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.     

The role of timber tree species in the nutritional ecology of spider monkeys in a certified logging concession,Bolivia

Selective harvesting of timber can lead to population declines in some primate species. As frugivorous primates are important seed dispersers in tropical forests, the reduction of their populations may affect the ecological sustainability of selectively logged forests. This paper is the first to quantify the importance of timber tree species in the diet and nutritional ecology of a primate species. We studied spider monkeys (Ateles chamek) inhabiting a certified forestry concession in Bolivia where post-logging population declines of this species have been recorded. We show that spider monkeys occupying unlogged areas obtained approximately 50% of their total intake of macro-nutrients from timber tree species and exhibited a distinct preference for foraging within trees that were of harvestable size. Timber tree species dominated the spider monkeys’ diet both during peak fruiting periods and during periods of fruit scarcity. We estimate that under current timber extraction intensities spider monkeys lose significant proportions of their food sources. Our results indicate that further extraction limits could be considered for Ficus boliviana, Spondias mombin and Pouteria nemorosa. We suggest that to ensure long-term ecological sustainability of certified forestry concessions, the importance of timber tree species in the ecology of seed dispersers needs to be taken into account.     

Optimal management of a flammable multi-stand forest for timber production and maintenance of nesting sites for wildlife

Decline of cavity-using wildlife species is a major forest management issue. One of the causes of this problem is the loss in cavity tree abundance, resulting from short rotation silviculture, stand-replacing disturbance events and timber harvesting in disturbed stands. Cavity tree availability cannot be guaranteed due to the stochastic nature of disturbance events. We developed a Markov model to predict future cavity tree availability under alternative tree felling and fire protection strategies using information on cavity tree dynamics and fire history. Stochastic dynamic programming was used to find a strategy that maximizes timber revenues less forest management costs, including the cost of an artificial nest-box program that must be implemented whenever cavity trees become critically scarce. The requirement to implement a nest-box program in such circumstances strongly influenced the optimal tree felling strategy and resulted in a higher probability of having cavity trees in the future. This reflected an increase in the retention of old growth forest and stands with fire-killed cavity trees as well as stands of younger trees to provide a future source of cavities. These results demonstrate the need to consider the costs of artificial habitat enhancement and the risk of future cavity tree scarcity in multiple-use forest management planning.     

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.     

Understanding patterns of tree adoption on farms in semi-arid and sub-humid Ethiopia

Trees on farms are a widespread feature of landscapes across a large part of Ethiopia with an important role in enhancing the resilience of smallholder livelihoods through the provision of ecosystem services. Despite their importance, little is known about what trees are planted or retained from natural regeneration by different types of farmers that results in the pattern of tree cover found in the region. We address this knowledge gap through analysis of household survey data from semi-arid and sub humid areas of Oromia regional state. A set of composite variables that represent distinctive patterns of tree cover on farms were derived from principal component analysis and Pearson correlation analysis. This revealed two major tree adoption strategies: farmer managed natural regeneration (FMNR) of trees to meet subsistence needs as well as contributing to other ecosystem services; and, high value agroforestry (HVAF) involving planted trees used largely to produce fruits, timber and fodder. Regression analysis further identified fine-scale variation in ecological and socio-economic factors that affect which of these two broad strategies are adopted by farmers. Favorable climatic conditions coupled with institutional arrangements to control free grazing were pre-conditions for HVAF, whereas poor biophysical potential and sloping land provided a positive incentive for farmers to adopt FMNR. Farmers with preferences for tree species with multiple utilities and locational flexibility favored FMNR while adoption of HVAF was more asset-driven. Our findings reveal that farmers integrate many native and exotic tree species on their farms to meet their variable farm conditions, needs and asset profiles in stark contrast to most tree promotion efforts that focus on a few, usually exotic, tree species. We recommend that future agroforestry promotion should embrace a diversity of tree species appropriate to matching the fine scale variation in ecological conditions and farmer circumstances encountered in the field.     

Man-made dipterocarp forest in Sumatra

Traditional plantations of Shorea javanica in Southern Sumatra deserve mention on three main points: (1) it is a rare case in Indonesia of successful cultivation of an indigenous species. This species being a Dipterocarp is an even more attractive reason: Dipterocarps are in the paradoxical situation of being the largest family of timber trees in natural forests of tropical Asia but are almost never used for silvicultural purposes; (2) the tree is grown in association with many other useful trees to constitute an agroforestry system of both cash and subsistence incomes; and (3) such plantations represent a good potential for the production of natural resin in the humid tropics.This paper is a slightly revised version of an internal report prepared for BIOTROP (SEAMEO — ASEAN Center for Tropical Biology). The project has been funded by BIOTROP, while the author is a French consultant to that organization.     

