Impact of Flora Communities on Nutrients Dynamics in Hyporheic Zone of Urban Spring Ecosystem <sup>†</sup>

Abstract

Hyporheic zone (HZ) is an interstitial part of groundwater that can provide a spectrum of subsurface habitats depending on the spatial distribution of upwelling groundwater. Differentiation of environmental factors affects the abundance and distribution of plants associated with outflows of groundwater. Plant communities in spring niches dependence on permanent, relatively cold water that not freeze in winter. High dynamics of redox conditions and low temperature increase the intensity of nitrification, denitrification and ammonification processes. We hypothesized that groundwater upwelling enrich surface water with biogenic compounds, and it depends on among others the flora communities. Research were conducted in two lowland spring niches in suburbs of Białystok. Interstitial samples were collected with mini-piezometers. The analysis of flora included: vascular plants and bryophytes. Nutrient analysis were conducted using chromatographic methods, organic carbon analyser and Kjeldahl analyser. The springs studied differed in their richness of species, which is associated with varying degree of human impact and the environmental factors (water quality, geological, morphological, hydrological). Hydrophilic vegetation performs a stabilizing function by assimilating nitrogen compounds and contributing to a variations in nutrients concentration. Many species of water bryophytes, due to their high sensitivity to water quality, are considered a bioindicator of oligotrophy and mesotrophy. The richness of vascular plants in niches in the suburbs was smaller compared to the flora of lowland springs located in natural areas, but the presence of species under protection indicates a high degree of naturalness of the environment. Plant community richness can be a good indicator of the ecological status of lowland springs.