Evaluation of Taper and Volume Models for Selected Commercial Timber Species in Gambari Forest Reserve, Ibadan, Oyo State, Nigeria

• P.O. Ige

  Department of Social and Environmental Forestry, University of Ibadan, Nigeria

  Author

• O.F. Akinnusi

  Department of Social and Environmental Forestry, University of Ibadan, Nigeria

  Author

Taper and Volume models are used in the estimation of tree growth, stand structure, and timber yield. Forest managers utilize these tools to help them make well-informed decisions on the planning and harvesting of forest resources. Hence, taper and volume models were developed for three commercial timber species (Cedrela odorata (28yrs), Cordia alliodora (28yrs), and Tectona grandis (25yrs)) in Gambari Forest Reserves, Oyo state, Nigeria. Systematic random sampling was used in collecting the data for this study, with 10% sampling intensity used in each selected plantation. Forty-Eight (48) Temporary Sample Plots (TSP) of equal size 20m x 20m were laid. All trees with diameter at breast height (Dbh) ≥ 10cm in each TSP were enumerated. Taper models and volume models were developed using four and five selected models, respectively and the best fit models were selected based on least Root Mean Square Error (RMSE), Alkaike Information Criterion (AIC), highest Coefficient of Determination (R2) and Weighted Score. In Cedrela odorata plantation, the Dbh and height were 28.85cm and 21.31cm, respectively. The Full Cubic model (d=2.096+0.142D+0.003H+0.0007D2+0.009H2+0.000015D3+0.00026H3+0.0138DH+0.000013D2H+0.00024DH2) and Logistic model (V=4.2631+87.892e-0.108D) were selected as the best model to develop taper and volume models, respectively for Cedrela odorata; In Cordia alliodora plantation, the Dbh and height were 21.94cm and 25.30cm, respectively. The Full Cubic model (d=1.005+0.074D+0.124H+0.0003D2+0.009H2+0.00006D3+0.0001H3+0.0076DH+0.00019D2H+0.00005DH2) and Gompertz Relation model (V=45.694-e1.937-0.227D) selected as the best model to develop taper and volume models, respectively for Cordia alliodora. In Tectona grandis plantation, the Dbh and height were 19.82cm and 20.16cm respectively. The Full Cubic model (d=1.471+0.105D+0.287H+0.021D2+0.031H2+0.00029D3+0.0014H3+0.0297DH+0.00196D2H+0.00273DH2) and Logistic model V=4.9851+132.608e-0.102D) were selected as the best model to develop taper and volume models respectively for Tectona grandis plantation. The findings of the study will serve as a baseline guide and information that can be used for more accurate estimation of timber yield of the selected tree species through the use of the developed models in Gambari Forest Reserve.

1. P.O. Ige, Department of Social and Environmental Forestry, University of Ibadan, Nigeria

   Department of Social and Environmental Forestry, University of Ibadan, Nigeria

2. O.F. Akinnusi, Department of Social and Environmental Forestry, University of Ibadan, Nigeria

   Department of Social and Environmental Forestry, University of Ibadan, Nigeria

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