The optimal selective logging regime and the Faustmann formula

This study analyzes the optimal selective logging regime of a size-distributed forest where individual trees compete for scarce resources such as space, light, and nutrients. The decision problem of the forest manager is formulated as a distributed optimal control problem. The interpretation of the first-order conditions allows a generalization of the Faustmann formula. In an empirical part, this article numerically determines the optimal management regime of a size-structured forest and shows that the optimal selective logging regime is associated with a normal forest under a wider variety of situations than stated in the previous literature.     

Integrating neighbourhood effects in the calculation of optimal final tree diameters

Modern silvicultural treatments are based on single trees whereas classic forest economics look at the stand level. To accompany each other it is necessary to transfer the established economic models to the single tree level. This paper is an approach to use the Faustmann model and the corresponding marginal rate of return (Pressler percent) to derive value increment rates of single trees taking into account neighbourhood effects due to competition between individual trees. Furthermore, optimal rotation periods and optimal final diameters for future trees will be calculated.     

The emergence of forest age structures as determined by uneven-aged stands and age class forests

This article explores the question under which conditions trees are managed in even- or uneven-aged stands or age class forests, respectively. The problem of uneven-aged management within stands and forests can be reduced to the analysis of simultaneous optimal times of harvest and regeneration of interdependently growing trees. Restricting attention to a market environment, a forest investment model is developed which accounts for the opportunity to manage trees or stands individually. As a consequence, age class forests evolve as the optimal compromise between two opposing effects. They allow for a combination of the advantages of uneven-aged management by utilizing differences in tree growth on a larger scale and of even-aged management by exploiting locally effective positive inter-tree dependencies on a smaller scale. Accordingly, the emergence of the forest structure is determined by the dynamics in the balance of value growth and impact rate differences.     

