Struktura krajobrazów delt rzecznych na Opolszczyźnie i ich znaczenie w regionalnym systemie ochrony przyrody

Krzysztof Badora

Abstrakt


Structure of landscapes of river inland deltas in the Opole region and their importance in the regional system of nature conservation

Summary

Landscapes of inland river deltas occur in zones of river outflow to dam reservoirs. They are among the rarest and most valuable types of landscapes in Poland. In old glacial landscapes of the Silesia Lowland, with no larger natural lakes, deltas occur only in zones of outflows of rivers to dam reservoirs. In the paper we analysed the structure of these landscapes within The Turawa Dam Reservoir, supplied with rivers Mała Panew and Libawa.

Typical features of delta landscapes of dam reservoirs are: a) anthropogenic genesis, b) great susceptibility to management of basic elements of the landscape system, c) very low stage of degradation and devastation (excluding exploitation of sands and gravel), d) exceptionally varied mosaic structure of plant communities and their changeability with time, e) low contrasts at landscape boundaries, f) very high dynamics of changes of boundaries, g) great wildlife values of the over - regional importance. In the spatial structure of landscapes three main groups of geocomplexes can be distinguished. Main differentiating elements are length and frequency of periods of floods:

- aquatic-terrestrial geocomplexes regularly periodically dry – characterised by great seasonal changes of ranges, high dynamics of geomorphologic processes and domination of aquatic vegetation Potametea and Litorelletea, and terophyte communities Bidentetea tripartiti and Isöeto- Nanojuncetea. Considering natural values this zone is of the greatest importance for protection of biodiversity, especially – for bird fauna.

- terrestrial geocomplexes periodically flooded – characterised by stability of geomorphologic processes and occurrence of terrestrial vegetation Magnocaricion, scarcer Phragmitetalia, locally there occur tree communities Salicetea purpurae. These geocomplexes predominate in the delta lowland,

- terrestrial geocomplexes rarely flooded during high water periods – characterised by stable mineral substratum and occurrence of meadow, sedge and dry-ground forest communities. Some of these geocomplexes are post-agriculture fallows.

Unique values of landscapes of river deltas of The Turawa Dam Reservoir were approved by assigning them high rank in national and European systems of nature protection. In the zone of mouth of Libawa and Mała Panew a nature reserve is projected (RP Ujscie Libawy). The whole The Turawa Dam Reservoir is regarded as and Important Bird Area of the European rank for waterbirds and was designated as protected area of Natura 2000 (areas designed for birds and habitats protection). Main objects of protection there are migratory concentrations of birds (flocks of thousands of waterfowl, gulls and waders, rare seabird species) and terophyte vegetation. Zones of river mouths are important foraging and stopover sites for breeding and migratory birds and most important biotopes for plants.



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