The studied section of the Upper Narew Valley between Suraż and Siemianówka is a natural marshy valley with a strongly meandering channel, subjected to intensive flooding. The river and its waters, as highly dynamic elements of the geographical environment, have created a high diversity of biotopes making the valley an area of outstanding nature value. At the same time, annual flooding by nutrient-rich waters is responsible for the valley’s high productive potential. The valley’s natural marshy meadows relatively valuable for economy have long been harvested for hay by farmers. The present study outlines the results of research of meadow vegetation diversity (fig. 1, tab. 1) and gives an assessment of the agricultural value and productivity of the grasslands (tab. 1, 2). A most extensive area, some 55% of the studied area, is occupied by Magnocaricion alliance communities represented by tall sedge fen vegetation subjected to paludification (mainly Caricetum gracilis with Carex elata), muddy tall sedge communities (Caricetum gracilis with Agropyro-Rumicion) and grassy reed beds (primarily Phalaridetum arundinaceae). Some sections of the valley subjected to less prolonged flooding and numerous local flat elevations are dominated by plant communities associated with variable moisture levels from the order Molinietalia (ca. 33% of the area) represented chiefly by Alapecuretum pratense meadows and, to a much lesser extent, sedge and grass meadows with common sedge (Carex nigra) defined by some botanists as Ranunculo-Caricetum. fuscae. Reed and reed-sedge swamps, marshy alder and ash-alder forest and low growth, fresh grassy meadows and dry-ground meadows occur only locally occupying some 11.5% of the study area. Meadows yielding fairly good-quality hay represented mainly by Phalaridetum arundinaceae (canary-grass, sedge-canary grass, meadow-grass and canary grass, sedge-meadow grass communities), Alopecuretum pratensis (meadow-grass-meadow foxtail, herbaceous-meadow foxtail and meadow foxtail communities) and fresh meadow communities (Arrhenatheretum) jointly account for some 59% of the area. Grasslands yielding hay of almost average fodder quality primarily represented by sedge and grass and sedge communities (Caricetum gracilis with Agropyro-Rumicion) occupy around 24% of the area. Tall sedge meadow communities (chiefly Caricetum gracilis with Carex elata) yielding low fodder quality hay make up ca. 8%. Grassland productivity is shown in table 1. Hay harvested from the studied valley meadows is rich in iron, relatively rich in manganese and registers a median content of zinc, copper, magnesium and phosphorus. Only calcium and, in part, potassium content is insufficient.
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