Editorial - Multiple-use forestry

The problem of multiple-use forestry arises because (1) a forest can be managed to provide a wide range of products and services, (2) the different uses are not perfectly compatible with each other, and (3) some products are not priced in markets and many of the services a forest provides have the characteristics of public goods. Examples of major forest products include, in addition to timber, edible berries, fungi, and hunting games. Forests also provide recreation opportunities and various environmental services (such as regulating local climate, reducing soil erosion, reducing pollutants in the atmosphere, regulating the global climate, providing habitats for wildlife, etc.). The outputs of nontimber goods in general depend on the quantity and structure of the forest, which can be changed by various forest management activities. However, a forest state most suitable for the production of one good is usually not optimal with respect to another good. Typically, there does not exist a set of management activities that simultaneously maximize the outputs of timber and all other goods.Another way to understand the conflicts between different uses is to view standing timber as an intermediate product of forestry investment, which is employed as an “input” for the production of timber products and nontimber goods. Thinking in this way, the conflicts arise partly because timber production and nontimber uses compete for the same input, and partly because of the differences in the “production technology” among different nontimber goods. A change in the standing timber may have positive impacts on some nontimber uses, but have negative effects on others. Because of the conflicts among different uses, it requires that both timber products and nontimber goods should be explicitly incorporated into forestry decision-making in order to achieve the greatest benefits to the forest owner and/or the public.Most of the economic analyses of multiple-use forestry decisions have explicitly or implicitly adopted the view that multiple-use should be achieved in individual stands. Each stand should be managed to produce an optimal mix of timber products and nontimber goods. Another view of multiple-use forestry is to manage each stand for a primary use, whereas multiple-use concerns are addressed by allocating different stands in a forest to different uses. A general argument in support of the primary-use view is that specialization makes for efficiency. The production of timber and nontimber goods is a joint process, however. Strictly speaking, one cannot separate timber production and the production of different nontimber goods. For example, managing a stand for timber production does not exclude the possibility of producing some nontimber goods in the stand. Since every stand usually produces more than one product, efficient multiple-use forestry requires that each stand should be managed for an optimal mix of timber and nontimber outputs. On the other hand, it may well be the case that the optimal multiple-use mix for a particular stand consists of a maximum output of one product. In this case the optimal multiple-use management decision would coincide with the optimal decision pertaining to a single use. In other words, it may be optimal to manage a particular stand for one primary use. Using the terminology of economics, primary-use may be efficient for stands in which the multiple-use production set is nonconvex. Recent research has explored several sources of nonconvexity in the multiple-use production set. However, there is no evidence supporting the argument that specialization is always more efficient than multiple-use management of individual stands. From an economics viewpoint, efficient primary-use is special cases of multiple-use stand management.A widely recognized limitation of multiple-use stand management is that, by considering each stand separately, one neglects the interdependence of nontimber benefits and ecological interactions among individual stands. The nontimber benefits of a stand depend on the output of nontimber goods from other stands. Likewise, the nontimber output from one stand affects the value of nontimber goods produced in the other stands. Ecological interactions among individual stands imply that the output of nontimber goods from two stands in a forest differs from the sum of the outputs from two isolated stands. These interdependence and interactions imply that the relationship between the nontimber benefits of a stand and the stand age (or standing timber stock) cannot be unambiguously determined - it depends on the flow of nontimber goods produced in the surrounding stands. Therefore, it is improper to determine optimal decisions for the individual stands independently. In stead, efficient multiple-use forestry decision should be analyzed by considering all the stands in a forest simultaneously.Another serious limitation of multiple-use stand management is that each stand is treated as a homogenous management unit to be managed according to a uniform management regime. One implicitly assumes that the boundaries of each stand is exogenously given and will remain unchanged over time. This assumption imposes a restriction on the multiple-use production set, thereby creates inefficiency. As an example, consider a large stand with a nonconvex production set. It may be possible to eliminate nonconvexity in the production set and push the production possibility frontier outwards by dividing the stand into several parts and managing each part for a primary-use. It may also be efficient to combine two adjacent stands into one to be managed following a uniform regime, because of the presences of fixed management costs, and/or because the relationship between some nontimber outputs and stand area is not linear.In contrast to income from timber production, nontimber goods produced at different time points are not perfect substitutes. The rate at which a forest owner is willing to substitute a nontimber good produced at one time point for that produced at another time point changes with the outputs of the nontimber good at the two time points. In general cases, the nontimber goods produced at one time point cannot be consumed at another time point, and the marginal utility of a nontimber good decreases when its output increases. This provides a motivation for reducing the variation in the output of nontimber goods over time. An effective approach to coordinating nontimber outputs over time is to apply different management regimes to different parts of a stand, or apply the same regime to adjacent stands, which would change the boundaries of the stands. Preserving the existing stand boundaries would limit the possibility of evening out the nontimber outputs over time, and thereby lead to intertemporal inefficiency in multiple-use management.In previous studies of multiple-use forestry decisions the nontimber outputs or benefits are usually modeled as functions of stand age or standing timber stock. Future flows of nontimber goods or benefits are incorporated into a stand/forest harvest decision model to explore the implications of nontimber uses for optimal harvest decisions. While stand age and standing timber stock may have significant impacts on nontimber outputs, other forest state variables, e. g. the spatial distribution of stands of different ages/species, may be of great importance to the production of nontimber goods. Recognition of such forest state variables could change the relationship between timber production and nontimber outputs and therefore change the optimal forest management decisions.In summary, multiple-use forestry is not simply an extension of timber management with additional flows of benefits to be considered when evaluating alternative management regimes. Recognition of multiple uses of a forest leads to two fundamental changes of the forestry decision problem. First, the optimal intertemporal consumption of forestry income is no longer separable from forest management decisions. In general, the optimal intertemporal consumption of forestry income depends on future flows of nontimber goods, implying that the consumption-saving decision should be made simultaneously with the decision on the production of timber and nontimber goods over time. Secondly, it is no longer appropriate to optimize the management regime for each stand separately. The nontimber outputs from a forest depend on the age distribution of individual stands, and on a wide range of other forest state variables such as the spatial distribution of stands of different ages and tree-species composition. Ecological interactions and interdependence among stands imply that management regimes for different stands should be optimized simultaneously. In addition to changing rotation ages and harvest levels, efficient multiple-use forestry requires optimizing the spatial allocation of harvests, redefining the boundaries of stands, coordinating the choices of tree species in regeneration of harvested area and so on.The lack of rigorous production functions for nontimber goods imposes a severe restriction on attempts to perform comprehensive economic analyses of multiple-use forestry decisions. This restriction in itself is no justification for ignoring many of the key aspects of multiple-use forestry problem and modeling the problem as one of determining the optimal rotation age or optimal harvest level. It requires that economic models of multiple-use forestry should be developed with special consideration of the vague and imprecise information regarding the relationships between nontimber outputs and forest state variables.Peichen GongDepartment of Forest EconomicsSE-90183 UmeåSweden     

