Fitting volume equations and taper functions to Pinus pseudostrobus Lindl. in pine forests of the Eastern Sierra Madre of Nuevo Leon, Mexico

Abstract

The objetives of this study were to fit eight volume equations, to fit five taper functions and to validate them in stems of Pinus pseudostrobus Lindl. harvested in a forest fraction of the Eastern Sierra Madre mountain range of the state of Nuevo León, México. Diameter measurements at different stem sections were conducted in trees harvested during commercial forest management operations. To fit the volume equations and taper functions, 2338 pairs of data (diameter-height) corresponding to 110 trees and to validate them, 418 pairs of data corresponding to 20 trees randomly selected were used. Volume equations and taper functions were fitted by least square techniques in linear, polynomial and multiple regression techniques. Validation tests consisted on comparing the statistics coefficient of determination, standard error and bias, including the error distribution, randomness and common variance. The results showed that the models that predict better total volume and diameter at any stem section were Schumacher y Hall and Kozak, respectively. Volume models do not predict as accurately total volume as it does the taper functions of Kozak for the 20 trees used to validate both mathematical technologies. Therefore, we recommend the use of this taper function to estimate commercial or total volume of trees of the specie Pinus pseudostrobus Lindl. of northeastern Mexico.