where: c is the intercept, and α,β and χ are the slope coefficient of the regression.
Model comparison and selection were based on average deviation (Brand and Smith, 1985; Chave et al ., 2005), slope coefficient of the regression (Nelson et al ., 1999), Akaike Information Criterion (AIC) (Burnham and Anderson, 2002; Chave et al ., 2005), confidence interval (CI) of the predictions, paired t-test and Coefficients of determination (r2).