Effects of widely spaced trees and livestock grazing on understory environments in tropical savannas

The effects of widely spaced trees ofAcacia tortilis andAdansonia digitata on their understory environments were investigated in four savannas located along a gradient of increasing livestock utilization in Tsavo National Park (West), Kenya. Plant species composition and biomass and the physical and chemical properties of soils that occur below tree crowns were compared to open grasslands. The tree-crown zones at lightly and moderately grazed sites had a unique understory flora and higher plant biomass, lower temperatures and bulk densities, and higher levels of P, K, Ca and mineralizable N than their associated opengrassland zones. In the heavily grazed savanna, few differences between tree-crown and grassland zones were found. The beneficial effects of savanna trees on their understory environments appear to diminish with increasing livestock utilization.     

Effects of intercropping systems of trees with soybean on soil physicochemical properties in juvenile plantations

The intercropping system of tree with soybean in juvenile plantations, as a short-term practice, was applied at Lao Shan Experimental Station in Mao’er Shan Forest of Northeast Forestry University, Harbin, China. The larch (Larix gmelinii)/soybean (Glycine max.) and ash (Fraxinus mandshurica) intercropping systems were studied in the field to assess the effects of the intercropping on soil physicochemical properties. The results showed that soil physical properties were improved after soybean intercropping with larch and ash in one growing season. The soil bulk density in larch/soybean and ash/soybean systems was 1.112 g·cm⁻³ and 1.058 g·cm⁻³, respectively, which was lower than that in the pure larch or ash plantation without intercropping. The total soil porosity also increased after intercropping. The organic matter amount in larch/soybean system was 1.77 times higher than that in the pure larch plantation, and it was 1.09 times higher in ash/soybean system than that in the pure ash plantation. Contents of total nitrogen and hydrolyzable nitrogen in larch/soybean system were 4.2% and 53.0% higher than those in the pure larch stand. Total nitrogen and hydrolyzable nitrogen contents in ash/soybean system were 75.5% and 3.3% higher than those in the pure ash plantation. Total phosphorus content decreased after intercropping, while change of available phosphorus showed an increasing trend. Total potassium and available potassium contents in the larch/soybean system were 0.6% and 17.5% higher than those in the pure larch stand. Total potassium and available potassium contents in the ash/soybean system were 56.4% and 21.8% higher than those in the pure ash plantation. Biography: FAN A-nan (1972–), female, Ph. Doctor in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China.     

林豆复合生态系统土壤理化性质的研究

本文对混种大豆的落叶松.大豆、水曲柳-大豆复合生态系统土壤理化性质进行研究。结果表明,在一个生长季内混种后的土壤物理性质得到了改善。落叶松.大豆与水曲柳一大豆复合生态系统的土壤容重为1.112g/cm3和1.058g/cm3均低于相对应的纯林:混种大豆后土壤总孔隙度增加。两种林-豆复合生态系统土壤有机质分别比对应纯林高1.77倍和1.09倍:落叶松一大豆复合生态系统全氮和水解氮含量分别高于落叶松纯林4.2%和53.0/%,水曲柳-大豆复合生态系统全氮和水解氮含量分别高于水曲柳纯林75.5%和3.3%:混种大豆后全磷含量降低,而有效磷含量则增加:落叶松-大豆复合生态系统全钾和有效钾比落叶松纯林高0.6%和17.5%,水曲柳-大豆复合生态系统全钾和有效钾分别比水曲柳纯林高56.4%和21.8%。图1表3参27。     

The biology, ecology and agroforestry potential of the raintree, Samanea saman (Jacq.) Merr.

