首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Between June 1993 and June 1994, 112 farmers in the oil palm (Elaeis guineensis)-cassava (Manihot esclentus) belt of southeastern Nigeria were interviewed to determine the status and agroforestry potential of Dacryodes edulis. Between 50% and 100% of respondents in different states within the belt owned D. edulis trees. On average, a farmer owned 9.3 trees, the largest number being 16, by farmers in Imo State. Twenty percent of farmers in the system rated D. edulis their best farm tree. It was present in all the farm niches: homegardens (51.4%), tree crop plots (20.7%) food crop plots (11.4%), secondary forest/fallow (14.2%) and virgin forest (2.5%). The tree is planted primarily for home consumption and sale to generate cash. At the current densities, on-farm D. edulis trees generally did not decrease yield of companion crops or trees. Except for ring weeding around the stem, D. edulis trees received little or no management attention. More than 50% of the trees produced 33 to 50 kg of fruit tree−1 annually. This is valued at US $0.4 to 0.8 kg−1. Farmers were willing to plant more D. edulis trees provided trees with traits such as less height for easy harvesting of fruits, larger fruit, more fruits, sweeter fruits and year round production of fruits were available. Possible agroforestry technologies into which D. edulis may fit include live fences, scattered trees in food crop fields, shade trees in tree crop plots and contour bund or hedgerow planting. Research is required to determine best tree accessions, canopy management strategies, optimum tree population and improved methods on post- harvest handling of fruits. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

2.
Koch  Niels Elers  Skovsgaard  J.P. 《New Forests》1999,17(1-3):11-22
Following the introduction of planned forestry and the regular high forest system more than 250 years ago, forests in Central Europe became increasingly shaped by plantation silviculture. Many natural woodlands were replaced by planted forests, and forest plantations are still being established through afforestation of extensive land areas. Nowadays, forests are managed for many different purposes, including wood production, recreation, ecological, cultural, and amenity values, biodiversity, and soil and groundwater protection. This brings new challenges to forest management and silviculture. To reach a sustainable forestry, in the sense of Brundtland (WCED 1987), we are now reshaping European forestry toward a more nature oriented silviculture. Maybe forestry in the United States and elsewhere can benefit from the mistakes made in Europe during the last two centuries and take a shortcut toward sustainable forestry.  相似文献   

3.
美国林业管理及林业资源保护政策演进分析和启示   总被引:4,自引:0,他引:4  
美国是世界上林业发达国家之一,林业发展的经验值得借鉴。基于文献资料,首先较为系统地分析了美国林业管理体系,进而分析了林业资源保护政策的演进,最后提出几点结论和启示。结果表明,美国高效精干的服务型林业管理体系和依法护林、治林和管林的林业经营传统值得借鉴。  相似文献   

4.
In the south-east United States, 70% of the forest area is privately owned, by an estimated 5 M landholders. If ecosystem or landscape-level management is to work, cooperation across private ownerships is essential. As a first step in garnering cooperation among landowners, a mail survey was carried out to understand their characteristics, attitudes, beliefs and interest in ecosystem management. A specific area of the Coastal Plain of South Carolina, typical of rural forest-dominated areas of this region, was chosen as the study site. Forestry-related uses, specifically timber production, are the main reasons why over half the respondents own their land. Only one-third of the respondents are familiar with the concept of ecosystem management. However, about 70% are interested in learning more about joint management with other landowners. The major concerns about participating in joint management are loss of land and timber values. Most of the landowners who would participate in a landscape corridor system, for example, want to maintain control of their land rights and limit outside intervention in the process.  相似文献   

5.
The state-level distribution of the size of family forest holdings in the contiguous United States was examined using data collected by the USDA Forest Service in 1993 and 2003. Regressions models were used to analyze the factors influencing the mean size and structural variation among states and between the two periods. Population density, percent of the population at least 65 years of age, percent of the population residing in urban areas, per capita income, income inequality, and per capita private forestland were found to be significantly correlated with the structure of landholding size. This paper suggests that the number and proportion of small-scale family forest owners in the United States are both increasing due to the increasing importance of non-timber amenities to forest landowners.
Y. ZhangEmail:
  相似文献   

6.
根据生态学的边缘效应理论、天然林的自然稀疏结果、造林树种的生态学特性以及水分平衡理论确定合理的造林密度,是保证造林成效的关键。针对区域的自然条件和社会经济状况,采取相应的营林手段是发展草原林业的重要保证。按照生态经济学原理,开展农林复合经营是保护生态平衡、摆脱贫困、发展农业经济的一个重要的途径。  相似文献   

