Species-specific and generalized biomass models for estimating carbon stocks of young reforestations

Biomass models are key to the correct quantification of aboveground biomass and carbon stocks. Most of the current available sets of biomass models were developed for adult trees although very few have been employed to accurately estimate biomass during the first years of reforestations, despite the increasing number of reforestations over recent years. In this study, species-specific and generalized models for aboveground biomass of single trees have been developed for the main 14 species used in reforestations in Spain. A comparison with the existing biomass models at individual tree level for larger trees of these species was also conducted to confirm the hypothesis that specific models are required for the first years of the reforestation. A new set of biomass models was fitted simultaneously per species, based on three different independent variables - root-collar-diameter, total height and crown projection area- and their combinations. The fitted models provide more accurate and unbiased predictions of aboveground biomass in the first years after reforestation when compared with previously existing models for adult trees. The generalized models can be applied to reforestations when the main species is unknown or for mixed plantations where species are not individualized. The set of models provided can be used in a wide variety of surveys and monitoring conditions depending on the available data, from classical field inventories to more novel approaches such as airborne LiDAR data or aerial photographs.

Automated summary

Biomass models are crucial for accurately estimating aboveground biomass and carbon storage. Existing models are mostly developed for adult trees and rarely for early reforestation stages. This study developed species-specific and generalized models for the main 14 tree species used in reforestations in Spain. The new models provide more accurate and unbiased predictions of aboveground biomass in the first years after reforestation compared to existing models for adult trees.