PARENT SESSION
Poster Session 39: Late Breaking and Newsworthy Posters
Friday, August 12, 8:30 AM - 10:30 AM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Soil carbon dynamics and grassland management in the Pyrenees.

Sebastia, Teresa^{*,1, 2}, Garcia-Pausas, Jordi¹, Rodríguez, Carolina¹, Vallecillo, Sara¹, Canals, Rosa-Maria³, Casals, Pere¹, Arco, Noèlia , Bartolomé, Jordi , Connolly, John , Garrido, Joan-Pere , Plaixats, Josefina , Romanyà, Joan , San Emeterio, Leticia, ¹ Technological Forestry Centre of Catalonia, Solsona, Spain² University of Lleida, Lleida, Spain³ University Public of Navarra, Pamplona, Spain

ABSTRACT- Maria-Teresa Sebastià^1,2, Jordi Garcia-Pausas¹, Carolina Rodríguez¹, Sara Vallecillo¹, Rosa-Maria Canals³, Noèlia Arcos¹, Jordi Bartolomé⁴, John Connolly⁵, Joan-Pere Garrido¹, Josefina Plaixats⁴, Joan Romanyà⁶, Leticia San Emeterio³, Pere Casals¹ Among the key factors regulating soil carbon accumulation in ecosystems, the role of management is still not well understood. Carbon stocks and dynamics were studied in a broad survey on 139 grasslands under an array of climatic and topographic conditions in the Pyrenees, and in grazing experiments. The survey was conducted in locations in the Western, Central and Eastern Pyrenees under different grazing regimes: abandoned, grazed by a single domestic species (cattle or sheep) and mixed grazing. Carbon stocks were determined in the soil, in the above and belowground biomass, and in the feces. The predicted soil carbon content (SOC) was lower in abandoned than in grazed areas, and increased under mixed grazing. Preliminary analyses suggest that the amount of SOC was more strongly related to cattle than to sheep feces, and that there was a positive relationship between SOC and belowground biomass. SOC was successfully modeled based on a few climatic, topographic and management variables easy to obtain and display on a Geographical Information System. For the experiments, two different locations in the Eastern Pyrenees were selected. At each site, three grazing treatments were randomly applied to six plots: abandoned, moderately and intensively grazed. Abandoned areas showed lower pools of labile and microbial active soil carbon than grazed areas, but the results were dependent on site and year after the start of the experiment. There was a significantly higher CO2 efflux in the abandoned than in the grazed areas, and we try to determine if this effect was related to the increased standing aboveground biomass, changes in belowground growth or increases in the microbial activity with abandonment.

Key words: Land use change, Carbon storage, Geographical Information System, Grazing experiments