7.
An agroforestry project was funded by the US Agency for International Development and implemented by the Pan American Development Foundation in Haiti from 1981 to 1991. This project is considered by many to be one of the most successful projects of its kind in Haiti, and in the tropics as a whole. Over the ten years of its implementation, the project, referred to in Haitian Creole as Pwoje Pyebwa (Tree Project), evolved from a tree production and planting project to a much broader soil-conservation-based program involving trees. This paper summarizes the training and extension systems that developed during that period. The socioeconomic background studies that were done before the project began, and the flexible, consultative mode of field-team implementation, incorporating elements of the learning process approach, were important to the success of the project. During the implementation of the project, however, concern for farmer input and participation should have been incorporated more systematically into the field operations of the regional teams.  相似文献   

8.
Most agroforestry-adoption studies are based on surveys of "non-adopters." An understanding of the circumstances that have led to a change of attitude of the adopters will be valuable in our efforts to enhance adoption rates. This study was undertaken to provide such knowledge based on a large agroforestry extension project involving 200,000 farm families and covering 25% of all rural households in Haiti. A questionnaire-based survey of the project participants was conducted covering 1,540 households and 2,295 fields in four regions of Haiti. Information was recorded about each farm and family member through interviews with farmers and visits to their farms. The results confirmed that farmers make decisions about tree culture based on household- and field characteristics. Different farmers consider trees differently depending upon how they fit into their farm-family strategy. In general, farmers installed tree hedgerows on fields of less secure tenure, of lesser fertility, and steeper slope, while on closer, more fertile fields of greater tenure security, tree seedlings and fruit trees were more common and there was a greater density of mature trees (>10 cm DBH). More money was realized from sale of tree products on actively cropped fields in more secure tenure and having more fertile soil. Older farmers managed a greater density of trees, especially when the land was in secure tenure status. This broad-based study shows that agroforestry implementation strategies in poor countries such as Haiti should be based on a thorough knowledge of how farmers use household and field characteristics to make adoption decisions. It also suggests that agroforestry-adoption studies should account for the dynamic changes occurring during extended time periods.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

9.
The main objective of this study was to assess the economics of alley cropping of loblolly pine (Pinus taeda L.) and switchgrass (Panicum virgatum) in the southern United States. Assuming a price range of switchgrass between $15 and $50?Mg?1 and yield of 12?Mg?ha?1 year?1, we investigated the effect of switchgrass production on the optimal forest management for loblolly pine stands under different stumpage prices. We considered the following potential scenarios: no competition between species for resources; reduced loblolly pine productivity due to competition with switchgrass; and reduced productivity of both species due to competition for nutrients, water and light. Findings also suggested that the optimal system would depend on the competitive interactions between switchgrass and loblolly pine crops, and the expected prices for each crop. Loblolly pine monoculture would be the most profitable option for landowners compared to intercropping systems with switchgrass below $30?Mg?1. However, when switchgrass prices are ??$30?Mg?1, landowners would be financially better off adopting intercropping if competitive interaction between crops were minimal. In order to realize higher economic returns for intercropping system, forest landowners must make some efforts in order to diminish the decline of productivity.  相似文献   

10.
Public participation in regional and local forest planning in Finland was researched. The questions were: (1) What is the purpose of public participation? (2) What are the challenges of public participation? The results are based on the analysis of discourse communities in a case study concerning a Regional Forest Programme and forest management planning. It was shown that the purpose of participation was to promote communication at the regional level and to gather information at the local level. The general conclusion is, that the regional forest programmes include practices to offer possibilities for communication among participants. This does not mean, that all the programme processes have reached consensus automatically. The case studied here reached compromise. The case study points out problems faced, if public participation would become common practice at the local level on non-industrial private forests lands. In forest management planning it would result in an excessively demanding mediator/expert role for the planner. The need to consider all relevant issues, e.g. biodiversity management, would also become apparent. The study supports the idea that public participation as communication has better possibilities to promote sustainable forest management than public participation as information gathering.  相似文献   

