Nutrients availability and hydrological conditions of selected wetland ecosystems in the Biebrza river valley

Nutrients availability and hydrological conditions of selected wetland ecosystems in the Biebrza river valley. Paper presents results of investigation of hydrological conditions and nutrients limitation and availability for wetland vegetation in selected sites within Biebrza river valley. Analysed sites were overgrown by tall sedge Magnocaricion vegetation (Caricetum gracilis and Caricetum elatae), wet meadow Molinio-Arrhenatheretea vegetation (Molinietum caeruleae), and sedge-moss Scheuchzerio-Caricetea nigrae vegetation (Caricetum lasiocarpae). There were noted a close relationship between vegetation types, hydrological regimes and kind of nutrient limitation. Low productive Molinio-Arrhenatheretea and Scheuchzerio-Caricetea nigrae vegetations fed mainly by groundwater were limited by phosphorus, while highly productive Magnocaricion vegetation, fed by river water, was subjected to nitrogen limitation. We have found big diversification of groundwater and surface water levels within habitats of different vegetation types along the Biebrza river valley. Magnocaricion vegetation present on flooded areas is characterized by significant water level fluctuations and long-lasting inundations. On areas covered by Molinio-Arrhenatheretea vegetation we noted majority of water levels not exceeding the level of the ground surface. Whereas Scheuchzerio-Caricetea nigrae vegetation, fed by groundwater, is characterized by low variation of groundwater levels