毛竹林生态系统经济阈值模型的研究

如何确定合理的挖笋量是毛竹林丰产经营的关键问题。本文通过在建瓯设立50块毛竹林标准地，分别建立了毛竹林笋产量预测模型与林分平均胸径预测模型。在此基础上，运用经济阈值的手段对毛竹林生态系统进行研究。提出了毛竹林生态系统经济阈值的概念及研究方法，建立了毛竹林生态系统经济阈值模型。并结合实例对毛竹林生态系统经济阈值模型的应用给予了说明。本研究不仅丰富了经济阈值的研究内容与应用范畴，而且也为毛竹林的优化经营和丰产培育提供新的依据与技术。     

蛀干害虫经济阈值刍议

本文简要叙述了研究害虫经济阈值所涉及的主要因素、林业害虫经济阈值的特点，以及制定林木蛀干害虫经济阈值的限制因素和建议。     

蛀干害虫经济阈值刍议

本文简要叙述了研究害虫经济阈值所涉及的主要因素，林业害虫经济阈值的特点，以及制定林木蛀干害虫经济阈值的限制因素和建议。     

我国森林害虫经济阈值研究进展

从我国森林害虫研究中的经济阈值概念、研究方法、确定模型、研究现状和存在的问题及对策等几个方面着手,对我国目前森林害虫经济阈值研究的状况及进展进行了综合评述     

用材林害虫管理经济阈值模式的研究

森林害虫是用材林的大敌。在森林害虫科学管理决策专家系统中 ,害虫危害的经济阈值是最重要的判别依据。该文通过大量的调查 ,系统的研究和实际检测 ,确定了食叶害虫种群控制、蛀干害虫种群控制和树干韧皮部害虫营林防治经济阈值模式     

用材林害虫管理经济阈值模式的研究

森林害虫是用材林的大敌。在森林害虫科学管理决策专家系统中,害虫危害的经济阈值是最重要的判别依据。该文通过大量的调查,系统的研究和实际检测,研究了食叶害虫种群控制、蛀干害虫种群控制和树干韧皮部害虫营林防治经济阈值模式。     

油茶尺蠖动态经济阈值的研究

运用人工模拟为害方法，研究了油茶尺蠖（ＢｉｓｔｏｎｍａｒｇｉｎａｔａＳｈｉｒａｋｉ）为害对油茶生长、发育的影响。严重为害不仅引起油茶减产，而且影响植株的生长势和生产潜力；轻度为害可使植株改变内部生理机能，生长出现补偿和超补偿现象。在研究为害程度与产量损失关系基础上，按经济阈值原理提出了油茶尺蠖的经济阈值动态模型，为油茶尺蠖的综合管理提供了理论依据。     

有害生物综合治理中经济阈值的估算方法

经济阈值概念在有害生物综合治理系统中起决策作用。根据美苏有些资料报道~([6、712]),采用经济阈值来限制化学农药的使用,不仅可以节省70—75%的喷药开支,而且大大减少喷药面积和用量。根据定义,经济阈值指“应决定采取防治手段以防有害生物种群上升到经济损害水平时的种群密度”(10)。     

杨树灰斑病优化管理技术的研究

本研究以杨树－杨树灰斑病生态系统为研究对象,在杨对生长模型和杨树灰斑病流行模型的基础上,建立了杨树灰斑病危害的损失量模型和多维动态经济阈值模型。模拟了杨树－杨树灰斑病的系统动态,并根据杨树灰斑病常用的管理措施,结合经济核算确定不同条件组合下的经济阈值,建立了杨树灰斑病的优化管理决策系统。     

杨树烂皮病优化管理技术的研究

以杨树—杨树烂皮病 (ValsasordidaNits )生态系统为研究对象 ,在杨树生长模型和杨树烂皮病流行模型的基础上 ,建立了杨树烂皮病危害的损失量模型和多维动态经济阈值模型。模拟了杨树—杨树烂皮病的系统动态 ,并根据杨树烂皮病常用的管理措施的防治效果 ,结合经济核算确定不同条件组合下的经济阈值 ,建立了杨树烂皮病的优化管理决策系统     