11.
Floodplain forests of the southeastern United States are species rich, often with a dense and diverse liana community. Long-term trends in the density and distribution of lianas may indicate shifts in the composition of plant functional types in these forests. Liana communities in non-fragmented forests in Panama and across the Neotropics have increased in size and density over the last two decades of the 20th century. Are similar changes occurring in temperate forests? Evidence from long-term studies of liana communities in two floodplain forests in South Carolina support the findings from tropical forests. In second-growth forests of the Savannah River system, data from five 1-ha plots established in 1979 and monitored for 22 years indicate a steady increase in liana size and density. Likewise, in old-growth floodplain forests of the Congaree National Park, liana density has increased over 12 years in six 1-ha plots after Hurricane Hugo disturbed the forests in 1989. The increase in liana density and size in these floodplain forests of the southeastern United States is of sufficient magnitude to suggest that lianas are likely influencing stand dynamics in these forests. Consequently, we argue that lianas should be included in models of temperate bottomland forest development of the southeastern United States.  相似文献   

12.
1IntroductionTheUnitedStates(US)isthethirdlargestcountryintheworldinsize.Thenationalterritoryis9629091km2andconsistsofthreeseparateterritories:the48continentalstates,AlaskaandHawaii.InJuly2002,theestimatedtotalpopulationintheUSwas280562489(theWorldFactbook2002).Withinthe48continentalstates,thetotalareais8080704km2,andthenationaltreecoveris32.8%(Dwyeretal.2000).Urbanandcommunityforestsarecomprisedofstreettrees,openspace,patchesofforestedareas,treesininstitutionalproperties,municipalparks,…  相似文献   

13.
Abstract

Community-based ecosystem management (CBEM) in the United States is closely tied to global processes. Increasing and shifting international market demands for ecosystem products and services together with global trends in climate change and biodiversity loss have tangible impacts in communities in every region of the country. Meanwhile, community-based natural resource management efforts in other parts of the world, particularly in developing countries, have a longer history than in the United States. This history, and the tools and techniques developed elsewhere for community-based resource management, can help to inform North American advocates and practitioners of CBEM. This paper has four objectives. The first is to identify key global trends that affect communities in the United States. These trends include demand and supply relationships (especially of forest resources) and environmental changes that will shape economic and policy choices in coming decades. Second, the paper examines countervailing forces of globalization and decentralization. How are shifting patterns of governance and control around the world affecting the prospects for sustainable community-based resource management? Third, the paper seeks to understand migration as a growing feature of many communities. What challenges and opportunities does migration pose for sustainable resource management? Finally, the paper summarizes a few of the tools and techniques used internationally that might have relevance in the United States.  相似文献   

14.
The need for knowledge, ranging from development of new products or processes to the effects of specific actions on the environment, is greater now than at any point in the past. The greater need for research has generated stakeholder involvement in the research process. As a result, all facets of research, from planning through publication of results, are often scrutinized by stakeholders. While the basic nature of scientific inquiry has not changed, now more than ever the credibility of scientific results is based on thorough planning, peer reviews of experimental designs and analytical approaches, and assurance that data are of the highest quality. Public interest in the quality and accuracy of federal research rose to a level that resulted in the Data Quality Act of 2001. The Act required the establishment of guidelines for Federal research organizations and cooperators. We present a case study of the U. S. Forest Service's policies for research quality assurance and quality control, including developing quality assurance statements and plans, as applied to comprehensive research on the federally-listed, endangered forest shrub pondberry (Lindera melissifolia (Walt.) Blume).  相似文献   

15.
Summary

With increasing opportunity costs of keeping land in forests because of increasing values for other land uses, such as for developed uses, forest ownership may become less attractive for some landowners and the return on investment less viable for both private and public landowners. This raises the question of what will become of the forests and the resources the forest supports, such as water and wildlife, if owners of the forests find it too costly to manage the forest. Land markets provide evidence on revealed behavior about what people are willing to actually pay for a bundle of rights necessary to gain access to land that can provide forest-based goods and services into perpetuity. However, owing to market failures and the nature of some forest land values, markets do not always reveal true forest land values, as discussed below. Allocation of land by use and cover types is a key determinant in sustainable forest management, with changes in land values providing important signals to land managers. Land valuation differs under market-oriented economies, emerging values in transition economies, and administered values in countries with command economies and is influenced by interactions between the environment and humans, including land ownership, use, and management.  相似文献   

