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Effect of two management techniques applied to the reduction of Juncus maritimus (Lam.) abundance in a selected temporary wetland

Sahib Nargis

Journal of Water and Land Development

2019

no. 41

120--132

Moderate management of temporary wetlands is one of the most proper methods for their restoration and conservation. The cessation of use may lead to high biomass domination by macrophytes as Juncus maritimus (Lam.) that changes plant community structure, threatens species biodiversity, and becomes a danger for their conservation. The experiment was carried out in Sidi Boughaba coastal reserve in Morocco. Two management techniques of wetlands were tested, cutting and uprooting of the rush. Four experimental plots (4.2 × 2.9 m) within the rush belt were set up, with intact plots as a control. Vegetation structure and water levels were monitored on 96 quadrats over two years. The six visits dates, three visits per year (February, April, June), were monitored over two years. The abundance and richness of species were studied, simultaneously with the density of the seed stock in each plot. Results showed that both techniques allowed the opening of the habitat with a significant increase of richness and abundance of species, particularly the restoration of characteristic species of the temporary wetland from the seed bank. The cut technique seems to have less of an effect on the seed stock, total seeds median value was 6.5 in cut plots versus 5 in uprooting plots, being regularly applied given the rapid encroachment of the rush.

Umiarkowane zarządzanie okresowymi środowiskami podmokłymi jest jedną z najbardziej właściwych metod ich odtwarzania i ochrony. Zaniechanie użytkowania może prowadzić do znaczącej dominacji biomasy makrofitów, takich jak Juncus maritimus, która zmienia strukturę zespołu roślinnego, ogranicza różnorodność gatunkową i stanowi zagrożenie dla ochrony siedlisk. Eksperyment prowadzono w przybrzeżnym rezerwacie Sidi Boughaba w Maroku. Testowano dwie techniki gospodarowania – cięcie i wykorzenianie sitowia. Założono cztery poletka doświadczalne (4.2 × 2.9 m) w pasie sitowia, stosując poletka bez jakichkolwiek zabiegów jako kontrolę. Strukturę roślinności i poziom wody monitorowano sześciokrotnie na 96 kwadratach w ciągu dwóch lat, trzykrotnie w ciągu roku (w lutym, kwietniu i czerwcu). Badano obfiobfitość i bogactwo gatunkowe oraz zagęszczenie banku nasion w każdym poletku. Wyniki dowodzą, że obie techniki umożliwiają otwarcie siedlisk ze znaczącym wzrostem bogactwa i obfitości gatunków, szczególnie przywracanie z banku nasion gatunków charakterystycznych dla siedlisk podmokłych. Technika wycinania skutkuje, jak się wydaje, słabszym wpływem na bank nasion, stosowana regularnie ułatwia gwałtowny rozrost sitowia.

Flow modeling in a jet engine

Hlavńa V., Rajčan P.

Journal of KONES

2010

Vol. 17, No. 4

191-197

It is possible to monitor effects related to flow in a jet aircraft engine by the three basic approaches - analytical, numerical and experimental Each approach has undergone changes and has been developed to the stage of its effective use. To efficiently manage the scientific and research work it is appropriate to use effective links among all three basic approaches. An experimental approach requires a test stand on which the characteristics of a usually geometrically reduced object or the actual object itself are verified. The principles of geometric and hydrodynamic similarities are applied. This approach is time and economically demanding and not all aerodynamic processes can be reliably simulated. Other disaavantages can be the occurrence of measurement errors, errors due to changes in the scale, influences of chemical reactions and influence of Reynolds number. Due to a very fast onset, development and challenges of IT, the numerical approach has become mostly used. It can provide sufficient information on an examined phenomenon in a particular object. It does not need any substantial simpliflcations, it is less financially demanding than the experimental approach, but it needs efficient processors with a huge memory capacity. Its disadvantage is a relatively large dependence of achieved results accuracy on the perfection of numerical models and models of turbulence in the areas with prevailing influence ofviscosity. The usage ofanalytical relations from mathematical andphysical analysis of the flow fleld is the fundamental of the analytical approach of observing the laws related to flowing. The paper deals with possibilities, procedures, advantages, and disadvantages of the mentioned approaches together with a presentation of some results from research and development activities carried out by the authors.