Carbon storage in the Mediterranean upland shrub communities of Montesinho Natural Park, northeast of Portugal

Carbon storage is one of the several important functions of shrub communities in terrestrial ecosystems and could represent an effective way to mitigate climate change. Accordingly, biomass carbon (above and belowground), litter carbon and soil organic carbon (SOC) were studied in three shrub species – Cistus ladanifer (C. ladanifer), Cytisus multiflorus (C. multiflorus) and Erica australis spp. Aragonensis (E. australis) – representing dominant shrub communities found in Montesinho Natural Park (PNM), NE Portugal. The experimental design envisaged testing the effects of species and topography on variables mentioned and procedures carried out included assessments in areas covered by the three communities mentioned, in different topographic conditions (gentle slope, about 5%; moderate, around 15%; steep, around 25%), with three replicates. Above and belowground biomass and litter were collected in 1 m2 plots, where soil samples at depths of 0-5, 5-10 and 10-20cm were taken (disturbed for C mass concentration, undisturbed for bulk density determinations). The aboveground biomass was separated in stems, branches, branchlets, leaves and fruits. Carbon mass concentrations determined in biomass, litter and soil were converted to kg C m-2 ground area. Results showed that: (1) under the conditions studied, over 80% of carbon is stored in the soil; (2) the contribution of biomass is higher in E. australis, representing about 20% of carbon storage in the system; (3) for total carbon storage in the whole system, species followed the patern E. australis (12.8 kg C m-2) > C. ladanifer (10.5 kg C m-2) C. multiflorus (10.5 kg C m-2); (4) effects of topographic conditions were not significant in the global C storage, with 10.6, 11.6 and 11.7 kg C m-2 in gentle slope, moderate and steep, respectively