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Vegetacija prodišč v odvisnosti od strukture in višine prodišč 
na primeru srednje Drave
Vegetation of the river gravel bars in the relation to bar 
structure and height on the case of middle Drava river stream
M a r i j a M e z n a r i č
1
, M i T j a k a l i g a r i č
2
, So N j a Šk o r N i k
2
1
  Gimnazija Franca Miklošiča, Prešernova 34, SI-9240 Ljutomer, Slovenia; 
marija.meznaric@guest.arnes.si
2
  Univerza v Mariboru, Fakulteta za naravoslovje in matematiko, Koroška c. 160, 
2000 Maribor, Slovenija
In the present study we studied species composition in relation to selected environmental 
variables (height, soil structure (proportions of mud, sand, gravel)) and age of the gravel 
bar on the gravel bars of the middle Drava River. The research included 29 selected gravel 
bars in the section Markovci - Zavrč and section Obrež - Središče ob Dravi. We determined 
the relative height of the gravel bars and estimated proportion of mud, sand and gravel (in 
percentage). We sampled the vegetation on 154 plots using the Braun-Blanquet method.
Using multivariate analyses (methods of classification and ordination) we compared 
the floristic composition of the relevés. 155 plant species were found which indicates high 
species richness and vegetation variability of researched gravel bars. DCA ordination of 
the relevés on the basis of species composition showed a continuous variation of species 
composition along the moisture gradient. With TWINSPAN classification three groups of 
relevés were separated. CCA ordination demonstrated that size of the particles in sediment 
and bar elevation (cm) were environmental variables that mostly correlated with the species 
composition of the gravel bars. Namely, both factors could affect the soil moisture; lower 
areas with fine sediment (mud) are wetter (and probably very fertile), while larger particles 
sediments (gravel) on higher places are dryer. The vegetation coverage increases with the 
content of mud and is as expected in positive correlation with the height and maximal height 
of the vegetation. Gravel on the other hand was in negative correlation with the height of 
the vegetation – lower pioneer plants, xerophile species, which are more resistant to drought 
and do not grow high, prevail on the soil with major proportion of gravel. The age of the 
gravel bar was not correlated with any of the variables. 
M a r i j a Me z n a r i č eT al.: Vegetacija prodišč v odvisnosti od strukture …