Canopy composition as a measure to identify patterns of nutrient input in a mixed European beech and Norway spruce forest in central Europe

The influence of canopy composition on litterfall and throughfall was investigated in a mixed spruce beech forest in central Germany. We hypothesised that different parts of the mixed canopy created distinct patterns of element inputs via litterfall and throughfall. The investigation was carried out in two plots, representing the most contrasting cases of mixed forests: a stand greatly dominated by spruce (SDP) and a stand greatly dominated by beech (BDP). The canopies of the two plots were classified in four categories: pure beech, pure spruce, mixed canopy and gap. Amounts of throughfall water were lower and major element fluxes were higher under spruce than under beech in both plots, indicating that the nutrient inputs under the canopies of individual trees are driven by species-specific properties of the canopies and are quite independent of the degree of admixture. With the exception of K⁺, mixed canopies showed intermediate element inputs via throughfall, compared with pure canopy classes. The K⁺ input was significantly greater under mixed canopies, and these differences were more pronounced in the SDP than in the BDP. Results suggest that individual spruce trees in the BDP induce greater spatial heterogeneity of throughfall input than individual beech trees in the SDP. Nutrient inputs via foliar litterfall were similar among the different canopy classes, but the Mg input was lower under spruce canopy. This effect was balanced by higher Mg input via spruce throughfall. In our study, throughfall was the main source of heterogeneity in nutrient inputs, while foliar litterfall had a homogenising effect.     

“近自然林”——一种理念的起源与传播

欧洲林业在走过了大面积纯林种植后,出现了地力衰退、病虫害频发、系统稳定性差等种种弊端,人们逐渐认识到遵循自然规律,以自然的力量改造、经营森林,将会使森林产生最大的生态效益、经济效益和社会效益。1886年,德国慕尼黑工业大学造林学教授卡尔嘎耶（KarlGayer）在其著作“gesmifchte wald（历史森林）--Jeine begriindung und pflege（没有培育和养护的林业）”一书中写到“我们师法自然而不应该过于远离大自然的规律,     

德国中部Soiling云杉-山毛榉混交林冠层组成对土壤CO2排放的影响

It was hypothesized that soil respiration can be affected by canopy composition. Hence, admixture of trees as a common forest management practice may cause significant change in the carbon cycling. This study was conducted in a mixed spruce-beech stand at Solling forest in central Germany to investigate the effect of canopy composition on soil respiration. The canopy cover was classified in four major canopy classes (pure beech, pure spruce, mixed and gap), and the area under each canopy class was identified as a sub-plot. Soil respiration in each sub-plot (n=4) was measured monthly from Jun 2005 to July 2006. Results show significant difference in annual soil respiration between the beech (359 g·m⁻²·a⁻¹ C) and gap (211 g·m⁻²·a⁻¹ C) sub-plots. The estimation of the total below-ground carbon allocation (TBCA) based on a model given by Raich and Nadelhoffer revealed considerably higher root CO₂ production in the beech sub-plot (231 g·m⁻²·a⁻¹ C) compare to the gap sub-plot (51 g·m⁻²·a⁻¹ C). The contribution of the root respiration to the total soil respiration was higher in the soil under the beech canopy (59%) compared with the soil in the gap (29%). The findings suggested that the condition under the beech canopy may cause more desirable micro-site for autotrophic respiration and consequently higher CO₂ release into the atmosphere.     

Partial sequencing of recent Portuguese myxoma virus field isolates exhibits a high degree of genetic stability

