Litter Productivity and Nutrient Return Characteristics of Three Typical Forest Stands in Golden Mountain

Objective: The paper aims to analyze the dynamic characteristics of litter production and nutrient return of the forest ecosystems in subtropical areas, and provide a theoretical basis for the nutrient cycling study in southwest Hubei Province and carbon sink function of the whole forest ecosystem. Methods: Three typical forest stands (Chinese fir plantation, Cryptomeria fortunei plantation and evergreen and deciduous broad-leaved mixed forest) in Golden Mountain Forest Farm in southwest Hubei Province were investigated and monitored continuously for the litter types and productivity and nutrient return. Results: The annual litter productivity of the three forest stands ranged from 161.77 to 396.26 kg·hm-2;Litters of branches, leaves and reproductive organs accounted for 14.14% - 20.85%, 33.26% - 78.33%, 7.52% - 42.18% of the total, respectively;The litter productivity and total litter productivity of each composition in the three forest stands show unimodal or bimodal changes over months, and the total litter productivity reached the highest value in January, April and October respectively. For different nutrient contents of the three forest stands, the common feature is C > N. The order of nutrient return amount from greatest to least is evergreen and deciduous broad-leaved mixed forest, Cryptomeria fortunei plantation and Chinese fir plantation. For different nutrient return amounts, the common feature is C > N, and the nutrient return amounts are 76.51-180.69 kg·hm-2 and 2.3 - 5.71 kg·hm-2 respectively. Conclusion: The annual litter productivity and nutrient return amount of the evergreen and deciduous broad-leaved mixed forest are the highest among the three forest stands. Therefore, protecting the evergreen and deciduous broad-leaved mixed forest and studying the litter changes of Chinese fir plantation and Cryptomeria fortunei plantation are of far-reaching significance for the development of sustainable forest management in this region and the further improvement of the carbon sequestration function of the whole forest ecosystem.

Litterfall production and nutrient return in different-aged Chinese fir(Cunninghamia lanceolata) plantations in South China

The amounts of litter produced and nutrients returned play a fundamental role in the productivity and biogeochemical and nutrient cycling of forest ecosystems.We monitored annual litterfall production, nutrient return,and monthly dynamics over a one-year period in Chinese fir plantations aged 10, 22, and 34 years. Our objective was to quantify litterfall and nutrient return over a complete harvest rotation of Chinese fir. Annual litterfall production increased with stand age and was recorded as（3,294.6 ± 360.4）,（3,733.9 ± 211.2）, and（4,876.1 ± 212.8） kg ha-1a-1in stands aged 10, 22 and 34 years, respectively. Total litter production was significantly greater in the stand aged34 years than in the stand aged 10 years（p ／ 0.05）. With the exception of miscellaneous components, needle litterfall constituted the highest proportion（27.5–43.6 %）, followed by branches/twigs（9.5–16.6 %）. In all three plantations,annual total nutrient return to soil was in the order of C（1,119.95–2,709.05 kg ha-1a-1） [ N（39.32–62.04 kg ha-1a-1） [ K（15.95–22.44 kg ha-1a-1） [ P（1.30–1.63 kg ha-1a-1）. C, N, K and P input to soil was significantly lower in the 10-year-old stand in comparison to the 22- and34-year-old stands（p ／ 0.05）. Litterfall production and nutrient return（C, N and K） followed similar patterns, and C and N input to soil was significantly related to litterfall production（needle, branch and total litterfall）. C, N, P and K input to soil and total litterfall production were mainly driven by needle litterfall.

Performance Analyses of Production Inventory Systems Considering Service Time and Product Returns of Online Shopping

This paper considers a production inventory system with service time and product returns, dependent on the characteristics of online shopping beliaviors. The customers arrive according to a Poisson process, in which the arriving customer requires an item in the inventory, as well as a server service that the service time is exponentially distributed. Moreover, there is one production facility to produce items according to (s, S) policy, and the production time also follows an exponential (listribution. In the beginning, the stationary joint distribution is obtained in the product form for the queue length and the on-hand inventory level. Additionally, the resulting distribution is applied to derive some performance measures, which can be adopted to numerically calculate the optimal (s, S) policy. Finally, numerical analyses are processed to investigate the effects of some system parameters on the performance measures. The numerical results clearly indicate that the product return rate has a significantly monotonic effect on the optimal policy and optimal cost.

