Effect of thinning on selected stand parameters and revenue generation of tectona grandis at longuza plantation, Muheza,Tanzania
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Date
2024
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Publisher
Sokoine University of Agriculture
Abstract
Various researches have reported the effect of thinning on stand
parameters of Tectona grandis in Tanzania. However, there is limited
information on the effect of thinning on growth and yield, and revenue
generation of Tectona grandis in Tanzania. This study assessed the
effect of thinning on growth and yield and revenue generation of
Tectona grandis at Longuza Forest Plantation. Data were purposely
collected from 168 circular plots of 9.78 m radius (0.03 ha) distributed
systematically in 9 thinned compartments. In each plot, all trees were
measured for diameter at breast height (Dbh) and total height of three
trees with largest, medium and smallest heights were measured.
Compartment register provided information on planting and thinning
year. Prices of wood volume at clear-felling, poles and expenses on
establishment and management costs of the surveyed stands were
collected. Growth and yield parameters described were Dbh,
dominant height, volume per ha, and stand density. Adequacy of
thinning was determined by calculating the remaining number of
stems per hectare (ha) and the deviation from scheduled values
expressed in percentages. Thinning timing was obtained by deducting
the age the compartment was supposed to be thinned as indicated in
the thinning schedule. An economic benefit was calculated by using
discounting method whereas net present value (NPV) was used to
determine the economic point of view. Thinning effect was assessed
by comparing measured values with mean values of Teak yield table.
One sampled t-test was used to compare if there were a significant
difference between measured and Teak yield table values. The
results have clearly showed that 88.9% of thinned compartments
were understocked and 11.1% were well stocked. Furthermore, 100%
and 75% of the first and second thinning were well-timed, whereas
25% of the second thinning was delayed by one year. Site classes I
and II comprised 66.7% and 33.3% of the surveyed compartments.
The effects of adequate and timely thinning on Dbh and volume were
2-42% and 9-53%, respectively. Heavy thinning in the first and
second thinning schedule maximized economic benefit of climatic and
ecosystem services provisioning goal by 181.5%. However, early
heavy first and second-intensity thinning was found to be one of the
essential treatments in producing higher financial returns but delayed thinning reduced the volume of logs produced with low quality and
thus graded lowly. Heavy, timely and adequately thinnings are
recommended. The results determines that Tectona grandis
plantations play a crucial role in providing quality timber and storing
carbon dioxide (carbon sink) from the atmosphere.
Description
Keywords
Thinning, Climatic and Ecosystem provision, Revenue generation, Tectona grandis, Longuza