Shelter efficiency of some traditional windbreaks in Tanzania

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University of Dar es Salaam
This study quantifies the wind protection aspects of single trees, and of combinations of scattered trees in a savanna woodland and a coffee cum shade trees system, as found in traditional Tanzanian agricultural practice. Anemometers, used as the main indicator in the wind protection studies, were compared and calibrated in a nearly homogeneous natural wind field within an accuracy of ± 2 %. The use of shaded Pichetmometer for measuring wind speed in roforest systems was also investigated. Their use in such systems is recommended, provided that an error of the order of 10 % is acceptable. Wind protection around the isolated single trees studied were found to be relatively poor. Our results showed appreciably greater protection at 2.5 m height than at 1.0 m, which is due to the leafy areas of the plants at the upper level in contrast to bare stems at the lower level. Investigation of wind speed reduction in the woodland showed indeed that the trees have collectively and cumulatively a significant influence in wind speed reduction compared to isolated ones. Wind speed reduction for average lines parallel to the wind direction confirmed a simple hypothesis we made, that before saturation points wind speed reduces on the average linearly along these lines. Wind speed reduction in the shade tree cum coffee system was on the average 0.53 when the shade and coffee trees were not pruned and stumped respectively. After pruning and stumping, this reduction decreased by nearly 30 %. Preservation of indigenous vegetation in arrays suitable for the intended farming system in the initial stages of planning and developing cropland is emphasized. The influence of tree (crown) management in these agroforestry systems and optimum tree combinations and planting densities in scattered form, like in our woodlands, are suggested as possible subjects on wind protection for further studies.
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Windbreaks, shelterbelts, Tanzania
Kainkwa, R.R.M (1992) Shelter efficiency of some traditional windbreaks in Tanzania, Doctoral dissertation,University of Dar es Salaam. Available at ( )