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Skradinski Buk is the seventh, final and longest tufa barrier in National Park Krka, Croatia. Despite numerous actions ensured by National Park protection category, uncontrollable growth of an invasive plant species Ailanthus altissima (Mill.) Swinge resulted with dried water channels along the Skradinski buk barrier. Removal of A. altissima reactivated five channels, which had been dried for decades. The invasive species was first removed during summer 2017, followed by several repetitive removals in the following months. Samples of periphyton and tufa were collected monthly, in the period from October 2017 to December 2018, from two control sites and five revitalized water channels, using a core sampler. In the frame of multidisciplinary research, physico-chemical, biological and geological parameters were measured. Reactivated channels showed higher nitrites concentration, lower pH and dissolved oxygen concentration caused by higher organic matter content originating from forest soil developed on tufa barrier during dry phase. Periphyton community showed more diversity in reactivated streams in comparison to control, presumably due to lower competition and predatory rates and/or intensive organic matter decomposition processes. Results of granulometric analysis displayed variations in grain size depending on season. During autumn and winter, more intensive rainfall and higher water erosion washed away sandy and muddy particles leaving only lithified tufa remains at all sites. Environmental data and periphyton assemblage patterns indicate establishment of stable conditions in the reactivated channels of Skradinski buk tufa barrier. Our results emphasize the need for interdisciplinary approach in long-term and sustainable management of the tufa barriers. |
