The establishment of a network of reserves is of fundamental importance to the loss of biodiversity. Seven different area
selection methods for the establishment of a reserve network were applied in the present study: (a) 5% cut-off value of the
grid cells with the highest species richness or conservation value, (b) complementarity analysis using as criteria species
richness or conservation value or rarest species richness, and (c) mixed complementarity analysis using as criteria species
richness or conservation value. These methods were applied in the orchid taxa of east Macedonia. The conservation values of
taxa were estimated on the basis of regional rarity, broad-scale rarity, and species specialization. The spatial overlap between
the resulting networks and the Natura 2000 network of the study area was assessed. Furthermore, the efficiency of the latter
network to protect the orchid taxa of the study area was examined. Our results suggest that: (a) a multiscale estimation of
rarity is necessary for the unbiased estimation of species conservation values; (b) species specialization adds valuable ecological
information to the assessment of taxa conservation values; (c) complementarity and mixed complementarity analyses on species
richness or conservation value safeguard all the taxa of the region; (d) complementarity analysis on the basis of the richness
of the rarest species safeguards all the rarest taxa, but not the total number of the remaining taxa; (e) the 5% cut-off value
on species richness or conservation value fails to protect all the taxa of the region, including a large number of the rarest
taxa; and (f) the Natura 2000 network, despite its large coverage in the study area, fails to safeguard all the taxa, including
some of the rarest. 相似文献
Question : How do interactions between rocky landscape features and fire regime influence vegetation dynamics? Location : Continental Eastern USA. Methods : We measured vegetation, disturbance and site characteristics in 40 pairs of rocky and non‐rocky plots: 20 in recently burned stands, and 20 in stands with no evidence of recent fire (‘unburned’ stands). Two‐way analysis of variance (ANOVA) was used to assess the main and interaction effects of fire and rock cover on plant community composition. Results : In burned stands, rock cover had a strong influence on vegetation. Non‐rocky ‘matrix’ forests were dominated by Quercus, and had abundant ground cover and advance regeneration of early and mid‐successional tree species. Burned rocky patches supported greater density of fire‐sensitive species such as Acer rubrum, Sassafras albidum and Nyssa sylvatica and had little advance regeneration or ground cover. Quercus had fewer fire scars and catfaces (open, basal wounds) on rocky patches, suggesting that rocky features mitigate fire severity. In unburned stands, differences between rocky and non‐rocky patches were less distinct, with both patch types having sparse ground cover, little tree regeneration, and high understorey densities of relatively shade tolerant A. rubrum, N. sylvatica and Betula lenta. Conclusion : Under a sustained fire regime, heterogeneity in rock cover created a mosaic where fire‐adapted species such as Quercus dominate the landscape, but where fire‐sensitive species persisted in isolated pockets of lower fire severity. Without fire, species and landscape richness may decline as early‐mid successional species are replaced by more shade tolerant competitors. 相似文献
In the development of the cellular slime mold Dictyostelium discoideum, the differentiation-inducing factor-1 (DIF-1; 1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl)hexan-1-one) plays an important role in the regulation of cell differentiation and chemotaxis; however, the cellular signaling systems involving DIF-1 remain to be elucidated. To obtain a probe for DIF-1, we synthesized a DIF derivative (DIF-1-NH2; 6-amino-1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl)hexan-1-one), and prepared an anti-DIF-1 antibody using a DIF-1-NH2-conjugated macromolecule as the immunogen. A 100-fold dilution of the antibody bound to DIF-1-NH2-conjugated resin, and this binding was inhibited by co-addition of 20 μM DIF-1 or DIF-1-NH2. In a monolayer culture of HM44 cells, a DIF-deficient D. discoideum strain, 0.5 nM exogenous DIF-1 induced stalk cell formation in ∼60% of the cells; this induction was dose-dependently inhibited by the antibody (diluted 12.5- or 25-fold). Furthermore, this inhibition by the antibody was recovered by co-addition of 2.5 or10 nM DIF-1. The results indicate that the anti-DIF-1 antibody recognizes DIF-1 and neutralizes its function. 相似文献
