity) in their major host cereal, maize grains. The species reproductive rate and grain-hosts preference were evaluated by a number of emerged adults. In combined infestation, both species competed intensively by simultaneously increasing their individuals’ emergence, 9-fold or greater than when reared alone. Even though both species simultaneously increased their progeny, S. zeamais was the dominant competitor and had a significant suppressant effect on P. truncatus. The selection result of grain-hosts showed that P. truncatus placed in the environment containing both uninfested maize grains and grains previously infested by S. zeamais, the insect prefers uninfested grains. Indeed, P. truncatus individuals’ emergences were significantly more important to uninfested grains than to infested grains. The weevil-infested grains seemed to have deterrent and detrimental effects on P. truncatus. Conversely, S. zeamais selection of grain-hosts was significantly (P = 0.0001) more attracted by P. truncatus infested grains than to uninfested grains. Sitophilus zeamais individuals’ emergences were significantly (P = 0.0008) more important to infested grains than to uninfested grains. The S. zeamais preference on grains previously infested would be stimulated by P. truncatus larval vibrations in grain.

数字经济与实体经济融合是否提升了企业创新能力——基于正反向融合度的非线性检验

促进数字经济与实体经济深度融合,依托数字技术与设备实现核心领域突破性创新,是高质量发展的关键。编制我国非竞争投入产出表,从供需双层面和广义狭义双范畴,可构建并测算我国数字经济与实体经济正、反向融合度,探究数字经济与实体经济融合对实体企业创新影响及内在机制。研究发现,融合度对实体创新的影响存在非线性效应,正向融合度整体提升实体企业创新质量和效率,这与技术吸收能力强化相关;反向融合度处于合理区间时才能拉动创新增长,否则将因成本效应和适应性不足降低实体工业创新质量和效率。

人民币汇率变动与企业创新的“质”与“量”——基于产业链溢出效应

本文利用2000~2014年的中国工业企业数据库、海关贸易数据库、企业专利数据库以及2007年中国投入产出表,基于产业链视角验证了人民币升值对制造业企业创新的影响。研究结果表明,人民币升值能显著提高企业创新能力,并且产业链在其中发挥着异质性效果:企业会因其所处产业链位置表现出创新“量”与“质”的差异。人民币升值对上游企业创新质量的促进作用更强,而对创新数量的影响并不明显。机制分析发现:人民币升值带来的进口中间品增加会在产业链中形成行业间技术溢出效应以及行业内竞争效应,均对企业创新模式产生重要影响;上游企业在全产业链中表现出“质量引领效应”。本研究为企业在“双循环”发展格局下利用行业生产网络效应提高自身创新提供建设性方向。

中国加入CPTPP的农产品贸易效应研究--基于WITS-SMART模型

粮食安全是国家安全的基石,面对国际市场不稳定性,加入CPTPP有望为中国夯实农产品贸易韧性提供新契机。在考察中国与CPTPP国家农产品贸易竞合关系的基础上,运用WITS-SMART模型建立局部均衡分析框架,研究中国加入CPTPP的农产品贸易效应,结果发现:第一,中国农产品竞争力整体不强,但与CPTPP国家依存关系较高,双边贸易潜力在关税完全削减时充分释放。第二,零关税情境下,贸易创造效应普遍大于转移效应,中国对CPTPP多数国家农产品贸易规模大幅扩张,进口增长主要源自种植业、畜牧业部门以及加拿大、澳大利亚、英国、日本等国家,出口增长主要集中于种植业部门以及日本、英国、马来西亚、墨西哥等国家。第三,加入CPTPP显著改善了双边经济福利,不过关税损失较为严重。因此,中国应破除部门利益障碍,加强与墨西哥、日本、英国等国经贸联系以充分挖掘CPTPP国家市场潜力,释放贸易自由化福利,持续提高农产品出口质量和国际竞争力以应对加入CPTPP带来的挑战。

集中采购政策对医药企业研发效率的影响——来自我国A股上市公司的实证检验

本文以我国2019年开始施行的医药集采政策为外生冲击,采用双重差分法从市场竞争的角度考察这一政策对制药企业的研发效率的影响。实证结果表明,医药集采政策使医药流通环节的市场竞争变得更加透明和充分,分别通过研发的规模效应和竞争效应提高了制药企业的研发效率。进一步的研究还表明,由于研发的规模效应,集采对研发效率的促进作用在融资约束弱、客户集中度高、规模小的制药企业中更为明显;而由于研发的竞争效应,这一作用对于创新药企业更为明显。

