Decomposition rate of plant material in the Parana Medio River (Argentina)

Two experimental sites were studied - the Parana Medio river major channel and the Colorado river, Argentina. These sites represented the minimal and maximal velocities of the 2 streams in the valley to be flooded for the Parana Medio dam. Plant samples were periodically analysed during 80 days and the data was fitted to an exponential decomposition model. Degradation coefficients for Panicum prionitis, Paspalum repens and Eichhornia crassipes were 0.0357-0.0682, 0.0182-0.0643 and 0.0120-0.0425 per day respectively. In the slow flow, the principal factor responsible for lost weight was leaching. When stream flow increased, loss of material due to fragmentation began to predominate.