Allometric equations to estimate aboveground biomass of Dalbergia cearensis species in the Brazilian seasonally dry tropical forest

Abstract

The semiarid savannas, in particular the Caatinga Biome, are important components of the terrestrial carbon cycle in terms of global carbon storage. Despite this importance, little information is available regarding biomass production potential of caatinga species. The objective of the study was to develop allometric equations to estimate aboveground biomass of Dalbergia cearensis Ducke trees. The semi-destructive method was used to collect samples in which the diameter at breast height (D), wood density (ρ), and tree height (H) were the aboveground dry biomass (AGB) estimation variables. The research was conducted in three different localities of the semiarid region in the state of Ceará, Brazil. Fresh biomass measurement was divided in two parts: trimmed fresh biomass and untrimmed fresh biomass. Measurements were taken for 30 trees. Height, trunk diameter, and branch diameters were measured for each individual. Leaf and small branch aliquots were taken. The volume of branch aliquots was utilized to calculate wood density. Tree dry biomass was obtained by adding trimmed dry biomass and untrimmed dry biomass (AGB, in kg). In all, eight allometric equations were developed for D. cearensis and tested for goodness-of-fit statistics. The best allometric equations were selected based on each model’s performance statistics (R2-adj, RSE, and AIC). Of the eight regression models developed and tested to estimate aboveground biomass of Dalbergia cearensis trees, six attained acceptable performance statistics. The regression model for D. cearensis that utilized the single compound predictive variables DH (model 1) was the most robust, followed by the model using single compound variables ρDH (model 2), and multiple variables D + H (model 3). The methodology applied in this study can be adopted to estimate biomass and volume of a broader set of other species from the Brazilian seasonally dry tropical forest.