Surveying farmers' agroforestry plots: experiences in evaluating alley-cropping and tree border technologies in Western Kenya

Evaluation of existing on-farm agroforestry plots should provide useful supplementary information for the design of improved agroforestry systems, in both research and development projects. Such evaluation has been little used, however, largely due to the methodological difficulties of surveying highly variable on-farm plots, and difficulties in identifying key variables for measurement. This paper describes a set of methods and tools used in evaluating plots of alley-cropping and tree borders around crop fields established by farmers working with the CARE Agroforestry Extension Project in western Kenya. Details of survey design, sampling, and implementation are discussed, and suggestions made for carrying out agroforestry surveys in other projects. A condensed version of the questionnaire is appended.     

Structure-function relationships during secondary phloem development in an angiosperm tree,Aesculus hippocastanum: microtubules and cell walls

We studied the dynamics of the cortical microtubule (CMT) cytoskeleton during differentiation of axial secondary phloem elements in taproots and epicotyls of Aesculus hippocastanum L. (horse-chestnut) saplings. Indirect immunofluorescence microscopy of alpha-tubulin and transmission electron microscopy revealed that fusiform cambial cells possessed a reticulum of CMTs in which individual microtubules were randomly arranged. During differentiation of these cambial cell derivatives into secondary phloem cells, the CMTs were rearranged to become helically oriented, regardless of phloem cell type. Although helical CMTs were a persistent feature of all axial elements of the secondary phloem (sieve elements, companion cells, phloem parenchyma, and fiber-sclereids), some modifications of this arrangement occurred as cells differentiated. Thus, at late stages of cell differentiation, sieve elements possessed nearly transverse CMTs, pronounced bundling of CMTs was seen in phloem parenchyma, and the density of CMTs in the helical arrays of fibers increased markedly. Additionally, phloem parenchyma possessed rings of CMTs in association with developing pit areas. Aspects of the development and chemistry of cell walls were also examined during phloem cytodifferentiation.     

Parasitoid Wasps as Flower Visitors in the Canadian High Arctic

Summary Collections and observations were made in 1963 and 1967 on insects visiting flowers at Hazen Camp and Gilman Camp on Ellesmere Jsland, N. W. T. Canada. The results giving the species of parasitoid Hymenoptera, the flowers visited, and their activity, are shown in this paper (Table 1).18 species with 50 specimens of 13 genera are listed. Most of them could be found feeding in the nectar of flowers and carrying pollen.The attractiveness of white blooms to parasitoid wasps, observed in different regions, also holds in the High Arctic, whereStellaria longipes visitors account for 35 in 7 genera out of a total of 41 in 13 genera.

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Zusammenfassung Parasitische Schlupfwespen als Blütenbesucher im kanadischen hohen Norden Im Sommer 1963 und 1967 wurden im Hazen Camp und Gilmann Camp auf der hochnordischen Ellesmere-Insel Beobachtungen und Sammlungen bezüglich Blüten besuchender Insekten durchgeführt. In der vorliegenden Arbeit sind in Tabelle 1 die gefundenen parasitischen Hymenopteren zusammengestellt.18 Arten mit 50 Individuen aus 13 Gattungen wurden gefunden, und zwar aus den Familien Chalcididae (3 Arten), Eulophidae (1), Pteromalidae (1), Braconidae (3), Ichneumonidae (9) und undeterm. (1). Am häufigsten war mit 22 Individuen die IchneumonideStenomacrus spec. anStellara-, Saxifraga- undDryas- Blüten vertreten. Es scheint, daß alle Ichneumoniden-Arten Nektar als Betriebsstoff für ihren Flug aufnehmen. Aber auch je eine Chalcididen-, Eulophiden- und Pteromaliden-Art wurden als Nektarfresser festgestellt.Von jeder beobachteten und anschließend gefangenen Schlupfwespe wird die Tätigkeit an der Pflanze skizziert. Am Körper der meisten Arten fanden sich Pollenkörper. Die in der Literatur aus anderen Gebieten der Erde berichtete besondere Attraktivität weißer Blüten auf parasitische Hymenopteren. wurde auch im Hohen Norden beobachtet: an den weißen Blüten vonStellaria longipes wurden 35 von 41 einzeln registrierten Individuen aus 7 Gattungen angetroffen.

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Contribution No. 920,Plant Research Institute of Agriculture, Canada Department, Ottawa, Canada.     

Antimicrobial flavonoids from the stem bark of Erythrina burttii

The chloroform extract of the stem bark of Erythrina burttii showed antifungal and antibacterial activities using the disk diffusion method. Flavonoids were identified as the active principles. Activities were observed against fungi and Gram(+) bacteria, but the Gram(-) bacteria Escherichia coli was resistant.     