Tree Culture of Smallholder Farmers Practicing Agroforestry in Gunung Salak Valley,West Java,Indonesia

This paper investigates the types of agroforestry system that exist in Gunung Salak Valley, West Java, Indonesia in order to characterize the differences in their basic structure and associated crop plant diversity. Data were collected through rapid rural appraisal, field observation and focus groups, followed by household survey of a sample of 20 agroforestry farmers. Five main agroforestry systems (homegardens, fruit tree system, timber tree system, mixed fruit–timber system, and cropping in the forest understory) exist in the study area, and all of them exhibit a noticeable diversity in terms of both species composition and utilization. Products from farming accounted for an average 24 % of household income. They comprised agroforestry products which contributed IDR 3.25 million/year and other agricultural products contributing IDR 1.66 million/year. The observed agroforestry systems include not only a form of forest dominated by ‘cultivated trees’, but also an anthropogenic vegetation formation derived from agricultural antecedents. In land-use classifications agroforestry systems are not recognized as forestry, but like forests they provide tree products and services. Classification will always be disfunctional if a binary system is applied, thus a more sophisticated approach should be adopted that incorporates the economic and environmental characteristics of a wider range of systems.     

Agroforestry and forestry-related practices in the Midwestern United States

A survey, conducted in 1990–1991 on agroforestry and forestry-related systems in eight Midwestern states, showed that three traditional and three nontraditional agroforestry systems are practiced in the region. Of 46 traditional systems reported, most common was agrisilviculture (28), then silvipasture (12) and agrisilvipasture (6). These systems often involved corn, soybeans, and hay planted with tree species for nut, timber, or Christmas tree production, and cattle. Non-traditional agroforestry systems were field windbreaks/shelterbelts (29), treeshrub intercropping systems (21), and boundary plantings (11). These systems involved a variety of northern hardwood species evergreens, and shrubs. There was also a preponderance of specialized systems (97) of growing trees with the production of mushrooms, nuts, syrup, wildlife, and other nonwood products. The survey is exploratory in nature and, although the results may not represent a complete count of people involved with agroforestry in the region, the numbers reported may indicate where a practice may be prevalent. The results reflect the fact that much work still needs to be done by agroforesters in this region. They also provide some basis for further research on more suitable systems, and for identifying other researchable questions on agroforestry for the region. The methodology also made possible a bigger nucleus for networking of agroforesters and other interested people in the Midwest. Finally, although not normally considered as agroforestry, the significance of the other specialized systems reported in this survey is that they offer varied ways of connecting forestry with other activities in a largely agricultural landscape, and that they may even be seen as opportunities for easier transition into agroforestry.     

Plant species in the Kilimanjaro agroforestry system

An inventory of plant species was conducted on farms, farm boundaries and homesteads in the Kilimanjaro agroforestry system. The survey covered 30 farms in 6 villages in Hai District on the slopes of Mount Kilimanjaro, Tanzania. Over 100 plant species spread over 40 families were identified and their uses obtained through interviews with farmers. The species identified include 53 tree species, 29 food crop species, 21 non-woody plants of economic value and 8 weed species. The food crops, trees and other economically useful plants are carefully chosen by the local farmers and intimately intercropped on the same unit of land. In most cases, the plants had two or more uses of which food, fuelwood, medicine, poles, timber and fodder were the most important.     

Cultural knowledge of forests and allied tree system management around Mabira Forest Reserve,Uganda

The cultural universe is sometimes confusing,surprising and murky, so many cultural maps get drawn,discussed and envisioned. A study was undertaken around Mabira Forest Reserve in central Uganda to identify the trees and shrubs culturally managed on-farm, assess the cultural practices of forest and tree system management and determine the relationship between farmer gender and forest and tree system management. We engaged 203 farmers in focus group discussions and semi-structuredinterviews to collect data. Qualitative data were jointly evaluated with farmers; quantitative data were analyzed in SPSS 20.0. The results showed a high likelihood for involvement of local people in tree or forest management for economic gain, as timber and fast-growing species were highly ranked. Food and medicinal species were also regarded as important, suggesting high prospects of integrating them into the local farming system or protecting them in the forest. Numerous cultural practices(including rituals, trenching, bark slashing, ring barking, spot weeding and use of organic manure and pesticides) of forest and tree system management were acknowledged. However, their knowledge was mixed and unclear about distinct cultural and supportive arrangements for natural forest and tree restoration. While gender was not a significant cultural attribute for knowledge of the forest and allied tree system management, age substantially affected farmer propensity for various timber products. Also farmer's family size influenced the collection of tree wildings and fodder. We encourage considering gender disparities and livelihood needs including income, during selection of cultural practices for forest and tree restoration.     

