Existing monitoring system in the area of floodplain forests influenced by the Gabeikovo hydro-power plant consists also from 48 monitoring plots situated in natural, seminatural or man-made floodplain ecosystems of different species composition, in-side architecture and structure. Apart from numerous production-ecological criteria, quantifying tree, shrub and plant production and productivity, leaf area index (LAI) was studied during the six years period 1994-1999. Even this study started in the 2nd vegetation period after the damming of the Danube river, the results show relatively high values of LAI in all vegetation periods ranging from 2.89 ha.ha-1 to 6.20 ha.ha-1. We can state, that the damming of the Danube river and the following changes in the ground water level have influenced the changes of the vitality of trees and shrubs within the period very specifically, what should be taken into consideration, when situation in the four monitoring plots is going to be presented.