engleski

Habitat loss on Đon Močvar – the largest pit bog in Croatia - due to depopulation and abandonment of traditional land use

Đon močvar (situated in central Croatia, 170 m a.s., in Quercus petrea-Carpinus betulus vegetation zone) represents the oldest (preboreal origin) and, with area of 11 ha, the largest peat bog not only in Croatia, but in broader Southeast European area. It is composed of a mosaic of different vegetation types – from typical transitional peat bog vegetation (ass. Drosero- Caricetum stellulate) and some elements of raised bog communities (Sphagnum capillifolium- Polytrichum longisetum), to the well developed ass. Rhinchosporetum albae, which was thought to be extinct in Croatia. With the richest flora of Sphagnum mosses (eight species) it represents the centre of diversity of this group in Croatia. Vascular flora is represented with many rare and Red listed species (27% of its total flora). However, the area is under strong pressure of vegetation succession and overgrowing by Molinia caerulea, Betula pubescens and Frangula alnus and consequently by several herbaceous species due to changed water regime and deposition of litter. To trace changes in vegetation during the time, we analysed aerial photographs from the period 1959- 2004. The first major step in vegetation change occurred between 1976 and 1990, when farm households in vicinity disappeared, and surface of wet meadows decreased from 35.3% to 3.5%. In the next period (1990-2000) forests had spread form 17.4% to 40.1% and than to 46.1% in 2004. However, surface of Rhynchosporetum albae had been decreasing from 5.7% in 1959 to 4.2% in 1990 and finally to 3.9% in 2004. Habitats with open water surface have almost disappeared, since they cover 11.6% in 1959 and only 0.12% in 2004. Since 1990 meadows overgrown by shrubberies occurred as new habitat type, represented by 5.7% in 1990 and by 11.5% in 2004. These processes are mainly caused by intensive depopulation of the region, followed by abandonment of traditional land use enabling rapid development of stands dominated by mentioned fast growing tree species.

succession; Sphagnum; Rhynchosporetum albae; threatened habitats

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