Development and validation of a simple approach to modelling tree shading in agroforestry systems

There have been a number of models developed which attempt to predict the shading patterns beneath individual tree or forest canopies. We describe a computer-based model which is able to estimate shading patterns through a discontinuous canopy of pruned trees. The model is designed to assist in the layout and management of agroforestry systems with widely spaced trees. The model was tested against data collected from a seven-year-old agroforestry system involving radiata pine, located near Canberra, Australia. The model was shown to slightly but consistently underestimate light penetration at ground level beneath the trees. However, the extent of bias (0.7% to 5%) was so small as to be of little significance in practice.     

Throughfall,stemflow and interception loss in a mixed white oak forest (Quercus serrata Thunb.)

Throughfall and stemflow measurements in a 60-year-old white oak stand (Quercus serrata Thunb.) were carried out during two periods totalling eleven months, from August to November 1993 and from May to November 1994, in order to clarify the rainfall partitioning of this forest. Troughs and spiral-type stemflow gauges connected to tipping bucket-gauges were used for throughfall and stemflow measurements. Seventy-five storms were analyzed individually. Coefficients of variation for throughfall and stemflow ranged between 5–25% and 20–70% respectively. Partitioning of net rainfall in throughfall and stemflow represent 72% and 10% of the gross rainfall respectively. Multiple regression analyses were carried out to determine the stemflow variability. In was determined that maximum rain intensity was highly correlated with stemflow and this variable explained a further 5.5% of the stemflow variation. Estimates of averaged lag time and drainage after rain cease for stemflow were 290 and 164 min, while estimates for throughfall were 60 and 104 min. respectively. The canopy saturation was estimated from continuous storms and showed a value of 0.6 mm. The trunk storage capacity was estimated at a value of 0.2 mm. The interception loss from the forest canopy was estimated in 18%. Interception loss was heighly correlated with rainfall characteristics such as duration and intensity.     

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.     

Simulating Spatial Distribution of Canopy Rainfall Interception of Forests in China

The canopy rainfall interception modei linked to environmental conditions and biological features is established on the basis of stationary observation and measurements in China. Upscaling from site observation to regional Ievel estimation of canopy rainfall interception has been made. The potential interception value of forests during the rainfall season in China according to rainfall records of May, July and September in the year 1982, has been simulated and mapped under the GIS software package Idrisi. It coincides well with the spatial and chronological pattern of rainfall in China and can be concluded to reflect the reality. The potential canopy rainfall interception of forests in China based on the potential distribution of forests provides a basis to regional water budget as well as rational use of regional water resources. It is also important to the assessment of forest ecosystem service in China, which is demanded by both scientists and policy makers for the evaluation of afforestation and nat     

辽东山区不同森林植被类型枯落物层截留降雨行为研究

对辽宁东部山区具有代表性的油松林、落叶松林、红松林、柞木林及杂木林5种森林植被类型枯落物层截留降雨行为进行了比较研究。结果表明,枯落物截留量随林内雨量的增加而增加,呈显的线性关系;枯落物截留率在低的林内雨量级时下降梯度较大,以后随林内雨量增大而逐渐减少,最后趋于某一定值,枯落物截留达到饱和。曲线估计的饱和截留率为：杂木林30％,柞木林23％,落叶松林20％,油松林15％,红松林10％。林冠层与枯落物层截留量依林外雨变化呈显的线性关系,总截留率在低雨量级时保持在较高的水平,随后急剧下降,并逐渐趋于某一稳定性,达到最大截留能力。由曲线推算的最大总截留率,杂木林和 柞木林为45％,落叶松林为40％,红松林和油松林约为30％。枯落物生长季相对于林内雨的截留率为14．31％－43．15％,平均值为31．15％,相对于林外雨量的截留量为11．15％－32．30％,平均值为24．05％。     

我国农林系统小气候研究概述

综述了我国自１９９０年以来农林系统小气候研究概况及进展。农林系统的小气候特征是：（１）热量平衡的各分量白天为正值,夜间为负值。热量平衡的各分量中,潜热通量占净辐射的比值最大,湍流热通量和土壤热通量均较小。（２）在农林系统中,随着植物覆盖度的增加,其净辐射、光照强度、温度日较差和风速随之减小,但空气湿度增加,（３）在农林系统中,随着土壤深度的增加,土温变化的振幅安几何级数减小,位相按等差级数落后。土     

