Diversity of Glomale Mycorrhizal Fungi in Maize/Sesbania Intercrops and Maize Monocrop Systems in Southern Malawi

The study investigated diversity and frequency of occurrence of glomale (Arbuscular- or Vesicular Arbuscular-) mycorrhizal fungi on three farming systems in a drought prone and nitrogen deficiency site in southern Malawi. The farming systems comprised of two agroforestry systems of Sesbania sesban (L) Merr intercropped with maize and Sesbania macrantha E Phillips & Hutch. intercropped with maize and a maize monocrop systems without fertilizer, with nitrogen, phosphorus and a combination of nitrogen and phosphorus. Species diversity and species frequency of occurrence were examined in soil samples obtained in the dry and wet seasons. Twelve glomale mycorrhizal species were recorded, four species being in the genus Acaulospora, four in Glomus, two in Gigaspora and two in Scutellospora. Species diversity in the two agroforestry systems were not significantly (p ≤ 0.05) different but had lower species diversity than maize monocrop with only Sesbania macrantha intercropped with maize significantly (p ≤ 0.05) lower. Species diversity was significantly increased by the inorganic nitrogen fertilizer. Inorganic phosphorus fertilizer had no effect. The study shows that the occurrence and persistence of glomale species are influenced by agroforestry combinations, and that the spores of most species are tolerant to dry conditions. Only four species responded to fertilizer application with the occurrence of spores of some species high and some low. Management practices have great implication in the persistence of spore propagules of glomale species. The order Glomale was revised in 2001 and upgraded to a phylum Glomeromycota.     

Erythrina brucei: Propagation attributes, leaf nutrient concentration and impact on barley grain yield

Erythrina brucei Schweinf. emend. Gillett (Papilionaceae),a tree species that is endemic to Ethiopia, is known to possess useful agroforestry attributes, but these attributes have not been quantified. To achieve this, propagation of the species, growth rate of young trees and their impact on barley (Hordeum vulgare L.), and leaf-nutrient concentrations were examined. Germination of seeds planted in plastic pots varied from 73 to 93%, and direct seeding in the field yielded 83%germination. Branch cuttings obtained from 2 to 3-year-old stock plants (n =150) resulted in 70 to 80% rooting within 8 to 12 weeks after setting cuttings into the rooting medium. Considerable nodulation occurred on leaves one year after planting out seedlings and stecklings. Leaf concentrations of Mg, N,P, and S were significantly lower in nodulated than in the non-nodulated leaves. On the other hand, leaf Fe concentration was higher in nodulated than in the non-nodulated leaves. There was no significant difference in Ca and K contentsbetween the nodulated and non-nodulated leaves. E. brucei-treatment significantly increased tiller and seed numbers, as well as seed weight. However, thousand-grain weight and grain size were similar in harvests from E. brucei-treated and the control plots. The results indicate that the species is easy to propagate by seed and vegetative means, grows fast, is desirable for intercropping, and has relatively high leaf-nutrient concentration.This revised version was published online in November 2005 with corrections to the Cover Date.     

Spatially distributed morphological characteristics of macropores in forest soils of Hitachi Ohta Experimental Watershed, Japan

Morphological characteristics of macropores in forest soil profiles were investigated at Hitachi Ohta Experimental Watershed in Japan. Nine individual profiles at different locations (various spatial scales in a catchment) and twenty profiles at one site (a small spatial scale) were excavated to the bedrock to investigate density, origin, diameter, direction, and gradient of macropores. Macropore densities in a soil profile ranged from 3.5 to 29.1 per m and from 5.4 to 75.1 per m², respectively. Subsurface erosion, root channels, and interactions between subsurface erosion and root channels accounted for 36.9, 36.5, and 19.0%, of the described macropores. The mean macropore diameter in organic-rich soil layer (17–20 mm) was larger than in the B horizon (11–14 mm) at both spatial scales. The dominant gradients of all macropores in the organic-rich soil layer and B horizon were at negative oblique angles. Approximately 90% of the macropores in the organic-rich soil layer and approximately 80% of the macropores in the B horizon fell within the range between −50 and 50 degree planar direction. Subsurface flow and root systems are believed to play important roles in determining the morphological characteristics of macropores. These characteristics appear to have variable influences in different soil horizons rather than at different spatial scales. A part of this paper was presented at the 103th (1992) and 105th (1994) Annual Meetings of Japanese Forestry Society.     