Samanea saman (Jacq.) Merr. (syn. Albizia saman (Jacq.) F. v. Muell.) is a large tree, native to tropical America, which has now become widespread throughout the humid and subhumid tropics. Although noted as a promising agroforestry species, there is little specific research that substantiates this potential. On the basis of a review of its biology, ecology and recorded uses, it is concluded that the most appropriate use for S. saman would be in an extensive silvopastoral system for cattle production. The tree provides excellent protective shade, and produces highly palatable pods that are suitable as a dry season feed supplement. Additionally, there are reports of enhanced grass production beneath its canopy indicating a potential role in maintaining or improving the productivity of tropical grasslands. It is concluded that the tree should receive more research attention, focusing particularly on its interaction with the herbaceous understorey and the identification of provenances adapted to a variety of environmental conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Acacia nilotica trees in rice fields: A traditional agroforestry system in central India

Time-tested, indigenous land-use systems can provide valuable information for the design of ecologically sustainable and socially acceptable agroforestry systems. One such traditional system is the growing of Acacia nilotica (L.) Willd. Ex Delile trees, locally known as babul, in rice fields of smallholder farmers in Madhya Pradesh State of Central India, an area with subhumid monsoon climate and hot summer. The functional characteristics of the system were collected through participatory rural appraisal involving intensive interactions with farmers in the region during six years, and through a structured-questionnaire survey in 25 villages, involving a total of 200 farm families. The farms had an average of 20 babul trees, ranging in age from <1 to 12 years, per hectare in upland rice fields, the tree-stand density being greater on smaller than on larger farms (>8 ha). Over a ten year rotation period, the trees provide a variety of products such as fuelwood (30 kg/tree), brushwood for fencing (4 kg/tree), small timber for farm implements and furniture (0.2 cu.m), and non-timber products such as gum and seeds. The babul + rice system was estimated to have a benefit/cost (B/C) ratio of 1.47 and an internal rate of return (IRR) of 33% at 12% annual discount rate during a ten-year period, though at a low level of income. Babul trees account for nearly 10% of the annual farm income of smallholder farmers (<2 ha). By practising the agroforestry (rice + babul) system, farmers get higher cash returns on a short-term (10-year) harvest cycle of trees, and the labour input (both family- and hired) on farms was distributed more uniformly throughout the year than in rice monoculture. Purchased inputs are seldom used in the system. The ease of management of the system, the self-generating and robust nature of the tree and the multiple products and services it provides, and easy marketability of the products are the major factors that encourage farmers to adopt the system. Furthermore, the farmers have secure ownership rights to their land, so that they are interested in long-term measures such as tree plantings on their farms. In spite of its long history and tradition as a sustainable approach to land use, the system has not attracted the attention of development agencies. More detailed investigations on its social, economic, and cultural attributes are warranted to not only improve this system, but provide insights into farmer adoption of agroforestry innovations.This revised version was published online in November 2005 with corrections to the Cover Date.     

Financial evaluation of smallholder timber-based agroforestry systems in Claveria, Northern Mindanao, the Philippines

In the Philippines, timber production on small farms has become profitable as a result of reduced supplies due to extensive deforestation and increasing demand. In the early 1990s, when the price of timber was high, farmers were promised huge returns from tree farming. However, widespread planting of few species has led to oversupply and a sharp decline in the price of farm-grown timber. Moreover, low intercrop yields as a result of competition from fast-growing trees and low timber yields due to poor tree management, further reduce net economic returns. In spite of this, interest in tree farming remains high. This paper examines the private profitability of two tree-maize systems, namely trees in blocks and trees in hedgerows, compared with the alternative of maize monocropping. The analysis reveals that maize monocropping provides higher returns to land at the current timber price, but considerably lower returns to labour, than the maize-tree systems tested. This suggests that tree farming is a more attractive option for labour and capital-constrained households or those with off-farm opportunities that compete for their labour. These farmers may raise productivity and income by planting trees on the excess land that cannot be devoted to annual crops. The analysis also indicates that wide-spaced tree hedgerows are superior to tree blocks, due to lower establishment and management costs, longer periods of viable intercropping and more rapid tree growth.     

