Prospects for easing land tenure conflicts with agroforestry in Mediterranean France: a research approach for intercropped timber orchards

Agroforesty plots offer the opportunity to combine annual agricultural production and long-term wood capitalization. The fallow scheme now in operation in Europe intends to reduce the surplus of agricultural products. Agroforestry management could be a valuable alternative to fallow or to forestry plantations on agricultural land.Agroforestry is attractive to agricultural landowners in Mediterranean France, as agroforestry stands are less costly than forestry plantations, are less prone to fire hazards, provide agricultural returns from intercropping during the first twenty years and have many environmental benefits.An experimental network of on-farm agroforestry plots has been set up since 1988 in the Mediterranean part of France. These plots include grazed paddocks (silvopastoral systems) and ungrazed fields (silvoarable systems). They gained support both from landowners and tenants: the former expect a high value treestock, while the latter have a free use of the space between plantation lines. Plantations have been designed to allow easy mechanical intercropping. First results from two experimental sites are discussed. The growth of the trees in the agroforestry plots is much higher than in the control forestry plots.     

Improving adoptability of farm forestry in the Philippine uplands: a linear programming model

In the Philippines, smallholder farmers have become major timber producers. But the systems of timber production practiced have several limitations. In intercropping systems, the practice of severe branch and/or root pruning reduces tree-crop competition and increases annual crop yields, but is detrimental to tree growth and incompatible with commercial timber production. In even-aged woodlots, lack of regular income and poor tree growth, resulting from farmers’ reluctance to thin their plantations, are major constraints to adoption and profitable tree farming. In the municipality of Claveria, Misamis Oriental, the recent practice of planting trees on widely spaced (6–8 m) contour grass strips established for soil conservation suggests ways to improve the adoptability (i.e., profitability, feasibility and acceptability) of timber-based agroforestry systems. Assuming that financial benefits are the main objective of timber tree farmers, we develop a simple linear programming (LP) model for the optimal allocation of land to monocropping and tree intercropping that maximizes the net present value of an infinite number of rotations and satisfies farmers’ resource constraints and regular income requirements. The application of the LP model to an average farmer in Claveria showed that cumulative additions of widely spaced tree hedgerows provides higher returns to land, and reduce the risk of agroforestry adoption by spreading over the years labour and capital investment costs and the economic benefits accruing to farmers from trees. Therefore, incremental planting of widely spaced tree hedgerows can make farm forestry more adoptable and thus benefit a larger number of resource-constrained farmers in their evolution towards more diverse and productive agroforestry systems.     

Tree planting pattern effects on forage production in a Douglas-fir agroforest

Resource sharing among agroforestry system components, as expressed by spatial patterns along interfaces between components, is a crucial factor in both understanding present systems and in designing new agroforestry applications. A study of the spatial pattern of forage production surrounding 9–10 year old Douglas-fir trees in a agrosilvopastoral plantation near Corvallis, Oregon, was conducted during 1988 and 1989. Transects of plots were clipped both between trees (tree/tree) and between trees and open pastures (tree/pasture). Best-fit regression models relating forage production to distance from trees (tree/tree R ² = 0.87; and tree/pasture R ² = 0.89) were combined into a single prediction model. Observed forage production increased rapidly with increasing distance from trees during the initial 4 m. Trees had little effect on forage production beyond 4.5 m (approximately 2 canopy diameters) from the nearest tree. Predictions of different combinations of tree density and planting pattern indicated a strong interaction between density and pattern with highly aggregated plantations better able to maintain forage production at high tree densities.     

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.     

