International Journal of Agroforestry and Silviculture

International Journal of Agroforestry and Silviculture Vol. 1 (9), pp. 110-113, September, 2014. © International Scholars Journals

Full length Research Paper

Gmelina arborea Roxb. Graded Stands with the Weibull Distribution Function in Oluwa Forest Reserve, Nigeria

1Ekpa, N. E., 1Akindele, S. O. and 2Udofia, S. I.

1Department of Forestry and Wood Technology, Federal University of Technology, Akure, Nigeria. E-mail:

2Department of Forestry and Wildlife, University of Uyo, Akwa Ibom State, Nigeria.

Accepted 13 June, 2014


The diameter distribution of growing stock is an essential starting point in many forest management planning problems. The three-parameter Weibull distribution model was used to grade the diameter classes of Gmelina arborea plantation in Oluwa Forest Reserve located in the tropical rainforest area of Nigeria. Data used for the study were diameter at breast height (dbh) taken at five years interval. The interval ranging from 11,16, 21, 26, and 31 years of plantation establishment. Quadratic mean dbh exhibited a strong linear relationship with Weibull parameters ‘a’ and ‘b’ and mean height exhibited a strong linear relationship with parameter ‘c’. Validation test as carried out on the quadratic dbh and Weibull parameter relationship further proved that the models were consistent and efficient and were therefore recommended for predicting the diameter distribution of the stand.

Key words:Gmelina arborea,diameter distribution, Weibull distribution function, plantation, Nigeria.