Agroforestry species of the Bolivian Andes: an integrated assessment of ecological, economic and socio-cultural plant values

Agroforestry is a promising method for enhancing land-use sustainability in the Bolivian Andes. However, its benefits in terms of rural development are under-recognized due to gaps in understanding users?? perceptions while taking into consideration both local and global environmental goals. Our study aimed to narrow these gaps by developing an analytical framework for analyzing the site-specific socio-ecological factors and interactions related to local woody species and assessing their ecological, economic, and socio-cultural plant values in order to identify the most promising agroforestry species. The framework was then tested in an indigenous community at 2,760?C3,830?m?a.s.l., incorporating vegetation surveys, environmental studies, and interviews on plant functions. Ecological, economic, and socio-cultural values and the ecological apparency of plants were calculated, and detrended correspondence and principal component analyses helped to reveal the socio-ecological context of significant factors for plant distribution and uses. Results showed dominating seral woody species along an altitudinal gradient. Although shrubs were more ecologically apparent than trees, trees were perceived to be more valuable as the usefulness and cultural importance of species increased with plant height and timber availability. Phytosociological factors played a minor but still significant role in perceived usefulness. Schinus molle and Prosopis laevigata (<3,200?m a.s.l.), Polylepis subtusalbida (>3,200?m a.s.l.), and Baccharis dracunculifolia (both zones) were evaluated as most promising for agroforestry use. In conclusion, our analytical framework proved to be a valuable tool for context-specific agroforestry plant selection. Nonetheless, economic, technical, and socio-cultural limitations of cultivating native agroforestry species were revealed as well. Agroforestry science and practice should, therefore, focus on enhancing reproductive potentials of existing woody vegetation, as well as problem-oriented horizontal dialogues between indigenous, expert, and scientific actors.     

Woody leguminous trees: New uses for sustainable development of drylands

Woody leguminous species are valuable crops because of their nutritional, economic, and ecological characteristics. Such crops have aided in the recovery of marginal lands for agricultural development due to their ability to fix nitrogen, control erosion, and act as a refuge for other species, in addition to their capacity to improve soil mineral composition and microbial biodiversity. Nevertheless, some leguminous trees are recognized to be one of the worst invasive species that affect negatively biodiversity and the entire ecosystem balance. In this study, we review new global uses for some woody leguminous crops, highlighting new nutraceutical and pharmacological properties, their uses as bioenergy sources, and their ecological uses for bioremediation opening new possibilities of management. We aim to bring knowledge on the multiple benefits that these woody plants continue to provide to humans from economic, social, and environmental standpoints.     

Hybrid improved tree fallows: harnessing invasive woody legumes for agroforestry

For several decades, agroforestry specialists have promoted the planting of fallow fields with nitrogen-fixing, fast-growing trees or shrubs to accelerate soil rehabilitation and provide secondary products like woodfuel. Yet, such ‘improved fallows’ have not been widely adopted, in part due to the costs of labour and seedlings. In some situations, however, farmers have developed novel approaches to agroforestry fallows by taking advantage of spontaneous invasions of woody leguminous tree species present in the vicinity of their fields. In this paper, we examine cases from Réunion, highland Madagascar, the Bateke plateau in Congo, and the Palni hills of southern India where farmers have adapted their cultivation practices to take advantage of the invasive characteristics of Australian acacias that were introduced earlier for other reasons. We focus on the key social, economic, and environmental factors that influence farmers in these places to gain opportunistic benefit from these introduced tree species that biologists have been deemed invasive and damaging to local ecosystems and biodiversity. We conclude that opportunistic fallowing of invasives can be viewed as a hybrid strategy combining elements of natural fallows and improved fallows—which we call ‘hybrid improved fallows’—in that it takes advantage of the ‘weedy’ characteristics of introduced leguminous tree species in the landscape and offers a cost-effective and pragmatic strategy for soil and vegetation management for farmers.     