Where's the beef?: Incorporating cattle into sustainable agroforestry systems in the Amazon Basin

Low external input agroforestry systems hold great promise as alternative, sustainable production systems for small-to-medium farmers in the Amazon Basin. The design of such systems is considered essential to stabilize agricultural production and avoid the cycle of continuing destruction of primary forest [Anderson A (1990) In: Anderson A (ed) Alternatives to Deforestation: Steps toward Sustainable Use of the Amazon Rain Forest pp 3–23. Columbia University Press, New York]. In order to be successful, these systems must be compatible with local ecological conditions and adoptable by farmers. Currently, many small-to-medium producers in the Amazon Basin use a slash and burn agricultural strategy that combines annual cropping with cattle grazing in mixed farming systems. While cattle play an important role in household economic survival, grazing-induced land degradation threatens the long-term viability of these farms [Loker W (1993) Human Organization 52(1)14–24]. This paper presents a model of a low external input agroforestry system that incorporates farmer preferences and practices but uses well-adapted grass-legume pastures, rotational grazing and the management of natural forest regeneration to enhance productivity in an ecologically sound manner. This system provides farmers with the benefits of both annual crops and cattle raising, avoids the land degradation that characterizes current practices and effectively incorporates trees into the production system.     

Characterization of wood-based multi-material systems under dynamic impact stress

ABSTRACT

Due to its naturally grown properties, wood has played a rather subordinate role as a material for technical applications up to now. In this paper, multi-material systems based on veneers of beech (Fagus sylvatica) with different reinforcing variants were investigated. In addition to the influence of different adhesive systems (urea formaldehyde and polyurethane), the effect of reinforcing by aramid fiber fabric and stainless steel foil in different climates was examined. At the center of the investigations were dynamically sudden loads, in the form of impact bending and dart drop tests (penetration and impact mode). It has been shown that the use of the reinforcing materials leads to a significant improvement in material properties. The penetration energy of the composites reinforced with the aramid fiber fabric could be increased by 43%. The maximum force in the dart drop test (impact mode) could be increased by 29% with the stainless steel foil, the damping decreased by 48%. The aramid fiber reinforcement achieved an increase in impact resistance by 27% in impact bending test, the steel reinforced achieved an increase of 39%. A clear dependency on both, the climate and the adhesive within the composite, could be demonstrated.     

A commentary on current approaches to forest population genetics

Some of the most frequently chosen approaches to forest population genetics as reflected in the present volume are discussed, and some topics possibly deserving more attention are addressed. Among the first are studies of self-fertilization as a characteristic of forest tree mating systems, gene markers as indicators of adaptive or phylogenetic differentiation, and methodological aspects of the measurement of genetic differentiation. The latter mainly concern generalizable methods of analysis and the involvement of gene markers in the determination of mating systems, detection of mechanisms of frequency dependent selection, and the incorporation of genetic profiles (characteristics of frequency distributions of genetic types) into population genetic analysis.     

The dynamic mating systems of conifers

Conifer mating systems vary among species and within species; both ecological variables and genetic variation cause mating systems to be dynamic. Within species, estimates of rates of outcrossing vary among populations, among loci, and among individuals within stands. The level of outcrossing varies with stand density, age, and the abundance of local and foreign pollen. Variation in the mating success of both males and females violates the assumption that populations are randomly mating and at equilibrium, and justifies more quantitative analyses of mating systems. Allelic frequencies in the pollen pool and in the pool of receptive female surfaces may vary through a season and among seasons, producing positively assortative mating in time. Seed and seedling viability selects against homozygotes for lethal alleles and favors heterozygous genotypes, biasing estimates of outcrossing. Particularly fruitful topics of research include the genetic consequences of polyembryony, differential male and female mating success, and associations between specific genotypes and floral phenology.     

