Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 30

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

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
Smal part (1100 ha-4,7 %) of the Landscape Park Pojezierze Iławskie is an agricultural area. On the arable soils of this area floristic and phytosociological studies of weed communities were performed. In total, 156 species of vascular plants were registered what makes 75 percent of the whole segetal population high diferentitation in field plants was found. Seven associations and three communities of segetal plants were distinguished. High quantitative participation of the field plant communities in the range of associations (72 percent studied areas) allows us to suggest that the degree of agrocenosis degradation is wery small in this area as compare to the majority of the agricultural areas in Poland. Taking into account floristical and ecological diferentiation, geographical range and syntaksonomical position three assiociations (Teesdaleo-Arnoseridetum minimae, Aphano-Matricarietum and Spergulo-Chrysunthemetum segeti) present high specific value and deserve of the active form of protection.
The object of the studies presented in this paper was the flora of field plantings of different origin. The vascular flora of the plantings examined comprises 254 taxons. including 53 trees and shrubs, and 201 herbaceous vascular plants. The flora is rich and diverse. In 26.8% of taxons it is presents in all types of plantings. More than half of the registered species occurs once or twice only in all 23 planting groups studied. A detailed analysis of the flora examined shows that field plantings in agricultural landscapes may, in a small number of cases, constitute a source of weeds diaspores propagating in fields.
Phytosociological data were collected in 1994–1996 in plots (relevés) at the Research Station for Organic Farming and Conservation Breeding of the Polish Academy of Sciences in Popielno included in a large-area experiment conducted according to the concept and method proposed by Prof. S. Nawrocki. In a four-field crop rotation (root crops – spring barley undersown with red clover and grasses – red clover/grass mixture – winter triticale), each field was divided into two management units, organic and integrated. Data were collected in relevés by the Braun-Blanquet method, each year at the peak of the growing season. Weed abundance (% cover) in cultivated fields and the number of weed species (species richness) in crops were determined, which provided a basis for calculating the Shannon- -Wiener indices of species diversity and evenness, and the Rényi profiles. The qualitative (species) and quantitative structure of weed communities was compared using the Sorensen index. A total of 115 weed taxa (species, subspecies and varieties) were identified in the examined agro-phytocenoses. Echinochloa crus-galli, Chenopodium album, Matricaria maritima subsp. inodora, Capsella bursa-pastoris, Thlaspi arvense and Stellaria media were the most abundant. Weed infestation was slightly higher in the organic farming system than in the integrated system. Organic farming contributed to higher weed species diversity in root crops, red clover/grass mixtures and winter triticale. Weed species richness was reduced in red clover/grass stands, while root crops and – to a lesser degree – spring barley undersown with red clover and grasses decreased weed species diversity. The species composition and in particular the quantitative structure of weeds were affected by crop species and cultivation regime rather than by the farming system. Weed communities of crops grown under organic and integrated farming systems were more similar with regard to species composition than the quantitative structure.
Two hundred species of vascular plants were identified in grasslands on the Popielno Peninsula, in the part used for agricultural purposes. Species diversity in plant communities, measured by the Shannon-Wiener index, was found to depend on soil type, land use type and phytosociological affiliation. Greater species diversity was observed in communities that developed on mineral soils, are used as pastures, and belong to the class Molinio-Arrhenetheretea. The biodiversity of grassland communities on the Popielno Peninsula is affected by habitat conditions. The relationship between vegetation biodiversity and habitat quality is difficult to grasp due to its multidimensional character. The methods of multivariate statistics may prove useful in this respect.
The aim of the study was to investigate the effect of some different environmental conditions prevailing during the development and ripening of Echinochloa crus-galli diaspores on their germination. Some seeds were tested in the autumn the same year, whereas others were divided into two groups: dispersed seeds and seeds within the inflorescence. Then the seeds of both groups were buried. After eight-month stratification in the soil, the diaspores were tested under the same conditions as the samples examined in the autumn. The seeds tested in the spring germinated faster than those tested in the autumn. Also the germination capacity of barnyard grass caryopses examined in the summer was almost twofold higher than the germination capacity of those examined in the autumn. Both autumn and spring tests revealed that the harvest time affected germination. The seeds obtained in the second half of August and at the beginning of September (in the middle of the growing season) were characterized by a higher germination capacity than the caryopses collected at the beginning and the end of the reproduction period. The results show that the germination capacity and rate were not influenced by the place of origin, habitat conditions and accompanying plants. It was found in spring tests that germination depended on the kind of dissemination unit stored in the soil. After eight-month soil stratification, dispersed caryopses germinated by approx. 20% better than those stored with a part of the inflorescence.
W pracy przedstawiono występowanie Solidago canadensis L. i S. gigantea Aiton w północno--wschodniej części Polski. Badania terenowe prowadzono w latach 2003-2009, w 9 następują¬cych miastach: Starogard Gdański, Orneta, Iława, Lidzbark Warmiński, Olsztyn, Mława, Ostrołę¬ka, Olecko i Suwałki (rys. 1). W każdym z badanych miast były obecne oba analizowane gatunki nawłoci. Zdecydowanie dominującym gatunkiem była S. canadensis. Na łączną liczbę 1030 sta¬nowisk aż 82% należało do tego gatunku. Większość skupień nawłoci nie przekraczała 100 m2 powierzchni. Zdarzały się jednak płaty S. canadensis o powierzchni około 5000 m2 i S. gigantea o powierzchni około 1000 m2. Oba analizowane taksony notowano na siedliskach o amplitudzie hemerobii w zakresie siedmiu stopni: od H3 do H9 (przy zastosowaniu 9-stopniowej skali Kowarika (1988)). Wyraźna większość stanowisk S. canadensis posiada charakter szeroko pojmowanej euhemerobii (H5 - H7). Podobną prawidłowość występowania wykazuje również S. gigantea, jednak z nieco większą tendencją do zajmowania siedlisk o charakterze mezohemerobowym (H4). Obserwacje z ostatnich lat pokazują rosnące tempo rozprzestrzeniania się obu inwazyjnych gatunków, pochodzących z Ameryki Północnej.
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.