Modelling and valuing the environmental impacts of arable,forestry and agroforestry systems: a case study

The use of land for intensive arable production in Europe is associated with a range of externalities that typically impose costs on third parties. The introduction of trees in arable systems can potentially be used to reduce these costs. This paper assesses the profitability and environmental externalities of a silvoarable agroforestry system, and compares this with the profitability and environmental externalities from an arable system and a forestry system. A silvoarable experimental plot of poplar trees planted in 1992 in Bedfordshire, Eastern England, was used as a case study. The Yield-SAFE model was used to simulate the growth and yields of the silvoarable, arable, and forestry land uses along with the associated environmental externalities, including carbon sequestration, greenhouse gas emissions, nitrogen and phosphorus surplus, and soil erosion losses by water. The Farm-SAFE model was then used to quantify the monetary value of these effects. The study assesses both the financial profitability from a farmer perspective and the economic benefit from a societal perspective. The arable option was the most financially profitable system followed by the silvoarable system and forestry. However, when the environmental externalities were included, silvoarable agroforestry provided the greatest benefit. This suggests that the appropriate integration of trees in arable land can provide greater well-being benefits to society overall, than arable farming without trees, or forestry systems on their own.     

Plant-soil-water relations in forestry and silvopastoral systems in Oregon

Plant-soil-water relations of a silvopastoral system composed of a Douglas-fir (Pseudotsuga menziesii) timber crop, subterranean clover (Trifolium subterraneum) as a nitrogen-fixing forage, and tall fescue (Festuca arundinacea) as a forage crop were investigated near Corvallis, Oregon, during 1983–1986. Treatments included all possible combinations of two tree-planting patterns (trees planted 2.4 m apart in a grid, and groups of five trees spaced 7.6 m between clusters) and two grazing/understory management systems (agroforests were seeded to subclover and grazed by sheep; forests were unseeded and ungrazed).Mean twig xylem water potential (XWP) for Douglas-fir trees ranged from –0.3 to –1.5 MPa on forest plots and from –0.3 to –1.2 MPa on agroforest sites. Pre-dawn and sunset XWP were more negative for forest than for agroforest plots during dry summer periods. Midday XWP was similar for both agroforest and forest plots on all dates. Soil water content at 50–100 cm depth was greater under agroforest plots as compared to forest plots in 1984, but not in 1985 (unusually dry spring). Average foliage nitrogen content of tree needles was 1.54% vs. 1.43% for agroforests vs. forests, respectively.Our data are consistent with the hypotheses that: (1) grazing of understory vegetation may reduce water stress of trees during dry periods by reducing transpirational water use by the forage plants; and (2) nitrogen-fixing vegetation combined with grazing increases nitrogen uptake of associated trees. However, neither mean foliar N nor average XWP differences experienced by trees in agroforest versus forest plantations were sufficient to have an effect on tree growth. Our data demonstrate that it is possible to produce a second crop (i.e. forage grazed by sheep) in timber plantations without reducing the growth of the main tree crop.Submitted as Oregon Agrocultural Experiment Station Technical Paper No. 10109.     

The role of agroforestry in industrialized nations: the southern hemisphere perspective with special emphasis on Australia and New Zealand

Agroforestry in Australia and New Zealand is dominated by silvopastoralism. Farmers may employ combinations of shelterbelts, shade trees, widely spaced trees over pasture, or more densely planted woodlots. In addition to wood production and shelter, erosion control, amenity and landscape planting, and conservation of natural forest are often important. Many farm forestry people show considerable innovation.In temperate wetter areas of Australia, eucalyptus and, to a lesser extent,Pinus radiata (radiata pine) dominate agroforestry tree plantings for wood, shade, shelter, and salinisation and erosion prevention. The One Billion Tree Program, initiated by the Australian Federal Government, provides limited funding for tree planting. Joint farmer ventures with the State or local industry are also common. Most State governments also provide advice, and planting is tax deductible. Local landcare groups, formed to encourage sustainable agriculture, often promote tree planting, particularly where soil degradation is a problem. Melbourne University and other Techncial Institutes offer training in agroforestry.In New Zealand, a third of the farms require trees for soil conservation. This, together with the growing recognition of the financial benefits of planting trees, has resulted in small landowners doing most of the current planting of 80,000 to 100,000 ha yr^–1. Most farmers plant radiata pine, but eucalyptus and other hardwoods, including willows and poplars, are also widely used. There are almost no government incentives for tree planting in New Zealand. The Farm Forestry Association is the major extension organization. Lincoln University has an important teaching and research commitment, and the New Zealand Forest Research Institute Limited has developed very useful management models.     

