In permanent observation plots across Switzerland, nitrogen (N) concentration in the foliage of mature beech has increased by 15% and phosphorus (P) concentrations in beech and mature Norway spruce ...decreased by 12 and 13% respectively between 1984 and 1995, leading to increased N:P ratios. Modelled N deposition was correlated with stem increment in both beech and spruce, with indications of P limitation in some beech plots. Experimental application of 0-160 kg N ha^sup -1^> yr^sup -1^> over four to five years caused nutrient imbalances in various afforestation plots comparable to those observed in the permanent observation plots. The changes in the trees caused by N treatment led to increased attacks by parasites such as Apiognomonia errabunda, Phomopsis sp., Phyllaphis fagi in beech and Botrytis cinerea, Sacchiphantes abietis and Cinara pilicornis in Norway spruce. The results suggest current N deposition in Switzerland induces significant changes in the forest ecosystem.PUBLICATION ABSTRACT
The structural details of wax glands and the physical form of the secreted wax is described for the apterae of three aphid species beech woolly aphid, spruce root aphid and woolly apple aphid. The ...glands are composed of greatly enlarged epidermal cells underlying a modified cuticle that forms distinctive wax gland plates. Secreted wax in the form of threads passes out of the cuticle as filaments, the arrangement of these filaments in the cuticle above each epidermal cell gives rise to the distinctive wax skein found in each species hollow, solid or honeycombed. It is suggested that the primary role of the secreted wax is to prevent the aphids becoming contaminated by their own secreted honeydew and that of other members of the colony. Other secondary roles considered include: individual microclimate isolation; protection from fungi, parasites and predators; waterproofing and frost protection.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The aim of this study was to analyse the distribution of the dominant leaf galls, Mikiola fagi and Neuroterus quercusbaccarum, in the canopies of mature trees. We made use of the Swiss Canopy Crane ...near Basel, Switzerland, to gain access to the canopy of a mixed temperate forest up to a height of 35 m. We scanned 6,750 beech leaves and 6,000 oak leaves. M. fagi showed a distinct vertical zonation with highest abundance in the top-most parts of the canopy as well as a significant aggregation on particular trees. N. quercusbaccarum showed an even more pronounced preference for particular trees and a general preference for Quercus robur over Q. petraea. In contrast to M. fagi, no vertical zonation could be detected. We think that both gall-inducing species have greater powers of dispersal than formerly assumed since they overwinter on the forest floor and yet are ables to 1) gain access to the entire canopy, 2) show preference for certain host trees. The highest density of M. fagi galls was in those parts of the canopy exposed to high solar radiation; their host choice is probably determined by micro-climatological factors.
An Ascochyta fungus was obtained during a survey of leaf spot diseases of Fagus crenata in the mountains of Aomori prefecture in 1995. The pathogenicity of the fungus to F. crenata was confirmed by ...inoculation. Its teleomorph was first found on artificially infected leaves after the leaves were placed in an incubator at 5°C with a 12-h photoperiod (approximately 500 Ix, daylight strip lamps) for 4 mo. The fungus was found to be the causal agent of yellow leaf spots of F. crenata and Quercus mongolica var, grosseserrata in the field. Comparison with similar fungi so far described from Fagaceae indicated that the anamorph is Ascochyta fagi and the teleomorph is an undescribed species of Didymella. The name Didymella fagi is introduced for the teleomorph. Correlation between the two morphs has been proved by cultural, morphological and pathological studies.
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FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UL, UM, UPUK, VKSCE, ZAGLJ
The relationship between supercooling and survival of the beech leaf mining weevil,
Rhynchaenus fagi was examined in exposures at constant temperatures between +10 and −15 °C, and in cycling regimes. ...Similar observations were made on naturally overwintering field populations.
No weevil survived cooling to, or below the supercooling point. The mean supercooling point of weevils exposed to temperatures at, or below +2 °C, or sampled from the field, was consistently below −21 °C. When exposed to a constant +2 or −5 °C, mortality was low, at 10 and 12% after 168 and 126 days respectively. Mortality increased rapidly in weevils exposed to temperatures below −10 °C, with 48% survival after 112 days at −10 °C and only 25% after 84 days at −15 °C. None of the dead weevils had frozen. Periods spent at +2 °C in cycling treatments which included exposure at −10 or −15 °C, extended the duration of survival at the lower temperatures compared to constant exposures at these temperatures, but mortality was still more rapid than at a constant +2 °C. Survival of naturally overwintering insects was consistently high over three winters.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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