Projecting the bird community response resulting from the adoption of shelterbelt agroforestry practices in Eastern Nebraska

Evolving agricultural policies have influenced management practices within agroecosystems, impacting available habitats for many species of wildlife. Enhancing wildlife habitat has become an explicit objective of existing agricultural policy. Thus, there is renewed focus on field borders and the use of shelterbelt agroforestry systems to achieve conservation goals in the Midwest. Two Representative Farms – a 283-ha dryland and 510-ha irrigated farm were created in Saunders County, Nebraska. The Habitat Analysis and Modeling System (HAMS) was used to describe the composition and spatial pattern of the existing farms and surrounding landscape, as well as for the landscapes surrounding selected Breeding Bird Survey (BBS) routes. Simulated land use changes resulting from the implementation of two shelterbelt scenarios, Agricultural and Wildlife, were incorporated on each Representative Farm and surrounding landscape. Landscape variables which influence breeding bird species richness and community composition as determined from BBS routes were measured on simulated farm landscapes. A more heterogeneous landscape results from implementing either scenario. The percent total woods was a significant determinant of bird species richness on the BBS routes and was important in influencing bird communities at the farm- and landscape-level. Other landscape metrics which influenced the bird community composition on BBS routes were woody edge percentages and edge density values. Policies promoting shelterbelts create edge habitats which ultimately favor birds within the Forest-edge/generalist guild while bird species in need of conservation such as grassland-field species would potentially be negatively affected. This revised version was published online in June 2006 with corrections to the Cover Date.     

Forest patches in Imperata grassland and prospects for their preservation under agricultural intensification in Northeast Luzon, The Philippines

Frequent burning and grazing and cultivation of cash crops increasingly threaten forest patches in hilly grassland in Northeast Luzon, yet their importance as a resource with multiple environmental functions and forest products persists. The aim of this study is to identify different types of forest patches, and their condition under present land-use intensification, and discuss prospects for their integration into sustainable local farming systems. Five types of forest patches are distinguished, both natural and planted ones, including rows of trees, woody patches, gallery forests, hill-slope forests and homegarden conglomerations. Natural woody patches and gallery forests in Imperata grassland are subject to degradation and land-use conversion under conditions of agricultural intensification. Woody patches in grassland affected by frequent burning and grazing cover small areas (66% below 50 m² as opposed to 28% in protected grassland) and contain relatively few woody plant species (25 woody species in total as opposed to 82 where protected). Yet where well managed, they may provide a variety of products for sale and subsistence, covering emergency needs and giving off-season cash income to rural communities. Moreover they serve like the gallery forest various ecological functions, carrying valuable indigenous tree species, retaining soil base nutrients, providing a continuous supply of organic matter and intercepting fine earth soil particles removed from bare surfaces. It is suggested that forest-patch management systems may be developed, taking into account both patch diversity and the diverse needs of rural communities, and to strengthen existing and undervalued functions of forest patches as permanent elements in an agricultural landscape.This revised version was published online in November 2005 with corrections to the Cover Date.     

黄土高原坡地林草复合系统景观边界植物多样性特征

以黄土高原坡地刺槐林—草地复合系统景观边界为研究对象,按一定的生态梯度调查分析了边界植物种的分布特点。结果表明,草地、林地斑块内都有自身的植物种类分布;草地斑块内有较高的植物多样性。在草地斑块内,距林缘8~16m区域为边界植物多样性边缘效应的显著区;林地斑块内β多样性变化剧烈,林缘处的群落相异系数(CD)、Cody指数都最大,共有度指数(CP)最小,CD、Cody与CP成反比。