An assessment of agroforestry systems in the southern USA

An assessment of the southern USA, based on a survey of land-use professionals and a review of the literature, revealed that it is a diverse region with substantial potential for agroforestry to address a combination of problems and opportunities. The survey indicated that silvopastoral systems are the most common form of agroforestry in the region. Increased economic returns, diversification, and enhancement of the timing of cash flows were the most frequently mentioned benefits associated with the establishment of silvopastoral systems. Some of the problems associated with alley-cropping systems — less frequently observed than silvopastoral systems — were lower-than-expected productivity or profitability, damage to trees when cultivating the crop component, and labor/management skill constraints. Based on the findings of the literature review and the survey, special opportunities for implementing agroforestry systems in the region were identified, including the following: to improve marginal lands; to serve as windbreaks and buffer strips for improved water quality and wildlife habitat; to enhance the economics of selected natural pine, hardwood plantation, and pine plantation systems; and to provide specialty products on small landownerships.     

Unexpected lack of influence of tree rows on the dynamics of wheat aphids and their natural enemies in a temperate agroforestry system

Trees at low density and cereals may be combined in silvoarable agroforestry systems: tree rows and their companion vegetation introduce an heterogeneity in the cropped field that may modify the dynamics of insects crop pests and their predators. This hypothesis was tested in tree-wheat systems by monitoring aphids and their predators for two years in southern France, in two fields in 2006 and one in 2007. Tree row vegetation diversity was either suppressed by weeding or stimulated by seeding flowering species that could attract adult predators of aphids. The dynamics of aphids and predators were recorded by tiller sampling and yellow trap monitoring. Between 3500 and 5000 aphids were collected from each studied field. Surprisingly, no differences could be evidenced on the dynamics of both aphids and their predators between agroforestry and monocropping plots, nor between weeded and flowered plots. The heterogeneity induced by the tree row in the cropped field was probably not strong enough to alter the populations dynamics. A high landscape diversity in the area due to nearby forest patches and fallows may have blurred the impact of the tree lines. Different results may be expected in areas with lower biodiversity like cereal monocropping zones.     

Diameter and height growth curves for widely-spaced trees in European agroforestry

Predicting timber volume can be important for decision- making. Conventional forest growth models are generally based on mensuration data acquired in fully stocked homogeneous tree stands, and do not consider the wide spacings often adopted in European agroforestry. In order to test the possibility of adapting conventional forestry growth models, diameter and height growth were measured on widely spaced trees. Parameters of a Gompertz double exponential function were adjusted for several tree species planted at wide spacings. Spacing, vegetation control, and individual tree shelters affected the parameters. At wide spacings, the asymptote for diameter growth was larger, and the asymptote for height growth smaller, compared to conventional forestry. This revised version was published online in June 2006 with corrections to the Cover Date.     

Simulating integration of agroforestry into livestock farmers‘ projects in France

Drawing on almost one hundred contemporary farmers‘ experiences, within a French agroforestry experimental network, socio-economic and ecological approaches are combined to assess a set of agroforestry techniques. Among this network, twelve livestock farms were selected in contrasting bioclimatic regions and classified according to land use, stock number and family situation. Farmers were interviewed to define the primary objectives assigned to agroforestry and to build up several scenarios of agroforestry development on their farm. A dynamic resource model was used to predict the effects of agroforestry development on crop and timber production as well as on labour organisation and amenities. An example of simulation, comparing three agroforestry management projects, based on new plantations at wide spacing, farm forestry and silvopastoral thinnings, is developed for a farm in the Cévennes (southern France). The outputs of the model, related to labour requirements, stock number dynamics and landscape diversity are discussed in relation to farmer‘s perception of the role of trees in the farm operation, and the indirect economic benefits sought. This revised version was published online in June 2006 with corrections to the Cover Date.     

