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11.
Phytophthora kernoviae and P. ramorum are introduced, invasive pathogens in the UK. Both species are adapted for aerial dispersion and have a wide host range, many of which are common to both pathogens. The diseases they cause are foliar necrosis and shoot tip dieback on both tree and ornamental hosts, and bleeding cankers on tree hosts. Inoculum is produced on infected foliage but not on bleeding cankers in both cases. Proactive measures to prevent disease spread and to evaluate the risks posed by these pathogens are being undertaken. Amongst others, these include using the detached leaf assay to get an indication of tree foliage susceptibility, and inoculating wounded stems of saplings to get an idea of under‐canopy sapling and nursery tree susceptibility. The sporulation potential on selected susceptible hosts was assessed, and finally, surveys which are still ongoing were carried out in south‐west England. Results of this work are presented and discussed. 相似文献
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John B. Graham Joan I. Nassauer William S. Currie Herbert Ssegane M. Cristina Negri 《Landscape Ecology》2017,32(5):1023-1037
Context
Wild bee populations are currently under threat, which has led to recent efforts to increase pollinator habitat in North America. Simultaneously, U.S. federal energy policies are beginning to encourage perennial bioenergy cropping (PBC) systems, which have the potential to support native bees.Objectives
Our objective was to explore the potentially interactive effects of crop composition, total PBC area, and PBC patches in different landscape configurations.Methods
Using a spatially-explicit modeling approach, the Lonsdorf model, we simulated the impacts of three perennial bioenergy crops (PBC: willow, switchgrass, and prairie), three scenarios with different total PBC area (11.7, 23.5 and 28.8% of agricultural land converted to PBC) and two types of landscape configurations (PBC in clustered landscape patterns that represent realistic future configurations or in dispersed neutral landscape models) on a nest abundance index in an Illinois landscape.Results
Our modeling results suggest that crop composition and PBC area are particularly important for bee nest abundance, whereas landscape configuration is associated with bee nest abundance at the local scale but less so at the regional scale.Conclusions
Strategies to enhance wild bee habitat should therefore emphasize the crop composition and amount of PBC.15.
The evidence at present available, although incomplete, gives rise to fears for the future of the edible snail Helix pomatia L. The scale of exploitation is increasing, particularly in Eastern Europe, to meet growing demand, mainly from the West. The growth of legislation to control collecting supports the evidence of declining numbers, but the legislation does not appear to be backed by sufficiently detailed population ecology studies. The need for co-ordinated international action on farming, legislation and ecological study is urged. 相似文献
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Phytotoxicity was demonstrated in the aqueous extract of wheat (Triticum aestivum, L.) straw suspensions. When extracts were incubated under anaerobic conditions, the development of phytotoxicity was greater at 20°C than at 10°C. The toxic products formed during incubation depended upon the incubation medium. Acetic and butyric acids were the major toxins produced in liquid straw fermentations during the first 2 weeks. However, after that time the acids did not account for the total toxicity, suggesting formation of unidentified phytotoxins. Acetic, propionic and butyric acids were the toxins formed in sand culture. The development and accumulation of phytotoxins were favored where the sand-straw mixtures were water-saturated. The implications of these findings to wheat cultural practice is discussed. 相似文献
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This work presents evidence from three different valuation studieson the influence of gender in the formation of forestry-relatedvalues. Previous studies examined gender differences withoutexplicitly considering their interaction with other explanatoryvariables. Three separate studies dealing with forest-relatedgoods and services, revealed statistically significant differencesin peoples' preferences, especially between older women andolder men, and older and younger women. In these studies, althoughthere was no overall difference in preferences attributableto gender, there were significant differences related to ageand income, in combination with gender. 相似文献
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Joan F. Webber 《Forest Pathology》1990,20(3):184-192
Three scolytid species consistently associated with Dutch elm disease were assessed and compared for their effectiveness as vectors of Ophiostoma ulmi. Assessments were based on the number of beetles within a sample carrying any detectable O. ulmi, the number of O. ulmi spores carried by individual beetles and the number of discrete gallery systems colonised by O. ulmi. 相似文献