Designing afforestation subsidies that account for the benefits of carbon sequestration: A case study using data from China's Loess Plateau

This paper presents a method for determining the subsidy required to motivate farmers to participate in timber afforestation programs designed to maximize social well-being. The method incorporates a carbon sequestration benefit function into the land expected value model in order to quantify the social benefit arising from carbon sequestration by the planted trees. This is used to calculate the optimal rotation age for newly planted forests that maximizes social utility. The minimum subsidy required to motivate farmers to participate in the afforestation program was calculated using a modified decision model that accounts for the subsidy's impact. The maximum subsidy offered by the government was taken to be the NPV of the carbon sequestration achieved by afforestation. Data on Robinia pseudoacacia L. trees planted on the Loess Plateau were used in an empirical test of the model, which in this case predicts an optimal subsidy of 254.38 yuan/ha over 40 years. This would guarantee the maintenance of forest on land designated for afforestation until they reached the socially optimal rotation age. The method presented herein offers a new framework for designing afforestation subsidy programs that account for the environmental service (specially, the carbon sequestration) provided by forests.     

农户扩大经济林种植规模意愿及规模水平影响因素分析——以浙江省为例

以Probit、Tobit回归模型为主要工具,利用浙江省236户农户调查数据,实证分析了农户扩大经济林种植规模意愿及规模水平的影响因素。研究结果表明:户主年龄、受教育程度、家庭人口数、是否参与标准化项目以及对经济林发展前景判断对农户扩大经济林种植规模意愿及规模水平有显著影响;而经济发展水平只对农户扩大经济林种植规模意愿有显著影响,家庭人均收入和家庭非农收入占比只对农户扩大经济林种植规模水平有显著影响。最后,提出相应的对策建议:加大经济林宣传力度,提高农户种植积极性;完善补贴政策,保障经济林的持续经营;加强经济林质量监督,提高农户经济林收入。     

Carbon Sequestration and Conservation of Tropical Forests Under Uncertainty

Concern for global warming has focused attention on the role of tropical forests in the reduction of ambient CO₂ levels and mitigation of climate change. Deforestation is a major land use change in the tropics, with forest resources undergoing degradation through the influence of logging and conversion to other uses. Land use change is a product of varied local and regional resource use policies. Management of forest resources is one such major temporal factor, influencing resource stability and the carbon pool. Under a given management policy, both the long period of forest growth, and the slow turnover and decay of the carbon pool, enhance the relevance of stand level management policies as cost-effective mechanisms mitigating climate change. Apart from regional level uncertainties like the nature of land use and the estimation of carbon storage in vegetation and soil, the carbon flux of tropical forests is greatly influenced by uncertainty in regenerative capacity of forests and in harvest and management policies. A case study from India is used to develop a transition matrix model of natural forest management, and to explore the economic implications of maintaining and expanding existing carbon sinks. The study further explores the significance of investments in additional carbon sinks in plantation forests, given continued uncertainty in natural forest management.     