Growth and yield of some indigenous trees in an Amazonian agroforestry system: a rural-history-based analysis

Over the years farmers of Japanese descent in the Brazilian Amazon have planted indigenous trees that yield various products and services: fruit, seeds,bark, latex, oil, and shade and wind breaks for understory crop plants. Production of timber is often the intended end use of such planted trees. Long-term growth performance of these trees nevertheless has not been well documented. The authors constructed 65-year growth curves for nine indigenous tree species based on measurements of diameter at breast height (dbh), height, and tree age data provided by farmers in the Brazilian State of Pará. An index of wood prices used to calculate state stumpage taxes was then applied to mean stem wood growth curves to produce price curves. These price curves estimate both present value of standing timber, and the value added from annual growth of standing timber in the agroforestry systems studied. The results of this study provide local farmers with a tool to estimate potential annual income from the growth of their trees, and a basis for planning timber harvest rotations. This study's approach may be applicable in other parts of the tropics, where growth information about indigenous trees commonly used in agroforestry is lacking.This revised version was published online in November 2005 with corrections to the Cover Date.     

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.     

Direct seeding of late-successional trees to restore tropical montane forest

Natural regeneration of large-seeded, late-successional trees in fragmented tropical landscapes can be strongly limited by a lack of seed dispersal resulting in the need for more intensive restoration approaches, such as enrichment planting, to include these species in future forests. Direct seeding may be an alternative low-cost approach to planting nursery-raised tree seedlings, but there is minimal information on its efficacy or when in the successional process this technique will be most successful. We tested directly seeding five native tree species into habitats representing passive and active restoration approaches: (1) recently abandoned pasture; (2) naturally establishing, young secondary forests; and (3) young, mixed-species (fast-growing N-fixers and commercially valuable species) tree plantations established to facilitate montane forest recovery in southern Costa Rica. We monitored germination, survival, growth, and above- and below-ground biomass over a 2-year period. Germination in pastures, secondary forests, and tree plantations was similar (∼43%). Seedling survival after one and two years was significantly higher under tree plantations (91% year 1, 75% year 2) compared to secondary forests (76, 44%) or pastures (74, 41%). Moreover, seedlings had greater total biomass and lower root:shoot ratios in the plantations, suggesting higher nutrient availability in that treatment. Costs for direct seeding were 10- to 30-fold less per 100 seedlings after 2-year compared to nursery-raised seedlings planted at the same sites; however, there are important trade-offs to the two restoration approaches. Planting nursery-raised seedling is a more effective but higher cost approach for rapidly establishing canopy cover and restoring large areas whereas direct seeding is a more efficient way to enrich an existing system. We particularly recommend using direct seeding as a complimentary measure to the more intensive restoration approach of planting fast-growing and N-fixing trees.     

我国东北地区树木引种驯化概况及发展策略

引种驯化是林木育种的重要手段,其不仅丰富了本地的树种资源,改善现有树种组成及比例,而且带来显著经济效益,也是保护生物多样性和景观生态平衡的需要,因此受到人们的极大重视。文中综述我国东北地区树木引种驯化情况,发现截至目前已成功引种63科、119属、500余种,主要包括用材树种、经济树种、观赏树种和生态树种;总结引种过程中的成功经验,讨论其中存在的问题,提出树木引种发展策略,以期为今后东北地区开展树木引种工作提供参考。     

Boom and bust of a moose population: a call for integrated forest management

There is increasing pressure to manage forests for multiple objectives, including ecosystem services and biodiversity, alongside timber production. However, few forests are currently co-managed for timber and wildlife, despite potential economic and conservation benefits. We present empirical data from a commercial Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) production system in southern Norway in which moose (Alces alces) are an important secondary product. Combining long-term hunting and forestry records, we identified temporal variation in clear-felling over the past five decades, peaking in the 1970s. Herbicide treatment of regenerating stands and a fivefold increase in moose harvest has lead to a reduction in availability of successional forest per moose of >90 % since the 1960s. Field estimates showed that spraying with the herbicide glyphosate reduced forage availability by 60 and 96 % in summer and winter, respectively, 4 years after treatment. It also reduced moose use and habitat selection of young spruce stands compared with unsprayed stands. Together these lines of evidence suggest that forest management led to an increase in moose carrying capacity during the 1970s and a subsequent decline thereafter. This is likely to have contributed to observed reductions in moose population productivity in southern Norway and is counter to sustainable resource management. We therefore call for better integration and long-term planning between forestry and wildlife management to minimise forest damage and the development of large fluctuations in ungulate populations.     

