Vrstni obrat in premiki v funkcionalnih tipih rastlin v primarni sukcesiji na rečnih prodiščih : doktorska disertacija

slovenian

doktorska dela

2016

Univerza v Mariboru, Fakulteta za naravoslovje in matematiko

Gravel bars are riverside or central river deposits, created and constantly altered by the river's current. Morphologically heterogeneous and dynamic environment of gravel bars enabled the development of various habitats and great diversity of species and groups. In this dissertation research, we wanted to contribute to the understanding of the primary environmental parameters that affect the gravel bar's vegetation in the case of primary succession. Our goals, set in the research, referred to studying the species turnover through individual studies in the primary succession (changes in the composition of plant species through time), as to the changes in ecological plant strategies / changes in plant functional traits, inhabiting the gravel bars. We have used and compared the results of two methods: permanent plot and chronosequence (space for time substitution). The data of vegetation and environmental parameters was sampled on 29 gravel bars of central Drava (chronosequence, N = 143) and the artificially lowered gravel bar at Borl (permanent plots, N = 442), from 2005 to 2011. We have discovered 211 plant species in 565 researched plots. Species analysis in relation to habitat preference produced the following shares: ruderal habitats (55.5 %), followed by forrest/bush (13.7 %), grassland (11.4 %), water/riverside habitats (10.9 %), and indifferent species (8.5 %). Indirect (PCA, DCA) and direct (RDA, CCA) methods of gradient analysis demonstrated the floral diversity of researched plots, determining that the chronosequence method cannot substitute the method of permanent plots when detecting specie turnovers in the primary succession on gravel bar habitats. Specie constitutions of equally old stages of plant groups on gravel bars are differentiated by the diverse local environmental parameters; thus not being possible to determine the specie constitution from the age of the vegetation constitution alone. The most prevalent environmental attributes explaining the differences in vegetation prove to be primarily - the height of the gravel bar and secondly - soil composition (ratio between gravel, sand and silt). We were also discovering shifts in the ecological strategies of plants through individual stages of primary succession, based on 15 morphologically-functional signs and the CSR primary strategy model. The CR strategy of competitive ruderals dominated (42.1 %). We have found disturbance and competitiveness to be the two deciding factors in habitation forming on gravel bars, while stress being of low relevance. While monitoring the primary succession, we have determined that the initial CR marks (the first phases of succession) make a shift in the C component. We can correlate the mentioned mark changes to the decreasing effect of flood disorders to the gravel bar and sediment deposition, which increases the supply of nutrients in the substrate and decreases (silt, sand) the effect of water shortages (stress) in the ground. A significant requirement for the preservation of biotic richness is the preservation of natural river dynamics, typically severely altered by human intervention in riverside ecosystems. Gravel bars represent one of the most endangered landscape elements. Research of the primary succession process in correlation with various environmental parameters is not only important for its' contribution to the understanding of fundamental environmental processes taking place in the environment, but also for being able to predict the consequences of human interference in these habitats and planning of measures to take in order to prevent or reduce these consequences.

08.08.2023