Is nitrogen in excess among plant species of Nemunas and other Lithuanian river basins

Abstract

Nitrogen deposition data together with inland water parameters provide indirect message that nitrogen load might have effects on vegetation of Baltic States. There is much concern about eutrophication of the rivers, although information about riparian plant species, their physiology and genetic parameters is still poor. Reacting to elevated nitrogen in the environment, various macrophyte strategies (abundance-, architecture-related) might be developed. Plant productivity finally 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 is aimed at comparison of nitrogen concentration among populations of some riparian and river plant species of Lithuania (project sponsored by Lithuania Research Council; SIT-02/2015). Around 250 populations of riparian and water macrophytes were sampled along main river basins in Lithuania: Nemunas, Venta, Lielupė, Seafront. Very high levels of nitrogen were determined for the most spread riparian plants of Lithuania. Among the tested species the highest concentration was characteristic for Echinocystis lobata. Comparing populations within each species, in most cases the highest concentrations of nitrogen were documented for sites neighbouring Curonian Spit. Relations between population nitrogen data and genetic diversity also some environmental factos such as river regulation is discussed. Species nitrogen concentrations were related to land cover types of neighbouring areas, empoying 2-level hierarchcial Corine classification system. Based on plant nitrogen concentrations it could be assumed that present quantities of this element, entering riparian ecosystems are big enough to cause the spread of native and invasive nitrophilous species.