Evaluation of the Land Production Potential in the Context of Returning Farmland to Forest in Karst Region:A Case Study of Guizhou Province

In this paper, we take Guizhou Province (the heart of southwestern Karst region in China) as the research object. By establishing gray forecasting model and time series forecasting model, we conduct the accuracy test on the actual production capacity of land and the forecasted production capacity of land in 2007 and 2008, and then conduct comprehensive forecast of the land production potential in Guizhou Province in 2020. On this basis, considering the nutritional standards needed by three kinds of life type (dressing warmly and eating one's fill, well-off life, relatively affluent life), we evaluate the land production potential in Guizhou Province under the project of returning farmland to forest. Based on the evaluation results, we put forth the relevant recommendations for achieving sustainable land use in the context of returning farmland to forest in Guizhou Province.

An EPQ Model with Imperfect Production Systems with Rework of Regular Production and Sales Return

The Economic Production Quantity (EPQ) model is commonly used by practitioners in the fields of production and inventory management to assist them in making decision on production lot size. The common assumptions in this model are that all units produced are perfect and shortages are not allowed. But, in real situation the defective items will be produced in each cycle of production and shortages and scrap are possible. These assumptions will underestimate the actual required quantity. Hence, the defective items can not be ignored in the production process. Rework process is necessary to convert those defective into finished goods. This study proposes EPQ model that incorporates both imperfect production quality and falsely not screening out a proportion of defects, thereby passing them on to customers, resulting in defect sales returns. To active this objective a suitable mathematical model is developed and the optimal production lot size which minimizes the total cost is derived. An illustrative example is provided and numerically verified. The validation of result in this model was coded in Microsoft Visual Basic 6.0.

玉米秸秆还田对土壤地力及固碳能力的影响

为探明农产品化肥减量后土壤养分的变化,促进玉米秸秆还田,提升土壤肥力,从2019年开始在黑龙江省大庆市所属4个牧场连续3年进行玉米秸秆还田试验,期间随机选取31处采样点分别进行3次抽样,分析土壤样品中pH、碱解氮、有效磷、速效钾、有机质、有机碳和水溶性盐等指标,以此判断玉米秸秆还田对土壤地力和固碳能力的影响。结果表明,长期玉米秸秆还田土壤中有机质含量由21.2 g·kg^(-1)增长至23.6 g·kg^(-1);秸秆还田土壤中有效磷的含量平均增长约144.0%,而未还田土壤中有效磷含量的平均增长约138%;碱解氮含量由166.50 mg·kg^(-1)增长至194.50 mg·kg^(-1),且2022年与2021年测定的碱解氮含量差异显著。可见秸秆还田后土壤固碳能力增加,肥力增强,而pH一直维持在7.92~8.23。因此,合理运用玉米秸秆还田可改善土壤耕作环境,减少土壤中盐分聚集,提高土壤对有机碳的固定效果,调节土壤的酸碱稳定性,对东北土壤生产力的可持续发展具有重要意义。

电炉企业收益变化与经济波动关系研究

经济衰退对电炉企业收益具有较强的负面影响。在市场经济环境下,电炉企业是我国国民工业经济结构的重要组成部分,电炉企业的发展不仅促进了国内的工业转型升级,还提高了中国的技术水平和创新能力。电炉企业收益的波动同品牌树立、产品研发、甚至生存都具有较高的关联性,这些因素直接影响企业的销售额、市场份额和利润率,从而对企业的盈利能力产生影响。为此,研究电炉企业收益变化与经济波动关系。从多个方面分析了电炉企业收益变化与经济波动之间的关系,探讨了经济波动对电炉企业收益产生差异性影响,详细描述了电炉企业收益在经济波动情况下的变化规律,以及电炉企业收益变化同经济波动下产业结构调整的关系,研究发现电炉企业发展促进经济的快速发展。

