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Zum Tode von Dr. Walter Bosshard

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Crown release improves growth of 20-year-old Betula alleghaniensis in tolerant northern hardwood stands

Twenty-year-old overstocked naturally regenerated yellow birch (Betula alleghaniensis Britton) were thinned near Thessalon, Ontario. Treatments consisted of either a control, or the removal of all competing trees at 1, 2, 3, or 4 m around the boles of the crop trees. The size of the openings created around the crop tree crowns was found to be more strongly correlated to diameter, clear bole length, and crown increment than the removal of competing trees using fixed distance from the stem. Crop trees responded well to thinning. Five-year diameter increment and crown diameter growth were positively correlated to size of the opening created around the crop tree crown. However, the relationship between height growth and size of canopy opening was weak. Clear bole length was found to be negatively correlated to the size of canopy opening. Few epicormic sprouts developed on the stems when all competing trees were removed at 1, 2, or 3 m around the crop tree boles. However, release at 4 m greatly increased the number and size of epicormic sprouts. Providing about a 15-m² opening around the crop tree crown, corresponding to approximately a 3-m removal of competing trees around the bole, provided a good balance between diameter increment and stem quality maintenance.     

Detection and molecular characterization of Suid herpesvirus type 1 in Austrian wild boar and hunting dogs

Aujeszky's disease (AD), caused by Suid herpesvirus type 1 (SuHV-1), is an economically important disease in domestic swine. Thus, rigorous control programmes have been implemented and consecutively AD in domestic swine was successfully eradicated in many countries, including Austria. However, SuHV-1 continues to thrive in wild boar populations, as indicated by high seroprevalences in a number of European countries and by occasional cases of AD in hunting dogs. For the first time, SuHV-1 was detected in Austrian wild boar and a molecular characterization of SuHV-1 isolated from wild boar and hunting dogs was performed. Results of preliminary serological analyses suggest a regional SuHV-1 seroprevalence of over 30% in free-living and almost 70% in fenced wild boar from Eastern Austria. Molecular typing of Austrian SuHV-1 isolates of wild boar origin revealed the presence of two genetically distinct variants of SuHV-1, both capable of infecting dogs that have been exposed to infected wild boar during hunting.     

Hearing in catfishes: 200 years of research

Ernst Weber stated in 1819, based on dissections, that the swimbladder in the European wels (Silurus glanis, Siluridae) and related cyprinids serves as an eardrum and that the ossicles connecting it to the inner ear function as hearing ossicles similar to mammals. In the early 20th century, K. von Frisch showed experimentally that catfishes and cyprinids (otophysines) indeed hear excellently compared to fish taxa lacking auxiliary hearing structures (ossicles, eardrums). Knowledge on hearing in catfishes progressed in particular in the 21st century. Currently, hearing abilities (audiograms) are known in 28 species out of 13 families. Recent ontogenetic and comparative studies revealed that the ability to detect sounds of low-level and high frequencies (4–6 kHz) depends on the development of Weberian ossicles. Species with a higher number of ossicles and larger bladders hear better at higher frequencies (>1 kHz). Hearing sensitivities are furthermore affected by ecological factors. Rising temperatures increase, whereas various noise regimes decrease hearing. Exposure to high-noise levels (>150 dB) for hours result in temporary thresholds shifts (TTS) and recovery of hearing after several days. Low-noise levels reduce hearing abilities due to masking without a TTS. Furthermore, auditory evoked potential (AEP) experiments reveal that the temporal patterns of fish-produced pulsed stridulation and drumming sounds are represented in their auditory pathways, indicating that catfishes are able to extract important information for acoustic communication. Further research should concentrate on inner ears to determine whether the diversity in swimbladders and ossicles is paralleled in the inner ear fine structure.     

