Comparisons between generalized and specific tree biomass functions as applied to tropical ash (Fraxinus uhdei)

Allometric equations were generated by harvesting tropical ash (Fraxinus uhdei (Wenzig) Lingelsh) trees growing on organic uplands soils in the island of Hawaii. One of these equations was used to estimate aboveground biomass of ten mature stands in the same area. Results indicated that the equation developed in situ, equations for white ash (Fraxinus americana L.), and generalized functions for temperate and tropical forests, provided relatively similar biomass estimates. Average differences between biomass estimates from the tested equations (excluding the one for moist tropical forests) and the function generated in situ ranged from 10 to 24%. One of the equations for white ash had the lowest sum of residuals followed by the generalized equation for temperate forests. The results suggested commonality among biomass estimates and, therefore, among relationships between tree dimensions probably because most of the aboveground tree biomass is in stem and branches, and these compartments are more stable than foliage mass. Equations to estimate commercial biomass and leaf area of tropical ash are also provided.