Above and belowground carbon stock of pine plantations and native oak forests coexisting in central Spain

Abstract

Abstract Promoting nature-based carbon sinks is one of the effective ways to minimise global warming. Different types of forests, resulting from different land-use histories, may coexist under similar macro-environmental conditions, but their efficiency as carbon sinks may differ. In central Spain, many areas are covered by coexisting patches of monospecific plantations of Pinus halepensis, established since the 1950’s, and native Quercus forest coppiced up to the 1960´s. We aimed to compare the carbon stock between both types of forests, considering both above and belowground compartments, in La Alcarria region (central Spain). In each plot, the diameter at breast height and height were measured in every adult tree, along with shrub cover. Three subsamples of litter and soil were collected per plot. The carbon pool of trees and shrubs was calculated using allometric equations, and for roots, litter, and soil, using the carbon content analysed in a laboratory or obtained from the literature. Carbon pools were analysed separately for three independent variables: plot type (Quercus/Pinus), tree basal area (m2/ha) and slope (°). Overall, Quercus forests stored more carbon than Pinus plantations. The carbon allocation pattern across compartments greatly varied between the two forest types, Pinus plots storing more than half (55%) of its carbon in the aboveground biomass of trees, while Quercus storing more carbon belowground (60%) in roots and soil. We conclude that native Quercus forests are more suitable for a long-term carbon storage, as belowground compartments represent an important part of its carbon storage capacity.