Abstract

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Multiple linear regression tree stem volume equations were developed for Azadirachta indica in North-West region of Nigeria and in other regions with similar vegetation and environmental factors. Complete measurements of Four Hundred and twenty (420) trees were carried out in the selected plantation of Azadirachta indica within 4 states of the region which includes: Katsina State; Kano State; Zamfara State; and Sokoto State. One hundred and five (105) trees were measure from each of the four states making a total of Four Hundred and twenty (420) trees. Data were collected through non destructive sampling method with the use of Spiegel Relascope and meter tape. Variables considered for data mensuration were merchantable height, stump diameter, diameter at breast height, and diameter at top of the stem before the crown. Stump diameter (Dst) ranged from 41cm to 67cm; diameter at breast height (dbh) ranged from 32cm to 60cm; and Top diameter ranged from 17cm to 48cm. Multiple linear regression analyses were conducted with the Statistical Package for Social Scientists (SPSS) version 18 to generate the tree stem volume equations. Various criteria were used to evaluate the ability of each model to predict a specified dependent variable. Five (5) multiple linear regression equations were developed and two best equations among the generated equations are as follows: V=0.329-0.699(D)+ 0.436(DH)-0.035(H); and V =1.109-2.227(D)+0.184(H). The R, R square, SEE, F-value and RMSE are 0.99, 99%, 0.01, 0.00004, 47149; and 0.00001, 0.96, 93%, 0.02, 0.0005, 4051 respectively. The equation developed was fitted to the data, and the resulting equations possessed desirable statistical properties and model behaviors.

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