Growth of widely spaced trees. A case study from young agroforestry plantations in France

Pessimistic forecasts often suggest that widely spaced trees enjoying free growth (no competition with other trees) will fail to provide high quality timber. This challenges the temperate agroforestry practice of planting widely spaced trees to produce high quality timber. We analyse tree growth data from recent temperate agroforestry plantations aged three to eight years, featuring low tree plantation densities (50 to 400 stems ha−1), the association of trees with intercrops (silvoarable systems) or animals (silvopastoral systems), and the use of plastic shelter tubes to protect trees (1.2 to 2.5 m high) and avoid damage by cattle or sheep in pastures or facilitate maintenance in silvoarable systems. The plantations are located in climates ranging from Mediterranean, dry central temperate plains, cold and wet central uplands to mild oceanic areas. Some plantations included a forestry control (high density of plantation, no tree shelter, no intercropping nor grazing). Trees were evaluated for height and diameter growth and stem form (straightness and absence of knots). Trees in most agroforestry plots grew satisfactorily, often faster than in forestry control plots. In some experimental plots, average annual height increments as high as 1 m and diameter increments as high as 1.5 cm were observed. Few agroforestry plantations were unsuccessful, and the reasons for the failures are discussed: animal damage in silvopastoral plots, but also a wrong choice of tree species unsuitable for local soil and climate characteristics. From these early results we can formulate some guidelines for designing future agroforestry plantations in temperate climates, concerning tree density, use of tree shelters and care required for widely spaced trees. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agroforestry systems for the temperate zone

Historical development of a permanent agriculture system based on the use of agroforestry in the temperate zone is traced. In general, reasons for a renewed interest in agroforestry include the end of cheap, subsidized fossil fuels; increased concern about soil erosion and marginal land use; an international awakening as to the dangers of indiscriminate use of pesticides, herbicides and other chemicals; and a need to balance food production with other land uses.For the forestry profession in particular, reasons for interest in agroforestry stem from a need to revitalize rural economies, the desire to increase timber exports, and potential resolution to land use conflicts between agriculture and forestry. Through use of agroforestry management systems, an increase in both economic and silvicultural benefits are obtainable.Two agroforestry management systems are reviewed which currently appear feasible for implementation in many industrialized countries of the temperate zone. These two systems include: 1) Animal grazing and intercropping under managed coniferous forests or plantations; and 2) Multicropping of agricultural crops under intensively managed, high value hardwood plantations.Michigan Agricultural Experiment Station Paper No. 12046.     

Agroforestry: working trees for sequestering carbon on agricultural lands

Agroforestry is an appealing option for sequestering carbon on agricultural lands because it can sequester significant amounts of carbon while leaving the bulk of the land in agricultural production. Simultaneously, it can help landowners and society address many other issues facing these lands, such as economic diversification, biodiversity, and water quality. Nonetheless, agroforestry remains under-recognized as a greenhouse gas mitigation option for agriculture in the US. Reasons for this include the limited information-base and number of tools agroforestry can currently offer as compared to that produced from the decades-worth of investment in agriculture and forestry, and agroforestry’s cross-cutting nature that puts it at the interface of agriculture and forestry where it is not strongly supported or promoted by either. Agroforestry research is beginning to establish the scientific foundation required for building carbon accounting and modeling tools, but more progress is needed before it is readily accepted within agricultural greenhouse gas mitigation programs and, further, incorporated into the broader scope of sustainable agricultural management. Agroforestry needs to become part of the agricultural tool box and not viewed as something separate from it. Government policies and programs driving research direction and investment are being formulated with or without data in order to meet pressing needs. Enhanced communication of agroforestry’s carbon co-benefit, as well as the other benefits afforded by these plantings, will help elevate agroforestry awareness within these discussions. This will be especially crucial in deliberations on such broad sweeping natural resource programs as the US Farm Bill.     

Landowner perceptions and the adoption of agroforestry practices in southern Ontario,Canada

