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A floristic inventory of segetal flora was carried out in abandoned fields and adjacent crop fields on rendzina soils in the Zamość region in the year 2010. This study found a total of 130 weed species belonging to 30 botanical families. The following families were represented most frequently: Asteraceae, Fabaceae, Poaceae, Lamiaceae, Scrophulariaceae, and Brassicaceae. In the segetal flora, apophytes are dominant (55% of the total flora), with the highest number of meadow and xerothermic grassland species among them. Archeophytes (38%) predominate in the group of anthropophytes. The species characterized by the highest constancy classes and reaching the highest cover indices posed the greatest threat to crops in the study area. The following weeds are most frequently found in fallow fields: Consolida regalis, Cichorium intybus, and Sinapis arvensis, while Papaver rhoeas is the greatest threat to cereal crops grown on rendzina soils.
The Irano-Turanian species – Russian olive (Elaeagnus angustifolia L.) – is one of most commonly planted tree in the shelterbelts in southern Ukraine. The consequences of introduction of the species from windbreaks, into areas of different land use in west and central Pontic desert steppe zone are evaluated. The above steppe is unique on a European scale and exists only in some parts of the Black and Azovian Sea coasts. In recent years, the socio-economical crisis in Ukraine (less intensively cultivation, as well as limited grazing) has been responsible for the intensification of the spread of alien tree species outside the windbreaks. Studies were conducted in Kherson Region, in the immediate vicinity of the Black Sea Biosphere Reserve, where the presence of aliens is undesirable. The analysis of phytosociological material (48 relevés with and without Russian olive) collected from areas of different land use type and limited human pressure (as abandoned field, former intensively grazed solonetz and extensively grazed desert steppe vegetation) show that E. angustifolia can impede the regeneration of the desert steppe. The species creates favourable conditions for the growth of geographically and ecologically alien nithrophilous weeds.
Our research was conducted on abandoned fields which had been undergoing spontaneous succession for 40–50 years and then were partly burnt. The main objective of the study was to examine if spontaneous fire in the early successional stage of pine forest causes a decrease in the number of species, diversity and density of seed banks, and an increase in the share of species forming long term persistent seed banks. Standing vegetation and soil seed banks were studied on 20 permanent plots on adjacent burnt and unburnt sites one and twelve years after spontaneous fire. One year after the fire the number of species in the seed banks of both areas was similar (11 and 12 species). In the burnt area the Shannon index and the floristical similarity between the seed bank and standing vegetation were lower, and seed density five times higher than in the unburnt area (15 691.5 m–2 vs.3426.5 m–2). This was mainly the effect of the high number of seedlings of Calluna vulgaris (L.) Hull and Spergula morisonii Boreau germinating from the burnt plots. Twelve years after the fire the number of species in both seed banks had increased little, but seed density in the burnt area (1742.5 m–2) had decreased 16 times, while that of the unburnt area had changed only slightly (2875.5 m–2). At the same time the Shannon index for the burnt area increased considerably, whereas for the unburnt one it did not change. Our study shows that the long-term persistent soil seed bank plays a fundamental role at the beginning of the post-fire regeneration of temperate coniferous forest vegetation. Germination of Calluna seedlings from the burnt soil seed banks in several times higher numbers than from unburnt soil seed banks may suggest that heat from the fire promotes a loss of dormancy in the heather seeds.
In July, 1992, fire swept through the Jelonka Reserve (52o35'33"N; 23o22'10"E). Litter, herbs layer and juniper shrubs were razed and the tree trunks of Pinus sylvestris and Populus tremula damaged, which resulted in their death the following year. Five research plots of 25 m2 each were established in the post-fire area. The species present there and their degrees of coverage were listed on the Londo scale between 1993 and 2002. The calculation of average degrees of coverage for individual populations allowed for the establishing of a chronological pattern of post-fire succession. The following findings have been made: 1) the primary function in colonization belongs to species of guerilla strategy of growth whose dormant buds survived fire underground (Holcus mollis, Calluna vulgaris and Populus tremula) or phalanx strategy of growth (Corynephoms canescens); 2) the dominants of the initial succession stage are perennial grasses, not therophytes; 3) the spatial pattern of succession is influenced by the occurrence of H. mollis or C. canescens in a particular location; 4) the initial stage terminates with the occurrence and further growth of C. vulgaris clumps; the post-fire succession in the Jelonka Reserve attained a brushwood stage faster in comparison to secondary succession, formerly triggered by the cessation of cultivation on arable land.
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