SECTION B: ENVIRONMENTAL SCIENCES, FORESTRY, WILED LIFE MANAGEMENT, FISHERIES AND AQUACULTURE
Volumes of current growing stock and future growth potentials are both important information for forest management. Tree volume equations are mathematical statements or expressions which relate tree quantity or volume to its measurable attributes such as base diameter, diameter at breast height, merchantable height and total height so as to obtain individual tree volume and the volumes of entire stands. This study seeks to develop tree volume equations using simple linear regression for Azadirachta indica in Sudano-sahelian region of Nigeria. A complete measurement of two hundred and forty-two (242) trees was carried out in some selected plantations of Azadirachta indica within two Local Government Areas of Katsina State situated within the Sudano-Sahelian eco-region (Katsina town in Katsina LGA and Dutsinma town in Dutsinma LGA). One hundred and thirty-six (136) trees and One hundred and six (106) trees were measured from Katsina town and Dutsinma town respectively. Data were collected through non destructive sampling method with the use of Spiegel Relascope and meter tape. Data consisted of stump diameter, diameter at breast height, top diameter, and merchantable height for the 242 trees. The results obtained revealed that the Stump diameter (Dst) of the sampled trees ranged from 41cm to 65cm; diameter at breast height (dbh) ranged from 32cm to 59cm; while the Top diameter ranged from 17cm to 46cm. Schumacher–Hall’s volume function was fitted to the data of each of the sampled trees. Simple linear regression analyses were conducted with the Statistical Package for Social Scientists (SPSS) version 18 to generate the volume equations. Various criteria were used to evaluate the ability of each model to predict a specified dependent variable. Two (2) tree volume equations from the Six (6) equations developed were ranked the best. The two best volume equations among the generated equations are as follows: LnV = 0.284 - 0.962Ln (D²H); and V = 0.019 + 0.737 (D²H); The R, R square, SEE, F-value and RMSE were 0.99, 99.7%, 0.01, 62214 and 0.0000001; 0.99, 99.6%, 0.01, 42637 and 0.00001 respectively. The equation developed was fitted to the data, and the resulting equations possessed desirable statistical properties and model behaviors.
Keywords: Azadirachta indica, Data, Tree volume equations, Sudano-Sahelian, Katsina State
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How to cite: Shuaibu R. B., (2015). Developing Tree Volume Equations for Azadirachta Indica (Neem Tree) in Katsina State, Nigeria. Gashua Journal of Irrigation and Desertification Studies, 1(1&2): pp. 204-213