Multipurpose tree yield data — their relevance to agroforestry research and development and the current state of knowledge

Agroforestry is not likely to be accepted, particularly by small-holders, unless it is proved superior to other forms of land use not only on ecological but also on economic grounds. It is therefore argued that economic parameters concerning the quantitative productivity of all agroforestry systems components have to be a matter of concern to both research and development in agroforestry.In the process of screening selected relevant literature and as a result of a search of ICRAF's Multipurpose Tree and Shrub Data Case, the yawning gap between the high level of knowledge on agricultural crops on the one hand and the low level on woody perennials on the other is exposed as a serious obstacle to the analysis of agroforestry systems and to the further development of agroforestry. The lack of knowledge on woody perennials, as substantiated in this paper, concerns particularly quantitative production data on trees and shrubs used in agroforestry systems.It is also argued in support of the views cited from other authors that what little there is by way of yield data on woody perennials is scattered and distributed over a vast amount of literature, and thus often difficult to access and to retrieve, and often difficult if not impossible to compare owing to different methods and parameters employed in attaining the data.Although the difficulties of yield assessment are appreciated, increased efforts to obtain more — and more comparable — data on te productivity of woody perennials are advocated. In support of this call for stepping up appropriate activities some preliminary suggestions are presented on how to standardize parameter of yield assessments to achieve better comparability and how to increase accessibility of yield data and promote retrieval of data by the establishment of supplementary data bases.     

Structure and regeneration status of Komto Afromontane moist forest, East Wollega Zone, west Ethiopia

We conducted a study in Komto Forest in East Wollega Zone, Oromia National Regional State, West Ethiopia for determining vegetation structure and regeneration status in this forest. We systematically sampled 53 quadrats (20 m × 20 m) along line transects radiating from the peak of Komto Mountain in eight directions. Vegetation parameters such as DBH, height, seedling and sapling density of woody species, and location and altitude of each quadrat were recorded. In total, 103 woody plant species of 87 genera and 45 families were identified. Analysis of selected tree species revealed different population structures. Generally, the forest was dominated by small trees and shrubs characteristic of secondary regeneration. Observations on the regeneration of the forest indicated that there are woody species that require urgent conservation measures. Based on the results of this study, we recommend detailed ecological studies of various environmental factors such as soil type and properties, and ethnobotanical studies to explore indigenous knowledge on uses of plants.     

临沂地区垂枝型木本植物种质资源调查与应用研究

为了对临沂地区的生态环境和园林绿化建设提供参考,对临沂地区主要垂枝型木本植物进行实地调查。结果表明,临沂地区园林中应用的垂枝型木本植物共有10种,隶属于7科9属,其中乔木2种、灌木8种。在调查研究的基础上,收集并保存优良垂枝型木本植物10种,并开展垂枝型木本植物种质资源评价和应用研究。     

A knowledge-based expert system for planning and design of agroforestry systems

Computer-based Expert Systems that use knowledge, facts, and reasoning techniques to solve problems, normally requiring the abilities of human experts, are increasingly being used in many activities. The United Nations University (UNU) Agroforestry Expert System (AES) is a first attempt to apply this technique to agroforestry. UNU-AES is a prototype Knowledge-Based Expert System (KBES) designed to support land-use (agricultural, forestry, etc.) officials, research scientists, farmers, and individuals interested in maximizing benefits gained from applying agroforestry management techniques in developing countries. This prototype addresses the options for alley cropping, a promising agroforestry technology which has potential applicability when used under defined conditions in the tropics and subtropics. Alley cropping involves the planting of crops in alleys or interspaces between repeatedly pruned hedgerows of fast-growing, preferably leguminous, woody perennials. The primary benefits from this technique include nutrient enrichment, soil improvement, and erosion control. UNU-AES, which is the first known attempt at the application of expert system procedures in the field of agroforestry, uses a total of 235 decision rules to develop its recommendations. With the inclusion of more climatic and socio-economic data and improved advisory recommendations, UNU-AES can be expanded to provide advice on alley cropping in more diverse geographical and ecological conditions and eventually address other agroforestry techniques.     

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.     

Agroforestry and the environment

Agroforestry is a traditional land use system that may contribute to the solution of environmental problems in agriculture. Agroforestry is the practice of deliberately integrating woody vegetation (trees or shrubs) with crops and/or animal systems to benefit from the resulting ecological and economic interactions. Recent research indicates that a wider adoption of agroforestry principles and practices is a key means by which the global agri-food sector might achieve more sustainable methods of food and fiber production by producing both economic benefits for farmers and environmental benefits for society. Agroforestry provides numerous provisioning, regulating, cultural and supporting ecosystem services and environmental benefits while promoting eco-intensification based on a more efficient use of the resources. Nevertheless, there is only little published recent information on the contribution of agroforestry to the environment in general and on climate change, carbon sequestration and forest fires in particular. In this special issue a number of articles are included that provide a kaleidoscope of the environmental benefits that agroforestry provides to the environment.

