Development of allometric equations for estimating above-ground biomass of woody plant invaders: The case of pittosporum undulatum in the azores archipelago

Abstract

The use of biomass for energy production has shown a growing interest in recent years. Pittosporum undulatum is a widespread invasive tree in the Azores archipelago with a considerable potential as an energy resource. Sustainable use of forest resources demands accurate and precise estimation of standing biomass but for the Azores only a few studies exist devoted to estimation of above-ground biomass (AGB). Here we used published allometric equations and developed new models for the estimation of P. undulatum total AGB in the exotic woodlands of the Azores. A total of 470 trees were sampled at 11 P. undulatum stands in São Miguel Island, and their total biomass and several dendrometric traits were recorded in the field. Several dendrometric variables were used as predictors for biomass: diameter at breast height, D; tree height,H; basal area, BA; canopy height, CH; canopy diameter, CD; canopy biovolume, BV; and number of branches at breast height, NB. For model comparison and evaluation R2, RMSE and AIC were used. The equations comprised models fitted to log-transformed data. There were significant and strong linear relationships between AGB and predictors BA and H. The considerable variability in P. undulatum stands, in terms of tree density and structure, should be considered when estimating biomass with allometric equations.