低温雨雪冰冻灾害对湖北森林资源的影响与思考——赴湖北灾后恢复重建工作技术指导组调研报告

湖北林业这次雨雪冰冻灾害主要表现在竹木损失惨重,经济林、新造林损毁严重等方面。从造林树种灾情看,其受灾重点为竹类、针叶树种、阔叶树种。存在问题:森林经营水平低,科技含量不高;林业次生衍生灾害潜在风险大;基础设施毁坏严重;森林抵御特大自然灾害相关研究不足。建议:加强技术指导,科学恢复与重建;预防为主,防止次生、衍生灾害;争取启动冰雪灾害防护技术研究。     

森林认证对森林可持续经营的影响研究

森林认证是作为解决世界森林问题,推动森林可持续经营的一种市场机制提出的。文章在理论分析和案例实证的基础上,论述了森林认证影响的内涵、范围及其所产生的环境、社会和经济影响。认为,森林认证促使森林经营产生了很多实质性的变化,而不仅仅是一种验证已经营良好森林的工具。     

森林认证促进生态环境保护的路径——基于顺昌县国有林场的调查

在对福建省顺昌县国有林场开展森林认证情况进行调查的基础上,对开展森林认证活动促进生态环境保护的路径调研结果表明:森林认证是通过森林资源经营管理单位开展认证知识培训、环境影响评估、生产作业监管、废弃物清理、认证年度审核、不符合项整改、野生动植物监测、高保护价值森林经营等生产经营管理活动来促进生态环境保护的,强化生产经营过程的监管,可以使所有生产作业都操作规范、安全环保,确保生产活动对环境的破坏降到最低程度。此外,顺昌县国有林场近年来采用的一种特殊的经营模式——不完全采伐保留阔叶树的主伐、在中幼龄阔叶树下营造杉木林、不炼山"耙带"式造林,可以减少水土流失,有利于生态环境保护。针对开展森林认证会增加森林生产经营成本但却能显著促进生态环境保护而提出政府应该加大森林认证宣传力度、建立森林认证补偿激励机制等建议。     

基于适应性管理视域的森林生态系统服务主导因子研究——以大小兴安岭森林生态功能区为例

基于适应性管理应用到森林生态系统管理的管理模式,以黑龙江省大小兴安岭森林生态功能区为例,利用主成分分析法从气候调节、生态保持、产品供给和休闲服务4个方面分析影响森林生态系统服务功能的主导因子及构成各个影响因子的核心指标。经研究发现产品供给和休息服务对森林生态系统服务功能的短期影响较大。其中,气候调节和生态保持则属于长期影响因素,对森林生态系统服务功能的短期影响较小。最后,在上述分析的基础上提出适应气候变化,改善生态环境;调整林产品供给结构,加强非林木产品供给能力;增强森林生态服务,扩大森林游憩影响;协调森林生态系统内部关系,提高森林生态系统服务质量等建议。     

国有林区森林资源管护承包对森林资源安全的影响

构建国有林区森林资源安全指标体系,基于2000—2016年黑龙江省国有林区森林资源的时间序列数据,采用熵权法测算森林资源安全综合指数,运用多元线性回归法分析森林资源管护承包对国有林区森林资源安全的影响。结果表明:2015—2016年黑龙江省国有林区的森林资源安全总体处于良好阶段;森林资源管护投资、个体承包管护面积占管护总面积的比例等对国有林区森林资源安全产生显著的正向影响;管护资本投入是对森林资源安全影响最大的人为干预因素,火灾发生次数是对森林资源安全影响最大的自然灾害因素。因此,为了保障国有林区森林资源安全,建议加大管护资金投入,增加管护人员数量,组建联合管护队伍,签订管护责任书,加强森林巡护,防范自然灾害的发生。     