     

ICRAF Field Station at Machakos

ICRAF has a Field Station at Machakos, 70 km south-east of Nairobi on a 40-ha site. It provides a good collection of a large number of multipurpose trees and shrubs useful in agroforestry, experimental designs, agroforestry technologie,, demonstration oof some agroforestry practices and interventions such as alley cropping, soil conservation technologies, etc. These demonstration-and trial-plots that are conducted by the Council's multidisciplinary team of scientists are also used to a limited extent for obtaining scientific information on the performance of the various species involved and of their response to management as well as interactions. The Station is visited regularly by an average of 350 individuals of various types per year, and is used for different kinds of training and field demonstrations.Principal Scientist, ICRAF     

Temperate agroforestry research: considering multifunctional woody polycultures and the design of long-term field trials

The many benefits of agroforestry are well-documented, from ecological functions such as biodiversity conservation and water quality improvement, to cultural functions including aesthetic value. In North American agroforestry, however, little emphasis has been placed on production capacity of the woody plants themselves, taking into account their ability to transform portions of the landscape from annual monoculture systems to diversified perennial systems capable of producing fruits, nuts, and timber products. In this paper, we introduce the concept of multifunctional woody polycultures (MWPs) and consider the design of long-term experimental trials for supporting research on agroforestry emphasizing tree crops. Critical aspects of long-term agroforestry experiments are summarized, and two existing well-documented research sites are presented as case studies. A new long-term agroforestry trial at the University of Illinois, “Agroforestry for Food,” is introduced as an experiment designed to test the performance of increasingly complex woody plant combinations in an alley cropping system with productive tree crops. This trial intends to address important themes of food security, climate change, multifunctionality, and applied solutions. The challenges of establishing, maintaining, and funding long-term agroforestry research trials are discussed.     

Improving multipurpose tree and shrub species for agroforestry systems

With the aid of an example of ICRAF's tree improvement research programme for the highlands of Eastern and Central Africa, a logical approach to selection and breeding of multipurpose trees and shrubs in agroforestry context is proposed. Criteria for selection of high priority species are proposed. Some species of high potential for agroforestry development in Sub Sahara Africa are proposed. The necessary sequential research steps are discussed.     

普洱市城市绿地系统树种规划研究

分析云南省普洱市城市绿地系统园林植物应用和自然植被现状及存在的问题,提出了根据地带性植被特征确定城市绿地树种的主要经济技术指标．在此基础上,规划基调树种10种,骨干树种20种,并根据树木观赏特性规划了其他树种,其中乔木树种110种、花灌木165种、藤本12种、竹类6种．     

Comparative growth performance of some multipurpose trees and shrubs grown at Machakos,Kenya

Growth rates of 29 multipurpose trees grown in an agroforestry arboretum for six years at a sub-humid to semi-arid climatic zone are presented. Exotic species such as Grevillea robusta, Sesbania grandiflora, Leucaena leucocephala, Cassia siamea and Sesbania sesban, some of which were outside their traditional climatic zones, had higher diameters, heights and bole volumes/tree (upto 130% more in certain cases) than of the indigenous species. However, poor performance of several species (both exotic and indigenous) would limit their agroforestry potentials at the evaluation site or other similar areas.     

Why tree-crop interactions in agroforestry appear at odds with tree-grass interactions in tropical savannahs

This paper describes recent research findings on resource sharing between trees and crops in the semiarid tropics and attempts to reconcile this information with current knowledge of the interactions between savannah trees and understorey vegetation by examining agroforestry systems from the perspective of succession. In general, productivity of natural vegetation under savannah trees increases as rainfall decreases, while the opposite occurs in agroforestry. One explanation is that in the savannah, the beneficial effects of microclimatic improvements (e.g. lower temperatures and evaporation losses) are greater in more xeric environments. Mature savannah trees have a high proportion of woody above-ground structure compared to foliage, so that the amount of water 'saved' (largely by reduction in soil evaporation) is greater than water 'lost' through transpiration by trees. By contrast, in agroforestry practices such as alley cropping where tree density is high, any beneficial effects of the trees on microclimate are negated by reductions in soil moisture due to increasing interception losses and tree transpiration. While investment in woody structure can improve the water economy beneath agroforestry trees, it inevitably reduces the growth rate of the trees and thus increases the time required for improved understorey productivity. Therefore, agroforesters prefer trees with more direct and immediate benefits to farmers. The greatest opportunity for simultaneous agroforestry practices is therefore to fill niches within the landscape where resources are currently under-utilised by crops. In this way, agroforestry can mimic the large scale patch dynamics and successional progression of a natural ecosystem. This revised version was published online in June 2006 with corrections to the Cover Date.     