林-茶间种模式对安吉白茶生长的防护功能分析

安吉白茶(Camelliasinensis(Linn.)cv.anjibaicha)是我国目前发现的珍稀茶种之一,茶叶中氨基酸含量高达6.29%,几乎是普通绿茶的2～3倍[1],并具有特殊浓郁的香味,因此具有极高的开发利用价值。它原产于浙江省安吉县天荒坪镇海拔800m左右的湿润山区,仅保存有一株母树,经本所与浙江省安吉县林科所等单位合作,通过全光照嫩枝扦插和组织培养,解决了造林材料问题,又在浙西北低山平地试种获得了成功,开始有规模地扩大种植。在安吉白茶种植中遇到的最大的困难是早春易受冻害,春末夏初的白叶期易受日灼伤害,这与安吉白茶引种地和原产地的生境存在较…     

Modelling of rainfall interception loss in agroforestry systems

Two models of interception loss have been tested against new field data obtained in widely-spaced stands of Sitka spruce trees. The Gash model and a modified version of the Rutter model, have been used with data from an automatic weather station, to predict interception loss using parameters obtained from observations made in 1988 and 1989. The predictions for an eight-week period during 1987 were compared with measurements of interception loss. Good agreement between observed and predicted interception loss was obtained with both models over the whole period. The modified Rutter model gave better predictions than the Gash model for individual storm events and performed better at the wider spacings. The sensitivity of both models to the major characteristics of the tree stand structure in agroforestry systems was also investigated and it was shown that interception loss was most sensitive to boundary layer conductance and free throughfall coefficient.     

An evaluation of silvopastoral systems in pine plantations in the Central Highlands of Ecuador

One of the most serious problems facing Andean nations today is population growth and the resultant pressures placed on limited natural resources. Currently,thousands of hectares of pine plantations in the central highlands of Ecuador are left unmanaged and unutilized, while at the same time local agriculturalists lack grazing land,firewood and other basic necessities which could be provided by appropriate forest management. This paper evaluates ten pine plantations in central Ecuador for their potential as silvopastoral systems, and discusses the possibilities of integrating local farmers into the appropriate management and use of them.

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Resúmen Uno de los problemas mas graves afrontando a los paises Andinos es el crecimiento de la población y las presiones que resultan sobre los recursos naturales. Al momento, miles de hectáreas de plantaciones de pino en la Sierra central del Ecuador se quedan sin que nadie les maneje ni les utilize; mientras tanto los agricultores cercanos sufren por falta de pastoreo, leña y otras necesidades que se podría conseguir a través del manejo forestal. Este documento examine diez rodales de pino en el Ecuador por su potencial como sistemas silvopastoriles, y discute las posibilidades de integrar agricultores pequeños dentro del manejo y uso apropriado de ellos.

     

The domestication and commercialization of indigenous trees in agroforestry for the alleviation of poverty

New initiatives in agroforestry are seeking to integrate into tropical farming systems indigenous trees whose products have traditionally been gathered from natural forests. This is being done in order to provide marketable products from farms that will generate cash for resource-poor rural and peri-urban households. This poverty-alleviating agroforestry strategy is at the same time linked to one in which perennial, biologically diverse and complex mature-stage agroecosystems are developed as sustainable alternatives to slash-and-burn agriculture. One important component of this approach is the domestication of the local tree species that have commercial potential in local, regional or even international markets. Because of the number of potential candidate species for domestication, one crucial first step is the identification of priority species and the formulation of a domestication strategy that is appropriate to the use, marketability and genetic potential of each species. For most of these hitherto wild species little or no formal research has been carried out to assess their food value, potential for genetic improvement or reproductive biology. To date their marketability can only be assessed by their position in the local rural and urban marketplaces, since few have attracted international commercial interest. To meet the objective of poverty alleviation, however, it is crucial that market expansion and creation are possible, hence for example it is important to determine which marketable traits are amenable to genetic improvement. While some traits that are relatively easy to identify do benefit the farmer, there are undoubtedly others that are important to the food, pharmaceutical or other industries that require more sophisticated evaluation. This paper presents the current thinking and strategies of ICRAF in this new area of work and draws on examples from our program. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of young agroforestry trees on soils in on-farm situations in western Kenya