超大规模市场支撑新质生产力发展的理论基础、内在逻辑与实践指向

新质生产力既是生产率水平大幅提升的先进生产力,又是在质态上具有高科技、高效能、高质量特征并符合新发展理念的先进生产力。基于斯密和马克思的相关思想可以发现,生产力水平的跃升和质态的优化受到市场规模的限制。市场资源是中国的巨大优势,超大规模市场的持续建设能够从消费结构性需求、囊括基础设施投资在内的大量投资需求、规模报酬递增引致的生产成本下降和创新收益提升以及促进战略性新兴产业和未来产业发展的“建构性市场”等多个方面为加快新质生产力发展提供有力支撑。这些支撑在发挥作用的同时面临着需求多样化、固定资产更新滞后、区域形成的“局部市场”以及制度型式不确定性等挑战,为使潜在的支撑力量转为实际的效能,需在实践中进一步推进传统产业的劳动分工与技术进步,推进固定资产更新换代,推进全国统一大市场建设、扩大有效市场规模,适时适度做实做优建构性市场。

预期收益·环境素养对绿色生产行为的影响

根据湖南株洲共260份农户的微观调研数据,通过OLS模型分析环境素养、预期收益对农户绿色生产行为的影响。结果表明:环境素养和预期效益均对农户绿色生产行为存在显著的正向影响;预期收益在环境素养对绿色生产行为的影响中存在中介效应,即中介作用,环境素养通过预期收益会影响到农户绿色生产行为。因此,加强绿色文化的宣传教育及其重要,应当加快完善绿色文化体系的构建,并打通多渠道的传播途径;也要强调绿色生产行为所带来的收益,从而带动农户的积极性,从而实现可持续发展。

基于LabVIEW的按键力与行程采集机器人系统

为达到多按键产品自动化测试效果并得到精密测量结果,设计了一套实现按键力与行程实时采集的机器人系统。整套系统包括机械手子系统和数值采集子系统两部分,机械手子系统实现工作空间范围的移动定位,其末端执行器即数值采集系统以CompactRIO为控制器,通过力传感器与直线电机模块完成力与行程的同步采集,并基于LabVIEW平台实现数值实时显示与处理。选取车用多按键开关产品为测试对象,通过试验分别验证了其自动化测试能力和重复测量精准度。结果表明,该系统能够自动执行多个目标点位的数值采集任务,且在重复测量工况下力值精度等级与相对线性误差系数分别为0.122%、0.024%,行程最大测量误差为29μm,对应的平均测量误差为8.75μm,实测数据结果满足关键部件技术指标,保证按键手感一致性检测要求。

区域协调发展与中国经济增长潜力分析——基于国际比较的视角

本文运用经济增长核算方法对中国各省1992~2022年的增长来源进行分解,发现中国区域人均GDP差距在缩小,这种收敛主要是人力资本差距缩小和全要素生产率差距缩小造成的。劳动力占比变化和资本投入差距的影响并不显著。基于各生产要素和生产力的跨国比较,本文发现中国已经从资本缺乏阶段走向资本富余阶段,资本回报率显著降低。和同阶段发展中经济体和发达经济体的比较表明中国人力资本和全要素生产率还有较大的提升空间。本文基于国际贸易数据反推得到出口隐含生产力,发现人均GDP还有向出口隐含生产力收敛的潜力。最后,本文基于上述发现认为,中国经济增长的潜力主要在于:提高受教育水平和教育质量;推动产业升级,向出口复杂度高的产品和服务转型;降低国内贸易壁垒。