福建省重点生态区位商品林赎买模式比较研究

阐述福建省重点生态区位商品林赎买改革模式,收集典型案例,对福建省现行的赎买、租赁、置换及改造提升等多种赎买模式进行归纳总结和优劣势分析。基于赎买过程中涉及到的政府、行业主管部门和农户3个利益主体,并结合赎买模式实施条件,得出不同利益主体选择赎买模式的建议:政府应选择保护林权权利人合法权益,促进林区社会和谐稳定的赎买模式;林业主管部门应选择有利于林分结构调整、优化生态公益林布局、提高林业社会地位的赎买模式;农户应基于收益最大化目标,结合家庭劳动力、林业依赖等情况选择赎买模式。     

Forest governance and economic values of forest ecosystem services in Vietnam

Forest ecosystems deliver valuable services to humanity. However, many forests are being degraded and their services have been undervalued. The main problem lies in the inadequate institutional arrangements for forest governance. This paper aims to assess the effects of alternative forest governance arrangements on the provision and economic values of forest ecosystem services (FES) in Vietnam. The study presents a framework for mapping land use and land cover (LULC) change stemming from actual and hypothetical changes in forest governance regimes, quantifies the resulting changes in the provision of FES, and estimates the associated economic values. In the context of the study site in the North Western uplands of Vietnam, we test three alternative forest governance scenarios: business as usual, with a dominant government role; a community-based governance regime; and a private, individual-based forestry governance regime. Scenarios are based quite closely on the way these regimes are (or might be expected to be) implemented in Vietnam. For each forest governance scenario, we map LULC changes based on land suitability analysis and transition likelihood for the period 2010 − 2020. The resulting maps are used as inputs into the InVEST (Integrated Valuation of Environmental Services and Tradeoffs) model, which is used to estimate the quantity of three specific FES: carbon storage/sequestration, sediment yield, and water yield. We apply economic valuation methods to value these services: the social cost of carbon is used to estimate the economic values of carbon storage/sequestration; the cost of removing sediment deposited in reservoirs is applied for valuing the reduction of sediment yield, and the residual value of water supply for hydropower generation is used for valuing water yield. The results show that forest governance regimes have a significant effect not only on forest LULC, but also on the quantity and values of FES derived from forests. The FES are differentially affected by alternative forest governance regimes: some FES increase in quantity and value under some governance regimes and decrease under others. Of the three forest governance regimes examined, there is no one regime that will always be ‘better’ than the others in terms of provisioning all considered FES. For the specific context of Vietnam, we find that the private forest governance scenario is inferior to the community-based governance scenario, as an alternative to the current state-based governance. Because our results pertain to the scenarios as constructed, rather than generally to broad categories of governance regimes, there remains the possibility that regimes can be constructed that outperform all of those examined here.     

Efficiency in forest management: A multiobjective harvest scheduling model

This paper presents a new forest harvest scheduling model taking into account four conflicting objectives. The economic factor of timber production is considered and also aspects related to environmental protection. We also incorporate adjacency constraints to limit the maximum contiguous area where clear-cutting can be applied. The model proposed is applied to a timber production plantation in Cuba located in the region of Pinar del Río. One factor to be taken into account in Cuban plantations is that the forest has a highly unbalanced age distribution. Therefore, in addition to the classical objectives of forest planning, we have the objective of rebalancing age distribution by the end of the planning horizon. Explicitly, the four objectives considered in the model are: (a) obtaining a balance-aged forest; (b) minimizing the area with trees older than the rotation age; (c) maximizing the NPV of the forest over the planning horizon; and (d) maximizing total carbon sequestration over the whole planning horizon. The solution to the proposed model provides a set of efficient management plans that are of assistance in analysing the tradeoffs between the economic and ecological objectives. The model is also applied to randomly generated simulated forests to compare its performance in other contexts. As the problem is a multiobjective binary nonlinear model, a metaheuristic procedure is used in order to solve it.     

