Mechanical properties of tree roots for soil reinforcement models

Evidence from forestry has shown that part of the forest floor bearing capacity is delivered by tree roots. The beneficial effect however varies and diminishes with increasing number of vehicle passes. Roots potential for reinforcing the soil is known to depend among others on root mechanical properties, distribution, morphology, etc. Rooting intensity and root patterns of forest trees are complicated, but some information is available. The objectives of this study are therefore as follows: (1) addressing the occurrence of field traffic on forest soils, (2) identifying root mechanical properties that play a role in soil reinforcement, (3) measuring root stress-strain relationships, root failure stress and strain and root behaviour under repeated loading and (4) simulating root reinforcement effect using a FEM (Finite Element Method) code capable of accounting for root properties in reinforcement simulations.The repeated loading experiments included repeated loading of tree roots to different loading levels and loading with different loading rates or elongation rates. These studies revealed that tree roots possess stiffness and failure strengths. They show elastic as well as plastic behaviour. They also show fatigue phenomena in repeated loading. Available FEM codes were studied with respect to their capability in dealing with soil reinforcement by roots. PLAXIS which is a commercially available FEM code was used due to its ability to calculate stresses, strains and failure states of soil mechanical problems. It can also cope with unsaturated reinforced soil. The finite element calculations conducted with PLAXIS are intended for soils loaded by forestry vehicles. These involved situations with and without reinforcement by tree roots. The reinforcement effects are, among others, decrease of wheel rut depth and rolling resistance, decrease of damage to soil structure by the wheel load and as a negative effect, physiological damage to the tree root system. The magnitude of these effects depends on a number of parameters: stiffness and strength of the tree roots, soil mechanical properties like cohesion, angle of internal friction, compression index, preconsolidation stress, depth of a hard sublayer (if present), distance between vehicle and tree, rooting patterns, adhesive and frictional properties of the soil-root interface, wheel load and contact surface. The presented simulation results, which are based on realistic input data, show the sensitivity of the reinforcement effect to the listed variables.</p

Gender Mainstreaming: Who Wins? Gender & Irrigated Urban Vegetable Production in West Africa

Gender roles in agriculture can be quite specific, not only in view of particular labor inputs during the production cycle but also in terms of who farms and who trades certain crops. Using data collected over ten years in West Africa, this study looked at market-oriented urban vegetable production in West Africa and Ghana in particular. Gender disaggregated data on key issues such as access and control of resources, division of tasks, decision-making process and challenges faced was collected from farmers and traders. With several exceptions, a clear gender distinction emerged across the sub-region: men dominate urban vegetable farming, while women manage vegetable marketing. The general differentiation is attributed to societal norms, but other factors play a role as well. Female farmers, for example, feel constrained by existing irrigation practices that are energy-intensive and conflict with household duties. Male farmers, on the other hand, feel significantly oppressed by their dependency on credit and prices dictated by market women, and feel disadvantaged when entering the vegetable retail market. Improved irrigation technology could facilitate a better gender balance on the farm, but mainstreaming gender balance in vegetable wholesale and retail is likely to disadvantage women

Dry spells and evidence for scaling of agricultural water management and smallholder irrigation in northern Ghana

United States Agency for International Developmen

Post-landslide soil and vegetation recovery in a dry, montane system is slow and patchy

Landslides are common disturbances in forests around the world, and a major threat to human life and property. Landslides are likely to become more common in many areas as storms intensify. Forest vegetation can improve hillslope stability via long, deep rooting across and through failure planes. In the U.S. Rocky Mountains, landslides are infrequent but widespread when they do occur. They are also extremely understudied, with little known about the basic vegetation recovery processes and rates of establishment which restabilize hills. This study presents the first evaluation of post-landslide vegetation recovery on forested landslides in the southern Rocky Mountains. Six years after a major landslide event, the surveyed sites have very little regeneration in initiation zones, even when controlling for soil coverage. Soils are shallower and less nitrogen rich in initiation zones as well. Rooting depth was similar between functional groups regardless of position on the slide, but deep-rooting trees are much less common in initiation zones. A lack of post-disturbance tree regeneration in these lower elevation, warm/dry settings, common across a variety of disturbance types, suggests that complete tree restabilization of these hillslopes is likely to be a slow or non-existent, especially as the climate warms. Replacement by grasses would protect against shallow instabilities but not the deeper mass movement events which threaten life and property

