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The geographic distribution and occurrence conditions of Juniperus thurifera subsp. africana in Morocco were studied. The literature and herbaria data, together with field observations formed the basis of detailed maps of distribution of the species in the Middle and High Atlas and allow us to analyze its vertical distribution. The taxon occurs in the sub-arid and arid zones of the Middle and High Atlas with a separate population in the Anti-Atlas, mostly between altitudes 2000 and 2700 m, with an altitudinal maximum at 3400 m and a minimum at 1700 m. It forms forests in the area of about 30 000 ha. In many places of the High Atlas it is the only wood source for local populations. It is strongly endangered because of over exploitation of the wood, over pasturing and lack of seedlings and young specimens.
Distribution pattern of δ¹³C values of plateau plants and their responses to environment along altitudinal gradients were investigated. In the growing season of 2003 (June– August), stable carbon isotope ratios (δ¹³C) of 174 plant samples belonging to 89 species of 20 families and 58 genera along the gradient 2800– 4400 m (above sea level) was studied in six sites on the east edge of Qinghai-Tibet Plateau. The results indicated that the range of δ¹³C values of plants is narrow from –30.2‰ to –25.2‰, which means that none of the species examined belonged to C₄ photosynthetic pathway and all of these species performed C₃ photosynthetic pathway. The average δ¹³C values of plants at 6 sites were positively correlated to altitude (r = 0.974, P <0.01). The results revealed that site-averaged δ¹³C values were negatively correlated with temperature (r = 0.907, P <0.05) as well as CO₂ partial pressure (r = 0.940, P <0.01). The combination of these two factors account for 80% of the variation of δ¹³C values (r² = 0.859, P <0.01). Varying precipitation with increasing altitude does not affect the plant δ¹³C values (r = 0.469, P> 0.05) as well as the sunlight duration(r = 0.630, P> 0.05).
Results of the studies on the floristic biodiversity of the kurgans in the Pontic desert steppe of the Black Sea Lowland (Kherson Region) are presented. Twenty-six of about 130 kurgans higher than 3 m, distributed over an area of approx. 1500 km2, were surveyed and the flora of 5 microhabitats within every kurgan (top, southern and northern slope, southern and northern foot) was examined. The richness of the kurgan flora is estimated at 305 species. Species of alien origin constituted 23% of the total flora, which indicates limited anthropogenic influence. Species of two classes, Festuco-Brometea and Stellarietea mediae were predominant, which also confirmed the semi-natural character of the kurgan flora. The lowest number of species was recorded on top, which was relatively rich in synanthropes, particularly therophytes (Stellarietea mediae). The north side was richer in species than the south side of the kurgans. Steppe species were the most stable and important component of the flora of the slopes (45-47% of the species represented the class Festuco-Brometea). The total flora of the foot contained more species and was more diversified than the flora of the slopes (although the mean number of species was similar in both habitats), but each species occurred at low frequency. There was a higher proportion of species which were introduced from the area surrounding the kurgans, e.g. weeds, halophytes, meadow species, as well as trees which are rarely found in the desert steppe zone. In spite of the small size of the kurgans, significant differences between the floristic composition of the various microhabitats were detected.
In this study we analyzed gaps originated in different seasons of the year vs. places of close vegetation in calcareous grasslands in terms of their suitability for seedling germination and establishment. Gaps, irrespective of the time of their origin, significantly promoted seedling emergence as compared with close swards. However, the season of gap creation influenced the rate of seedling germination/emergence. Seedlings occurred more frequently in autumn and spring gaps than in the summer ones. The highest mean number of seedlings and of their species were noted in autumn openings. However, the subsequent survival of seedlings in autumn gaps was low. On the contrary, in spring gaps juveniles occurred with the significantly highest mean number, frequency and species richness. The above results pointed to the positive, although very limited role of artificially created gaps as places favouring seedlings establishment.
A numerical analysis of the phytosociological relevés from ancient and recent woodland on a mesic forest site in central Poland was carried out. Three groups of forest stands were recognised: planted with Pinus, recent and ancient oak-hornbeam Tilio-Carpinetum. The species of ancient woodland occurred mainly in ancient oak-hornbeam forest stands, however some ferns: Dryopteris carthusiana, D. dilatata and D. filix-mas, and an orchid species Epipactis helleborine, are to be found mainly or exclusively in recent forests. The occurrence of ancient forest species in recent woods may be putatively explained by long-distance wind dispersal or by the thriving in situ in unrecognised small wood patches. Twelve ancient woodland indicators (i.e. 36% of a total number found in the region under study) occur exclusively in ancient woodland. It underlines the role of passive species protection in the maintenance of the regional species diversity.
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