To study genetic changes underlying myxoma virus evolution in its new host, the European rabbit (Oryctolagus cuniculus), we sequenced selected genomic regions of nine recent virulent field strains and a live attenuated vaccine strain (“MAV”, Germany). DNA was extracted from cell culture passaged myxoma virus. A total of 4863 bp (approximately 3% of the genome) of 10 regions spanning 12 genes of the myxoma viruses was sequenced and compared to the original virulent strain “Lausanne” and its attenuated field derivative strain “6918”. The field strains displayed a maximum of three (strains C43, C95) and a minimum of one (strains CD01, CD05) nucleotide substitutions. These were distributed through all analysed coding regions, except gene M022L (major envelope protein), where all strains were identical to “Lausanne” and “6918”. Two new single nucleotide insertions were observed in some of the field strains: within the intergenic region M014L/M015L and within gene M009L, where it leads to a frameshift. These insertions were located after homopolymeric regions. The vaccine strain displayed 37 nucleotide substitutions, predominantly (95%) located in genes M022L and M036L. Interestingly, regions M009L and M014L/M015L of the vaccine were not amplified successfully, suggesting major genomic changes that could account for its attenuated phenotype. Our results support a high degree of genetic stability of myxoma virus over the past five decades. None of the analysed genome regions by its own seems sufficient for the genetic characterisation of field strains.     

Impact of Stolbur Phytoplasmas on Potato Tuber Texture and Sugar Content of Selected Potato Cultivars

Potato stolbur is a phytoplasmal disease that seriously affects yield and tuber quality in South Eastern Europe, Russia and the Mediterranean areas. In 2007 and 2008, field experiments were carried out to determine stolbur resistance of processing potato cultivars at Sannicolau Mare (Romania) by determining consistency and concentration of reducing sugars (fructose and glucose), sucrose and phytoplasmas in potato tubers. In both years, non-symptomatic potato tubers showed sucrose levels in the range of 3,000 mg kg⁻¹ fresh weight (FW). In contrast, sucrose concentrations were up to 11,820 mg kg⁻¹ FW in 2007 and 19,560 mg kg⁻¹ FW in 2008 in tubers showing severe symptoms. These high values severely affect suitability of tubers for processing as sucrose serves as substrate for the formation of reducing sugars that are the limiting factor in fried potato production for Maillard-related discolouration. The cultivars examined differed considerably in susceptibility to stolbur disease. Whereas cvs. ‘Courage’ and ‘Lady Rosetta’ showed high numbers of diseased tubers and high sucrose concentrations, ‘Lady Claire’ had a lower incidence of symptomatic tubers and lower sucrose concentrations. However, fully resistant cultivars were not observed. Across all cultivars examined, phytoplasmal concentration was significantly higher in symptomatic tubers than in non-symptomatic ones.     

Comparative study on the antioxidant and biological activities of carvacrol, thymol, and eugenol derivatives

Four derivatives of thymol, carvacrol, and eugenol were synthesized: 4-(hydroxymethyl)-5-isopropyl-2-methylphenol, 4,4'-methylenebis(5-isopropyl-2-methyl)phenol, 4-allyl-6-(hydroxymethyl)-2-methoxyphenol, and 4-(hydroxymethyl)-2-isopropyl-5-methylphenol. The obtained derivatives showed remarkably better antioxidative properties according to 1,1-diphenyl-2-picrylhydrazyl assay (50% inhibitory concentrations = 4-156 microg/mL) and Rancimat assay (protection factors = 1.55-5.84) when compared with parent compounds and values similar to or better than those of butylated hydroxytoluene and vitamin C. At concentrations of 10 mM carvacrol derivatives had no toxic effect on viability of Escherichia coli K-12 (determined by minimum inhibitory concentrations). Other phenol derivatives showed reduced cytotoxic effect on E. coli K-12 at concentrations of 2-5 mM on the basis of 50% lethal dose measurements. In comparison with the parent compounds, phenol derivatives showed reduced cytotoxic effect for Saccharomyces cerevisiae cells (determined by yeast colony reduction). On the other hand, the majority of synthesized compounds had dose-dependent antiproliferative effects on human uterine carcinoma cells (HeLa), which makes them potentially interesting for the adjuvant experimental cancer treatments. The 4,4'-methylenebis(5-isopropyl-2-methyl)phenol derivative of carvacrol showed lower inhibiting capacity also for the HeLa cells, which makes this particular derivative attractive as an efficient antioxidant with negligible cytotoxic effects.     