Guidelines for Managing Wildlife Habitats in Southwestern Ponderosa Pine Forests of the United States

IntroductionEcoledcalrelahonshipsanddePendenceofwildlifesPe-ciesonsouthwesternPOnderosapine(Pineponderosa)fOrestsarecloselyrelat6dtohabitatuse.Foraginghabits,seasOndfoodPreferences,anduseoftreesforfeedingarelawtydePendentuponthestrUctureandspahalar-rangme…     

Reimplementation of the Biome-BGC model to simulate successional change

Biogeochemical process models are increasingly employed to simulate current and future forest dynamics, but most simulate only a single canopy type. This limitation means that mixed stands, canopy succession and understory dynamics cannot be modeled, severe handicaps in many forests. The goals of this study were to develop a version of Biome-BGC that supported multiple, interacting vegetation types, and to assess its performance and limitations by comparing modeled results to published data from a 150-year boreal black spruce (Picea mariana (Mill.) BSP) chronosequence in northern Manitoba, Canada. Model data structures and logic were modified to support an arbitrary number of interacting vegetation types; an explicit height calculation was necessary to prioritize radiation and precipitation interception. Two vegetation types, evergreen needle-leaf and deciduous broadleaf, were modeled based on site-specific meteorological and physiological data. The new version of Biome-BGC reliably simulated observed changes in leaf area, net primary production and carbon stocks, and should be useful for modeling the dynamics of mixed-species stands and ecological succession. We discuss the strengths and limitations of Biome-BGC for this application, and note areas in which further work is necessary for reliable simulation of boreal biogeochemical cycling at a landscape scale.     

Photosynthetic gas exchange and accumulation of phytotoxins in mangrove seedlings in response to soil physico-chemical characteristics associated with waterlogging

We evaluated photosynthetic gas exchange and the accumulation of iron, manganese and sulfur in seedlings of five mangrove species (Aegiceras corniculatum (L.) Blanco, Avicennia marina (Forsk.) Vierh., Bruguiera gymnorrhiza (L.) Lamk., Hibiscus tiliaceus L. and Rhizophora stylosa Griff.) growing under anoxic soil conditions at low irradiance. Seedlings of the viviparous mangroves showed no significant responses to root anoxia. The presence of ferrous sulfate or manganous sulfate had a smaller effect on CO(2) assimilation, transpiration rate and stomatal behavior than the presence of sodium sulfide. Sodium sulfide inhibited photosynthetic gas exchange and caused complete stomatal closure in all species. Stomatal closure was probably the result of the damaging effect of sulfide ions on root cell membranes. Some leaf epinasty and wilting were also observed in response to the Na(2)S treatment in all species. A combination of FeSO(4), MnSO(4) and Na(2)S had a smaller effect on photosynthesis than Na(2)S alone, especially for Avicennia marina and Rhizophora stylosa seedlings, which maintained appreciable rates of CO(2) assimilation (2.49 and 3.84 &mgr;mol m(-2) s(-1), respectively) in the presence of all three phytotoxins. Roots of phytotoxin-treated seedlings of all species accumulated significant amounts of the corresponding toxin compared with roots of the control plants. The FeSO(4) or MnSO(4) treatments had no effect on foliar concentrations of iron or manganese, whereas the Na(2)S treatment resulted in an accumulation of S in the leaves of all species. Interactions between Fe(2+) and Mn(2+) and sulfide in the culture medium appeared to reduce their uptake by the seedlings. We conclude that high concentrations of sulfides in mangrove sediments may adversely affect both growth and survival of mangrove seedlings at low irradiances.     

Biogeography of mangrove and saltmarsh vegetation: implications for conservation and management in Australia

Despite an undeserved reputation for being dull and homogenous systems, mangal and saltmarsh in Australia have highly complex patterns and processes. Their role as key edge systems between land and sea has implications for many species which have larval stages in mangal and saltmarsh, but spend adult life as benthic, pelagic or demersal species. Many such species are also important commercially. Mangal and saltmarsh are both highly dynamic systems, reacting rapidly to changes in hydrological condition and sedimentation. In many areas of the world mangal and saltmarsh are threatened systems, especially near human habitation. Appropriate management strategies for mangal and saltmarsh are therefore critical for both conservation and sustainable use, the two key objectives of the Convention on Biological Diversity. Clearing and associated development, invasion of alien species, pollution effects and poor management are the key threats to these systems. Management at a bioregional level, including the development of a comprehensive system of protected areas, is identified as the key management strategy which will ensure an adequate future for these dynamic systems.     

An evaluation of the Acacia albida-based agroforestry practices in the Hararghe highlands of Eastern Ethiopia

Growing Acacia albida as a permanent tree crop, on farmlands with cereals, vegetables and coffee underneath or in between, is an indigenous agroforestry system in the Hararghe highlands of Eastern Ethiopia. However, there is practically no systematic record or data on the merits and benefits of this practice.The paper presents the results of an investigation into the effects of the presence of A. albida on farmlands on the yield of maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench). Twenty seven plot pairs each consisting of one plot underneath the A. albida foliage cover and the other in the open, away from the tree-on farmers' fields, in a 40 km radius around the Alemaya College of Agriculture, were sampled and the yield components analyzed. A statistically significant increase in crops yields by 56% on average was found for the crops under the tree canopies compared to those away from the trees. This increase was caused by the improvement in 1000 grain weight and number of grains of plants under the tree, indicating that the trees enhanced the fertility status of the soil and improved its physical conditions in terms of crop growth.Additional benefits from the A. albida trees include supply of fuelwood and fodder. Quantitative estimates of these outputs as well as their monetary values are presented in the paper. However, in order to realize these benefits to a discernible extent, higher stand densities of the tree than at present are required.Based on an enquiry about the farmers attitude towards A. albida, the prospects for an extension of this promising agroforestry technique are discussed against the background of the state and trends of development of agriculture in the area. It is surmised that despite some shortcomings like the relatively slow and highly variable growth of A. albida and a conflict with the spreading cultivation of Ch'at (Catha edulis Forsk.), the prospects of extension of this technique are good. It is recommended that its propagation should be incorporated into the programmes of the extension agencies of the various governmental agencies concerned with land use.