Soil samples were taken at different distances from the trunks of four- to five-year-old trees of six species planted on-farm in western Kenya. The tree species wereCordia africana, Croton megalocarpoides, Grevillea robusta, Acacia tortilis, Prosopis juliflora andSesbania sesban. Samples were also taken inside and outside a fenced plantation ofProsopis juliflora. Soil samples were analysed for total C%, total N%,¹³C abundance,¹⁵N abundance, extractable P and pH.The most sensitive indicator of effects of trees on soils was¹³C abundance, which reflected a shift in inputs of C from C₄ grasses to C from C₃ trees. All species except Prosopis lowered the¹³C abundance by 0.5–1 -units. This was equivalent to an increase of 3–5% of the percentage of C contributed by C₃ species. Prosopis trees did not decrease the¹³C abundance because of the abundant grass-growth around them. Cordia, which had the most pronounced effects, raised the C%, N% and extractable P by 27%, 26% and 55%, respectively. Nitrogen and C were well correlated (r ²=0.97) in the whole material. Effects on soil pH were in both directions, i.e. it was raised under the Prosopis plantation by 0.33 units, while it was lowered under Acacia by 0.21 units.Effects of agroforestry trees were thus seen in as short time as five years in practical onfarm situations.¹³C abundance is recommended as a particularly sensitive indicator of the influence of trees on sites previously dominated by C₄ crops and grasses.     

Growth,yield and stem form of young African mahoganies (Khaya spp.) in mixed-species plantations and successional agroforestry systems

New Forests - African mahoganies can be an alternative for wood production in agroforestry systems and/or mixed-species plantations. In this study, we aimed to evaluate the growth, yield and stem...     

The scope and potential of agroforestry in Central America

Although agroforestry practices have been used in Central America since pre-Columbian times, scientific initiatives in agroforestry began only about 15 years ago in this region. This paper describes the evolution of agroforestry in the Central American region, and discusses the relative merits of generating new procedures or encouraging traditional practices. This is followed by an analysis of several particularly promising practices—use of N-fixing trees to shade cacao and coffee, timber trees in pastures, and living fenceposts. Finally, a list of research gaps and recommendations for future efforts is presented. It is concluded that, from the perspective of scientific knowledge, agroforestry in Central America has taken off but the link between scientific knowledge and effective field application is still lacking.     

A computerized database as decision support tool for the selection of agroforestry tree species

Whether in agroforestry in temperate or tropical zones, choosing the right species is one of the most crucial stages of experiments and for reforestation, erosion control or land-improvement projects.Over the last decade, ICRAF has developed a tool to help researchers, extension workers, foresters and others in the decision process. The Multipurpose Tree & Shrub Database (MPTS) contains information about more than 1,000 species. Most of these species are grown in the tropical and subtropical zones, but many of them have a potential for temperate areas as well.MPTS contains first-hand, site-specific information about multipurpose tree species. This information makes it possible for the user to compare his or her site conditions with the site conditions described in the database, and allows him/her to draw conclusions about the possible species performance. MPTS also contains secondary information from publications.Candidate species are searched by entering keywords from a list of 19 correlated criteria, such as soil information, expected services or wood and non-wood products. Detailed information about the selected candidates (e.g. morphology, management, environmental responses) is provided.Beyond this, MPTS is a quick reference tool for the multiple use of tree and shrub species. In future it will include a comprehensive guide to germplasm information. Current activities include the implementation of an interactive use-interface and links to related databases.     

On-farm research in a silvopastoral project: a case study

The Silvopastoral Project is being implemented by CATIE in the Atlantic humid lowland of Costa Rica, in order to develop alternatives to the current destructive mode of livestock production. The overall approach is briefly described and two superimposed on-farm experiments are discussed in more detail. The main constraints for on-farm research within the project are analysed: the limited previous knowledge of the area and of the local species, the difficulty of achieving a common understanding about research with collaborating farmers, the need for additional staff supervision and the complexity of the statistical analyses. An attempt is made to draw lessons from the ongoing project regarding how to resolve the apparent contradiction between rigorous scientific requirements and questions of immediate value to extension, the compromises to be achieved between different types of evaluation (statistical, risk, etc.) and the potentials and limitations of farmers' participation in research.     

