Carbon storage in the different compartments of two systems of shrubs of the southwestern Iberian Peninsula

Quantifying carbon and biomass is relevant information needed in the fight against global warming. Since in Mediterranean ecosystems the agroforestry surface is very large, estimating carbon stocks and their distribution in the different compartments (above ground biomass, root, litter and soil) of these ecosystems is very important. In this work, fixed carbon was quantified in the two most abundant systems of thermophilic shrub of southwestern Iberian Peninsula: Rockroseland (Cistus ladanifer L.) and Broomland (Retama sphaerocarpa L.). Biomass was estimated through regression functions from morphology parameters. The results showed that the distribution of carbon among the compartments depends on the species. It was estimated that 34.7 Mg ha(-1) of carbon retained in the C. ladanifer system, distributed among the different reservoirs. The shrub system of R. sphaerocarpa stores 24.3 Mg ha(-1) of carbon. The carbon stored in biomass was differently also distributed among its components in each species. In C. ladanifer, carbon in above ground biomass is more than 85 % of the total biomass, and 15 % corresponds to carbon in root. However, in R. sphaerocarpa carbon stored in roots goes up to 48 %. These values show that it is important to quantify the carbon stored in all the components of the ecosystem (including the root), and show how important it is to maintain shrubs as reservoirs of carbon in Mediterranean agroforestry.