秸秆还田技术在农业生产中的应用与推广策略

秸秆还田技术不仅可以减少环境污染、提升土壤肥力,还可以改善农作物生长环境、保护水土资源、减少土壤侵蚀和保持土壤湿润度。该文从秸秆还田技术的优势入手,分析其在农业生产中的应用现状,探讨了在政策支持、科技引导、示范推广等方面的推广策略与措施,旨在促进秸秆还田技术在农业生产中的广泛应用,实现农业生产的可持续发展和环境保护目标。

金融市场风险溢出对银行理财产品收益的效应研究

随着《关于规范金融机构资产管理业务的指导意见》的正式实施,银行理财产品在债券市场与货币市场的投资比重增大,分析投资者所承担的金融市场风险溢出效应,有利于投资者对银行理财产品进行选择。本文运用溢出指数法测度债券市场与货币市场风险溢出对银行理财产品收益率的效应或者风险贡献,并运用GARCH模型检验溢出指数法测度的有效性,继而就《关于规范金融机构资产管理业务的指导意见》实施前后的影响进行对比分析。研究表明:债券市场对银行理财产品投资收益有相对较大的风险溢出效应,货币市场的风险溢出效应相对较小,且债券市场变化对银行理财产品投资收益的影响存在滞后效应。《关于规范金融机构资产管理业务的指导意见》实施前后,债券市场、货币市场对银行理财产品投资收益的风险溢出效应呈现前高后低。《关于规范金融机构资产管理业务的指导意见》实施后,债券市场和货币市场对银行理财产品收益的风险溢出效应并没有因投资比重增加而显著增强。未来,银行理财产品投资者承担的风险主要来源于银行的投资管理。银行需要在债券市场进一步加强投资管理,以降低银行理财产品投资者的风险。

退货政策宽松度对消费者网购意愿的影响——基于SOR模型的有调节双中介效应分析

在网络购物中,由于产品收货时间滞后于支付时间而导致退货现象频发,因此退货政策成为影响消费者行为的重要因素之一。基于“刺激-组织-反应”模型(SOR模型),并结合信号理论,以感知质量和感知风险为中介变量,以产品异质性和店铺口碑为调节变量,通过有调节的双中介效应检验考察退货政策宽松度对消费者购买意愿的影响及其传导路径,结果表明:宽松的退货政策使消费者产生更高的感知质量和更低的感知风险,感知质量的提高和感知风险的降低会增强消费者购买意愿,从而形成“退货政策宽松→感知质量提高→购买意愿增强”和“退货政策宽松→感知风险降低→购买意愿增强”两条传导路径;在口碑较好的店铺中,退货政策宽松对消费者感知质量和感知风险的影响更强;对于异质性较弱的产品,退货政策宽松对消费者感知风险的影响更强。这些研究结果不仅有助于揭示退货政策影响消费者购买意愿的机制,而且对消费者、网络店铺和电商平台都具有重要的管理启示。

灌溉基础设施对我国种植业全要素生产率的动态影响研究

灌溉基础设施建设对改善农业生产条件,提升农业生产力具有重要意义。利用农业投入产出数据重新计算1980-2018年27个省(自治区)种植业全要素生产率,并在此基础上采用结构断点模型实证分析灌溉基础设施在不同时期对种植业全要素生产率的不同作用。结果表明:虽然过去40年灌溉基础设施在促进种植业全要素生产率提升方面发挥了重要作用,但其边际影响跨地区存在显著差异,并随农业农村转型发展逐步降低,这导致灌溉基础设施投资的边际收益率随时间呈现递减趋势。基于上述结果提出,改善灌溉基础设施投资区域布局,优化公共投资方向是提升灌溉基础设施效率的有效手段。

