Comparison of five diagnostic methods for detecting bovine viral diarrhea virus infection in calves.     

Monika Hilbe  Hanspeter Stalder  Ernst Peterhans  Michael Haessig  Marlies Nussbaumer  Christoph Egli  Christian Schelp  Kati Zlinszky  Felix Ehrensperger 《Journal of veterinary diagnostic investigation》2007,19(1):28-34

Five diagnostic techniques performed on skin biopsies (shoulder region) and/or serum were compared for detection of bovine viral diarrhea virus infection in 224 calves 0-3 months of age, 23 calves older than 3 months but younger than 7 months, and 11 cattle older than 7 months. The diagnostic methods used were immunohistochemistry (IHC), 2 commercial antigen ELISAs, 1 commercial antibody ELISA, and real-time RT-PCR. Results of 249 out of 258 skin and serum samples were identical and correlated within the 3 antigen detection methods and the real-time RT-PCR used. Twenty-six of these 249 samples were BVDV-positive with all antigen detection methods and the real-time RT-PCR. Nine out of 258 samples yielding discordant results were additionally examined by RT-PCR, RT-PCR Reamplification (ReA), and antigen ELISA I on serum and by immunohistochemistry on formalin fixed and paraffin-embedded skin biopsies. Virus isolation and genotyping was performed as well on these discordant samples. In 3 cases, transiently infected animals were identified. Two samples positive by real-time RT-PCR were interpreted as false positive and were ascribed to cross-contamination. The antigen ELISA II failed to detect 2 BVDV-positive calves due to the presence of maternal antibodies; the cause of 2 false-positive cases in this ELISA remained undetermined. Only persistently infected animals were identified in skin samples by IHC or antigen ELISA I. The 3 antigen detection methods and the real-time RT-PCR used in parallel had a high correlation rate (96.5%) and similar sensitivity and specificity values.  相似文献   

Winter embolism,mechanisms of xylem hydraulic conductivity recovery and springtime growth patterns in walnut and peach trees     

Améglio T  Bodet C  Lacointe A  Cochard H 《Tree physiology》2002,22(17):1211-1220

Xylem vessels of Prunus persica Batsch (peach) and Juglans regia L. (walnut) are vulnerable to frost-induced embolism. In peach, xylem embolism increased progressively over the winter, reaching a maximum of 85% loss of hydraulic conductivity (PLC) in early March. Over winter, PLC in walnut approached 100%, but the degree of xylem embolism varied during the winter, reflecting the ability of walnut to generate positive xylem pressures in winter and spring. In contrast, positive xylem pressures were not observed in peach. Controlled freeze-thaw experiments showed that frost alone is insufficient to increase embolism in peach; evaporative conditions during thawing are also required. However, when both species were protected from frost, PLC was zero. At bud break, there was complete recovery from embolism in walnut, whereas PLC remained high in peach. Three mechanisms responsible for the restoration of branch hydraulic conductivity were identified in walnut: the development of stem pressure, the development of root pressure and the formation of a new ring of functional xylem, whereas only one mechanism was observed in peach (new functional ring). The climatic conditions necessary for the manifestation of these mechanisms were investigated.  相似文献   

Which grow better under the canopy of Norway spruce planted or sown seedlings of European beech?     