Effect of dietary iodine on growth and iodine status of growing fattening bulls

The aim of the present study was to assess the influence of different levels of iodine supplementation on animal growth and the iodine content of food from beef cattle. In a dose–response experiment with 34 growing fattening bulls of the “German Holstein” breed, in the range from 223 to 550 kg body weight, three iodine dosages were tested. The animals were fed a corn silage/concentrate ration. Iodine concentration in the diet amounted to 0.79 (Group 1), 3.52 (Group 2) and 8.31(Group 3) mg I per kg dry matter (DM). After slaughtering, I was determined in blood, serum, plasma, thyroid, liver, kidneys and meat (M. longissimus dorsi, M. glutaeus medius) by ICP-MS. I-supplementation did not significantly influence DM intake, daily weight gain (1453 (1), 1419 (2) and 1343 (3) g; p > 0.05) or slaughtering performance, but the weight of the thyroid gland increased significantly with the highest I dosage (32 (1), 26 (2) and 42 (3) g animal^− 1, p < 0.05). I-supplementation significantly increased I-concentration in muscle, liver, kidney and thyroid gland (p < 0.05). The contribution of beef food to I-intake of humans is relatively low, therefore there is no need to reduce the EU-upper limit (10 mg kg^− 1 feed) for growing fattening cattle from the view of consumer safety. In view of animal health and performance more dose–response studies seem to be necessary.     

Biomass and nutrients allocation in pot cultured beech seedlings： influence of nitrogen fertilizer

Allocation of biomass and nutrient elements including Nitrogen to above and belowground compartments of beech seedlings (Fagus sylvatica L.) treated by labeled nitrogen fertilizer in the form of ¹⁵NH₄ and ¹⁵NO₃ were investigated at the end of two successive growing seasons. Pot cultured beech seedlings were grown at a green house on intact soil cores sampled from three adjacent stands including beech, Norway spruce and mixed beech-spruce cultures of Solling forest, Germany. Comparing biomass allocation and nutrients concentrations of the seedlings between the control and ¹⁵N-fertilized treatments revealed no significant effect of N fertilization on nutrients uptake by seedlings over the experiment. The form of N input influenced its movement into plant pools. It was demonstrated that beech seedlings take up nitrogen mainly in the form of nitrate, which is then reduced in the leaves, although the differences between the retention of NO₃ ^?-N and NH₄ ⁺-N in plants were not statistically significant. Percent recoveries of ¹⁵N in trees were typically greater after ¹⁵NO₃ than after ¹⁵NH₄ additions. It was indicated that immobilization of 15N tracer in fine roots was a slower process comparing other plant compartments such as stem and coarse roots, but a powerful sink for N during the course of study.     

Genetic variability of PRRS virus in Austria: consequences for molecular diagnostics and viral quantification

Porcine reproductive and respiratory syndrome virus is a virus with a relatively high level of sequence variation, especially between the European and the American-type strains. This high degree of sequence variations will influence the accuracy of results obtained by molecular diagnostic methods, especially if mutations are located in the primer or probe binding regions of PCR or real-time PCR based assays. In order to provide the basis for the development of an accurate, region-tailored assay we have analysed samples obtained from several Austrian pig herds using a series of RT-PCR assays. Subsequent sequencing of the PCR products from ORF5 and phylogenetic analysis revealed the occurrence of both the European and the American-type of porcine reproductive and respiratory syndrome virus in Austria. Since vaccination with the American-type vaccine is not authorized in Austria the import of vaccinated animals is the most likely explanation for the occurrence of these strains. The study highlights the importance of a detailed study on the sequence variations occurring in the region of interest before the development of a reliable PCR-based assay.     

Measuring forest damage of ungulates: what should be considered

Principles and criteria for the objective assessment of ‘damage' are presented as a basis for objective discussion and to promote targeted research. The topic will be considered from three different viewpoints – theoretical background, silviculture, and nature conservation. Examples of methods to assess ‘damage' are given, as are the criteria and indicators for target values for growing stock.

The objective existence of damage must be established by comparing the current status against a target. Only if the present status no longer permits achievement of the desired target can damage be claimed. The same is true for verification of ‘benefit' resulting from an impact leading to a favorable status. Establishing the degree of browsing damage on forest regeneration allows forecasts of damage to be made, but the actual damage can only be determined at a future time, for example when the timber is harvested or when the function of the forest is seen to have been compromised. The earlier the forecast is made the more uncertain it is, because the compensatory responses of the forest can only be forecast to a limited extent. Silvicultural targets depend on the requirements of both, the forest owner and the public. Main indicators for assessing ungulate damage on forest regeneration are total tree density, species composition, and height structure. From the viewpoint of nature conservation the determination of target values is particularly difficult. The measurement of damage involves choosing the most relevant indicators of favorable condition of woodland habitats and assessing these in the field. With adequate resources this can be done quantitatively using a wide range of standard field measurement techniques. Alternatively, where resources are limited, it can be done qualitatively by scoring different areas for a range of indicators. As yet, such qualitative methods are in their infancy. Specific research is now being undertaken in some European countries.