In most regions there are many possible ways of combining numbers of sites into reserve systems that represent a range of natural features. The 'irreplaceability' of a site is operationally defined as the percentage of these alternative systems in which it occurs. This is a fundamental measure of the conservation value of the site in terms of its potential contribution to the achievement of a reservation goal or, alternatively, the options for reservation that are lost if the site is lost. The measure allows decisions to be made on the future of individual sites in the context of their value, in combination with other sites, to the conservation of the full range of natural features in a region. It also provides a logical framework for the design of whole systems of reserves, with decisions proceeding from the most to the least irreplaceable. Irreplaceability can be measured directly for small data sets but must be predicted for regional data sets. A promising approach to prediction is discussed that requires validation with more extensive trials. The irreplaceability of a site depends on a specific reservation target and changes as some of the site's features become progressively represented in reserves elsewhere. The concept of irreplaceability undermines notions of conservation value that are static or based on a single static system of sites to achieve a reservation goal.

A previously described model of grass growth was used to analyse the effect of the severity of defoliation and the duration of the subsequent regrowth on the overall balance between photosynthesis, gross tissue production and leaf death and so on the amount that could be harvested/consumed per hectare under intermittent defoliation. Maximum yield per hectare was shown to be achieved whenever the fluctuations in LAI during regrowth and defoliation led lo the same low average LAI that was previously shown to give maximum yield (amount harvested/consumed per hectare) under continuous grazing. Thus, it is suggested that production under both continuous and intermittent defoliation may best be characterized, and diverse managements may be rationalized, on the basis of the average sward state, the average achieved. The analysis leads us to reconsider some widely held concepts of the growth and utilization of grass applied in both agronomic and ecological theory, and the provision of practical guidelines for management.

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There were insufficient data to establish whether oral EPA was better than placebo. Comparisons of EPA combined with a protein energy supplementation versus a protein energy supplementation (without EPA) in the presence of an appetite stimulant (Megestrol Acetate) provided no evidence that EPA improves symptoms associated with the cachexia syndrome often seen in patients with advanced cancer.