A model to calculate ex ante the threshold value of interaction effects necessary for proposed intercropping projects to be feasible to the landowner and desirable to society

This article describes an approach to evaluate the difference in net present valued economic returns that would be expected from temperate intercropping as compared to annual cropping or tree farming alone. This tool can be used by landowners to provide a threshold level of the value of interaction effects required for a proposed intercropping project to break even, based on current data. The landowner would then need to consider, using information from other sources, whether the threshold is realistic for given site conditions. The threshold value is useful to agricultural policy-makers to consider economic instruments that would induce landowners to adopt intercropping, if it should be considered socially beneficial to do so. The approach measures the financial gap that exists between intercropping and annual cropping alone and compares this gap to the beneficial interaction effects that are associated with intercropping. The approach is demonstrated using experimental results from an on-going intercropping study at the University of Guelph, Guelph, Canada. A base model scenario using black walnut trees with annual crops is set up with a 5% discount rate, 96 trees per hectare, and sawlog prices for black walnut of $1066 per 1000 bdft as a base case. The base model predicts that black walnut and corn intercropping returns $555 per hectare less than the annual crops alone, over the entire rotation of trees. This amounts to about $42 per hectare per year in annual terms, at a 6% rate of discount. This is the threshold that would need to accounted for by the net present value (NPV) of on-farm interaction effects. This estimate depends on the specific assumptions made and the experimental situation, and should not be interpreted as reflecting returns possible in other circumstances. This revised version was published online in June 2006 with corrections to the Cover Date.     

杨小舟蛾防治指标研究

通过测定周至县分布最广、受杨小舟蛾［Ｍｉｃｒｏｍｅｌａｌｏｐｈａ ｔｒｏｇｌｏｄｙｔａ（Ｇｒａｅｓｅｒ）］危害最重的８年生１５号杨在不同失叶水平下的材积损失，确定了其经济防治阈值。在测定杨小舟蛾幼虫食叶量及对其发生规律和防治技术研究的基础上，结合当地实际，制定了杨小舟蛾各世代的防治指标，拟定了其综合防治策略。     

试论害虫综合治理（IPM）战略思想

有害生物综合治理（ＩＰＭ）是联合国粮农组织于１９６７年正式提出的关于农业有害生物防治的理论。文章对几种ＩＰＭ的定义及异同,进行了综合评述。并对其中心问题－经济阈值和经济危害水平的内涵及研究方法,做了较说的介绍,对森林害虫的综合治理具有一定的能者价值。     

油松种子园甘肃鼢鼠防治试验研究

以化学防治为开端，迅速压低鼢鼠口密度，以人工机械捕杀残留鼠，生物措施巩固防治效果，使害鼠种群数量始终维持在经济阈值以下。     

Estimation of the Gentan probability using the price of logs in private plantation forests

The Gentan probability is defined as the probability that a newly planted forest stand will be harvested at a certain age. In this study, the Gentan probability was estimated using the price of logs, in accordance with the notion that the probability is influenced by economic factors. In order to estimate the Gentan probability, we adopted a probability density function based on the forest owners’ decision-making process, which consisted of a decision criterion, a decision criterion function and a criterion threshold. The price of logs was employed for the criterion, and the decision criterion function was defined as the value of the forest stand based on the price of logs. Moreover, the mechanism of changes in the threshold was formulated based on the random walk concept. The parameters of the suggested Gentan probability were calibrated to fit the harvesting tendencies observed in the past. Finally, the Gentan probability distributions estimated using the prices of logs over the past 20 years were compared with those estimated using felling age means and variances. The two distributions were closely correlated during most years. The proposed Gentan probability model takes advantage of short-term yield predictions such as an analysis of forest owners’ reactions to the current price changes.