Putting Back the Trees: Smallholder Silvicultural Enrichment of Post-Logged Concession Forest in Peruvian Amazonia

This paper presents a case of planting and management of natural regeneration of shihuahuaco (Dipteryx spp.) by recent migrants in a Peruvian Amazonian logging frontier. We interviewed residents of three communities of smallholders in Irazola District, Province of Padre Abad, Region of Ucayali, located within the historic and actual boundaries of an active logging concession, and conducted growth studies of shihuahuaco trees planted in two mixed-species agroforestry fields, over a period of 3 years. We found that the majority of landholders were managing the natural regeneration of valuable hardwood timber trees, and planting seedlings on their lands. Growth of shihuahuaco trees in agroforestry fields was comparable to growth rates in managed silvicultural plantations, which suggests the potential for local smallholders activities to contribute to conservation of genetic stock and eventual renewal of populations depleted by logging. We recommend greater recognition and inclusion of local people, with their innovative and productive silvicultural practices, in efforts to remediate the impacts of selective logging of high-value timber species.     

Risk evaluation and tree improvement as components of intensive forest management in Japan

Forestry practice differs from agricultural crops practice owing to the huge size of trees, their longevity and the variety of uncontrollable conditions under which they grow. Even with intensive forest management, the actual effects of investment of labour and materials in the forest seem to be fairly small because of the size of the forest and the long harvest rotation. Since we expect to produce both a higher quantity and a higher quality of timber with intensive forestry, it is very important to have adequate counter-measures to the fatal or destructive factors which affect forest establishment and growth. In Japan, in the field of forest tree breeding, we are making maps as information sources for decision making, in which iso-lines show the degrees of damage due to fatal factors such as pests and diseases. If there is more than one fatal factor overlapping in an area, it might be difficult to grow forests for commercial purposes. We have to decide how to use the forest land in these areas, or how to take counter-measures such as tending, chemical control, genetic improvement or even a change in the tree species. As forestry has a long harvest rotation, it is necessary to have ‘a quality control system’ in management, in which a follow-up assessment of planting materials, tending techniques in combination with site conditions, and fatal factors will be made. In this situation, forest tree improvement (breeding) seems to be of prime importance in intensive forest management in the future.     

Compatibility of timber and non-timber forest product management in natural tropical forests: Perspectives,challenges, and opportunities

Tropical forests could satisfy multiple demands for goods and services both for present and future generations. Yet integrated approaches to natural forest management remain elusive across the tropics. In this paper we examine one combination of uses: selective harvesting of timber and non-timber forest product (NTFP) extraction. We analyze the current status of this combination and speculate on prospects and challenges regarding: (i) resource inventory, (ii) ecology and silviculture, (iii) conflict in the use of multipurpose tree species, (iv) wildlife conservation and use, (v) tenure, and (vi) product certification. Our conclusions remain preliminary due to the relative paucity of published studies and lessons learned on what has worked and what has not in the context of integrated management for timber and NTFPs. We propose at least three ways where further research is merited. One, in improving ‘opportunistic’ situations driven by selective timber harvesting that also enhance NTFP values. Two, to explicitly enhance both timber and NTFP values through targeted management interventions. Three, to explicitly assess biophysical, social, regulatory and institutional aspects so that combined benefits are maximized. Interventions for enhancing the compatibility of timber and NTFP extraction must be scaled in relation to the size of the area being managed, applied timber harvesting intensities, and the dynamics of multi-actor, forest partnerships (e.g., between the private sector and local communities). In addition, training and education issues may have to be re-crafted with multiple-use management approaches inserted into tropical forestry curricula.     

Agroforestry and soil conservation needs of smallholders in Southern Zambia

An agroforestry and soil conservation needs assessment survey conducted in southern Zambia revealed valuable insight into needs, constraints and development options as perceived by smallholders themselves. Inadequate efforts to conserve soil are due to technical and socio-economic factors, they do not result from a lack of awareness of the widespread erosion threat. Fruit tree planting, windbreak establishment as well as the protection of the natural Faidherbia albida regeneration in cropland are popular agroforestry interventions whose positive effects are widely acknowledged. Forty-two perennial species were found to directly contribute to people's diet. Although local fuelwood and fodder shortages as well as the need for fencing are recognized only few respondents envisage agroforestry solutions such as fuelwood and fodder tree planting or live fencing. Most smallholders are interested in tree planting but have so far only planted few trees. Those planted are usually exotic fruit trees. Drought hardly, termite and browse resistant perennials adapted to smallholder tree planting must be provided by the extension services. The widespread exclusion of women from decision making and the lack of tenure security hampers female participation in agroforestry development and consequently threatens sustainable development altogether.