A mail-out survey questionnaire was developed by the Agroforestry group at the University of Guelph to determine the level of awareness and interest in the adoption of agroforestry systems by landusers from four townships in Wellington County, Ontario. The questionnaire investigated: (1) the current level of knowledge regarding windbreaks, woodlots and plantations, intereropping, riparian plantations and silvipasture, (2) the present level of participation in each of these systems on-farm, (3) the perceived benefits and/or drawbacks of each of these initiatives with respect to total farm income, income diversity, land rehabilitation, land value/equity, soil/water conservation, labour intensity, overhead and return on the term of investment.The majority of respondents were familiar with conventional agroforestry systems such as windbreaks and woodlots/plantations (80%, 62% respectively), therefore the level of interest in the adoption of these practices was significant (74%, 66% respectively). Response rates were lower for silvipasture, riparian plantations and intercropping, most likely as result of the low level of familiarity with these practices (20%, 32%, 4% respectively). Respondents commented that agroforestry systems would have a neutral effect on farm income, and would increase land stewardship. In some cases, interested landusers indicated a willingness to participate in agroforestry systems even though they anticipated increases in overhead and labour intensity; however, this was only true if they held land stewardship as a priority. Landusers were more concerned with the economic aspects of agroforestry, as a determinant to the future adoptability of particular practices. Age, gender, farm operation and farm size were not correlated with the adoption of agroforestry systems.The success of agroforestry programs on farms in the study area is largely dependent on the attitudes and willingness of landusers to participate in non-traditional agricultural systems.     

Agroforestry and its application in amelioration of saline soils in eastern China coastal region

Some environmental problems, especially soil salinity hinder the regional sustainable development of eastern China coastal region. Salinity mainly comes from tide weave, seawater flooding and seawater intrusion. Over exploitation of groundwater,which is the result of unfitful land use systems, leads to seawater intrusion and salt concentration increase. Agroforestry systems can enrich soil fertility and prevent soil salinization, furthermore help maintain biodiversity and enhance productivity. For the intergrated multiple ecosystems the most critical issue is to select optimum tree species and rationally arrange these plants. The basics of this multiple ecosystem is that different plants will occupy variable ecological niches within an area, both in space and in soil depth.Shelterbelts and trees intercropping with agricultural crops are major types of the multiple ecosystem. Shelterbelts can reduce wind speed and consequently lessen evaporation and erosion of the soil, increase pasture growth by up to 60% on exposed sites, increase crop yields by up to 25%. Besides intercropping with jujube, other agroforestry multiple ecosystem such as forestry plus agriculture,forestry plus agriculture plus fishery, and forestry plus animal husbandry are the most appropriate ways to utilise land resource in this region.     

Biomass production for biofuels using agroforestry: potential for the North Central Region of the United States

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.     

Tree gardening and taungya on Java: examples of agroforestry techniques in the humid tropics

Agroforestry is a general concept for a land management system combining trees and agricultural crops. For application, various specific techniques can be chosen. Each of these techniques is adjusted to a specific set of environmental as well as socio-economic factors. Agroforestry cultivators or managers belonging to varying social strata and institutional groupings may practice different forms of agroforestry, even within the same general region. This is demonstrated on the basis of two contrasting types of agroforestry which are found on the Indonesian island of Java. Tree gardening or the cultivation of a wide variety of crops in a multiple-storeyed agroforestry system is an indegenous practice on private lands, while taungya or the intercropping of young tree plantations with staple crops is practiced on state forest lands. Both systems are described as to their management characteristics, past development as well as possibilities and constraints for further development. These two practices are then compared as to various attributes, like producer group, production purpose, area of cultivation, land ownership situation, structural organization of crop combinations, possibilities for improved cultivation techniques, and suitability for application in rural development for specific target groups.This paper is a slightly revised version of a contribution to a lecture series on agro-forestry organized by the Departments of Forestry, Wageningen University.     

Adequate design of control treatments in long term agroforeestry experiments with multiple objectives

Agroforestry experiments usually include control plots of either pure crop or pure tree stands. A clear distinction should be made between intensively managed biophysical controls and farming system controls with realistic labour input and management regimes. Trying to draw biophysical conclusions from farming system controls (or the reverse) is often not justifiable. The design and management of these elusive control plots is a complicated issue which is often overlooked. Many factors beyond the control of the experiment manager can disturb long term field agroforestry experiments. Some examples from French agroforestry experiments illustrate how uncontrolled factors may bias the results, including the proportion of harvested to planted trees, the weeding regimes, and the use of tree- shelters. The analysis of agroforestry data could be more efficient when considering a continuum of tree – crop mixture management options between the agroforestry plot and the non agroforestry plot. The concept of biophysical control plots becomes then less essential. A relevant modelling approach of interactions between trees and crops should 1) perform correctly for any tree/crop proportion and even for pure stands, when setting the parameters of the other component to zero, 2) provide for the inclusion of new, uncontrolled factors that could emerge through time. The biological efficiency of agroforestry systems may however be a subordinate criterion for agroforestry adoption, as observed at the moment in France. Agroforestry systems with poor biological outcomes can even be very attractive in some ecological or sociological conditions, and only farming system controls may bring this aspect to light. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agroforestry practice and policy in the United States of America

