Biogeochemical impacts of submerging forests through large dams in the Rı́o Negro, Uruguay

The Bonete, Baygorria and Palmar dams of the Rı́o Negro successively submerged complex floodplain forests. The forest area submerged was greater than 280 km2and resulted in large inputs of carbon, nitrogen and phosphorus to the reservoirs. After 46 years wood released 40, 34 and 71% of their original contents of carbon, nitrogen and phosphorus, respectively. During the same period the total amount of nutrients released by wood in comparison to leaves and litter is slightly less (0·7) for nitrogen, almost double (1·73) for phosphorus and more than three times (3·5) for carbon. These results suggest that wood decomposition in water may have a role in the trophic state of reservoirs.