Browsing by Author "Mosha, Simon John"

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Basic density and strength properties of grevillea robusta cunn. and cordia afrjcana lam. grown in agroforestry in Moshi, Kilimanjaro, Tanzania.
(Sokoine University of Agriculture, 1999) Mosha, Simon John
Basic density and some strength properties of wood from Grevillea robusta Cunn. and Cordia africana Lam. grown in agroforestry in Moshi, Kilimanjaro region were studied with an overall objective of assessing the quality of these agroforestry tree species. The specific objectives were to conduct survey of end uses of the wood from G.robusta and C.ajricana grown in agroforestry, to determine tree characters such as tree form, branching habit and crown size, basic density and its variation within and between these tree species, some strength properties (Modulus of elasticity, Modulus of rupture, Work to maximum load, Total work, compression, shear and cleavage) and their variation within and between these tree species and the relationship between basic density and the strength properties for the two species. Sampling and data collected were done using standard methods according to Lavers (1969). Data analysis were done using both qualitative statistics and computer statistical analysis programme (SAS). The main results were as follows: the current end uses for these species were construction, furniture, fuelwood, shade for coffee, fodder, poles, tool handles, amenity, utensils and medicine. trees of C. africana had larger crown size and diameter at breast height (dbh) than G. robusta. Trees of G. robusta had longer and more straight bole (9.5 m) than that of the former (5.5 m). G .robusta also had slightly larger proportion of heartwood (65%) than C. africana (64%). Average basic density for G. robusta and C. africana were 0.48 g/cm3 and 0.37 •5 g/cm respectively. Basic density showed significant difference between sites, species, trees and within trees. Average strength property values for G .robusta and C. africana were; Modulus of elasticity (4988.0 N/mm2 and 4711.3 N/mm2) Modulus of rupture (47.85 N/mm2 and 47.46 N/mm2), Work to maximum load 0.07 mmN/mm3 and 0.06 mmN/mmJ, total work (0.11 mmN/mm3 and 0.10 mmN/mm3) respectively. Other strength properties were Compression (30.8 N/mm2 and 27.11 N/mm2), Shear (8.37 N/mm2 and 7.34 N/mm2) and Cleavage (16.29 N/mm and 12.35 N/mm) respectively. For all strength properties studied, there were significant differences between the two species, site, trees and within trees of the same species. G. robusta was found to be stronger than C. africana. For both species, trees from the lower altitude zone were stronger than those at higher altitude zone. It is recommended that, wood from G. robusta should be used where high strength is required. C. africana trees are suitable for shade due to their larger crown size. Denser and stronger timber should be selected from the low altitude zone.