FLUCTUATION OF AGROCLIMATIC ZONES AND ITS IMPACT ON AGRICULTURAL PRODUCTION IN CHINA

Accumulated temperature above 100℃ (Σ t) and minimum annual temperature (Tm) are the major indexes for demarcating agroclimatic thermal zones. The paper calculated the return period (τ) of Σ t and Tm, and the shift ofΣ t-and Tm-isopleths with T. The results show: (1) According to the magnitude of shift of Σ t-and Tm-isopleths, in Northeast China, Inner Mongolia and northern Xinjiang the fluctuation of thermal resources in growing season from year to year is the greatest and strongly impacts the yield of annual thermophilous crops, but in the Changjiang River basin the fluctuation of the low temperature in winter is the greatest and seriously injures the perennial subtropical tree crops. ( 2) In the anomalous cool summer year with t = 30, the northern boundaries of the southern subtropical, northern subtropical and warm temperate zones and the southern boundary of the frigid temperate zone in China could be expected to shift southward 150, 220, 250 and 300 km from their normal positions,

不同施氮量对秸秆还田条件下棉麦轮作生产的影响

为了研究长江流域棉区棉(Gossypium spp.)麦(Triticum aestivum L.)轮作两熟种植模式下如何降低氮肥投入而提高棉田的综合效益,试验设置了5个氮肥用量处理,分别为低氮(N1,50%N3)、少氮(N2,75%N3)、中氮(N3,棉花季和小麦单季纯氮用量分别为180.0、150.0 kg/hm2)、高氮(N4,125%N3)、富氮(N5,150%N),分析了不同施氮量对小麦和棉花的生育进程、农艺性状、产量性状及棉花纤维品质的影响,并对不同处理间的经济效益、土地利用率和生产效率进行了分析。结果表明,棉麦轮作总的生产周期在344 d左右,在长江流域棉区发展棉麦轮作是可行的;不同施氮量间小麦的有效穗、穗粒数、产量随着施氮量的增加先增加后减少,综合2年的试验结果,当氮肥水平为高氮(187.5 kg/hm2)时,小麦产量最高;不同施氮量间棉花株高、单株结铃数、子棉产量和皮棉产量差异显著,当氮肥水平为高氮(225.0 kg/hm2)时,子棉产量最高;棉麦周年生产中总产出、生产效率、净利润、收益率和产投比随施氮量的增加呈先增后减的趋势,当施肥量为高氮时值最大,总生产周期和土壤利用率随施氮量的增加而增加。

多源土地利用/覆被产品在黄土高原应用和精度评估

为准确掌握黄土高原土地利用/覆被的时空格局,基于6种不同来源的土地利用/覆盖数据产品,MCD12Q1,ESA-CCI-LC,GlobeLand30,GLASS,CAS-LUCC和ChinaCover,开展了黄土高原地区退耕还林(草)实施以来土地利用/地表覆被时空格局和转类特征的研究,对不同来源数据产品的精度进行了验证分析。结果表明:(1)分类特征和变化趋势上,MCD12Q1和GLASS产品与其他产品的差异最大,其次为ESA-CCI-LC产品,GlobeLand30,CAS-LUCC和ChinaCover产品的差异相对较小。(2)除MCD12Q1产品外,不同来源土地利用/覆被产品各类型面积随时间变化趋势基本一致。(3)空间转类上,GLASS产品与其他产品的差异最大,解译类型明显错误;其次为MCD12Q1产品,转林类和转草类也存在明显错误,退耕还林(草)特征表现不明显;ESA-CCI-LC和GlobeLand30在黄土丘陵沟壑区退耕还林(草)的转类特征表现不足;CAS-LUCC和ChinaCover退耕还林(草)特征明显。(4)抽样精度上,GlobeLand30,CAS-LUCC,ChinaCover产品的总体精度最高,分别为86.61%(K=0.84),91.68%(K=0.90),89.45%(K=0.87);其次为ESA-CCI-LC(73.83%,K=0.69);MCD12Q1,GLASS产品的精度最低,分别为59.43%(K=0.51),36.31%(K=0.24)。(5)土地利用/覆被多源数据产品的融合有利于提高产品的精度,与融合前产品GlobeLand30,CAS-LUCC和ChinaCover相比,融合产品总精度可提高了2.25%~7.30%。综上,CAS-LUCC产品的精度最高,且2000—2010年退耕还林(草)表现与实际较为相符。