16.
Changes in biomass and soil carbon with nitrogen fertilization were simulated for a 25-year loblolly pine (Pinus taeda) plantation and for three consecutive 7-year short-rotation cottonwood (Populus deltoides) stands. Simulations were conducted for 17 locations in the southeastern United States with mean annual temperatures ranging from 13.1 to 19.4 °C. The LINKAGES stand growth model, modified to include the “RothC” soil C and soil N model, simulated tree growth and soil C status. Nitrogen fertilization significantly increased cumulative cottonwood aboveground biomass in the three rotations from a site average of 106 to 272 Mg/ha in 21 years. The equivalent site averages for loblolly pine showed a significant increase from 176 and 184 Mg/ha in 25 years with fertilization. Location results, compared on the annual sum of daily mean air temperatures above 5.5 °C (growing-degree-days), showed contrasts. Loblolly pine biomass increased whereas cottonwood decreased with increasing growing-degree-days, particularly in cottonwood stands receiving N fertilization. The increment of biomass due to N addition per unit of control biomass (relative response) declined in both plantations with increase in growing-degree-days. Average soil C in loblolly pine stands increased from 24.3 to 40.4 Mg/ha in 25 years and in cottonwood soil C decreased from 14.7 to 13.7 Mg/ha after three 7-year rotations. Soil C did not decrease with increasing growing-degree-days in either plantation type suggesting that global warming may not initially affect soil C. Nitrogen fertilizer increased soil C slightly in cottonwood plantations and had no significant effect on the soil C of loblolly stands.  相似文献   

17.
Internationally, conservation easements are increasingly popular land management tools for private landowners, government agencies and non-governmental organizations seeking to preserve forests and other natural settings. This paper reports a study of the design and use of conservation easements by organizations and public agencies in the USA. More than 355 conservation organizations and 16 state agencies holding at least 3,598 forestland easements were identified. Demonstrated shortfalls in baseline forest inventories, record keeping, and professionally-developed management plans were evident on working forest easements. Failure to address these shortcomings runs the risk of jeopardizing the legitimacy of the easement approach even where favorable legal and tax conditions exist. Management restrictions varied broadly, with a minority of respondents prohibiting such techniques as clearcutting and salvage logging. Concerns for the use of chemicals, best management practices, and streamside management zones were commonly reflected in easement language, whereas logging road design and the cultivation of old-growth conditions remain largely undeveloped. Implications from the US experience, where easements are relatively well-developed, highlights the need for professional forestry advice—particularly for non-industrial or small-scale forest owners—in both easement development and implementation, the need for careful planning, and the need to carefully consider the respective goals of the forest landowners in crafting the easement documents. In the cases of developing nations, consideration of the differing needs of landowners may require increased flexibility in management documents.  相似文献   

18.
岷江上游地区土地利用变化及潜在生态服务价值评估   总被引:4,自引:0,他引:4  
为了定量分析岷江上游地区生态系统服务功能及其价值变化,运用遥感、地理信息系统和一系列数学方法对其评估,为更好的管理生态系统提供合理化建议.结果表明:土地利用转换主要发生在森林,农田和草地之间.从1986年到1994年,农田面积增加了60801hm^2,比1986年增长了477%;林地面积减少了89012.17hm^2,占原有面积的4.97%.人口增长和森林砍伐降低了森林生态系统服务价值,相应地农田生态系统服务价值升高.生态系统总的服务价值从1986年到2000年减少了771.11亿元.本文还探讨了生态系统服务价值变化的驱动力,其中国家政策在生态系统服务功能保护上起到了一定的作用.  相似文献   

19.
Precautions against forest fires,a significant element in the prevention and reduction of natural disasters in China,are very important to the development of public emergency systems,as well as to the safety of forest resources,ecology,people’s lives and properties.The USA has extensive experience in forest fire management,which has been widely accepted and used by other countries.The precautions taken by China and the USA to prevent forest fires have been compared in a great number of previous studies.However,most of the studies have focused merely on fire extinguishing technologies and management methods;they have lacked a comparative study on the legal aspects of management.This paper will consider five distinct aspects related to forest fire management between China and the USA and will analyze the similarities and differences as well as study other features to facilitate work related to precautions against forest fires in China.  相似文献   

20.
As demand for energy increases in the United States, alternative energy sources are being sought both domestically and abroad. Biofuels have been promoted as a major source of alternative energy, but sustainable supply of biomass still remains a major challenge. Agroforestry offers a potential way to integrate perennial woody bioenergy crops with traditional agricultural crops to satisfy energy demands without sacrificing food production in the North Central Region of the United States. We suggest shelterbelts, alley cropping and working riparian buffer strips as ideal candidates for biomass production in agroforestry settings in this region. In addition to satisfying domestic energy demands, these systems could also potentially increase water quality, sequester carbon, improve aesthetics, and provide critical wildlife habitat. However, obstacles to implementing agroforestry systems for biomass production, such as a competitive price structure and stable markets, must be overcome before large-scale adoption by landowners.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号