Estimación de los cambios en los stocks de carbono del suelo agrícola a escala regional: impacto de los usos del suelo y del manejo en la Comunidad Autónoma de Aragón

Soil organic Carbon (SOC) plays an important role in the mitigation of climate change effects since it is related to the reduction of atmospheric CO2 levels depending on land use and management. In this Dissertation, we have estimated the potential of agricultural land to sequester SOC in the Autonomous Community of Aragon, using the dynamic model RothC at a regional level. The average rate achieved of carbon sequestration (for a period of 20 years) was about 1.02 Mg C ha-1 year-1 considering the application of farmyard manure and the maintenance of crop residues (C inputs). The most important driver for SOC was the C inputs. Thus, the major C stocks were obtained in irrigation systems with an annual average rate of 2,13 Mg C ha-1 year -1. Starting from the current situation, the future changes of SOC stocks for the period (2010-2100) under 4 climate change scenarios (CGCM2-A2, CGCM2-B2, ECHAM4- A2 and ECHAM4-B2) was also assessed. In general, under climate change scenarios, agricultural soils of Aragon have revealed some losses of soil organic carbon compared to the reference scenario. Simulations showed that the response of SOC to climate change was entirely explained by air temperature. Furthermore, the biggest losses of carbon stocks have concerned mainly the ECHAM4 A2 climate change scenario (higher temperature rise and rainfall decrease) and by minority within the category of irrigated crops. Planning alternatives consisting of some soil management in this scenario with the greatest impact such as: No tillage for the rainfed cereals and vegetation cover for the woody crops, has led to out a doubling of the carbon sequestration average rate. Thereby, the increased carbon content has reached 4.07 Mg C ha-1 for the category of dry cereals and exceeded 8 Mg C ha-1 for each class of woody crops (orchards, vineyards and olive groves) in the period 2010-2100. In view of the importance of C inputs in organic C soil sequestration and the impact of climate change on determining soil organic C stocks. No tillage and plant cover could be effective strategies in reducing CO2 emissions and increasing soil potential to sequester C under current and climate change conditions.