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Significance of current velocity gradients for distribution patterns of charophytes versus mosses and vascular plant communities in a lowland stream

Jakubas E., Gąbka M.

Oceanological and Hydrobiological Studies

2015

Vol. 44, No. 2

139--150

The study focused on the relationships between charophytes and the surrounding species composition and environmental factors in a lowland stream (Flinta stream, Western Poland). A total of 32 vegetation plots (4 m × 4 m) and 13 environmental variables were tested. Detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used to describe the relationships between the species composition and the selected variables. Dominance curves of aquatic plants, response curves (GAMs model) of charophytes and other macrophytes to the velocity gradient (the most important environmental factor, the Monte Carlo test) were prepared. In this study, 2 species of charophytes were recorded: Chara vulgaris and Chara globularis and 5 other co-occurring macroscopic algae, 2 mosses and 10 vascular plants. In the studied stream, charophytes occupied the separate niche. Chara vulgaris stands with moss vegetation were found in stream sections with the highest velocity of the water current (0.29 m s-1 mean), and the Chara globularis (with dominant Potamogeton species), preferred sections with the smallest water current velocity (0.19 m s-1 mean). Charophytes seem to respond to ecological gradients differently from mosses and vascular plants. These differences are related to current velocity, pH, conductivity and organic matter in bottom sediments, and to the niche differentiation associated with them.

The influence of co-occurring vegetation and habitat variables on distribution of rare charophyte species lychnothamnus barbatus (Meyen) in lakes of Western Poland

Gąbka M., Burchardt L., Owsianny P.

Polish Journal of Ecology

2010

Vol. 58, nr 1

13-25

At present Lychnothamnus barbatus (Meyen) Leonhardi belongs to the rarest species of charophytes in the world. In Europe it is classified as threatened with extinction. The problem of extinction of this species is intriguing, in particular in the context of its widespread occurrence in Europe and Asia till the last decade of the 20th century. Records of L. barbatus from Wielkopolska region (Western Poland) are know from 15 lakes. The most of them was stated in 19th and on beginning of 20th centuries. Now, this species is growing in 6 lakes, from among 2 sites are new. This study was undertaken to a) determine the abundance of L. barbatus and the co-occurring plant species at different sites in lakes, b) determine the most important ecological parameters controlling the structure communities with L. barbatus co-occurring and quantitative responses of this species. In 7 lakes (area 5.5-197 ha, depth max. 7.8-38 m, trophic state: meso-eutrophic) in western Poland the species composition and coverage of vegetation were studied at the 23 plots with L. barbatus occurrence in relation to the measured variables. Seventeen environmental parameters were measured including: depth of water, pH, conductivity, SO[4^2-], NH[4^+], NO[^3-], PO[4^3-], Na[^+], K[^+], Ca[^2+], Mg[^2+], chlorophyll a, Secchi disc visibility, colour, O[2] dissolved, saturation, total Fe during the period July-September. The DCA and CCA analyses were used to assess the relation between vegetation parameters and environmental variables. L. barbatus preferred the water rich in Ca[^+], Mg[^2+] and SO[4^2-] and with high concentrations of nutrients, especially NH[4^+] and PO[4^3-], and moderate values of electrolytic conductivity. In the studied lakes, L. barbatus occupied the separate niche. This species formed the communities in very shallow marginal zones of lakes (0.4-1.5 m) with other macrophytes like: Chara vulgaris, C. tomentosa, Potamogeton nitens, and monospecific stands on margins of steep lake slopes (4-6 m) with Chara globularis fo. hedwigii and Nitella mucronata. The process of extinction of this species seems to be related with increasing turbidity related in turn to algal blooming in lakes and with the spatial competition of vascular macrophytes, especially Ceratophyllum demersum.