Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 36

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  dolina Sanu
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
An basin of a large or medium river is a large biogeosystem, shaped by the history and natural processes, that is an integrated functional unit with its own hydrological balance, circulation of elements and energy. The author deals with the nature of ecological corridors on the basis of river San, a medium-size river in European terms, and it’s ecological functions. He focuses on the threats and lists ways of preventing degradation of the ecological macrosystem.
4
61%
In 2001-2004 148 phytosciological releves using the Braun-Blanquet method were recorded in abandoned meadows and the abandoned arable fields adjacent to them, presently overgrown by grassland with weil developed turf. The study area was located in the San valley on alluvial soils. On the basis of the collected material, 6 associations and 10 temporarily distinguished plant communities were distinguished. Out of them 7 were classified in the class Molinio-Arrhenatheretea, 4 in Phragmitetea, 2 in Artemisietea, and 3 were difficult to assign to a clear syntaxonomic position. Phytoindicative analysis of habitat showed that all of the communities were semi-heliophilous (L = 5.9 - 7.4). They occurred on soil with varying soil moisture (F = 3.8 - 8.8), soil pH (R = 4.9 - 7.4) and nitrogen content (N = 3.8 - 8.1). In all the communities, the accumulation of unmown, aboveground biomass was observed. In abandoned meadows in wet or periodically excessively moist soils Deschampsia caespitosa, Juncus effusus and perennial dicots (Filipendula ulmaria, Lythrum salicaria, Cirsium rivulare, Lysimachia vulgaris) spread. In the remaining communities the species characteristic of the class Molinio-Arrhenatheretea was frequent and ahundant, among others: Poa pratensis, Festuca rubra, Festuca pratensis, Rumex acetosa and Vicia cracca. In all the distinguished communities the specics from the classes Artemisietea, Agropyretea and the alliance Agropyro-Rumicion crispi from the class Molinio-Arrhenatheretea were present. Regardless of habitat conditions the most frequent species were: Cirsium arvense, Urtica dioica, Galium rivale, Anthriscus sylvestris, Agropyron repens, Equisetum arvense, Mentha longifolia, Carex hirta, and Ranunculus repens, whereas Calystegia sepium, Eupatorium cannabinum, Epilobium hirsutum and Myosoton aquaticum grew nearly exclusively on wet sites and Saponaria officinalis and Reseda lutea on the dry ones. As far as grasslands originating from the spontaneous creation of turf in recently abandoned arable land are concerned, meadow species from the class Molinio-Arrhenatheretea, with some species from the class Stellarietea mediaei, dominated. In all the phytocoenoses, except for the Urtica dioica community, the presence of trees and shrubs initiating the succession towards secondary woodland was observed. In wetter sites Salix cinerea, Salix alba, Salix triandra, Salix purpurea and Salix viminalis occurred, and in the moderately moist and dry sites Crataegus monogyna, Crataegus rhipidophylla, Rosa canina, Prunus spinosa, Pyrus pyraster, Cerasus avium and Salix capreai were most frequent. The low number of constant species (constancy III-V) and the dominance of sporadic species indicate that the communities are far from stable. The most consistent composition was displayed by Festuca rubra-Poa pratensis, Carex brizaicles, Bromus erectus communities and the Caricetum acutiformis association. Floristically, the richest was the Bromus erectus community (mean no. of species per releve - 33.2.), and the poorest was the Phalaris arundinacea community (17.7 species).
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.