Reducing financial risk in agroforestry planning: a case study in Costa Rica

We used fluctuations in net income from alternative cropping systems to assess the financial risk associated with an agroforestry system. Mean-variance analysis was used to derive a set of minimum-risk farm plans for a 15-hectare farm in Costa Rica. Monocultural coffee production provided the highest expected net income, but also had the greatest economic risk. As risk was reduced, the optimal agroforestry system diversified to include other cropping systems in addition to the coffee monoculture. Risk aversion was, however, accompanied by significant reductions in expected net income for the cropping systems studied. The inclusion of additional cropping systems whose net incomes are negatively correlated with the systems considered here could help reduce the economic risk facing rural agriculturalists in this region.This research was supported by the Utah Agricultural Experiment Station, Utah State University, Logan, Utah 84322-4845. Approved as journal paper no. 4211.     

Branch characteristics of widely spaced Douglas-fir in south-western Germany: Comparisons of modelling approaches and geographic regions

Models of Douglas-fir branch and whorl characteristics were developed from contrasting spacing experiments in southwest Germany. The dataset was based on 100 young (20–30 years old), unpruned and partially pruned trees from a 100, 200, and 1200 stems ha⁻¹ spacing experiment on Douglas-fir that was replicated 3 times across the region. The material was used to predict (1) the number of branches whorl⁻¹, (2) branch angle, (3) status (living/dead) of the branches within the living crown, (4) maximum branch diameter whorl⁻¹, and (5) relative diameter of branches within a whorl. For each of these models (except branch status), both a linear and nonlinear, generalised hierarchical mixed effects equation was developed. The comparison of the linear and nonlinear approaches showed that both had a relatively similar level of bias, but the nonlinear equations generally performed better (reduction in mean absolute error of 1.1–69.5%). Overall, individual branch and tree properties were sufficient to give logical and precise predictions of the branch characteristics for the models across the range of sampled stand densities. In addition, the models showed a similar behaviour compared to models on Douglas-fir crown structure from the Pacific Northwest, USA. This suggests that the allometric relationship between tree size and branch characteristics for a given species may be relatively consistent across regions, even ones with highly contrasting growing conditions like in this study. The models performed well across a range of stand conditions and now will be further integrated into an individual tree growth and yield simulations system.     

Pine needle consumption and bark stripping by sheep grazing annual pastures in young stands of widely spaced Pinus radiata and P. pinaster

The consumption of the pine needles and the stripping of bark by sheep grazing annual pastures in three open stands of P. radiata and one of P. pinaster were measured. The P. radiata were four years old and the densities were 250, 500 and 750 trees ha^-1. The P. pinaster included two, three and four year-old trees and the density was 440 trees ha^–1.Needles were eaten immediately after the sheep were admitted and this continued throughout the year. Within ten weeks of the start of winter grazing, sheep stocked at 7–10 ha^–1 had eaten about half of the accessible needles on both species where densities were less than500 trees ha^–1. The estimated consumption was about 260 g sheep^–1 day^–1 for the P. radiata. Bark stripping then commenced and continued throughout spring and summer on most plots. In some plots at low tree density, bark was stripped from more than 35% of the trees. In denser stands, needle consumption per tree was less and bark was stripped from less than 5% of the trees.Bark damage was most common on the smaller trees, and severity of stripping was negatively correlated with tree size. Of all the trees with bark damage, 22% of the P. pinaster and 14% of the P. radiata had more than half of the stem circumference stripped. A number of these will probably suffer both stem distortion and growth retardation, and some may die.Methods of reducing the incidence of bark damage are discussed.     

黑莓幼树光合特性的研究

为探索美国黑莓优质、丰产栽培技术,对黑莓的光合特性进行了研究。结果表明,在河北省文安县栽培的黑莓叶片光合速率日变化呈双峰曲线,最高峰在9时,次高峰在13时,存在“午休”现象。光合速率的季节变化亦呈双峰曲线,最高峰在6月份,次高峰在8月份。光合速率的光补偿点和饱和点分别为60μmol.m-2.s-1和1 380μmol.m-2.s-1。     

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.