Basic density and strength properties of grevillea robusta cunn. and cordia afrjcana lam. grown in agroforestry in Moshi, Kilimanjaro, Tanzania.
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Date
1999
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Publisher
Sokoine University of Agriculture
Abstract
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.
Description
A dissertation submitted in partial fulfilment of the requirements for the degree of master of
science in forestry
Keywords
Grevillea robusta cunn, Cordia afrjcana lam, Agroforestry, Moshi, Kilimanjaro, Tanzania