PPP test for Asian countries and regions: new evidence from a wild bootstrap AESTAR test

This article investigates the effects of time-varying variance on the asymmetric exponential smooth transition autoregressive (AESTAR) unit root test. We propose a wild bootstrap-based implementation of the test, which is asymptotically valid under time-varying variance. We apply our proposed method to test the Purchasing Power Parity (PPP) hypothesis for Asian countries and regions, and find that our proposed test provides stronger evidence against the PPP hypothesis than the conventional AESTAR test.     

温度胁迫对玉米种子萌发出苗的影响

[目的]以辽宁中西地区主栽玉米品种为研究对象,研究温度对玉米种子萌发至出苗的影响,为防寒减灾粮食生产安全提供科学依据。[方法]通过恒温土培法和分期播种试验,研究播种至出苗的生物学下限温度、有效积温指标和玉米适宜播种期及温度指标。[结果]玉米发芽率、发芽势随着温度升高呈非线性变化,规律性显著。16℃以下发芽率随温度变化迅速,而发芽势变化缓慢;16℃以上则相反。随着温度升高和播期推迟,播种至出苗生育进程加快,出苗天数随温度呈指数函数变化。供试验的玉米种子恒温6℃不萌发、8℃不出苗,恒温12℃与恒温26℃相比出苗延长24d;分期播种温度12.5℃与22.3℃相比出苗延长12d。低温播种影响出苗率,恒温土培8℃以下出苗率为0%,12℃出苗率为36%,分期播种Ⅰ期出苗率78%。[结论]玉米种子萌发下限温度为8℃,播种至出苗需要≥8℃的有效积温在120.0℃·d以上,玉米播种初始气温在12.0℃以上,辽宁中西部适宜播种期在4月下旬至5月上旬。研究结果可为玉米单粒播种苗全苗壮防寒减灾粮食生产安全提供技术支撑。     

土壤种子库在生态园林工程中的应用潜力 研究

土壤种子库作为自然生态系统的基因库，是传统生 态修复的主要手段之一，但在生态园林建设中并未引起足够 的重视。以广东省深圳市为例，选取梧桐山自然保护区2种 具有代表性的群落类型(常绿阔叶混交林和荔枝纯林)，研究 了土壤种子库的萌发特征，以及覆盖物(椰糠和园林废弃物) 对常绿阔叶混交林土壤种子库演替初期群落生长的影响。结 果表明：1)2种林型土壤种子库物种丰富度相当，分别为常 绿阔叶混交林9种、荔枝纯林8种，荔枝纯林土壤种子库密度 和覆盖率分别为576.29粒/m2 、15.31%，明显高于常绿阔 叶混交林236.93粒/m2 、7.57%；2)覆盖物能显著提升常 绿阔叶混交林土壤种子库种子萌发的数量及早期演替群落的 覆盖度，具体表现为：椰糠组(密度：648.58粒/m2 、覆盖 率：13.74%)＞园林废弃物组(密度：368.56粒/m2 、覆盖 率：11.11%)＞对照组(密度：236.93粒/m2 、覆盖率： 7.57%)；3)2种林型土壤种子库与地上植被的物种相似度均 很低，分别为常绿阔叶混交林0.16，荔枝纯林0.19。结果表 明，从土壤种子库的物种丰富度、密度和早期演替群落盖度来 看，梧桐山土壤种子库在生态园林工程中的应用潜力很大，可 以作为深圳乃至华南地区生态园林建设的重要手段。同时，在 实际工程应用中，可以运用椰糠等覆盖物促进种子的萌发及演 替早期群落的形成。     

油脂定性试验菜籽油中棉籽油检出测量不确定度评定的探讨

探讨油脂定性试验——菜籽油中棉籽油检出测量不确定度的评定。用已知棉籽油含量的菜籽油进行检测分析测量过程的不确定度分量,合成相对不确定度(Uc)=18.21%。选择与被测样色泽接近的油脂加标对照,可以有效提高测定准确性。     

Seeds of accumulation: Molecular breeding and the seed corn industry in Hawai‘i

This paper examines how the application of advances in molecular biology change the relationships between nature and capital through a case study of Hawaiˋi's seed corn industry. Hawaiˋi's relatively minor role as a winter nursery changed in the late 1990s after the seed corn industry was reshaped by a series of techno‐scientific innovations and organizational restructuring. We draw attention to a molecular breeding technique called marker‐assisted selection (MAS) that accelerates crop improvement cycles by making parent lines selection more efficient and by taking advantage of extra growing seasons in tropical locations such as Hawaiˋi. Additionally, we argue that a wider application of MAS enhances seed firms’ geographical flexibility, allowing them to capitalize on the institutional rents of Hawaiˋi's agrarian politics and overcome challenges that might emerge in the future.     

加强国家重点林木良种基地建设和管理对策建议

国家重点林木良种基地是我国林木良种生产基地的精华,加强其建设和管理,对于转变林业发展方式、建设现代林业、实现绿色增长、增加农民收入极为重要。需要制定规划,进一步明确建设目标和主攻方向,建立科研生产管理相结合机制,培训技术和管理人才,强化经营措施,不断提高林木良种产量和品质,加快林木良种审定和推广应用进程。     

Dimensions of hunting satisfaction: Multiple‐satisfactions of wild turkey hunting

Abstract

Dimensions of hunting satisfaction were studied among a sample of hunters who received permits to hunt wild turkeys in Michigan. Principal components analysis revealed seven dimensions of turkey hunting satisfaction: preparation, search, harvest, nature, out‐group social, companionship, and season. Although some components of turkey hunting satisfaction were similar to those studied previously for deer hunters, components found in this study to be important to turkey hunters’ satisfaction point to the importance of studying hunting groups of diverse species in order to understand more fully the satisfactions people derive from hunting.     

Applied Policy Analysis of the Rice Marketing Subsector of Guinea-Bissau

Simple analytical techniques are used to diagnose and demonstrate problems observed in the rice marketing subsector of Guinea-Bissau. The problems are typical of those encountered by liberalizing economics. The recommendations favor policies that enhance competition.     

关于油茶产业发展的思考

发展油茶产业对于保证我国食用油供给安全、保护生态环境、增加农民收入等具有重要战略意义。当前我国油茶产业发展存在生产技术落后、开发投资缺失、经营体制不顺等问题,使油茶产业发展受到影响。在分析了油茶产业发展的背景、现状、问题的基础上,从技术进步、投入机制优化、林权制度改革、宏观调控等方面提出了油茶产业发展对策建议。     

袁州区油茶产业化经营分析与思考

从袁州区油茶产业发展现状出发,在分析总结的基础上,针对袁州区油茶产业在实行产业化经营过程中面临的问题,提出了推进袁州区油茶产业化经营的思路。