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Wetland zones along lake shores as barrier systems: field and experimental research on nutrient retention and dynamics

100%

Rzepecki M.

Polish Journal of Ecology

2002

tom 50

nr 4

Populations of fish in relation to riparian ecotone development in the Narew River catchment

100%

Penczak T.

nr 1-2

Number of species (S), density (N) and standing crop (B) were investigated in 331 sites in the catchment of the Narew River, the biggest tributary of the Vistula, against 4 categories of riparian ecotone intensity in various-width rivers. All populations were first analyzed together, then within the scope of three most abundant ecological spawning groups. The image obtained is to some extent blurred by anthropogenic alterations as well as humancreated ecotones, yet it is evident that a total lack of bankside trees had a negative impact on the values of S, N and B of all investigated populations. Exceptions are only small streams of the Bialostocka Upland, where at a high percentage of submerged vegetation and occasionally stony bottom (washed away moraine bars), the lack of riparian trees did not cause any decrease in any of the three populational parameters. The uninterrupted compact forestation of the banks was positively correlated with S, N and B only in the lower Narew River, where the river bed was more than 100 m wide, hence where the access of light was not already limited. For lithophilous species a river's naturalness was a more important factor conditioning their abundance than the development of riparian ecotones. Indifferent species displayed a high, positive dependence on the development of ecotones, while phytophils (whose development is vegetation-dependent) formed the most qualitatively and quantitatively abundant populations at a weak, and in some rivers, even medium forestation of the banks.

Buffering role of land-water ecotones in the structuring of the fish community of the Sorraia system

100%

Coelho M. M. , Pires A. M. , Collares-Pereira M. J. , Sousa E. C. , Zalewski M.

nr 1-2

To test the role of riparian ecotones in fish community dynamics three different sites along the Sorraia system, were selected. Each station has been under distinct anthropogenic pressure, and characterized by a mosaic of habitat conditions. Fish were collected by electrofishing from October 1991 to October 1993 using two distinct sampling scales, (50 m and small sectors defined according to discontinuities in the dominant vegetation). The variation in species abundance and distribution was correlated with physical factors. The results showed the preference of barbel and nase for riparian vegetation and greater depth and of roach for zones with macrophytic vegetation and high current velocity. Fish community of the Sorraia system does not exhibit a consistent pattern of temporal variation, what is usually observed in Southern streams of the Iberian Peninsula. This fact is probably related to the landscape disturbance.

Riparian ecotones, invertebrates and fish: life cycle timing and trophic base

100%

Bretschko G. , Waidbacher H.

nr 1-2

Riparian ecotones are either within the bankfull lines (instream ecotones) or beyond (bank vegetation and floodplains). Instream ecotones (e.g. gravel bars) are most intimately and permanently interconnected with the stream system. The third order river Melk was channelized some decades ago with devastating effects on the fish fauna. The restoration of instream ecotones and of the riparian vegetation improved the fish population immediately. Instream ecotones are equally important for the fish community in high order streams. Data are given for the 9th order Danube. The duration of floodplain inundation is unpredictable but generally short in the temperate climatic zone. Fish do not migrate far into the inundated terrestrial vegetation but stay in or near to the enlarged backwaters. In backwaters separated from the main stream, a potamal fish population survives in an otherwise rhithral stream section. Floodplain inundation is predictable and lasts over long periods in the tropics. Fish and invertebrates are adapted to use the vast resources of habitats and food by active migration into the inundated forests.