Disturbance, succession and stability: a ten year study of temporal variation of species composition after a catastrophic flood in the river Paraná, Argentina

The River Paraná is the second largest river of South America and its flood plain is covered by different kinds of forests and herbaceous vegetation. It is subject to an annual pulse of flooding; floods larger than the normal annual ones at irregular periods of few year and catastrophic extraordinary floods few times in a century. The last catastrophic flood was in 1983, followed by a short lived high flood in 1992. The catastrophic flood destroyed almost completely the herbaceous vegetation. Our hypotheses are, on the one hand, that the plant communities of this area will be restored rapidly, and on the other, that there will be a succession process which will produce a shift of communities so that, those on the higher part of the elevation gradient will encroach the ones at its lower part. We analyse, by means of the floristic composition, the effect of disturbance induced by catastrophic floods on the vegetation stability and dynamic processes, in an internal depression and pond of the riparian plant communities in an island of the River Paraná valley. The results strongly support the first hypothesis