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1. Macroinvertebrate species and information on thirty-nine variables were recorded at forty-six sites on twelve Cornish streams affected to varying extents by past metalliferous mining. 2. Relationships between macroinvertebrate communities and environmental variables were examined using canonical correspondence analysis (CCA). Copper was the strongest correlate with Axis 1 of the analysis, suggesting that it may have a major role in determining community structure. There were also strong correlations between Axis 1 and aluminium, alkalinity, pH, dissolved organic matter and algal cover, and between Axis 2 and discharge.3. CCA distinguished four site groupings. In spite of seasonal changes in position on the ordination, as revealed through CCA and detrended correspondence analysis (DCA), sites retained their group membership. There were differences in the proportions of the major taxa within the four CCA-derived groups. In the group with the highest copper concentration, Ephemeroptera were absent, but triclads and chironomids were abundant, with Orthocladiinae the dominant group. 4. Changes in the occurrence of spedes along the metal gradient reflected changes in sensitivity. 'Tolerance' plots of selected species based on the CCA site ordination diagram were used to identify environmental thresholds. 5. As well as direct toxic effects of copper and aluminium on invertebrate communities, co-precipitation of these two metals could be an important physical factor. Further modifying influences resulting from interactions between toxic metals and pH, alkalinity, hardness and dissolved organic matter contributed to the complexity of conditions affecting the faunat community in metal-contaminated streams. 6. The most severely contaminated sites, with mean copper concentration exceeding 500(xgp', were all characterized by a reduced community dominated by the flatworm Phagocata vitta, the chironomids Chaetocladius melaleucus and Eukiefferielia claripennis and the net-spinning caddis Plectrocnemia conspersa. The necessity for spedes identification is demonstrated in relation to variation in metal tolerance.

We present the use of a spatially explicit model of woodland dynamics (LANDIS-II) to examine the impacts of herbivory in the New Forest National Park, UK, in relation to its management for biodiversity conservation. The model was parameterized using spatial data and the results of two field surveys and then was tested with results from a third survey. Field survey results indicated that regeneration by tree species was found to be widespread but to occur at low density, despite heavy browsing pressure. The model was found to accurately predict the abundance and richness of tree species. Over the duration of the simulations (300 yr), woodland area increased in all scenarios, with or without herbivory. While the increase in woodland area was most pronounced under a scenario of no herbivory, values increased by more than 70% even in the presence of heavy browsing pressure. Model projections provided little evidence for the conversion of woodland areas to either grassland or heathland; changes in woodland structure and composition were consistent with traditional successional theory. These results highlight the need for multiple types of intervention when managing successional landscape mosaics and demonstrate the value of landscape-scale modelling for evaluating the role of herbivory in conservation management.

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