During the last decades, the concentration of greenhouse gases (GHGs) in the atmosphere has risen up to unprecedented levels since the beginning of the industrial revolution, reaching 405.5 ppm in 2018. This increase is expected to continue over the XXI century, causing a large number of environmental as well as socio-economic problems. However, trees are able to capture carbon though the photosynthesis, and therefore, increasing the forest cover might be one of the most effective strategies to offset CO2 emissions across the globe. The area covered by trees can be increased by means of the deliberate planting of trees in areas that were once covered (i.e. reforestation) or not covered (i.e. afforestation) by forests. However, it has also occurred as a consequence of the spontaneous revegetation of formerly cultivated areas that have been abandoned as a consequence of its low productivity and/or the difficulties for the mechanization of the agrarian labour, leading to a low economical profitability. This forest expansion in abandoned agricultural lands has been particularly pervasive in the Northern Hemisphere, where it has apparently contributed to the development of a persistent carbon (C) sink. However, whereas the C stocks developed as a consequence of this process have been quantified in some regions such as Eastern Europe and the former Soviet Republics, in others such as Southern Europe they have not. Moreover, there are still a large number of uncertainties concerning C accumulation in different parts of the forest (i.e. above- and below-ground biomass, woody debris, litter, soil), as well as on the role played by mean annual rainfall and temperature, and soil nutrient concentrations, among other factors, in this process, particularly in Mediterranean environments.
The overall objective of this project is to improve our knowledge on the process of carbon accumulation over forest expansion in abandoned agricultural lands, in a vast region of Central-North Spain (Castilla y León) that has been severely affected by this process. Specifically, we aim to quantify the C stocks developed as a consequence of forest expansion in abandoned agricultural lands, and shed light on the factors responsible for the process. The project has been developed in the Institute for Sustainable Forestry Management (iuFOR), located in Palencia (Spain), but depending on the University of Valladolid, with a two-month secondment in the School of Geosciences of the University of Edinburgh (United Kingdom).