Abstract. Functional diversity has been seen as the key to predicting the stability, invasibility, resource capture, nutrient cycling and productivity of communities. However, it has been unclear how to estimate it. Ten criteria for an index of functional diversity are developed. These include that it should reflect the range of characters present and the abundance of the species with those characters in the community, and be unaffected by the measurement units used or by the number of species. An index that meets all ten criteria, FDvar, is investigated. It is based on the variance in characters, weighted by the abundance of the species with those characters. Tested with artificial and randomly generated data, it showed reasonable use of the 0 ‐ 1 range (mean 0.60, range 0.0009 ‐ 0.975) and intuitive behaviour. Tested with field data from eight sites in New Zealand, it gave a good spread of values (mean 0.65, range across sites 0.34 ‐ 0.84), showed good ability to distinguish between the communities and its performance was ecologically intuitive. Illustrative correlations are made with mean annual temperature and soil fertility, determined by a bio‐assay. FDvar is recommended for general use. 相似文献
In all member countries of the European Community, the influence of European directives is increasing. This is especially the case with directives on the conservation of natural habitats and wild fauna and flora (European Council Directive 92/43 EEC from 1992 (Council of the European Union 1992) and the directive on the conservation of wild birds (European Council directive 79/409 EEC from 1979 (Council of the European Union 1979). These directives are expected to influence the future development of nature-based sport and outdoor recreation significantly. Many German sport organisations are expecting negative consequences for the future development of nature-based sport in mountain areas. This paper summarises key findings of a study commissioned by the German Sport Association.
This project develops guidelines for the application and interpretation of these directives, as well as for their practicable use and management. The study shows that the potential negative effects of nature-based sport and outdoor recreation activities can be categorised into three general types. Furthermore, large sport events should be evaluated separately in the future. Finally, the crucial role of management plans is discussed, which are essential if NATURA 2000 areas are to be established successfully. The management plan assists in the selection of suitable measures, helps to resolve conflicts, and increases the level of acceptance and its transparency for the public. This paper will demonstrate that the consultation and participation of local people including members of sport and recreational organisations is essential to achieve the best result in the interest of nature conservation in general and conservation of endangered habitats or species specifically. 相似文献
Abstract. A first classification for serpentine annual grasslands distributed throughout northern and central California is proposed. This study has followed the Braun‐Blanquet phyto‐sociological system based on floristical, biogeographical and bioclimatic features of the sampled areas. Numerical analyses of classification and ordination were applied to the floristic relevés. Minimum Variance Clustering grouped relevés into basic classification units that allowed us to define low‐hierarchical syntaxonomical units (associations) and ‘communities’. A Principal Coordinate Analysis was used to extract those ecological parameters related to the axes that separate those classification units from the previous dendrogram. The results showed that differences in species composition was mainly due to a continentality gradient and the shady effect of an overstory vegetation. On the basis of both analyses we propose a first syntaxonomic scheme on ultramafic (mainly serpentine) annual plant communities of the biogeographical Californian Region that comprises four associations, two subassociations and some provisional communities. 相似文献
Abstract. Integrated synusial phytosociology combined with traditional measures of diversity is used to describe the structure of vascular vegetation diversity along the forested riparian landscape of the upper Oise valley (Belgium and France). The two dimensions (longitudinal and lateral) of the geomorphological complex are examined at four scales: synusia, phytocoenosis, tesela and catena. The results support the following hypotheses: (1) the environmental gradients observed, particularly the lateral ones, are very complex; (2) there is a clear lack of coupling between the tree, shrub and herb layers, which indicates a differential response to the underlying influence of environmental controls; (3) moderate flooding‐induced disturbance enhances herb species richness; (4) stressful environments support a low plant species diversity but a high synusial richness; (5) natural factors (substrate, climate, disturbance) are more important at the synusia and phytocoenose scales, but (6) anthropogenic disturbances, mainly through forest and river management, are more important at the landscape level. By considering plant communities as structural‐dynamic entities of ecosystems in a landscape context, integrated synusial phytosociology provides a basis for decomposing a complex system since the different hierarchical levels are both nested and thus strongly relational and process‐based. 相似文献