“New Forests” from the Twentieth Century are a Relevant Contribution for C Storage in the Iberian Peninsula

Abstract

Land-use changes are one of the major drivers of global change. In many developed countries socioeconomic changes have induced forest expansion during the last centuries, with still seldom explored implications for ecosystem services. We assessed the growth rate and the contribution of these “new forests” on C storage under the imprint of land-use history from Mediterranean to temperate forests in two biogeographical regions in the Iberian Peninsula, using data from 6422 plots of the Spanish National Forest Inventory (1986–2007) and the land-cover map of 1956 to distinguish among pre-existing and new forests (appeared after 1956). Almost a quarter of current forests were new forests and they represented 22% of the total C pool. New forests maintained similar C stocks than pre-existing ones (~45 Mg ha⁻¹), but they are growing at rates 25% faster. Considering the whole Spanish forested territory, the new forest growth rate would offset around 9% of the rate of total C emitted in Spain between 1986 and 2007. The effects of land-use history on forest growth and C stocks varied with environmental conditions (for example, growth of new forests in areas with less water availability was higher than in pre-existing ones), supporting the idea that agricultural legacies may prevail in the long term. In a time when European forests exhibit the first signs of carbon sink saturation, our study endows a relevant ecological role to new forests appearing in the second half of the twentieth century.