森林乔木冠层雨水再分配特征及机制研究综述

森林乔木冠层对降雨的再分配具有重要的水文生态意义,有助于定量评价不同区域、尺度、类型的森林冠层雨水利用效率,可为深入研究森林冠层变化对区域水分循环的调节作用提供科学依据。文中从森林冠层雨水截留、林内穿透雨、树干茎流和林下凋落物截留4个方面评述了近20年来国内外对森林乔木冠层影响雨水再分配的研究最新进展。研究认为,由于森林冠层雨水再分配的生态机理仍未明晰,因此建立精确度高的截留模型仍将作为此类研究的重难点之一;引入激光雷达技术获得森林冠层三维结构,以及多角度、多通道的多种传感器观测垂直空间多层次的森林冠层雨水再利用规律将会成为未来的研究方向之一;目前林冠雨水截留研究缺乏其与区域水文变化之间的关联性研究,将林冠雨水再分配研究的成果转化为区域水文问题的解决方案也将会是未来研究的趋势之一。     

The tree tenure factor in agroforestry with particular reference to Africa

Rights over trees are often distinct from rights over land. Tree tenure consists of a bundle of rights over trees and their produce which may be held by different people at different times. These rights include the right to own or inherit trees, the right to plant trees, the right to use trees and tree products, the right to dispose of trees and the right to exclude others from the use of trees and tree products. Factors affecting who had rights include the nature of the tree, the nature of the use and the nature of the person or group. Landowners and tree plants tend to be relatively advantaged in terms of their rights to trees. Those with temporary claims to the land and, in some case, women, tend to be disadvantaged. The implications of tree tenure issues for the design of agroforestry projects are discussed.

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Resumen Los derechos sobre los arboles muchas veces son distintos a los derechos sobre la tierra. La propiedad del arbol consiste en un lote o derechos sobre arboles y sus productos que pueden ser mantenidos por distintas personas en distintos tiempos. Estos derechos incluyen el derecho a poseer o heredar arboles, el derecho a plantar arboles, el derecho a usar arboles y los productos arboreos, el derecho a disponer de los arboles y el derecho a excluir a otros del uso de los arboles y los productos arboreos. Se incluyen en los factores que afectan quienes tienen determinados derechos la naturaleza de los arboles, la naturaleza de su uso y la naturaleza dela persona o grupo. Terratenientes y plantadores de arboles tienden a tener ventajas en terminos de sus derechos sobre los arboles. Aquellos con derechos temporales y en algunos casos las mujeres tienden a estar en desventaja. Aqui se discute la problematica de las implicancias de la tenencia de los arboles para el diseno de proyectos silvo-agropecuarios.

     

阔叶树截留降雨试验与模型——以色木槭为例

通过实验室模拟试验,得到不同雨强和叶面积指数组合下的色木槭截留降雨过程,并考虑树冠湿润度的影响。结果表明:单位叶面积次降雨最大截留量随雨强增大而减小,枝叶截留速率随树冠湿润度变化而变化。构建色木槭截留降雨随雨强和叶面积指数变化的模型,对模型模拟验证,模拟精度为92.7%。     

Farmer perspectives on agroforestry opportunities and constraints in cape verde

In the água de Gato Watershed on the island of Santiago, Cape Verde Islands, 51 farmers were surveyed regarding their attitudes and knowledge of agroforestry. The farmers identified eight constraints to agroforestry implementation, with virtually all indicating that a source of loan funds was the major concern. Space or land constraints and availability of tree seedlings were identified as constraints by 94% and 88%, respectively. Despite these concerns, 92% of the farmers expressed a willingness to adopt or improve agroforestry practices in the watershed, with 73% expressing a willingness to establish fruit trees, 53% willing to establish trees or shrubs for fuelwood, and 16% willing to plant trees for shade.     

Management strategies for Indonesian rubber production under yield and price uncertainty: a bioeconomic analysis

A simplified version of the BEAM Rubber Agroforestry Model is embedded in a dynamic economic model to examine the impact of uncertainty about prices and climate on decision variables. Solutions, in terms of optimal levels for decision variables are found using a Monte Carlo stochastic framework. These solutions were used to derive risk-efficient frontiers corresponding to different levels of the decision variables. The results underline the importance of including uncertainty in dynamic bioeconomic systems since profits under uncertainty turned out to be quite different from those obtained with prices and climate assumed to be constant. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agroforestry in Nepal: research and practice

Agroforestry research and practice in Nepal is reviewed. The social and ecological complexity of the country is outlined along with some of the methodological problems. The central importance of trees for fodder and areas that they can be planted on farms are discussed. The role of adjacent forest for compost, firewood and tree seedlings is also highlighted. A system containing Nepalese Alder is outlined and assessed as an agroforestry system that is increasingly being adapted in the middle hills of eastern Nepal.     

