THE IMPACT OF PRICE AND YIELD RISK ON THE BIOECONOMICS OF RESERVOIR AQUACULTURE IN NORTHERN VIETNAM

A bioeconomic model of reservoir aquaculture in northern Vietnam is used to investigate the impacts of fish price and yield variability on the level and riskiness of expected net revenue. Net revenue is volatile compared with similar enterprises in other countries, mainly due to high yield variability. This reflects the nascent nature of the industry in Vietnam and the potential for efficiency and productivity improvements. Increasing production intensiveness, as well as reservoir size, was found to increase profits and decrease revenue risk. Among the management parameters studied, expected net revenue was found to be most sensitive to the length of the production cycle and to the harvest rate, while revenue risk was most sensitive to cycle length. Reservoir size was found to affect net revenue less than anticipated. Although common carp monoculture was found to maximize expected profit, the current species mix minimizes risk, thereby suggesting high risk aversion by northern Vietnam's poor farmers.     

越南杉木种源早期评价与选择

杉木良种选择研究对越南杉木人工林有重要意义。以9个越南杉木种源与1个中国杉木无性系为研究对象,于越南3个试验点开展种源试验,并做早期选择。结果表明：种植2a后,在同一试验区不同的种源生长差异明显,同一种源在不同试验区生长不一。越南北部是杉木最适合的生长地区,南部次之,中部最差,这可能与当地的气候等因素有关。在越南北部, CL9、 CL7、 CL6、 CL4、 CL2和CL1种源为优良种源;在中部, CL4和CL1种源是优良种源;在南部,优良种源为CL8、 CL9与CL2。本试验早期研究结果有助于为越南杉木人工林选择适应种植地区和优良种源区规划提供借鉴。     

Hot water treatment prevents Aphelenchoides besseyi damage to Polianthes tuberosa crops in the Mekong Delta of Vietnam

Polianthes tuberosa is a commercially valuable flower crop in the Mekong Delta of Vietnam that is propagated by the harvesting and planting of bulbs. Cultivation of P. tuberosa is infected by an endemic Aphelenchoides besseyi nematode that damages a high proportion of plants and persists within the bulbs. Here we report on the comparison of hot water and pesticide treatments as control methods to protect P. tuberosa from A. besseyi damage, and conclude that a hot water treatment consisting of soaking bulbs in water for 30 min at 57 °C is the most efficacious method to produce healthy flowers in a cost effective manner.     

越南竹产业现状及发展对策

在阐述了越南竹类资源概况及竹产业现状的基础上,总结出越南当前竹产业发展存在的主要问题,并有针对性地提出了如何使越南竹产业走向良性循环轨道的对策。     

Extensive shrimp farming,mangrove clearance and marine fisheries in the southern provinces of Vietnam

Within the last decade shrimp farming in the Mekong Delta of Vietnam has increased by 3500%. Shrimp farming became un-sustainable in the early 1990's due to the un-planned development of this industry and the resulting self pollution of the farms, the destruction of mangrove forest and the outbreak of viral diseases. Historical data on fisheries, fishing effort and mangrove coverage were obtained from the province Minh Hai (lately divided in Ca Mau and Bac Lieu). Analysis of catch and effort data of marine fisheries in the Mekong Delta indicated a severe danger of over-exploitation of fish stocks and further decline can be expected if fisheries management only considers the demand for fish. The relation between the total fish catch (t/year), the mangrove area (ha), the engine capacity (HP) of the fishing fleet and the social incentive for fishing could be described with the model: Total catch=0.449*Mangrove area + 0.614 Engine capacity + 654 Social factor. One hectare of mangrove forest supports a marine catch of 450 kg/year     

Ordering the exemplary urban spaces: A critical analysis of Hanoi's embellishment projects

Vietnam has a long tradition of social engineering through which the ordering of urban space has effectively been used to enforce the state's vision of political and social order. With the country currently in transition from a centrally planned to a market‐oriented economy, the ordering of urban spaces is currently all the more important. This is prominently manifested in the numerous beautification projects that are being implemented in Vietnamese cities. This article explores recent ordering endeavours and considers the way they are legitimated and contested in Vietnam's new socio‐political context. Three beautification projects in Hanoi are examined using materials from policy documents, professional journals and media coverage. The article argues that state ordering actions and the ‘exemplary’ urban spaces they seek to create are embodiments of a complex system of orders of powers in transitional Vietnam, in which political visions of modernist socialism and the new market‐oriented agenda are sometimes in alignment and sometimes clash. Overall, the state's failure in sustaining these ‘exemplary’ urban spaces is emblematic of this hybrid system.     

