Suchergebnisse

AbstractThe authors carried out the analysis of changes in the plant overgrowth of the lakes based on cartographic materials. Among 6 793 lakes with the area exceeding 1 ha located in the lakelands of Northern Poland, 893 lakes were selected for the analysis. The lakes were selected on the grounds of the existing bathymetric plans and information on their overgrowth and depth relations. Over the last 50 years lake area declined by 1.9% (from 140 975.0 ha do 138 273.7 ha) and so did the lake area covered with emergent plants, i.e. by 0.27% (from 11 219.0 ha down to 10 637.2 ha). Emergent plants cover on average 7.69% of the lake area. In the case of the lakes of smaller areas (below 80 ha) or medium areas (80÷200 ha) the extent of plant overgrowth was 14.3 and 9.6% respectively. The article presents two indicators which determine plant overgrowth of the lakes. These are the coefficient of overgrowing the lakes (%) and the coefficient of overgrowing the shoreline (ha·km-1). These coefficients make it possible to study the extent of lake overgrowing in the South Baltic Lakeland, regardless the direction of these changes.

With the increasing threat to forests in Europe from the invasive pine wood nematode (PWN) Bursaphelenchus xylophilus, effective methods are needed to monitor and reduce populations of its insect vector, the pine sawyer beetle Monochamus galloprovincialis. In the present study, we tested the effectiveness of different trap types (multiple-funnel, cross-vane, and triangular), colours (black, white and clear), and lubricant (polytetrafluoroethylene, PTFE) treatments (different PTFE formulations and timing of trap treatment) on the catches of M. galloprovincialis and three most commonly captured non-target beetle species (the xylophagous Spondylis buprestoides and two predators, Thanasimus formicarius and T. femoralis) in Poland. Of the traps not treated with PTFE, the white and black 6-funnel traps were most effective in trapping M. galloprovincialis beetles, while the catches in the cross-vane traps (both white and clear) were low. Trap treatment with PTFE significantly increased trap effectiveness, regardless of PTFE type and time of application. The catches of S. buprestoides were affected by trap type, while those of T. formicarius depended on trap colour and size. Both species seem to respond positively to ethanol and/or α-pinene in the lure composition. PTFE treatment had a significant effect on the catches of T. femoralis. In conclusion, for the monitoring of M. galloprovincialis, we recommend the white cross-vane traps treated with dry PTFE. They are less but still effective in catching the target species, while their use, together with lures containing no ethanol and α-pinene, greatly reduces the catches of non-target insects S. buprestoides and T. formicarius.

Abstract
The paper presents the results of bathymetric mapping of selected tidewater glaciers in the St. Jonsfjorden (Svalbard) between 2004 and 2007. We also used the bathymetric data collected by the Norwegian Hydrographic Service (NHS) as well as the shaded relief images based on them. The most clearly visible traces in submarine marginal zones of the glaciers come from the Little Ice Age (LIA), i.e. the cooling period which in the area of St. Jonsfjorden might have ended no later than about 1900. At the beginning of the 20th century, i.e. during a warm period, the glaciers of St. Jonsfjorden reached their maximums. The youngest traces in the seafloor of the fjord and the bays date from this period, similar to the case of the land marginal zones. In front of the cliff of the Dahl Glacier there is a clearly visible zone of submarine moraines. It finishes exactly along the line of the LIA maximum. The sea-floor relief of the fjord and bays shows traces which we interpret as having been formed during the Late Weichselian (13-10 ka B.P.). At that time, the Dahl Glacier advanced onto the northern part of Hermansenøya; its main stream passed to the north of the island. Simultaneously, the Konow-Osborne Glacier terminated 2 to 4 km from the fjord mouth, leaving about 15 km2 of the fjord ice-free.