Species-site matching in mixed species plantations of native trees in tropical Australia

Mixed species plantations using native trees are increasingly being considered for sustainable timber production. Successful application of mixed species forestry systems requires knowledge of the potential spatial interaction between species in order to minimise the chance of dominance and suppression and to maximise wood production. Here, we examined species performances across 52 experimental plots of tree mixtures established on cleared rainforest land to analyse relationships between the growth of component species and climate and soil conditions. We derived site index (SI) equations for ten priority species to evaluate performance and site preferences. Variation in SI of focus species demonstrated that there are strong species-specific responses to climate and soil variables. The best predictor of tree growth for rainforest species Elaeocarpus grandis and Flindersia brayleyana was soil type, as trees grew significantly better on well-draining than on poorly drained soil profiles. Both E. grandis and Eucalyptus pellita showed strong growth response to variation in mean rain days per month. Our study generates understanding of the relative performance of species in mixed species plantations in the Wet Tropics of Australia and improves our ability to predict species growth compatibilities at potential planting sites within the region. Given appropriate species selections and plantation design, mixed plantations of high-value native timber species are capable of sustaining relatively high productivity at a range of sites up to age 10 years, and may offer a feasible approach for large-scale reforestation.     

Financial attractiveness of smallholder tree plantations in the Amazon: bridging external expectations and local realities

This paper compares the financial attractiveness of forest and agroforestry plantations promoted by external organizations with tree growing practices of Amazonian smallholders. Based on 80 case studies and interviews with 112 forestry professionals from Brazil, Bolivia, Peru and Ecuador, the paper characterizes the economic, environmental and structural implications, and identifies the respective financial costs and benefits. Six case studies provided data for in-depth financial analyses. The results showed that the expectations of externally promoted smallholder tree and agroforestry plantations were not met. Despite significant inputs, smallholders generated at best annual net incomes of US$200–$200–1,000 per ha from NTFP plantations, and up to US$800–$800–1,000 from timber plantations in the year of harvest. This corresponded to around one-third of the initially expected returns. Overall, only around 1% of the smallholders participating in such initiatives managed to produce and commercialize any plantation products. Smallholders’ practices of complementary tree growing in conjunction with agriculture and managing natural regeneration of timber and NTFP products were often underestimated by professionals. They required low input, didn’t rely on external support, were highly flexible in risky environments, and some presented financial returns comparable to some well functioning plantations.     

Advances in European agroforestry: results from the AGFORWARD project

In global terms, European farms produce high yields of safe and high quality food but this depends on the use of many off-farm inputs and the associated greenhouse gas emissions, loss of soil nutrients and other negative environmental impacts incur substantial societal costs. Farmers in the European Union receive support through a Common Agricultural Policy (CAP) that comprises direct payments to farmers (Pillar I) and payments related to rural development measures (Pillar II). This paper examines the ways in which agroforestry can support European agriculture and rural development drawing on the conclusions of 23 papers presented in this Special Issue of Agroforestry Systems which have been produced during a 4-year research project called AGFORWARD. The project had the goal of promoting agroforestry in Europe and focused on four types of agroforestry: (1) existing systems of high nature and cultural value, and agroforestry for (2) high value tree, (3) arable, and (4) livestock systems. The project has advanced our understanding of the extent of agroforestry in Europe and of farmers’ perceptions of agroforestry, including the reasons for adoption or non-adoption. A participatory approach was used with over 40 stakeholder groups across Europe to test selected agroforestry innovations through field trials and experiments. Innovations included improved grazing management in agroforestry systems of high nature and cultural value and the introduction of nitrogen fixing plants in high value timber plantations and olive groves. Other innovations included shelter benefits for arable crops, and disease-control, nutrient-retention, and food diversification benefits from integrating trees in livestock enterprises. Biophysical and economic models have also been developed to predict the effect of different agroforestry designs on crop and tree production, and on carbon sequestration, nutrient loss and ecosystems services in general. These models help us to quantify the potential environmental benefits of agroforestry, relative to agriculture without trees. In view of the substantial area of European agroforestry and its wider societal and environmental benefits, the final policy papers in this Special Issue argue that agroforestry should play a more significant role in future versions of the CAP than it does at present.     