林业产业结构升级对国有林区改革绩效的影响

基于2003—2016年东北、内蒙古重点国有林区87个林业局的面板数据,以林业总产值、森林管护面积、年末在岗职工人数作为衡量指标,采用面板数据固定效应模型分析林业产业结构升级对国有林区改革绩效的影响机制。结果表明:林业产业结构高级化对国有林区改革绩效具有促进效应,但产业结构升级速度过快也会在一定程度上对国有林区改革绩效产生抑制效应;林业财政投资额对林业总产值具有显著促进作用;年末在岗职工人均工资对森林管护面积和年末在岗职工人数具有显著促进作用;林业工作站数量对森林管护面积具有显著促进作用。因此为推动国有林区改革工作顺利进展,重点国有林区林业产业结构升级应与经济发展水平和生态环境状况相适应。     

黑龙江省国有重点林区森林生态服务政府供给影响因素实证分析

根据黑龙江省国有重点林区的调查问卷数据,建立了森林生态服务政府供给的影响因素与政府供给关系的结构方程模型。研究表明森林生态供给投入、森林生态政策、社会经济环境、森林资源经营管理是影响森林生态服务政府供给的关键因素。森林培育技术虽然有利于森林生态服务政府供给,但在黑龙江省国有重点林区,森林培育技术对森林生态服务政府供给影响不显著。     