Agroforestry practices and the policies influencing development and adoption within the United States are reviewed. Agroforestry is defined as ‘intensive land-management systems that optimize the benefits from biological interactions created when trees and/or shrubs are deliberately combined with crops and/or livestock’. The five agroforestry systems identified as having importance in the US are tree-agronomic crop systems (alley cropping and intercropping), riparian vegetative buffer strip systems, tree-animal systems (silvopasturing), forest/speciality crop systems (forest farming) and windbreak systems (shelterbelts). A lack of federal policy relating specifically to agroforestry exists. If agroforestry is to achieve its full potential in the United States, adequate financial, institutional and technical support for its development must be provided.     

Agroforestry in Europe: a review of the disappearance of traditional systems and development of modern agroforestry practices, with emphasis on experiences in Germany

Agroforestry is a new name for a rather old practice. From a historical point of view, various agroforestry systems existed in Europe, of which the wood pastures (Neolithicum), the Dehesas in Spain (~4,500 years old) and the Hauberg of the Siegerland (established in the Middle Age) are the most prominent. Other widespread systems in Europe were hedgerows, windbreaks and Streuobst (orchard intercropping). Due to mechanisation and intensification of agriculture, trees have been progressively removed from agricultural fields and traditional agroforestry systems slowly disappeared. Today, agroforestry systems are again increasing in interest as they offer the potential to solve important ecological and, especially, biodiversity problems, while at the same time enabling the production of food, wood products and fodder for cattle. Although agroforestry systems offer many advantages, many farmers are sceptical of these systems and are critical and risk-averse with regard to adopting new practices. However, in comparison to traditional systems, modern agroforestry systems can be adapted to current farming practices. By selecting suitable trees and appropriate tree management, high-quality timber can be produced without influencing agricultural crops excessively. In future, agroforestry systems will become increasingly important as they offer the prospect of producing woody perennials for bioenergy on the same land area as food and/or fodder plants, while enhancing overall biodiversity.     

Program design for agroforestry extension in the south-eastern USA

Before prioritising regional agroforestry training and extension content, it is necessary to discover which practices are common, what benefits are perceived, which barriers prevent use, and how people feel about practices. Agroforestry taps both agriculture and forestry agencies to increase the possible set of educators for landowners and managers. Interdisciplinary activities also present barriers to professionals unfamiliar with some topics or not served by lead partner agencies. To understand motives, barriers and needs involved in agroforestry extension and training activities for professionals, the Center for Subtropical Agroforestry (CSTAF) designed a survey to gauge knowledge, practice and information needs of professionals in Alabama, Florida and Georgia. Landowners in Alabama and Florida received similar survey questionnaires. Initial interviews of a test group with open-ended questions formed the basis for a closed-ended mail survey to all agriculture and natural resource extension agents and county foresters in the subtropical area. Response rates for various professional groups varied between 14% and 43%, and most ranked the potential for use of agroforestry as moderate or high. In all three states, wildlife habitat, water quality and soil conservation were the most important benefits seen by extension professionals. The most important concerns identified were lack of familiarity, lack of demonstrations, no financial incentive, and lack of information about agroforestry. These data provide insights about how to prioritise research and materials development and indicate that agroforestry training can be expected to be of value to at least half of the regional forestry and extension professionals.     

Agroforestry for high value tree systems in Europe

Most farm-based agroforestry projects focus on the integration of trees on arable or livestock enterprises. This paper focuses on the integration of understorey crops and/or livestock within high value tree systems (e.g., apple orchards, olive groves, chestnut woodlands, and walnut plantations), and describes the components, structure, ecosystem services and economic value of ten case studies of this type of agroforestry across Europe. Although their ecological and socio-economic contexts vary, the systems share some common characteristics. The primary objective of the farmer is likely to remain the value of tree products like apples, olives, oranges, or nuts, or particularly high value timber. However there can still be production, environmental or economic benefits of integrating agricultural crops such as chickpeas and barley, or grazing an understorey grass crop with livestock. Three of the systems focused on the grazing of apple orchards with sheep in the UK and France. The introduction of sheep to apple orchards can minimise the need for mowing and provide an additional source of revenue. Throughout the Mediterranean, there is a need to improve the financial viability of olive groves. The case studies illustrate the possibility of intercropping traditional olive stands with chickpea in Greece, or the intercropping of wild asparagus in high density olive groves in Italy. Another system studied in Greece involves orange trees intercropped with chickpeas. Stands of chestnut trees in North-west Spain can provide feed for pigs when the fruit falls in November, and provide an excellent habitat for the commercial production of edible mushrooms. In Spain, in the production of high quality walnut trees using rotations of up to 50–60 years, there are options to establish a legume-based mixed pasture understorey and to introduce sheep to provide financial and environmental benefits.     

