Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain

[摘要] Accurate estimates of C stocks and fluxes of soil organic carbon (SOC) areneeded to assess the impact of climate and land use change on soil C uptakeand soil C emissions to the atmosphere. Here, we present an assessment of SOCstocks in forests, shrublands and grasslands of peninsular Spain based onfield measurements in more than 900 soil profiles. SOC to a depth of 1 m wasmodelled as a function of vegetation cover, mean annual temperature, totalannual precipitation, elevation and the interaction between temperature andelevation, while latitude and longitude were used to model the correlationstructure of the errors. The resulting statistical model was used toestimate SOC in the ∼8 million pixels of the Spanish ForestMap (29.3 × 10⁶ ha). We present what we believe is the mostreliable estimation of current SOC in forests, shrublands and grasslands ofpeninsular Spain thus far, based on the use of spatial modelling, the highnumber of profiles and the validity and refinement of the data layersemployed. Mean concentration of SOC was 8.7 kg m⁻², ranging from 2.3 kg m⁻²in dry Mediterranean areas to 20.4 kg m⁻² in wetter northernlocations. This value corresponds to a total stock of 2.544 Tg SOC, which isfour times the amount of C estimated to be stored in the biomass of Spanishforests. Climate and vegetation cover were the main variables influencingSOC, with important ecological implications for peninsular Spanishecosystems in the face of global change. The fact that SOC was positivelyrelated to annual precipitation and negatively related to mean annualtemperature suggests that future climate change predictions of increasedtemperature and reduced precipitation may strongly reduce the potential ofSpanish soils as C sinks. However, this may be mediated by changes invegetation cover (e.g. by favouring the development of forests associatedto higher SOC values) and exacerbated by perturbations such as fire. Theestimations presented here provide a baseline to estimate future changes insoil C stocks and to assess their vulnerability to key global changedrivers, and should inform future actions aimed at the conservation andmanagement of C stocks.

[学科分类] 地球化学与岩石