Influence of different Taxodium ascendens stands on the open ranges and system performance in Jiangsu Province, China

This paper reveals the results of an eight-year experiment set up to identify the effects of four tree spacing configurations (1.5 × 4 m, 1.2 × 5 m, 2 × 3 m and 1.5 × 2 × 6 m) on open ranges and the relationship between open ranges and species coexistence in Taxodium ascendens-intercrop systems. Relative interrow open ranges and relative interplant open ranges were significantly different among four tree spacings. All relative open ranges (relative interrow open ranges, relative interplant open ranges, relative canopy open ranges and relative space-volumed open ranges) decreased with increasing age. The wider interrow or interplant spacings of trees offered wider (relative) interrow or interplant open ranges for intercrops. All of the tree spacings, except spacing 2 × 3 m, had negative relative interplant open ranges in nine-year-old stands, suggesting that the canopies between a plant and its neighbouring plant were in direct competition, and no interplant open range existed between two individual trees. Up to age nine, spacing 1.5 × 2 × 6 m showed no marked disadvantage in growth performance as compared to the other three spacings, but provided wider interrow open ranges for intercrops. Starting with tree stands of age four years, the yields of interplanted wheat (Triticum aestivum), soybean (Glyciae max) and rape (Brassica napus) decreased significantly as a result of the decrease of open ranges in tree stands. The yields of wheat, soybean and rape were lower in tree spacing 2 × 3 m than in other spacings. There was a positive correlation between wheat yields and canopy open ranges. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of spacing on growth and biomass production of Gliricidia sepium (jacq) walp in an alley cropping system in Sierra Leone

This paper describes a study into the influences of spacing on the early performance and biomass production of Gliricidia sepium in an alley cropping system in southern Sierra Leone. Four between-row spacings of 2, 4, 6 and 8 m were combined with three within-row spacings (0.25, 0.50 and 1.00m) in a split plot experimental design.Survival, tree height and leaf nitrogen content were not affected by between- or within-row spacings. For the other parameters measured, namely root-collar diameter, branch production, total biomass and nitrogen yields per hectare, it was found that for equivalent tree densities, the lower the rectangularity of planting, the better the performance of the individual trees, and consequently the greater the yields per hectare.Total biomass production per unit area was, expectedly, greatest where the spacings between hedgerows were closest, while production per plant decreased with closer within-row spacings. The total fresh and dry weights of leaves and stems, as well as leaf nitrogen yields per unit area were strongly influenced by between-row spacing and less so by within-row spacing.     

Do socio-psychological factors matter in agroforestry planning? Lessons from smallholder traditional agroforestry systems

Most of the well planned rural development forestry programs of the 1970s, and agroforestry in particular, were either not adopted by the intended beneficiaries or failed to meet the needs and aspirations of the rural people, particularly in the developing countries. The reasons for non-adoption in some cases appear to be technical, bio-physical, social and economic (termed as rational reasons by the planners), but in other situations the reasons are not so easily recognisable and comprehended (termed irrational reasons). These irrational reasons are the perceptions and attitude of the farmer towards farm practices, and their role in agroforestry planning has remained almost completely neglected. The present study is based on a household survey of the farmers in traditional agroforestry systems of Western Himalaya and investigates the importance of perceptional and attitudinal aspects of the farmers with regard to agroforestry adoption and extension. In the present study, farmers’ perceptions of restrictions on felling of trees from their own land and attitudes towards agroforestry were the most important sociopsychological factors which influenced tree growing. This study implies a need to take into account the socio-psychological factors of the farmers for planning socially acceptable agroforestry programs. The importance of study of various de jure rules and regulations controlling the use of on-farm tree resources and related exemptions and their association with farmers’ perceptions and tree growing is highlighted to develop policies to encourage tree growing in agroforestry.     

A rainfall interception model for inhomogeneous forest canopy

The process of rainfall interception by an inhomogeneous forest canopy composed of tree crowns with some gaps among them were considered, and the previous theoretical models of rainfall interception were modified to model an inhomogeneous canopy instead of a statistically homogeneous canopy. The paper deals with the following. First, the process of rainfall interception in tree crowns and that of rainfall in the gaps among them are studied respectively to acquire the average rainfall interception of a forest canopy. Based on the model derived by Liu (1987) and setting the canopy density value, both the relevant partial equations and a formula to estimate rainfall interception were derived. Moreover, the new model was solved through a numerical method and was illustrated with typical values of some ecological factors; three groups of curves were acquired by calculation with the VisualBasic program. A model of rainfall interception by an inhomogeneous forest canopy is classified as a multi-layer model, which is different from previous models (models where all the parameters represent the whole canopy). The results from the model in this paper could be used to determine the relationship between interception and each ecological factor in detail. __________ Translated from Scientia Silvae Sinicae, 2007, 43(3): 8–14 [译自: 林业科学]     

A mathematical model for generating land-use allocation alternatives for agroforestry systems

Agroforestry has been considered a viable land-use system particularly in the tropical regions. In developing or designing agroforestry systems, various concerns have to be addressed namely: (1) economic; (2) biological and physical; and (3) silvicultural and ecological considerations. This paper addresses these concerns from an interdisciplinary perspective. A land-use allocation model which ensures the simultaneous consideration of these concerns is proposed.