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Notizen: Abstract The objective of the study was to describe the annual and seasonal production of live biomass of six plant species or communities of the uplands of the UK –Calluna vulgaris, Vaccinium myrtillus, Nardus stricta, Molinia caerulea, Eriophorum vaginatum and Agrostis–Festuca grassland. The species or communities are important for the management of the uplands to meet both biodiversity and agriculture objectives. The annual and seasonal production of live biomass was determined for sites within six regions of England and Wales in 1995, 1996 and 1997. The six regions were North-east England, North-west England, North Pennines, South Pennines, South-west England and Wales. In each region, the Institute of Terrestrial Ecology's Land Classification Scheme was used to select three or four 2 km × 2 km squares that contained a mosaic of C. vulgaris and upland grassland plant species. Uniform plots of 1 ha were selected from each 2 km × 2 km square, within which three measurements were made on each sampling occasion. Biomass of each species or community was measured within 1·0 × 0·5-m quadrats using the same standard procedures. Measurements of annual production of current season's shoots of the pioneer, building, mature and degenerate phases of C. vulgaris and of V. myrtillus were made in October, and of the annual production of live biomass of N. stricta, M. caerulea and E. vaginatum in August. A simulated grazing regime was imposed for the Agrostis–Festuca grassland with cuts being made to a height of 4 cm at 8-week intervals. The annual production of live biomass produced was estimated as the sum of four harvests taken during the growing season. Seasonal measurements of the amount of live biomass of all the species were also made in April, June, August and October. For C. vulgaris, there were significant (P = 0·05) differences between the pioneer, building, mature and degenerate phases in the annual production of current season's shoots, with greater amounts being produced by the phases of greater age and with higher biomass. There were significant year (P 〈 0·05) and region (P 〈 0·05) effects, with the lowest production in 1995 and in the South-west of England. The values were higher than those observed in previous studies in Scotland, and these were interpreted as being associated with a longer growing season rather than higher summer temperatures. There was no difference between years and regions in the annual production of V. myrtillus. For the grass species, there were small differences in annual production of live biomass between years and regions. However, the annual production of live biomass of N. stricta was significantly (P 〈 0·01) lower in 1995 than in 1996 and 1997 and significantly (P 〈 0·001) lower in the South Pennines region than elsewhere. The effect of a range of weather and other environmental variables on the annual production of live biomass of each species of grass was explored, but they provided only a limited insight into the reasons for the observed differences and were found to be of limited value as predictors.

Notizen: Abstract A limitation to using n-alkanes in plants as faecal markers for estimating diet composition in herbivores is the small number of dietary components that it is possible to determine. One approach to overcoming this is to group species on the basis of their n-alkane concentrations and to consider these groups as dietary components. Feeding selectivity within a group, however, may change the proportion of a particular species in the group ingested and hence its n-alkane contribution to the diet ingested. This could potentially affect estimates of the composition of the diet. Simulations (380) of feeding selectivity within a group of herbage species were undertaken to assess the effects of selectivity on estimates of diet composition. The dataset was from a study whose aim was to estimate the proportions of the herbage component, composed of nineteen species, and of four individual browse species in the diet of red deer grazing a montado ecosystem in S. Portugal in the summer. Simulations were undertaken of total avoidance of each species in the group of herbage species, and selection of each species at 0·5, 1·5, 2·0 and 3·0 of its actual proportion within the group. Feeding selectivity had no effect on 0·36 of the outcomes of the simulations. Over 0·90 of the simulations were within ± 0·05 of the values calculated assuming no selection within the group of herbage species. It is concluded that, in the particular case studied, the effect of selection within a group on the estimates of other dietary components was relatively small and that the group of herbage species could be analysed as a single dietary component.