Comparison of statistical models for the estimation of tree biomass and for the estimation of carbon stock above the soil in he Cerrado biome

Abstract

In this work, different statistical models were compared for estimating individual tree biomass and the total biomass and carbon stocks above the soil, in the three compartments (arboreal, herbaceous-shrub and litter) of a typical Cerrado in the west of Bahia state, Brazil. The forest inventory was carried out in 20 plots of 1000 m² (20 m x 50 m). In order to fit the statistical models, 90 trees of different species and diameter classes were cut and weighed. Models were fitted for the diameter measured at 30 cm from the soil (D30cm≥5cm) and the diameter measured at 1.30 m from the soil (DAP1,30m≥3,5 cm). The equation chosen was applied to the data of the trees collected in the forest inventory, and thus, the stocks per hectare and the total in the tree compartment were estimated. Samplings of the herbaceous-shrub and litter compartments were performed by fixed subplots. For sampling of the herbaceous-shrub and litter compartments, 20 subplots of 4 m² (2 m x 2 m) and 20 subplots of 1 m² (1 m x 1 m) were systematically allocated, respectively. The carbon stock was estimated by the biomass conversion factor. The equation resulting from the adjustment of the Schumacher & Hall (logarithmic) model (R2 = 93.53%; Sxy = 44.92%) was chosen to estimate the biomass stock of the studied Cerrado trees. The total biomass above the soil, considering the three compartments, was estimated at 18.77 Mg ha-1, which corresponds to a Carbon total stock of 8.67 Mg ha-1. The arboreal compartment was responsible for most of the stocks (58%), followed by litter (26%) and herbaceous-shrub (16%).