Effects of spacing on growth,yield and wood properties of Tectona grandis at Longuza forest plantation, Tanzania
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Date
2024
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Publisher
Sokoine University of Agriculture
Abstract
In forest management, understanding the influence of spacing on
tree growth is crucial, as it goes hand in hand with stand growth as
well as yield at the final harvest. Also, spacing, especially narrow
spacing, has been used to control the stem quality of trees, as it
influences the stem straightness as well as the branching behaviour.
On the other hand, tree growth, particularly radial growth, means an
increase in wood materials such as cell wall substances, latewood,
and earlywood. Those wood materials influence the physical and
mechanical properties of wood. Behind those influences, an
understanding of the influence of spacing on the final harvest is
required to decide on appropriate spacing to economize the value of
the final harvest. However, information on the spacing influence on
growth, yield, and wood properties of Tectona grandis at an older
age in Tanzania is limited. Thus, this study is intended to evaluate
the influence of spacing on the growth, yield, and wood properties of
24-year-old Tectona grandis at Longuza Forest plantation, Tanzania.
Data were collected from a spacing trial with a randomized complete
block design with three treatments, namely 2 x 2 m, 3 x 3 m, and 4 x
4 m, replicated three times. For growth and stem quality, all trees'
diameter at breast height (dbh), height, and stem quality were
evaluated. Then, dbh data were used to obtain basal area (Ba),
volume, and the mean annual increment (MAI). Furthermore, three
trees from each spacing were sampled for physical and mechanical
properties.
The basic density (BD) was determined using
over-dry weight and green volume, while the heartwood (HW)
percentage was calculated using the cross-sectional area of the HW
and disk underbark. Moreover, all mechanical properties were tested
using a Monsanto tensiometer machine. An analysis of variance
(ANOVA) was used to evaluate the influence of spacing. Then,
Tukey’s Honest Significant Difference test (p = 0.05) was used for
multiple comparisons of means. Results revealed that at the older
age of 24 years, spacing did not statistically influence all growth and
yield parameters studied. A 4 x 4 m spacing produced trees with
higher dbh and height, while higher Ba, volume, and MAI values
were observed at 3 x 3 m. Stem quality was statistically different in
some spacings, where only 2 x 2 m differed statistically from 4 x 4
m. All physical and mechanical properties evaluated were not
statistically influenced by spacing except CLST to grain, whereby the
spacings of 2 x 2 m and 3 x 3 m had significantly higher values than
a spacing of 4 x 4 m. In conclusion, results showed that despite the
growth and yield parameters not being statistically influenced by
spacing, a spacing of 3 x 3 m could ensure a higher yield compared
to other spacings. Also, it produces trees with high stem quality,
similar to closer spacing, without affecting both physical and
mechanical properties. This is because the values of those
properties appear to have slight differences among the spacings.
Keywords: Tectona grandis, Spacing, Volume, Stem quality, Basic
density, Heartwood percentage
Description
MSc Dissertation
Keywords
Tectona grandis, Spacing, Volume, Stem quality, Basic density, Heartwood percentage