Agroforestry vs. forestry for the rural poor: a socio-economic evaluation

The paper evaluates Forest Farming for the Rural Poor (FFRP) component of social forestry in the Indian State of Orissa within the framework of the stated socio-economic policy objectives. Both the distributional equity and efficiency aspects have been accounted for in the analysis. Based on two criteria (net present value and land expectation value) the socio-economic profitability and optimum rotations have been determined for dense plantations in three site qualities and compared with the results for agroforestry. The net socio-economic benefits for agroforestry are shown to be larger than for dense plantations in SQI. The reverse was found for SQII, the net socio-economic benefits are comparatively less in agroforestry than in the dense plantations. The net socio-economic benefits in SQIII are negative for both the agroforestry and dense plantations. It is found that for the FFRP policy to be socially profitable in SQIII, the investment funds should be acquired by diverting consumption-oriented funds from rural development programmes.     

Economic aspects of agroforestry

Agroforestry is analysed by means of economic concepts. The paper is mainly theoretical, since there are little adequate data to test the conceptual framework.Agroforestry needs not be limited to integration of agriculture and forestry on a plot, but may also include integration on a holding. Design and evaluation of agroforestry systems require thorough knowledge of relationships between agriculture and forestry. Complementary and supplementary relationships, mainly resulting from biological factors, were identified, which make agroforestry an efficient system of land use.Agroforestry can be an appropriate technology in areas with fragile ecosystems and subsistence farming. The objectives of participants in an agroforestry programme may not coincide with social objectives, and so do not lead to the socially optimum combination of agriculture and forestry. For that social optimum institutional arrangements will often be required.This paper is s shortened updated version of part of a lecture series on agroforestry, organized by the Departments of Forestry, Agricultural University, Wageningen [29].The author thanks his colleagues C.P. Veer and K.F. Wiersum for helpful comments.     

The potential for carbon offset trading to provide added incentive to adopt silvopasture and alley cropping in Missouri

Global carbon trading may present a unique opportunity to change the rural landscape by allowing landowners to make an environmental impact with financial incentives. By enticing point source polluters to trade to an optimal level of pollution by offsetting their emissions with compatible carbon reduction projects, markets are able to facilitate a cleaner environment. Agroforestry provides a set of practices that can sequester carbon with managed tree and crop plantings. However, the initial lack of financial resources has been an obstacle to its adoption in the United States. This paper explores the potential for carbon offset trading to provide an added incentive to adopt agroforestry practices. Chicago Climate Exchange carbon sequestration projects are used as a baseline assessment, and the requirements that Missouri landowners would need to do in terms of contracting and ownership are identified. Data from landowners in central Missouri and the Ozarks (353 individuals) are used to determine characteristics of potentially interested landowners in agroforestry. A model to evaluate agroforestry profitability scenarios is used to compare the added carbon credit trading revenue to traditional alternate uses for the property. The findings from this analysis indicate that in the current context carbon trading does not provide an added incentive value for Missouri landowners to adopt either silvopasture or alley cropping practices because of the low magnitude of annual return.     

Tree Quality in Agroforestry Systems Managed by Small-Scale Mayan Farmers in Chiapas,Mexico