绿色债券融资能否发挥“鲇鱼效应”:绿色债券对企业技术竞争潜力的作用

绿色债券融资在为企业提供绿色转型资金的同时,也可以通过对发行主体及融资项目的审核、资金使用的跟踪、引导社会资金进入等实现对发行主体的治理,激励企业加大研发投入,提升技术竞争潜力。基于2016-2021年我国沪深证券交易所发行过债券的上市公司样本,实证分析发现,绿色债券资金具有资源、监督和激发作用,能够在提升企业技术竞争潜力中发挥“鲇鱼效应”。分析师关注在绿色债券资金对企业技术竞争潜力的提升作用中具有中介效应,企业ESG评级、环保费改税政策可以增强绿色债券资金对企业技术竞争潜力的提升作用,代理成本会减弱绿色债券资金对企业技术竞争潜力的积极效应。国有企业、中西部地区企业、资本密集型企业的技术竞争潜力受绿色债券融资的影响更为明显。

税收竞争力影响中国对RCEP其他成员国直接投资的实证研究

RCEP其他成员国逐渐成为中国对外直接投资的热点国家,而东道国的税收竞争力水平在一定程度上代表着当地的投资环境,对吸引中国OFDI具有重要影响。研究发现,RCEP国家税收竞争力的提升显著促进了中国对外直接投资。从中介效应来看,东道国税收竞争力的提升进一步加快当地产业结构的优化升级、促进当地经济的发展,同时促进了中国对外投资增加。从调节效应来看,税收协定的更新对东道国的税收竞争力有正向调节作用,有助于吸引外资流入。中国要做好RCEP成员国纳税环境的调查研究,加强政府间的税收合作,着眼于税收竞争力的提升,推进税制改革,不断优化税收团队。中国企业要充分调研国内外市场,提高对东道国的税收环境变化的敏感度,降低对外投资涉税风险,重视国际化专业化人才培养。

垂直对外直接投资与服务创新

随着产业结构服务化,服务业已经成为中国经济的主导部门,服务创新能力是实现中国经济高质量发展的重要驱动力量。本文利用1996—2018年服务企业微观数据,考察垂直对外直接投资(OFDI)对服务企业创新能力的影响,得到以下结论:第一,进行垂直OFDI的企业,专利授权数增加12.75%。这种影响主要集中在生产性服务业,在消费性服务业中没有发现证据。这说明,垂直OFDI对创新的影响存在行业异质性,本地化倾向较高的消费性服务业无法通过垂直关联来增强其创新能力。第二,垂直OFDI的创新效应具有显著的门槛特征,只有高生产率企业和大型企业采用垂直OFDI能增强创新能力,中小企业和低生产率企业难以从垂直OFDI中享受创新溢出。此外,没有发现垂直OFDI战略的区域差异性。第三,“逃离竞争效应”在服务企业创新活动中具有重要的作用,竞争压力越大的行业,垂直OFDI的创新效应越强。第四,机制研究表明,研发成本水平下降和市场规模扩张有助于增强垂直OFDI的创新效应。

数字化转型助力津门老字号企业品牌发展研究

数字经济改变着人们的生活与工作方式,历史底蕴和文化价值深厚的老字号品牌如何在数字经济时代传承创新、改革发展已成为研究热点。基于2011—2021年天津老字号企业面板数据,构建时间、个体双向固定效应模型和中介效应模型,探究企业数字化转型对品牌竞争力的影响及其作用机制。结果表明,老字号企业数字化转型能够显著提升品牌竞争力,企业创新水平对数字化转型提升品牌竞争力具有中介作用。基于此,对老字号企业转型发展提出相关对策建议,促进老字号企业利用数字化转型推动品牌发展,提升竞争力。

港城环境协调发展对城市经济竞争力影响的门限效应分析

基于2000~2021年中国东部地区13个沿海港口城市相关数据,构建协调度模型和面板门限模型,探析港城环境协调发展及其对城市经济竞争力的影响。研究结果表明:1)在港城环境协调度等级上,东部地区大多数港口与其腹地城市处于中度失调或严重失调阶段,整体上港城环境协调发展程度有待提升;2)港城环境协调度对城市经济竞争力具有显著影响,并且随着港口和城市经济发展,这种影响效应略微减弱,在协调度的影响变量中,固定资产投资、对外贸易是提升城市经济竞争力的显著因素;3)目前沿海港口城市港城环境协调度和城市经济竞争力之间呈“U”型关系,且处于“U”型曲线拐点右侧,因此,需坚持生态优先发展理念、扩大固定资产投资和积极发展对外贸易,以进一步提升城市经济竞争力。