Ammer  Christian; Mosandl  Reinhard 《Forestry》2007,80(4):385-395

Direct seeding and planting of European beech (Fagus sylvaticaL.) are two common techniques for the conversion of pure Norwayspruce (Picea abies [L.] Karst.) stands into mixed stands. Thisstudy tested whether the growth of sown beech seedlings differsfrom that of planted seedlings of two stock types. Thereforeat two experimental sites repeated measurements were made ofheight, stem and first order branch diameter on sown and plantedseedlings over a period of nine years. The results showed thatthe growth responses of planted and sown seedlings to the environmentalconditions below the canopy of overstorey Norway spruce wererather similar. No differences between planted and sown seedlingswere found in their diameter and their estimated abovegrounddry weight. For all three batches the ratio between the estimatedbranch dry weight and the estimated main stem dry weight (branch-shoot-ratio(BSR)) was increased with age. Due to intraspecific competitionBSR was lowest for the sown seedlings irrespective of theirage. Differences in growth dynamics between planted and sownseedlings were found. For example, differences in the heightor the estimated aboveground woody dry weight between sown andplanted seedlings at a given age were not constant. Height,diameter and estimated dry mass of the seedlings in relationto age could be modelled precisely by a second-order polynomialfunction in the hitherto studied period.  相似文献   

Versuche mit Toxaphen-Staub zur Festsfellung der Bienengefährlichkeit und der Wirkung gegen Kohlschotenrüßler und Rapsglanzkäferler und Rapsglanzkäfer     

Dr. Christian Bauers 《Journal of pest science》1954,27(3):35-36

Zusammenfassung Es wurden Versuche zur Kl?rung der Bienenungef?hrlichkeit und der Wirkung des Kontaktinsektizids Toxaphen angelegt. In orientierenden Laborversuchen konnte eine 100% ige Abt?tung von Kohlschotenrü?lern und Rapsglanzk?fern auch mit der H?lfte der normalen Aufwandmenge (20 kg/ha) erreicht werden. In Freilandversuchen waren die Abt?tungsziffern beider genannten Sch?dlinge als befriedigend bis gut zu beurteilen. Bienenverluste traten troB St?ubung w?hrend des Bienenfluges nicht ein. VorausseBung für den Erfolg scheint nach den bisherigen Feststellungen eine Trockenperiode von mindestens 8 bis 10 Stunden zu sein, da das Mittel eine geringere Anfangswirkung besiBt. Weitere Versuche sind geplant.  相似文献   

Durability of thermally modified timber from industrial-scale processes in different use classes: Results from laboratory and field tests     

Christian Robert Welzbacher  Andreas Otto Rapp 《Wood material science & engineering》2007,2(1):4-14

Material from four common European processes of industrial heat treatment of timber was examined comparatively with reference to biological laboratory standard tests and field tests in soil contact and above ground. The thermally modified timber (TMT) used in the study was: Plato wood from the Netherlands, ThermoWood from Finland, New Option Wood (NOW) from France, and oil-heat-treated wood (OHT) produced in Germany. Tests of resistance to basidiomycetes (EN 113, 1996) and tests of resistance to soft rotting microfungi and other soil-inhabiting microorganisms (EN 807, 1997) showed substantially lower mass losses of TMT compared with controls. Only slight differences in mass loss were found between the four thermally modified materials. Based on results from laboratory standard tests all tested heat-treated materials were classified as durable to moderately durable [durability class (DC) 2-4], analogous to the classification of natural durability (EN 350-1, 1994). In contrast, the classification of TMT samples after 5.5 years' exposure in soil contact, in accordance with EN 252 (1990), was slightly durable to not durable (DC 4-5), whereas the classification obtained after 5.5 years' exposure in double layers in European hazard class (EHC) 3 (EN 335-1, 1992) was very durable to moderately durable (DC 1-3). On the basis of 5.5 years' field testing, thermally modified material (independent of the treatment process and supplier) appears not to be suitable for in-ground contact application. However, the suitability of TMT for use out of ground in EHC 3 was ascertained and is recommended.  相似文献   

Decay-influencing factors: A basis for service life prediction of wood and wood-based products     

Christian Brischke  Rolf Bayerbach  Andreas Otto Rapp 《Wood material science & engineering》2006,1(3):91-107

