Agriculture Commons^™

A Stem Profile Model Calibrated By Nonlinear Mixed-Effects Modeling, Yuqing Yang, Shongming Huang, Shawn X. Meng

Conference on Applied Statistics in Agriculture

A stem profile model was developed for black spruce (Picea mariana (Mill.) B.S.P.) trees in Alberta, Canada using a nonlinear mixed model approach. The model included two random parameters to capture between-subject variation and a general covariance structure to model within-subject residual autocorrelation. After evaluating various covariance structures, the 4-banded toeplitz and the spatial power structures were chosen for further evaluation. The 4-banded toeplitz structure provided a better fit. The model was further evaluated using an independent data set to examine its validation accuracy. Model validation results showed that the model was able to accurately predict stem diameters at the …