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Research Journal of Forestry

Year: 2007 | Volume: 1 | Issue: 2 | Page No.: 40-54
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Authors

V.A.J. Adekunle

Keywords

Research Article

Non-Linear Regression Models for Timber Volume Estimation in Natural Forest Ecosystem, Southwest Nigeria

V.A.J. Adekunle
Department of Forestry and Wood Technology, Federal University of Technology, P.M.B. 704, Akure, Nigeria
Tree species diversity was assessed and the efficiency of nonlinear regression models for timber volume estimation in a complex natural forest ecosystem is established in this study. The study was carried out in the tropical rainforest ecosystem of southwest Nigeria using two forest reserves with the same logging history and management practice. Eight plots of equal size (50x50 m) were selected using systematically cluster sampling technique and complete enumeration was carried out in each plot. All trees encountered in each plot were identified with their scientific names and measured. Four non linear models were developed for each forest reserve separately while five were developed for data involving the two reserves together. The results revealed that there were 61 important tropical timber species distributed among 24 families in the two reserves. The most abundant tree species is Strombosia pustulata while the family with the highest number of species is Sterculiaceae with seven species. The mean dbh and height are 39.12 cm and 18.77 m, respectively and highest percentage of the trees belong to the least diameter class (20-29 cm). The assessment criteria (correlation coefficient (R), coefficient of determination (R2), Standard error of estimate (SE) and F-ratio) with the validation results (using simple linear regression equation, percentage bias and probability plots of residuals) show that all the models were of good fit. Very high R and R2 values, small SE and percentage biases and significant F-ratio were obtained. All the models were discovered to be very adequate for tree volume estimation in the study area. They were therefore recommended for further use in this ecosystem and in any other forest ecosystem with similar site condition.
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Egbewole zaccheaus Tunde Reply

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