The need for a reliable database and a corresponding methodology to predict service life of wood and wood-based products emanates from the European Construction Products Directive, as well as from a strong interest by the building industry. A literature review on decay-influencing factors and on previous approaches to implement methods and tools for service life estimations was the basis for a concept for service life prediction of wooden components. The effect of various indirect decay factors was found to be reducible to a few direct decay factors, with material resistance, as well as wood moisture content, wood temperature and their dynamics among the key factors for fungal decay. Approaches that consider only indirect factors, e.g. climate indices, suffer from poor correlation with service life or decay rates. Therefore, the overall consideration of all possible influences, reduced on the key direct decay factors in first instance, is recommended. To fill a theoretical model with a reliable database, various data sources need to be considered, in decreasing order of priority: in-service performance, field test data, laboratory test data, survey analysis and expert opinion.  相似文献   

Habitat factors for land snails in European beech forests with a special focus on coarse woody debris     

J?rg?MüllerEmail author  Christian?Str?tz  Torsten?Hothorn 《European Journal of Forest Research》2005,124(3):233-242

Analyses of land snails and habitat factors in acid beech forests were conducted in southern Germany (northern Bavaria). The objectives were to study the effects of habitat characteristics on snail density and species richness. Habitat structures were determined for 37 plots in one big forest. We found a significant relationship between the number of snail species and individuals and the following set of habitat factors coverage of herbaceous layer, growing stock, mean diameter at breast height of the three largest trees (DBHmax), stand age, total dead wood volume per ha, and advanced decomposed dead wood volume per ha. We use maximally selected rank statistics to estimate cutpoints separating stands with low densities, from stands with high snail densities. Here, we define cutpoints for a significant higher snail density at a stand age of 187 years, 57 m³/ha dead wood, 40 m³/ha advanced decomposed dead wood, 63 cm DBHmax and more than 1% herbaceous layer. For species richness, cutpoints are estimated at 338 m³/ha stand volume, 170 years stand age, 50 m³/ha total dead wood amount, 15 m³/ha advanced decomposed dead wood and 56 cm DBHmax. The microhabitat analysis shows a higher pH value and a higher Calcium content at the bottom of large snags and under large lying dead wood pieces in comparison to litter, upper mineral soil and at the bottom of vital living trees. Snail species and individual density are significantly linked to these patterns of chemical parameters. The identified cutpoints are a good base for ecological management decisions in forest management.  相似文献   

Regeneration patterns in boreal Scots pine glades linked to cold-induced photoinhibition   总被引：1，自引：0，他引：1  

Slot M  Wirth C  Schumacher J  Mohren GM  Shibistova O  Lloyd J  Ensminger I 《Tree physiology》2005,25(9):1139-1150

Regeneration patterns of Pinus sylvestris L. juveniles in central Siberian glades were studied in relation to cold-induced photoinhibition. Spatial distribution of seedlings in different height classes revealed higher seedling densities beneath the canopy than beyond the canopy, and significantly higher densities of seedlings < 50 cm tall on the north side of the trees. These patterns coincided with differences in light conditions. Compared with plants on the north side of canopy trees (north-exposed), photosynthetic photon flux (PPF) received by plants on the south side of canopy trees (south-exposed) was always higher, making south-exposed plants more susceptible to photoinhibition, especially on cool mornings. Chlorophyll fluorescence data revealed lower photochemical efficiency and increased non-photochemical quenching of small (20-50 cm in height), south-exposed seedlings from spring to early autumn, indicating increased excitation pressure on photosynthesis. Maximum rate of oxygen evolution was less in south-exposed plants than in north-exposed plants. Increased pools of xanthophyll cycle pigments and formation of the photoprotective zeaxanthin provided further evidence for the higher susceptibility to photoinhibition of south-exposed seedlings. A linear mixed model analysis explained many of the physiological differences observed in seedlings according to height class and aspect with early morning temperature and PPF as predictors. The link between photoinhibition and differential distribution of seedlings by height class suggests that photoinhibition, together with other environmental stresses, decreases the survival of small, south-exposed P. sylvestris seedlings, thereby significantly affecting the regeneration pattern of central Siberian pine glades.  相似文献   