Viraemia and abortions are not prevented by two commercial equine herpesvirus-1 vaccines after experimental challenge of horses

Eighteen horses, vaccinated on a number of occasions over a period of 12 to 20 months with either a live equine herpesvirus-1 (EHV-1) or an inactivated EHV-1 vaccine, were challenged by the intranasal instillation of the subtype 1 virus isolated from the 1983 outbreak of abortion and paralytic disease at the Lipizzan Stud, Piber, Austria. The prechallenge serum titres of all vaccinated horses were remarkably low, although most horses had received their last vaccine dose only 3 weeks before test-infection. Higher titres were obtained with the inactivated product than with the live virus vaccine. However, no obvious differences were found between the two vaccines in their ability to prevent disease, in that all vaccinated and two 'sentinel' horses became infected and developed viraemia and some degree of clinical disease after challenge; five of the 10 in-foal mares aborted.     

Year-round antibody profile of groups of horses of a herd kept in isolation after differently terminating use of an experimental viral combination vaccine]

The commercial vaccine "Resequin F Konz." devised against viral respiratory infections of horses contains the abortigenic Equine Herpesvirus-1 (EHV-1). Therefore we had used it in our protection project of the Austrian Lipizzaners+ primarily to prevent abortions. Taking into account the recent perception that for young horses the respiratory-pathogenic EHV-4 type is essential Behringwerke Marburg added this particular virus to their market product to produce a multicomponent experimental vaccine. We examined this vaccine for its antibody induction as well as their persistence against each of its viral components. On groups of foals we did this regarding its prophylactic effect against respiratory infections. Furthermore, we investigated its immunogenicity in adult horses, hoping for a potentiating effect of EHV-4 against EHV-1, mediating enhanced protection against abortion caused by the latter virus. This experimental vaccine proved excellently tolerable, its immunogenicity against either equine herpesvirus type was considerable, was very good against both equine influenza subtypes, was low, however, against retroviruses types 1 and 3. Recommendations are made for seasonal optimal spacing of vaccinations, taking into account the prevalent dissemination phases of the viruses involved, the different age groups of horses and their respective use.     

Both ApxI and ApxII of Actinobacillus pleuropneumoniae serotype 1 are necessary for full virulence

Most serotypes of A. pleuropneumoniae produce more than one toxin in vivo. To determine the value of the production of more than one toxin in the development of disease, we tested the pathogenicity of isogenic strains of A. pleuropneumoniae serotype 1 that are mutated in the toxin genes apxIA and/or apxIIA or in the transport genes apxIBD. Bacteria mutated in both apxIA and apxIIA, or in apxIBD, were unable to induce pathological lesions, thereby confirming the conclusion that ApxI and ApxII are essential for the pathogenesis of pleuropneumonia. Infection with isogenic strains lacking either ApxI or ApxII did not consistently lead to pleuropneumonia unlike the parent strain S4074. ApxII seemed at least as important as ApxI for the development of clinical and pathological symptoms. Only one of the four pigs inoculated with a mutant strain unable to produce ApxII developed mild pneumonia whereas two out of the three pigs inoculated with a mutant strain unable to produce ApxI developed more severe lesions. The results indicate that both ApxI and ApxII of A. pleuropneumoniae serotype 1 are necessary for full virulence.     

Functional genomic analysis of the Wnt-wingless signaling pathway

The Wnt-Wingless (Wg) pathway is one of a core set of evolutionarily conserved signaling pathways that regulates many aspects of metazoan development. Aberrant Wnt signaling has been linked to human disease. In the present study, we used a genomewide RNA interference (RNAi) screen in Drosophila cells to screen for regulators of the Wnt pathway. We identified 238 potential regulators, which include known pathway components, genes with functions not previously linked to this pathway, and genes with no previously assigned functions. Reciprocal-Best-Blast analyses reveal that 50% of the genes identified in the screen have human orthologs, of which approximately 18% are associated with human disease. Functional assays of selected genes from the cell-based screen in Drosophila, mammalian cells, and zebrafish embryos demonstrated that these genes have evolutionarily conserved functions in Wnt signaling. High-throughput RNAi screens in cultured cells, followed by functional analyses in model organisms, prove to be a rapid means of identifying regulators of signaling pathways implicated in development and disease.