Effects of information, education, and communication campaign on a community-based health insurance scheme in Burkina Faso

Objective : The study analysed the effect of Information, Education, and Communication (IEC) campaign activities on the adoption of a community-based health insurance (CHI) scheme in Nouna, Burkina Faso. It also identified the factors that enhanced or limited the campaign&#x0027;s effectiveness. Design : Complementary data collection approaches were used. A survey was conducted with 250 randomly selected household heads, followed by in-depth interviews with 22 purposively selected community leaders, group discussions with the project management team, and field observations. Bivariate analysis and multivariate logistic regression models were used to assess the association between household exposure to campaign and acquisition of knowledge as well as household exposure to campaign and enrolment. Results : The IEC campaign had a positive effect on households&#x2019; knowledge about the CHI and to a lesser extent on household enrolment in the scheme. The effectiveness of the IEC strategy was mainly influenced by: 1 frequent and consistent IEC messages from multiple media channels (mass and interpersonal channels), including the radio, a mobile information van, and CHI team, and 2 community heads&#x2019; participation in the CHI scheme promotion. Education was the only significantly influential socio-demographic determinant of knowledge and enrolment among household heads. The relatively low effects of the IEC campaign on CHI enrolment are indicative of other important IEC mediating factors, which should be taken into account in future CHI campaign evaluation. Conclusion : The study concludes that an IEC campaign is crucial to improving the understanding of the CHI scheme concept, which is an enabler to enrolment, and should be integrated into scheme designs and evaluations

Many Rivers To Cross

The central concept in this article is that of “Educability” operation defined as the ‘probability that children will earn what they are supposed to learn' and with the factors both genetic and environmental which affect this. The main emphasis, although not the only one is on factors related to cognitive development since so much of the current theory and practice of curriculum development and methods of teaching is dependent on notions about the nature of cognition. Much of the research on the development of cognitive skills and hence of the derived theory were carried out with Western children. Hardly were the minority used. Similarly most of the curriculum building based on the theories has gone on in Western educational systems. We adapt such curricula, almost unaltered and in other cases in our current jargon “adapted to meet our local needs”. But very seldom, if ever have we questioned their fundamental psychological basis. Do the theories of cognitive development on which they rest stand up in the Ghanaian context or do the children in Ghana, develop cognitive concepts in Mathematics just the same way as British children? If not, what the modes of concepts formation and Ghanaian children and what are the implications for curriculum development for teaching/learning. (Mathematics Connection: 2001 2: 61-64

Test speed and other factors affecting the measurements of tree root properties used in soil reinforcement models

Measured values of the mechanical properties of tree roots are found to be affected by a number of factors. Shear properties of tree roots are found to be partly influenced by size of the testing equipment, level of soil compaction, deformation of the root material and estimated width of the shear zone in the soil, etc. Among others, tensile root properties are found to be affected by factors such as season, age, root types or species, root preparation before experiment, clamping procedure of the root, and rate of elongation used. The aims of this paper were (1) finding an appropriate clamping procedure for root measurements; and (2) studying the effect of elongation rate on stress–strain relationships of beech (Fagus sylvatica L.) roots. It was found that problems associated with root clamping (i.e., in root experiments) such as breakage of the root sample close to the jaws of the clamping devices and slippage may be eliminated by introducing wooden blocks of appropriate hardness within the jaws of the clamps and exerting a suitable clamping force, respectively. An appropriate wood hardness and suitable clamping force were found by conducting a number of initial trial experiments. Tensile experiments conducted with beech roots pairs showed that elongation rate does influence the stress–strain relationships of roots. In general, stress values of beech roots were found to increase between 8 and 20% for an increase in the rate of elongation from 10 to 400 mm/min. Similar findings have been reported in textile fibres