Increasingly, plantations for food, fiber and wood, are necessary to provide a growing world population. Agroforestry systems become more and more important, however these systems usually develop in marginal conditions, limited land, restricted funding, occasional technical support and above this, there is limited documentation and evaluation of innovated traditional systems in indigenous and small-scale contexts, which challenge forest scientists. The aim of this research was to assess the quality of trees in plots managed by Mayan indigenous farmers who planted agroforestry systems with fine wood species to increase the value of land and labor in localities with highly-marginal social conditions in Northern Chiapas, México. Twenty oldest plots were selected within a group of previously established plots (eight with improved fallow, six with shaded coffee and six with maize crop associated to trees) where forest inventories were carried out in nested 100 and 1000 m²-circular plots. In all plots tree diameter, height, quality indicators and the incidence of the pest Hypsipyla grandella were measured. Trees in the maize-associated-to-trees system are favored by the practices applied to annual crop during the first 3rd–5th years, a period in which they are free from the interference of other trees and benefit from favorable light conditions, weeding and a higher intensive care from the farmer while shaded coffee and improved fallow have higher tree densities and a more closed canopy condition than maize associated to trees. In consequence, maize associated to trees shows 68.1 % stems with good form; shaded coffee and improved fallow averaged 40.5 and 39.7 % of good quality stems, respectively; improved fallow exhibited a greater number of suppressed trees than shaded coffee and maize associated to trees (p < 0.0001). In addition, maize associated to trees showed the highest proportion of trees with commercial value with 56.9 %, followed by improved fallow with 28.2 %, and shaded coffee with 11.8 % (p < 0.0001); the rest were trees with domestic uses. However, maize associated to trees significantly result with high incidence of H. grandella probably due to the crown exposure. Timber volume averaged 92.9 ± 68.9 m³ for improved fallow, 77.3 ± 24.8 m³ for shaded coffee, and 52.5 ± 39.7 m³ for maize associated to trees. The value of the fine wood represents increment in income, variety of products and self-employment for households. Nonetheless, improved fallow and coffee plantations might benefit from the elimination of competitors from larger trees to favor promising immature ones and pruning, while maize crop associated to trees might benefit from opportune pruning for controlling the stem borer as well as tree replacement to achieve long term replacement and harvesting.     

农用林业及其与社会林业的关系

本文论述了在用林业的概念及分类,以及农用林业与社会林业的关系,农用林业是一独立学科,没有社会林业的介入,农用林业照样生存。农用林业是社会林业的基础,社会林业又是农用林业及其用户—农民的中间桥梁。     

The potential of intercropping as an alternative land use system in temperate North America

The success of many intercropping systems in North America is attributable to the generation of a short term return from an agricultural crop during the early, unprofitable years of a longer term crop that is fruit, nuts or wood. This highly-efficient use of land and related profitability are important not only in the development of intercropping systems per se, but also in other applications which have tremendous potential independent of profitability. For example, intercropping can be effectively used during the establishment phases of hardwood plantations where it is essential to have a high level of weed control, the costs of which are often recovered with the agricultural production. Intercropping can also be used to grow trees rapidly and with a form that can be easily integrated into recreational or park situations, or urban fringe areas. In an urban context, intercropping can be used to grow trees in agricultural areas that are likely to be developed where traditional forestry options are not appropriate and the value of younger, thrifty trees may enhance property values far in excess of the cash value of the wood.     

苏北平原地区森林贡献与效率测算及分析

以苏北地区1991--2001年的数据，采用随机前沿生产函数的效率模型和超越对数生产函数对农田林网和小片林对农业总产值、种植业产值和畜牧业产值的贡献程度进行计量并分析，结果表明：农田林网对上述3个产值的生态贡献率为负值，小片林对上述3个产值的生态贡献率为正值，林业、种植业和畜牧业之间存在明显的联合生产效果。需要扩大小片林面积和对现有农田林网进行适当改造，以期取得更好的效果。     

Productivity and nutrient cycling in young Acacia senegal farming systems on Vertisol in the Blue Nile region, Sudan

Acacia senegal, the gum arabic-producing tree, is the most important component of traditional dryland agroforestry systems in the␣Sudan. The spatial arrangement of trees and the type of agricultural crop used influence the interaction between trees and crops. Tree and crop growth, gum and crop yields and nutrient cycling were investigated over a period of 4 years. Trees were grown at 5 × 5 m and 10 × 10 m spacing alone or in mixtures with sorghum or sesame. No statistically significant differences in sorghum or sesame yields between the intercropping and control treatments were observed (mean values were 1.54 and 1.54 t ha⁻¹ for sorghum grain and 0.36 and 0.42 t ha⁻¹ for sesame seed in the mixed and mono-crop plots, respectively). At an early stage of agroforestry system management, A. senegal had no detrimental effect on crop yield; however, the pattern of resource capture by trees and crops may change as the system matures. A significant positive relationship existed between the second gum picking and the total gum yield. The second gum picking seems to be a decisive factor in gum production and could be used as an indicator for the prediction of the total gum yield. Soil organic carbon, N, P and K contents were not increased by agroforestry as compared to the initial levels. Soil OC was not increased by agroforestry as compared to sole cropping. There was no evidence that P increased in the topsoil as the agroforestry plantations aged. At a stocking density of 400 trees ha⁻¹ (5 × 5 m spacing), A. senegal accumulated in its biomass a total of 18.0, 1.21, 7.8 and 972 kg ha⁻¹ of N, P, K and OC, respectively. Agroforestry contributed ca. 217 and 1500 kg ha⁻¹ of K and OC, respectively, to the top 25-cm of soil during the first four years of intercropping.