The research objective was to develop an updated allometric equation of the total aerial biomass (M) of trees measured on the field and inventory sites of Mexico’s Sinaloan tropical dry forests. Results showed that: (a) the improved on site allometric equation increases precision in contrast to the conventional biomass equation previously reported, (b) deviations close to one order of magnitude occur between on site measurements of M and projections estimated with ex situ allometric equations, and (c) site evaluations may also deviate more than double when using ex situ allometric equations. Two procedures to increase tree and M precision when adjusting ex situ allometric equations were tested: (i) to use all available tree allometric functions to estimate a mean based on the central limit theorem or (ii) to calibrate ex situ equations by adjusting with local parameters through the use of statistical programs. These options would eventually increase tree and site estimations of total aerial biomass (M) in regional evaluations and eventually on dry forests of Northern Mexico.

Keywords: contrast analysis of on and off-site equations, Theorem of the Central Limit, local calibration of ex situ allometric equations.