Abstract
The aim of this study is to present short-term changes in the spatial structure of water vegetation in Lake Rotcze. Field studies were carried out during the growing seasons of 2000 and 2005. The obtained results allowed to estimate the following parameters that characterize the spatial structure of macrophytes: species frequency in particular ecological groups, the average vegetation cover in these groups, the average cover of particular species, both in the whole reservoir and in different depth ranges, as well as the PVI (Percent Volume Infested) coefficient for ecological groups. The frequency and cover of some species and ecological groups of macrophytes changed during the study period.