Methods for biomass stock estimation in Mediterranean maquis systems

As a result of Kyoto Protocol agreements, the scientific community increased its efforts to enhance the availability of biomass and organic carbon stock data in forest ecosystems. Nevertheless, a considerable data shortage has been recognized in estimating the stock of above-ground biomass (AGB) in Mediterranean maquis systems. This work aims at contributing in addressing such shortage by testing quick and non-disruptive methods to estimate the AGB stock in maquis species. Two methodologies were tested in three widespread sclerophyllous evergreen species (Pistacia lentiscus, Euphorbia dendroides, and Cystus monspeliensis). Both methodologies were based on the estimation of the apparent volume (AV): the first one assumed the shrub shape (or canopy) to be similar to a regular tridimensional solid, while the second method was based on plant digital images analysis. Results showed some differences in AV values estimated through the two methodologies, although a high correlation was found between them (R2 = 0.92-0.98) and with the AGB weight obtained from plant samples (R2 = 0.89-0.96). As a consequence, the shrubs apparent density values (i.e., weight/AV) vary depending on the method used for AV estimation. This should be taken into account when AV is used for AGB estimation. Besides, measurements of above-ground biomass were carried out to characterize the studied area. Results showed high variability in AGB values, ranging from 7.04 to 48.05 Mg ha-1 of dry matter. ? SISEF.