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The river valley of the French upper Meuse and its floodplain, constitutes a relatively natural ecosystem which still contains many endangered species of high conservation value. For example, several birds (Crex crex, Numenius arquata) as well as plant species (Gratiola officinalis, Inula britannica, Teucrium scordium, Ranunculus lingua and Mentha pulegium) which have declined seriously in France in recent times are found in the upper Meuse floodplain. Phytosociological studies and water level measurements have shown that the floristic diversity is mainly influenced by hydrological fluctuations and agricultural practices. The plant communities are structured along a topographical gradient in the high water bed reflecting the duration of floods and the ground water table depth. Agricultural practices have influenced the vegetation changes by selecting species adapted to particular management practices (e.g., fertiliser use, grazing, cutting regime). The data collected in this study from the upper Meuse as enabled 13 grassland and wetland ecotopes to be defined which are correlated with different environmental factors. Fertiliser use, grazing and reduction in the frequency of the cutting lead to a lower species richness because they encourage competitive species. However, it is also demonstrated, that maximum biodiversity is not always synonymous with high conservation value because some impoverished ecosystems, e.g., sedges and tall forb formations, may contain endangered plant and bird species. Knowledge of the boundaries between the different plant communities enables likely changes in floristic composition after modification of one or more site factors to be forecasted. Such factors include, water table depth and flood frequency, cutting regime, fertiliser use and grazing pressure. Thus, the definition of these ecotopes, corresponding to correlations between water regime, agricultural practice and vegetation composition, could lead to the establishment of guidelines for water and agricultural managements that could be involved in restoration projects. 相似文献
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Structure of plant communities and landscape patterns in alluvial meadows of two flood plains in the north-east of France 总被引：1，自引：0，他引：1
Flood frequency and agricultural pressure can effect pattern and diversity in the plant communities and the landscape of flood plain meadows. The flood plains of north-east France are valuable semi- natural ecosystems with a high diversity of plants. This study was carried out in two valleys with plant communities showing the same zonation along a moisture gradient. About 350 measurements in each valley were carried out on 50 m2 sampling sites. Two study areas were intensively measured within each of the two valleys (1300 ha in total). Hydrological, geological and human factors have determined the unique landscape pattern of each valley. Using vegetation maps (1/5000) of the two valleys, landscape structure in terms of the size, number and form of patches were compared and the characteristics of the disturbance regimes (natural and human disturbance) creating each landscape are analysed. Variations of landscape indices are discussed in relation to the increase in agricultural pressure. Using quantitative parameters of landscape ecology to analyse vegetation mosaics provides an assessment of agricultural pressure and natural constraints on the flood plain scale. Agricultural intensification led to a decrease of meadow complexity whose natural rough shapes are made straight. Moreover flooded meadows lost thus natural connectivity with ditches and river which determined biodiversity and ecological processes of flood plains. 相似文献
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