广西大青山柚木人工林生长过程研究

[目的]研究柚木人工林生长过程及其与气象因子的相关性,为柚木抚育经营提供理论依据。[方法]以优良、中等和差3种生长类型的30余年生柚木人工林为对象,基于样地调查,选取优势木、平均木、被压木进行树干解析,对比分析其生长过程,应用灰色关联分析法揭示气象因子对柚木生长的影响。[结果]表明:3种生长类型林分柚木胸径、树高和材积生长过程基本一致,各分级木的生长过程亦相似,其胸径平均和连年生长量随年龄的增大呈先增加后逐渐降低的趋势,树高生长整体上呈下降趋势,材积生长则呈递增趋势。各优良林分的林木及各类型林分的优势木,其胸径、材积平均和连年生长量较大,速生期持续时间长,生长衰减慢,而其树高生长量的优势相对不明显;30余年生时柚木尚未达数量成熟龄。各类型林分间柚木生长与气象因子关系的差异仅体现在胸径,优良林分胸径连年生长量主要受极端低温影响,而中等和差林分则与年均降水量相关性最大;各分级木间柚木生长与气象因子的关系无明显差异;影响树高和材积连年生长量的最主要气象因子分别为年均降水量和年均气温。[结论]柚木各生长类型及分级木的生长过程整体趋势基本一致,其差异主要体现在生长量大小和快速生长期长短。约30年生柚木人工林仍未达到数量成熟,后期抚育经营对于其优质大径材高效培育仍不可忽视。     

Stocking rate mediates responses of mid-rotation loblolly pine in west-central Arkansas. 2. Profitability

Further study is needed on loblolly pine (Pinus taeda L.) growth in a systematic array of plantation designs or stocking rates commonly used in temperate forestry and agroforestry practices. Our objective was to determine loblolly pine growth responses and agroforestry implications of 13 plantation designs (i.e., stocking rates in trees ha⁻¹ [TPH]) at mid-rotation (14 years old). Survival, diameter at 1.3 m above soil surface (dbh), height, basal area (BA), and volume (V) were measured in unthinned plantations ranging from 490 to 2,300 TPH. Stocking rate was positively correlated with BA (r ≥ 0.67) and V (r ≥ 0.55) and negatively correlated with survival (r ≤ −0.83) and dbh (r ≤ −0.83). Plantations with ≥2,000 TPH had closed canopies and excessively high BA and V at mid-rotation. The 4- and 5-row plantations (≥12 m alley spacing) had small dbh (≤17.5 cm). Single-row plantations with ≥3.6 m within row spacing and ≤700 TPH, and the 3-row multiple-row plantations (1,200 TPH), had acceptable BA (29.4–33.2 m² ha⁻¹) and V (127–136 m³ ha⁻¹). Basal area was ≥30 m² ha⁻¹ in most plantations indicating thinning is needed to optimize individual tree growth. Besides timber, an array of design-dependent agroforestry and forestry products should drive the selection of any one of these plantation designs: pine straw or biomass production at ≥1,800 TPH, and alley cropping or silvopasture in single-row (≤1,000 TPH) and multiple-row plantations (<1,400 TPH).     

Agroforestry in the arid zones of India

The arid regions of India cover over 300,000 km² and are spread over six States, mostly in the northwestern parts of the country. In spite of the hostile environmental conditions, several indigenous agroforestry practices are being practised in this region. The Central Arid Zone Research Institute (CAZRI) has made considerable progress in improving these indigenous practices and also developing new land use technologies some of which involve agroforestry approaches. Notable among these include sand-dune stabilization, shelterbelt plantations, tree planting techniques in difficult land forms, silvopastoral and agrisilvicultural systems, introduction and improvement of fruit trees and other indigenous trees, etc. Some of these technologies are adopted on a large scale by farmers in the arid zone of India, and have attracted international attention in other arid parts of the world. This paper is a summary of the results of these agroforestry initiatives of CAZRI.     

