Summary 1The influence of fertilizer addition and mammalian herbivore exclosures (a 2 × 2 factorial design, with four replicates at each of two sites) on the cover, species composition and diversity of the understorey vegetation of the boreal forest in the south-western Yukon, Canada, were investigated from 1990 to 1999. This was done to test whether vegetation composition was controlled by resource level alone (bottom-up control), herbivory alone (top-down control), or by both (interactive control). 2 The density of the major herbivore, the snowshoe hare, varied 25-fold, declining from 148 km -2 in 1990 to 8 km -2 in 1994, and increasing to a second peak of 198 km -2 in 1998. 3 In control plots most species were remarkably constant in percent cover. After 10 years, most of the major species showed significant responses to fertilizer with four species increasing ( Festuca altaica , Mertensia paniculata , Epilobium angustifolium , and Achillea millefolium ), and three declining ( Linnaea borealis , Lupinus arcticus , Arctostaphylos uva-ursi ). Some species took up to 5 years before a response was detected. 4 Fertilization caused (i) a decline in the number of species, and species evenness in the community, (ii) a reduction in the proportion of woody species, and (iii) an increase in herbaceous dicotyledons and grasses. 5 The exclusion of herbivores had virtually no impact on the abundance of the vegetation or on species diversity, except in 1990-92 during a decline from a peak of 148 hares km -2 to 29 hares km -2 . 6 These results suggest that the percentage cover and composition of herbaceous vegetation in the boreal forest are determined almost exclusively by the productivity of the site (bottom-up control) and that the activities of mammalian herbivores may be important only during peaks in hare population densities (interactive control). 7 Results were both species-specific and time-dependent, suggesting that long-term studies are needed to discriminate between long-term responses to treatments and transient phenomena.

The aggressiveness of 20 Northern Ireland single-lesion isolates of Phytophthora infestans was compared following their inoculation onto detached leaflets of three potato cultivars chosen on the basis of their differing levels of race-nonspecific resistance to late blight: Bintje (highly susceptible); Cara (moderately resistant); and Stirling (more resistant). Five isolates from outside Northern Ireland were included for comparative purposes: two from the Republic of Ireland; two from the USA (representing the US-1 and US-8 clonal lineages); and one from Mexico. To control the variation between tests, a balanced incomplete block design was used, as opposed to either a complete block design or the method of inclusion of standard isolates, where such variation would have increased the error. Highly significant variation for disease parameters, including latent period, infection frequency, area under the lesion expansion curve (AULEC) and sporulation capacity, was found between isolates. These differences were much more marked on the cultivars exhibiting higher levels of race-nonspecific resistance. There was a significant interaction between isolate and cultivar for all parameters assessed and, overall, no one isolate was the most aggressive across all three potato cultivars. However, a group comprising seven of the 20 Northern Ireland isolates was consistently found to exhibit the highest levels of aggression towards all three cultivars for each of the disease parameters. These results demonstrate that significant variation for foliar aggressiveness exists within the Northern Ireland population of P. infestans , and indicate the importance of selecting appropriately aggressive isolates for evaluation of host resistance to late blight within breeding programmes.

Aim:  To identify the prevalence of nutrition risk among community‐living older people in Christchurch, New Zealand and to establish the frequently occurring risk factors for poor nutrition. Methods:  A convenience sample of 152 community‐living older people was recruited from five medical centres and a falls prevention service. Interview in the home included nutrition risk assessment as measured by the Seniors in the Community: Risk Evaluation for Eating and Nutrition questionnaire. All participants at nutrition risk were either provided dietary advice at the time of interview or offered referral to a nutrition‐related intervention. Results:  Of the participants, 23% (n = 35) were ‘at risk’ of poor nutrition and 31% (n = 47) were ‘at high risk’. The four frequently occurring risk factors for those ‘at high risk’ were: unintentional weight change (79%), eating alone (72%), perception of own weight (68%) and low milk product intake (66%). Conclusion:  Seniors in the Community: Risk Evaluation for Eating and Nutrition questionnaire identified that approximately half of a sample of community‐living older people in Christchurch were at risk of poor nutrition. The implications of low scores on the nutrition risk screening questionnaire deserve further exploration.

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SUMMARYPerennial ryegrass evaluation schemes categorize varieties into three maturity (early, intermediate and late) and two ploidy (diploid and tetraploid) groups, and compare the relative yield, persistence and nutritive quality of varieties within these groups. The present study compared these groups for herbage yield, dry matter (DM) concentration and, using near infrared reflectance spectroscopy (NIRS), four quality characteristics (in vitro content of digestible dry matter (CDDM), water-soluble carbohydrate (WSC) and crude protein (CP) concentrations, and buffering capacity). A total of 1208 plots were sown across 5 years in Irish Recommended List trials and then harvested 6–7 times in each of 2 harvest years. This also allowed an assessment of the effect of sward age. Maturity group had no significant effect on annual herbage yield, quality or DM concentration except for in vitro CDDM (P<0·01) but differed significantly for in vitro CDDM (P<0·01), WSC concentration (P<0·01) and buffering capacity (P<0·05) at the first silage harvest. Tetraploid swards had greater annual herbage yields (P<0·001), in vitro CDDM values (P<0·001) and WSC concentrations (P<0·01), but lower CP and DM concentrations (P<0·001) than diploids. Swards in their first full year produced an additional 5·17 t/ha DM (P<0·001) and had a higher (P<0·01) WSC concentration at the second silage harvest than in their second year, but did not differ significantly for in vitro CDDM and WSC, CP or DM concentrations. The present study showed that differences exist in yield, nutritive quality and ensilability indices between maturity and ploidy groups. These observations justify their assessment in variety comparative trials and facilitates particular groups being selected for individual farming systems to increase efficiency.