BIOMASS EXPANSION FACTOR AND ROOT-TO-SHOOT RATIO FOR Pinus spp. IN SOUTHERN BRAZIL

Abstract

Biomass Expansion Factor (BEF) and Root-to-Shoot Ratio (R) are variables utilized for quantification of carbon stock in forests. These are considered as constant values in most studies.  This work shows that BEF and R area not constants for Pinus spp. grown in southern Brazil. Data from 70 sample trees over different diameter classes and age were used to demonstrate the correlation between BEF and R, and forest inventory data, such as DBH, tree height and age. Dry total biomass, carbon stock and CO₂ equivalent were simulated by using the IPCC default values of FEB and R, corresponding average calculated from data using in this study and as well as the values estimated by regression equations. The mean values of FEB and R calculated in this study were 1.47 and 0.17, respectively, that means that 47% of total biomass corresponds to tree crown and 17% of it comprises tree roots or below-ground biomass. The correlation coefficients between BEF and R with tree DAP, H and age were significant. The relation of BEF and R and the tree mensuration variables showed a descendent curve of negative exponential behavior. Some equations to express FEB and R as functions of the tree variables showed better performance than others, and equation 12 gave the best fit. The simulations indicated that use of fixed values of BEF and R, either IPCC default or average actual data, may lead to unreliable estimates of carbon stock inventories and CDM projects. It was concluded to take into account the variations of FEB e R and use regression equations relating them to DBH, tree height and age are fundamental to get reliable estimates of forest tree biomass, carbon sink and CO₂ equivalent.