Plant-soil interactions in multistrata agroforestry in the humid tropicsa

Multistrata agroforestry systems with tree crops comprise a variety of land use systems ranging from plantations of coffee, cacao or tea with shade trees to highly diversified homegardens and multi-storey tree gardens. Research on plant-soil interactions has concentrated on the former. Tree crop-based land use systems are more efficient in maintaining soil fertility than annual cropping systems. Certain tree crop plantations have remained productive for many decades, whereas homegardens have existed in the same place for centuries. However, cases of fertility decline under tree crops, including multistrata agroforestry systems, have also been reported, and research on the causal factors (both socioeconomic and biophysical) is needed. Plantation establishment is a critical phase, during which the tree crops require inputs but do not provide economic outputs. In larger plantations, tree crops are often established together with a leguminous cover crop, whereas in smallholder agriculture, the initial association with food crops and short-lived cash crops can have both socioeconomic and biological advantages. Fertilizers applied to, and financed by, such crops can help to `recapitalize' soil fertility and improve the development conditions of the young tree crops. Favorable effects on soil fertility and crop nutrition have been observed in associations of tree crops with N<sub>2</sub>-fixing legume trees, especially under N-deficient conditions. Depending on site conditions, the substitution of legume `service' trees with fast-growing timber trees may lead to problems of competition for nutrients and water, which may be alleviated through appropriate planting designs. The reduction of nutrient leaching and the recycling of subsoil nutrients are ways to increase the availability of nutrients in multistrata systems, and at the same time, reduce negative environmental impacts. These processes are optimized through fuller occupation of the soil volume by roots, allowing a limited amount of competition between associated species. The analysis of temporal and spatial patterns of water and nutrient availability within a system helps to optimize the use of soil resources, e.g., by showing where more plants can be added or fertilizer rates reduced. Important research topics in multistrata agroforestry include plantation establishment, plant arrangement and management for maximum complementarity of resource use in space and time, and the optimization of soil biological processes, such as soil organic matter build-up and the stabilization and improvement of soil structure by roots, fauna and microflora. This revised version was published online in June 2006 with corrections to the Cover Date.     

Evaluation of plantation and early development of five alternatives to ponderosa pine in silvopastoral systems in northwest Patagonia,Argentina

Previous studies of afforestation in Patagonia indicate that 30–50 % tree cover produces positive effects on the pasture. This coverage level is achieved by applying pruning and strong thinning to reduce the volume of timber production per area unit. From an economic standpoint, in order to not reduce the income level of the system, it is necessary to find tree species that could replace ponderosa pine (Pinus ponderosa) and maximize income per volume unit of wood. We evaluated the feasibility of implementation of five broadleaved tree species (native and exotic) with higher intrinsic wood quality than ponderosa pine. We tested the influence of tree cover generated by a framework of silvopastoral plantation on the increase in survival, regrowth and absolute increase in height, and compared ecophysiological variables (net photosynthetic activity, stomatal conductance, intrinsic water use efficiency) of different species to the status of a traditional plantation without tree cover. Additionally values of air temperature and relative humidity were registered under both cover conditions. Preliminary results support the conclusion that three of these five species could be considered as alternatives to ponderosa pine species for establishing silvopastoral systems with higher timber value. Our Based on the results, the use of tree cover generated under the current plantations of P. ponderosa could increase the success of the establishment of these species.     

Role of woody perennials in animal agroforestry

Two main roles are identified in the review: the productive one, where woody perennials yield a material output (fuel, fodder, etc.), and the ‘service’ type, with no tangible product (shelter, nutrient recycling, etc.). In their productive role trees and shrubs may supply fodder in browsing systems, or industrial material, wood products and food in forest and plantation grazing systems. Service roles, rarely divorced from productive ones, arise mainly from relationships between woody perennials and the herbaceous vegetation growing in their vicinity. As a fodder source, the relatively low productivity and palatability of high protein content foliage from most woody perennials would indicate a supplementary role, particulary during dry seasons in arid and semiarid zones. In these type of lands pod-bearing trees seem to have a greater potential for improving fodder production in silvopastoral systems. The negative effect of trees on pasture production in forest and plantation grazing is compensated by their contribution to the system through other products. Available data would support the potential of certain species of woody perennials to foster pasture growing underneath, mainly through soil enrichment. Windbreaks can also indirectly benefit pasture growth, by decreasing water loss from the soil. It is postulated that research efforts in animal agroforestry should be focused on woody perennials for browsing systems, particularly on pod-bearing trees having beneficial effects on the herbaceous layer growing underneath.