乡土树种在城市森林中的运用探析

乡土树种在城市森林建设中具有重要的作用,具有文化底蕴充分、适生生态性强、性能价格比高和管理便利的优点,作者针对目前存在的问题提出若干对策,此文对理解"城市森林"建设为何重用乡土树种很有帮助。       

对推进我国农村城镇化主线的思考

目前,我国进入新一轮经济周期,推进中国城镇化是新的经济增长点之一。农村城镇化的本质是农业现代化。只有打破常规,充分利用我国现阶段运用积极的财政政策和稳健的货币政策启动需求的机遇,集中财力,以推进农业现代化为主线,求得农业生产力的跨越式发展;切实依靠农村政治、经济制度和农业生产技术的创新,以农业经济体制的转型和农业经济增长方式的转移,使我国广大农村从传统的自给和半自给的小农经济跃上商品化、专业化、规模化的新台阶;以此奠定城镇的经济基础,切实推进中国农村的城镇化。农业现代化不但可以解决我国"三农"问题中的一系列深层次的矛盾,使我国城镇化得以有序健康地发展,而且也可以使生机勃勃的农村经济板块驱动城市经济板块,形成彼此互动、并驾齐驱的崭新格局,使我们摆脱目前宏观经济运行的困境,推动我国经济持续稳定地增长和繁荣。     

福建省武平县林下经济发展SWOT分析

以生态经济学原理为视角,采用SWOT分析方法,分析福建武平县林下经济发展的优势和劣势,面临的机遇和威胁,同时提出了武平县林下经济发展的对策与建议。     

Increasing rubber planting density to shade Imperata: a bioeconomic modelling approach

The profitability to smallholders of rubber production in Imperata infested areas of Indonesia was assessed using an existing bioeconomic model. An Imperata groundcover component was incorporated within the model as follows: tree girth = f(Imperata groundcover) = f(relative shading) = f(crown height, canopy width, tree spacing) = f(tree girth). The first two relationships represent extensions to the original model.Cumulative tree girth was predicted for rubber planting densities from 400 to 1000 stems/ha. At low tree planting rates, competition from Imperata restricts tree growth. At high tree planting rates, Imperata is controlled, but there are negative consequences from inter-tree competition. These two effects of higher planting rates counterbalanced, such that tree girth was approximately constant across the range of tree densities.Tree girth is a driving force in determining latex yield. Latex yield was translated into present value net economic returns within the model, by reference to prices and costs associated with rubber production in South Sumatra, Indonesia in 1995. Economic returns from planting 400 to 1000 trees/ha were calculated. Rubber growing by smallholders on Imperata infested land, was found to be profitable. Maximum profitability was obtained at 600 trees/ha. However, the sensitivity of net economic returns, with respect to tree density, was not great. This was due to the counterbalancing effects of changes in tree density.     

Stochastic control modeling for forest stand management under uncertain price dynamics through geometric brownian motion

In this paper, a stochastic control model is constructed by incorporating geometric Brownian motion to capture uncertain price dynamics into a one-stage and two-state stochastic dynamic programming model. The proposed model is designed to search for optimal harvest timing under price uncertainty without considering other forestry operations,e.g., thinning. We consider the option of abandoning forest management for an alternative use of forest land besides replantation. Our experimental analysis shows that the optimal harvest timing under stochastic log prices is delayed when a price level is crucially low for maintaining the management. It is also shown that when the current log price is sufficiently high, the optimal harvest timing derived from both the stochastic and deterministic approach becomes the same. With a downward trend of stochastic price dynamics, the optimal harvest timing tends to be hastened overall. This is because of the depreciation effect on the future return, which stimulates harvesting in an earlier period. This research was supported by a Grant-in-Aid for Scientific Research (No.11660155) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.     

Economic analysis of cut-and-carry,and alley cropping systems of mulch production for plantains in south-eastern Nigeria

Organic mulch is beneficial to plantain because it maintains soil fertility, prevents erosion and suppresses weeds. Mulch availability is however a major constraint. Mulching in a cut-and-carry system withPennisetum purpureum Schum. (elephant grass) was compared with mulching with the prunings ofAlchornea cordifolia (Schum. & Thonn.),Dactyladenia barteri (Hook. f. ex Oliv.)Engel. (Syn.Acioa barteri),Gmelina arborea (Roxb.) andSenna siamea (Lam.) Irwin & Barneby (Syn.Cassia siamea) in alley cropping systems. Plantain inPennisetum mulch treatment gave the highest bunch yield, but similar net revenues per hectare as theDactyladenia treatment, whileGmelina, Alchornea andSenna treatments produced the lowest incomes. But when the land required to producePennisetum mulch was included in the economic analysis, the net revenue per hectare was negative over three years of cropping. The returns to labour were also much lower for thePennisetum compared to the alley cropping systems. Among the in-situ mulch sources,Gmelina had the highest labour requirement because of the high pruning frequency. In addition, weeding inGmelina, Alchornea andSenna treatments resulted in high labour demand due to the rapid decomposition of the mulch materials leaving the soil bare for weeds to invade.Dactyladenia alley cropping was the most profitable of the five plantain production systems studied.IITA Journal Paper No: 94/004/JA.     

翅果油树研究进展

对翅果油树的植物学、细胞学、分类学、生理生化、生态学和群落学、经济生物学等方面的研究进行了较全面的总结,并提出了今后的研究方向,旨在促进翅果油树的研究和开发.     

城市森林净化能力计量研究及经济补偿政策的探讨

本文分析目前森林净化能力的计量研究方法和存在的问题,提出通过建立城市森林净化能力计量模型,实行差别化生态效益经济补偿政策的观点和相应补偿办法。     

发展农业机械化增加农民收入

对农业机械化的经济性进行了分析，明确指出发展农业机械化增加农民收入，土地要规模经营，要适应产业结构调整和农村经济体制要求，在政府大力扶持下，走市场化、社会化、集约化发展之路。     

小城镇产业发展战略分析

科学的产业政策是小城镇发展的决定因素。为此,结合我国小城镇实际,总结出小城镇产业调整与优化的原则;提出了小城镇产业发展的总体思路;并在详细地分析鸦鸿桥镇产业特点的基础上,提出了该镇“工贸型”产业发展战略,以及以强化市场建设为中心的产业发展措施。