豆科树种无性快速繁殖技术研究与进展

豆科树种目前已广泛应用于荒山绿化、饲用及观赏。文中从扦插(嫩枝扦插、硬枝扦插、根插)，组织培养等方面综述了豆科树种无性快速繁殖技术的研究和进展。指出目前豆科树种嫩枝扦插技术研究还局限在对某一树种繁殖途径的探索阶段；硬枝扦插技术研究较为系统和深入，对不同树种扦插生根的影响因素有了比较深入的了解，并因此建立起较为成熟的技术体系；根插方法简单，成活率高，但是研究普遍较少；豆科树种组织培养虽较为困难，但某些树种也已经建立起了较为完善的再生体系。此外，还对豆科树种快速繁殖的生理基础研究进行了讨论，建议加大对豆科树种快速繁殖技术和生理机制的研究力度，为解决优良种质资源快速扩繁奠定基础。     

Designing forest vegetation management strategies based on the mechanisms and dynamics of crop tree competition by neighbouring vegetation

Plant interactions can be defined as the ways plants act uponthe growth, fitness, survival and reproduction of other plants,largely by modifying their environment. These interactions canbe positive (facilitation) or negative (competition or exploitation).During plantation establishment or natural forest regenerationafter a disturbance, high light levels and, sometimes, increasedavailability of water and nutrients favour the development ofopportunistic, fast-growing herbaceous and woody species whichcapture resources at the expense of crop trees. As a consequence,the growth and survival of crop trees can be dramatically reduced.Although the effects of this competition are well documented,the physical and physiological mechanisms of competition arenot. Moreover, the competition process is never constant intime or space. We present a conceptual competition model basedon plant growth forms common in global forests, i.e. graminoids,forbs, small shrubs, large shrubs and mid-storey trees, andmain-storey trees. Their competitive attributes and successionaldynamics are examined. An overview is presented on the way forestvegetation management (FVM) treatments influence these componentsand outcomes regarding crop tree performance and diversity conservation.Finally, a synthesis of literature yields FVM guidelines forefficiently optimizing crop tree performance and safeguardingdiversity. Future research needs to further sustainable FVMare presented.     

云霄县木本植物资源调查与评价

通过实地调查、样地分析,对云霄县的木本植物资源开展了调查.结果表明:云霄县境内有木本植物114科378属832种,其中野生木本植物有89科260属601种,栽培的木本植物73科173属277种,优势科为蔷薇科、茜草科、豆科等26科,优势属为以悬钩子属、冬青属、榕属等41属.乔木315种、灌木364种、木质藤本128种、...     

Elevation patterns of woody taxa richness in the evergreen Afromontane vegetation of Ethiopia

Plant species distributions show patterns along elevation gradients. Regardless of the diverse Afromontane vegetation in Ethiopia(AFE), studies of elevation patterns of woody plants are limited and they are restricted to small areas or single/few Mountains. Moreover, there is no general consensus on the patterns of woody taxa distribution by elevation. The objectives of this study were to examine the elevation patterns of woody taxa richness and their relationship with elevation in the AFE. Data were collected and compiled from the Flora of Ethiopia and Eritrea(Vols. 1–7). About 5918 plant species of 243 families were examined and their elevational distributions were recorded. The distributional ranges of woody taxa were aggregated at 19 points(sites) at 100 m intervals starting from 1500 to 3400 m a.s.l. Single-factor analysis of variance(one-way ANOVA) was used to test the hypothesis that mean species richness of woody taxa decreases from the lower to the upper limit of AFE. Simple linear correlation and regression were used to show the relationships of woody taxa richness with elevation. We documented the presence of 505 woody taxa(441 species,31 subspecies and 33 varieties) representing 267 genera and 90 families in the AFE. In terms of habit, 279 taxa are shrubs, 178 are trees and 48 are lianas. The distribution of woody taxa(trees, shrubs and lianas) showed a slight increase at the lower portion and a monotonic decline with increasing elevation. Species richness of trees, shrubs and lianas was negatively and significantly correlated with elevation(r =-0.985,-0.984,-0.981, respectively; all p 0.001). Our hypothesis was accepted because mean richness significantly decreased from the lower to the upper limit of AFE(p 0.001). Generally, monotonic patterns of decline in richness were observed for trees, shrubs and lianas. The contribution of shrubs to total richness increased with increasing elevation whereas that of trees and lianas decreased.