Fitting volume and taper functions to four pine species planted in Northeastern Mexico

Abstract

The objective of this study was to observe the goodness of fit of eight volume models and four taper functions to four pine species (Pinus brutia Ten., Pinus eldarica Medw., Pinus halepensis Mill., and Pinus estevezii Mart.) planted in northeastern Mexico. Trees were measured in diameter at several sections of the stem. The 90 p. 100 of the total available information (145, 39, 227 and 48 trees for volume and 2,350, 1,280, 4,407 and 1,320 for taper) were used to fit four taper functions (Clutter, Amidón, Kozak, Newnham) and eight volume equations by least square techniques in linear and non-linear regression analysis. To test the goodness of fit, volume and taper functions were fitted to 10 p. 100 of the remaining information with estimators of the coefficient of determination, standard error, and total volume. The results showed that different models described best total volume for different species. However, the Schumacher and Hall equation consistently had the best goodness of fit. The variable-form taper resulted in more precise volume estimates for the test trees. The taper functions, in general, described best total trees volume of test trees than the volume equations. Therefore, the variable-form taper function of Newnham is recommended for describing the stem profile and total volume of plant species in northeastern Mexico.