Effects of elevated concentrations of atmospheric CO2 and tropospheric O3 on leaf litter production and chemistry in trembling aspen and paper birch communities   总被引：2，自引：0，他引：2  

Liu L  King JS  Giardina CP 《Tree physiology》2005,25(12):1511-1522

Human activities are increasing the concentrations of atmospheric carbon dioxide ([CO2]) and tropospheric ozone ([O3]), potentially leading to changes in the quantity and chemical quality of leaf litter inputs to forest soils. Because the quality and quantity of labile and recalcitrant carbon (C) compounds influence forest productivity through changes in soil organic matter content, characterizing changes in leaf litter in response to environmental change is critical to understanding the effects of global change on forests. We assessed the independent and combined effects of elevated [CO2] and elevated [O3] on foliar litter production and chemistry in aspen (Populus tremuloides Michx.) and birch-(Betula papyrifera Marsh.) aspen communities at the Aspen free-air CO2 enrichment (FACE) experiment in Rhinelander, WI. Litter was analyzed for concentrations of C, nitrogen (N), soluble sugars, lipids, lignin, cellulose, hemicellulose and C-based defensive compounds (soluble phenolics and condensed tannins). Concentrations of these chemical compounds in naturally senesced litter were similar in aspen and birch-aspen communities among treatments, except for N, the C:N ratio and lipids. Elevated [CO2] significantly increased C:N (+8.7%), lowered mean litter N concentration (-10.7%) but had no effect on the concentrations of soluble sugars, soluble phenolics and condensed tannins. Elevated [CO2] significantly increased litter biomass production (+33.3%), resulting in significant increases in fluxes of N, soluble sugars, soluble phenolics and condensed tannins to the soil. Elevated [O3] significantly increased litter concentrations of soluble sugars (+78.1%), soluble phenolics (+53.1%) and condensed tannins (+77.2%). There were no significant effects of elevated [CO2] or elevated [O3] on the concentrations of individual C structural carbohydrates (cellulose, hemicellulose and lignin). Elevated [CO2] significantly increased cellulose (+37.4%) input to soil, whereas elevated [O3] significantly reduced hemicellulose and lignin inputs to soil (-22.3 and -31.5%, respectively). The small changes in litter chemistry in response to elevated [CO2] and tropospheric [O3] that we observed, combined with changes in litter biomass production, could significantly alter the inputs of N, soluble sugars, condensed tannins, soluble phenolics, cellulose and lignin to forest soils in the future.  相似文献   

Multiscale computation of solar radiation for predictive vegetation modelling     

Christian Piedallu  Jean-Claude Gégout 《Annals of Forest Science》2007,64(8):899-909

The recent development of large environmental databases allow the analysis of the ecological behaviour of species or communities over large territories. Solar radiation is a fundamental component of ecological processes, but is poorly used at this scale due to the lack of available data. Here we present a GIS program allowing to calculate solar radiation as well locally as at large scale, taking into account both topographical (slope, aspect, altitude, shadowing) and global (cloudiness and latitude) parameters. This model was applied to the whole of France (540 000 km²) for each month of the year, using only a 50-m digital elevation model (DEM), latitude values and cloudiness data. Solar radiation measured from 88 meteorological stations used for validation indicated a R ² of 0.78 between measured and predicted annual radiation with better predictions for winter than for summer. Radiation values increase with altitude, and with slope for southern exposure, excepted in summer. They decrease with latitude, nebulosity, and slope for north, east, and west exposures. The effect of cloudiness is important, and reduces radiation by around 20% in winter and 10% in summer. Models of plant distribution were calculated for Abies alba, Acer pseudoplatanus, and Quercus pubescens, for France. The use of solar radiation improved modelling for the three species models directly or through the water balance variable. We conclude that models which incorporates both topographical and global variability of solar radiation can improve efficiency of large-scale models of plant distribution.  相似文献