Possible causes of high concentration nitrogen among riparian plant species

Abstract

Nitrogen deposition data together with inland water parameters provide message that nitrogen load is big enough to cause marked changes of vegetation in Baltic States. There is much concern about eutrophication of the rivers, although information about riparian plant species is still poor. Various macrophyte strategies (abundance, architecture) might be developed. Plant productivity firstly depends on processes ongoing in the leaves. Data about plant leaf saturation with nitrogen remains poor. Usually studies refer on Ellenberg indicatory values or other indirect parametrs. Present study aimed at comparison of nitrogen concentration among populations of riparian plant species of Lithuania (project sponsored by Lithuania Research Cuncil; SIT-02/2015). Around 250 populations were sampled along main river basins in Lithuania: Nemunas, Venta, Lielupė, Seafront. Median values (N % d. m.) of nitrogen concentration for the species were as followed: Echinocystis lobata - 4,2; Nuphar lutea (L.) Sm. - 4,1; Phragmites australis - 4,0; Phalaris arundinacea - 3.6; Bidens frondosa - 3.6; Stuckenia pectinata - 3.1; Lythrum salicaria - 3,0. Species nitrogen data was related to land cover types of neighbouring areas, empoying 2-level hierarchcial Corine classification system. Among the tested plants the highest concentration was detected for invasive in Lithuania species Echinocystis lobata., at the same time, among the tested populations the highest concentrations of nitrogen were characteristic for populations growing near Curonian Spit. The highest amounts of nitrogen were determined for the most spread riparian species of Lithuania. It could be concluded that present level of nitrogen amounts, entering riparian ecosystems is big enough to cause spread of nitrophilous species.