Biomass carbon stock in CAP afforestation on abandoned agricultural land in continental Mediterranean environments

Abstract

Rural abandonment has led to the afforestation of a large area of former cropland and pasture in the Mediterranean region of Europe under the 1992 EU CAP Afforestation Scheme. This study evaluates (1) the area covered by afforestation and (2) the impact of silvicultural practices (systematic and selection thinning and pruning of branches below 2 m) on storage of biomass carbon in afforested abandoned agricultural land with Pinus halepensis Mill. and Quercus ilex L. in Campo de Montiel, central Spain. Afforestation covers an area of 16,480.8 ha (2.7 %) in the study area. Nearly 30 years after planting, unmanaged afforestation stored 20.94 Mg C ha⁻¹ in the biomass (0.7 Mg ha⁻¹ yr⁻¹), while non-afforested plots stored 0.44 Mg C ha⁻¹. In a four-year experiment, systematically thinned plots and selectively thinned plots stocked 1.31 and 1.02 Mg C ha⁻¹ yr⁻¹, respectively, with no significant differences between the thinning types, whereas control plots stocked 0.98 Mg C ha⁻¹ yr⁻¹; plot position had a relevant effect on the stocked carbon. Pruning had a positive but marginally significant effect on carbon stock. We conclude that (1) the studied CAP afforestation sites have increased vegetation C stocks by ca. 30 times compared to secondary succession, and (2) thinning increased short-term C accumulation in the planted pines.