Review - Roger A. Sedjo (2003): Economics of Forestry

Ashgate Publishing Limited, Gower House, Croft Road, Aldershot, Hants GU11 3HR, England (www.ashgate.com). 498 p. £ 100.00. ISBN 0-7546-2237-1 (hardback).Being one volume in the series of the International Library of Environmental Economics and Policy (T. Tietenberg and W. Morrison, gen. eds.), this book is a collection of some of the most significant journal essays in forest economics and forest policy. In compiling this volume, Roger Sedjo did a great service to the forest economics profession.This volume includes twenty-five essays originally published between 1849 and 1996 in a dozen journals, and one chapter from the Third Assessment Report of the International Panel on Climate Change (IPCC, 2001) which addresses the biological sequestration of carbon in terrestrial ecosystems. These are organized into four parts: the harvest rotation issue, timber supply, multiple-use and non-timber outputs, and global issues. An introduction essay to this volume, written by the editor, provides an overview of the major issues in forest resource management and discusses some the most important contributions to the forest economics literature.The eleven essays in the first part of the book provide a rather complete coverage of the most important contributions to the literature on optimal rotation age, which is a fundamental issue in forest management and forestry investment. Four of the essays (Faustmann 1849, Ohlin 1921, Bentley and Teeguarden 1965, and Samuelson 1976) address the basic formulation and interpretation of the optimal rotation model. Four essays (Löfgren 1985, Newman, Gilbert and Hyde 1985, Reed 1984, and Brazee and Mendelsohn 1988) extend the basic rotation model to examine the rotation age decision in the presence of deterministic trends and uncertainty in timber yield and price, respectively. Based on the Faustamnn rotation model, Klemperer (1976) and Chang (1982) examine the impacts of taxation on forest value and on the optimal rotation age. Koskela (1989) provides a detailed analysis of the impacts of taxation on timber harvest decisions under price uncertainty. What I feel missing in this part is a comparative statics analysis examining the impacts of changing economic parameters on the optimal rotation age.Part II includes five essays on economic analysis of long-run timber supply. Clawson (1979) reviews the historical development of forest resource and forest utilization in the United States. Vaux (1973) examines the long-run potential supply of timber from forest plantations in California. Berck (1979) investigates the difference in harvesting behavior between private forest owners and public managers. Lyon (1981) and Lyon and Sedjo (1983) examine the optimal exploitation of old-growth natural forests and the transition to steady state. While these essays all focus on the long-run timber supply in the United States, the methods developed and used in these papers could be applied for any other region. The exploitation of old-growth natural forests and the long-term availability of timber have been without doubt two major concerns in the United States. In many parts of the world, however, concerns about timber supply in the short-run have also had great influences on the development of forest policy. It would have been appreciated if a couple of essays addressing the short-run supply of timber had been included.Part III contains three essays dealing with the problem of multiple-use forest management. Gregory (1955) develops an economic framework for multiple-use management based joint production theory. Hartman (1976) examines the multiple-use rotation age decision. Swallow, Parks and Wear (1990) investigate the problem of non-convexities involved in multiple-use rotation age decisions. The merits of these essays lie in that they use rather simple models to demonstrate the importance of incorporating non-timber benefits in forestry decisions and the complexities of the multiple-use problem. In his 1976 essay, Hartman points out that in many situations management practices applied to one stand affect the value of non-timber outputs derived from the adjacent stands; such interdependence needs to be incorporated into multiple-use decision analysis. I certainly would like to find in this volume one or two essays examining the impacts of stand interdependence on the optimal decision. Another important issue in multiple-use management, which is not covered in this volume either, is the valuation of non-market priced outputs and services. Yet I believe that this omission is well motivated, for there are two separate volumes in this series devoted to non-market valuation methods (R. T. Carson, ed. Direct Environmental Valuation Methods, Volumes I and II).The seven essays in Part IV deal with a set of forest economic and policy issues related to global warming and biodiversity conservation. Parks and Hardie (1995) examine the cost-effective subsidies to convert marginal agricultural land to forests for the purpose of carbon sequestration. Hoen and Solberg (1993) analyze the potential and cost-effectiveness of increasing carbon sequestration in existing forests by changing forestry practices. van Kooten, Binkley and Delcourt (1995) examine the effect of carbon taxes and subsidies on the optimal rotation age. The chapter from the Third Assessment Report of IPCC (2001) provides a comprehensive review of the literature on the ecological, environmental, social and economic aspects of carbon sequestration in terrestrial ecosystems. While forests and forest management could play an important role in mitigating climate change, increasing level of atmospheric dioxide and climate change would inevitably affect the productivity of forest ecosystems, thereby could have significant impacts on future timber growth, harvest and inventory as well as carbon storage in forest ecosystems. Joyce et al. (1995) present a framework for analyzing the potential effects of climate change on the forest sector. The remaining two essays in this part examine the costs and benefits of biodiversity preservation, respectively. Montgomery, Brown and Adams (1994) estimate the marginal cost of preserving the northern spotted owl. Simpson, Sedjo and Reid (1996) examine the expected value of the marginal species as an input to pharmaceuticals.The editor points out in the introduction chapter that there are many other important contributions that are not included in this volume, some of these are mentioned, others not. In addition to the few omissions noted earlier, several important economic and policy issues such as uneven-aged stand management, deforestation, international trade, sustainable forestry, forest recreation, wildlife management and so on are not discussed. Moreover, none of the journal essays published since 1997 is selected. That there are many other important contributions does not mean the essays included in this volume are less important, however. While each forest economist may present a different list of the most important papers, most (if not all) of the essays in this volume would appear on anyone's list. I strongly recommend this book for research scientists and graduate students of forest economics as an essential addition to their reference library.     

非农就业对家庭营林劳动力投工女性化的影响研究

根据劳动力转移新经济学理论和家庭内部劳动力分工理论,基于2018年浙江省14个县(市)681户营林调查户样本数据,运用Tobit模型分析了非农就业对营林劳动力女性化的影响。结果表明:非农就业对女性劳动力单位面积营林投工量和女性营林投工比例具有显著正向影响;非农就业对不同林种营林投入女性化有明显差异,对经济林农户家庭营林投工女性化有显著正向影响,而对用材林农户家庭营林投工女性化作用不明显。提出完善农村劳动力社会保障制度;加强农村女性劳动力营林生产技能培训;发挥女性劳动力的营林生产优势等建议。