越南北部草地贪夜蛾发生情况调查

越南是草地贪夜蛾的重要虫源地,其发生情况对我国草地贪夜蛾的动态有明显影响。2019年9月15-21日,在越南山罗省安州县对草地贪夜蛾田间发生和为害情况进行了调查。结果表明,调查区域均发生草地贪夜蛾为害,玉米田间虫株率为50.7%,百株虫量为110.7头;不同玉米生长期(苗期和穗期)的虫株率和百株虫量差异显著,苗期大喇叭口期虫株率和百株虫量(84.9%和201.1头),显著高于苗期小喇叭口初期(53.2%和114.7头)和抽雄期(14.2%和16.2头);田间虫株率和百株虫量之间的幂函数模型为y=0.842 8x~(1.212 5)。因此,要进一步加强与越南相关部门的合作,掌握越南草地贪夜蛾发生和为害动态,为我国草地贪夜蛾的监测与防控提供依据。     

越南黄连国家公园福建柏群落的研究

越南黄连国家公园位于越南北部,总面积约29845 hm2,最高海拔3143 m（番西邦）,与中国云南省金平县接壤。由于人为砍伐、毁林开荒,目前福建柏原生群落主要分布在黄连国家公园西南区域,主要分布于海拔1400~1900 m,最高可达2176 m。在对该区域4个样地（总面积2400 m2）和5个样圆福建柏群落实地调查的基础上,对群落的物种组成、区系成分、种内种间竞争、物种多样性进行了统计和分析,结果表明：该群落中共有维管植物74科120属143种,其中蕨类植物有8科9属10种,裸子植物4科4属5种,被子植物62科106属128种 该群落植物区系地理成分以热带分布类型为主,占有较大比例,且起源古老 群落为复层异龄结构,乔木层的优势种主要有福建柏、蕈树、越南多花含笑、叶轮木、锈毛梭子果、鸡毛松、锈毛棋子豆、微毛布惊、灰毛杜英、大叶柯、睦南木莲、沙坝厚皮香等种 群落物种多样性指数较高,各样地间多样性指数变幅不大,福建柏群落物种多样性在群落不同层次的变化规律为：乔木层〉灌木草〉草本层〉层间植物〉更新层 福建柏种间竞争主要为：沙坝厚皮香、蕈树、大叶柯、锈毛梭子果、越南多花含笑、公孙锥、叶轮木、野柿、越南琼楠、锈毛棋子豆等种。     

低温对火龙果种植的影响及其防御措施

在总结温度对火龙果生长发育的影响及低温对火龙果冻伤的危害的基础上,分析了我国不同温度气候带火龙果的引种栽培模式及其低温防御措施,为我国火龙果种植生产及火龙果南种北移提供了具体的指导建议。     

越南开发南海金枪鱼资源的历史和趋势

近十年来,越南将南海的金枪鱼资源作为其＂外向型＂渔业的重要支撑,不断增加捕捞强度,产量逐年升高。本文总结了越南发展南海金枪鱼渔业的过程,分析了南海金枪鱼资源的开发趋势。越南现代化的金枪鱼捕捞技术主要来自日本,使用的渔具主要有金枪鱼延绳钓、手钓、刺网和小型围网,捕捞的种类主要为鲣鱼、黄鳍金枪鱼和大眼金枪鱼,主要作业区域在西沙群岛南部海域和南沙群岛海域。越南2009年金枪鱼的产量已达到5.9×104t,计划2015年达到30×104t。根据越南海洋渔业研究所（RIMF）的评估,南海中西部的金枪鱼资源量为66~67×104t,可捕量23.3×104t,其中鲣鱼的可捕量21.6×104t,黄鳍金枪鱼和大眼金枪鱼的可捕量1.7×104t。随着全球金枪鱼捕捞配额的缩减和越南＂外向型＂渔业经济的发展,越南将继续加强对南海金枪鱼资源的开发。