Root growth of maize in an Italian ryegrass living mulch studied with a non-destructive method

The use of living mulch (LM) systems for maize (Zea mays L.) cultivation may reduce soil erosion and nitrate leaching. However, the yield of maize cultivated in LM is lower than in conventional farming systems. This decrease has often been attributed to belowground competition, but the lack of a suitable method to demonstrate such competition has prevented further investigation. A recently developed method allows for the direct and non-destructive observation of root growth in LM. Maize expressing a green fluorescence protein was grown in monoculture or together with Italian ryegrass (Lolium multiflorum Lam.). Root growth was screened in minirhizotrons from the time of sowing to the anthesis of the maize.Compared with the maize cultivated without Italian ryegrass, the cultivation in the LM significantly (p < 0.05) reduced the shoot dry matter (56%), leaf area (39%) and mean root density (41%) of the maize at anthesis. An analysis of variance showed that the reduction due to the living Italian ryegrass in the root density of the maize was not significantly different from the reduction in leaf area. Similarly, the reduction in the root density and shoot dry matter of the maize were not significantly different. The roots of the LM maize grew in the soil where the LM was removed but also where the LM continued growing. This study constitutes the first direct quantification of root growth and distribution in a LM system.     

Experimental infection of South American camelids with bluetongue virus serotype 8

Bluetongue (BT) is an infectious, non-contagious disease of wild and domestic ruminants. It is caused by bluetongue virus (BTV) and transmitted by Culicoides biting midges. Since 1998, BT has been emerging throughout Europe, threatening not only the na?ve ruminant population. Historically, South American camelids (SAC) were considered to be resistant to BT disease. However, recent fatalities related to BTV in captive SAC have raised questions about their role in BTV epidemiology. Data on the susceptibility of SAC to experimental infection with BTV serotype 8 (BTV-8) were collected in an animal experiment. Three alpacas (Vicugna pacos) and three llamas (Lama glama) were experimentally infected with BTV-8. They displayed very mild clinical signs. Seroconversion was first measured 6-8 days after infection (dpi) by ELISA, and neutralising antibodies appeared 10-13 dpi. BTV-8 RNA levels in blood were very low, and quickly cleared after seroconversion. However, spleens collected post-mortem were still positive for BTV RNA, over 71 days after the last detection in blood samples. Virus isolation was only possible from blood samples of two alpacas by inoculation of highly sensitive interferon alpha/beta receptor-deficient (IFNAR(-/-)) mice. An in vitro experiment demonstrated that significantly lower amounts of BTV-8 adsorb to SAC blood cells than to bovine blood cells. Although this experiment showed that SAC are generally susceptible to a BTV-8 infection, it indicates that these species play a negligible role in BTV epidemiology.     

Carbon stocks of soil and vegetation on Danubian floodplains

Riparian forests are assumed to play a crucial role in the global carbon cycle. However, little data are available on C stocks of floodplains in comparison to other terrestrial ecosystems. In this study, we quantified the C stocks of aboveground biomass and soils of riparian vegetation types at 76 sampling sites in the Donau‐Auen National Park in Austria. Based on our results and a remotely sensed vegetation map, we estimated total C stocks. Carbon stocks in soils (up to 354 t ha^–1 within 1 m below surface) were huge compared to other terrestrial ecosystems. As expected, soils of different vegetation types showed different texture with a higher percentage of sandy soils at the softwood sites, while loamy soils prevailed at hardwood sites. Total C stocks of vegetation types were significantly different, but reflect differences in woody plant biomass rather than in soil C stocks. Mature hardwood and cottonwood forests proved to have significantly higher total C stocks (474 and 403 t ha^–1, respectively) than young reforestations (217 t ha^–1) and meadows (212 t ha^–1). The C pools of softwood forests (356 t ha^–1) ranged between those of hardwood/cottonwood forests and of reforestations/meadows. Our study proves the relevance of floodplains as possible C sinks, which should be increasingly taken into account for river management. Furthermore, we conclude that plant‐species distribution does not indicate the conditions of sedimentation and soil C sequestration over the time span of interest for the development of soil C stocks.     

Global climate change and its impacts on the terrestrial Arctic carbon cycle with special regards to ecosystem components and the greenhouse‐gas balance

The climatic changes on earth may have serious implications for the carbon (C) cycle in the terrestrial Arctic throughout the 21st century. Arctic vegetation takes up carbon dioxide (CO₂) from the atmosphere producing biomass. In a cold and often moist soil environment, dead organic matter is preferentially preserved as soil organic matter (SOM) due to the inhibition of decomposition processes. However, viable soil microbes exhale huge amounts of CO₂ and methane (CH₄) annually. Hence, Arctic ecosystems exhibit annual fluxes of both carbon‐based (CO₂ and CH₄) greenhouse gases (GHGs) that are in an order of magnitude of millions of tons. Rising Arctic temperatures lead to the degradation of much of today's permafrost in the long run. As a result, large quantities of frozen SOM may become available for decomposers, and GHGs that are entrapped in permafrost may be released. At the same time, warming tends to stimulate the growth, development, and reproduction of many Arctic plants, at least transiently. The present northward migration of boreal shrubs and trees into southern tundra areas may be amplified by that, increasing the ecosystems' gross primary production and, thus, their C sequestration. On the other hand, rising temperatures boost SOM decomposition and microbial respiration rates. In general, soil temperature and soil moisture are key environmental variables to control the intensity of aerobic and anaerobic respiration by microbes, and autotrophic respiration by plants. On the basis of published data on Arctic CO₂ and CH₄ fluxes, the calculations on the terrestrial C‐based Arctic GHG balance made in this review reveal a current annual GHG exchange that ranges between a weak storage of ≤ 225 Tg CO₂ equivalent (eq.) y^–1 and a huge release of ≤ 1990 Tg CO₂ eq. y^–1. Hence, the Arctic GHG balance does apparently already contribute positively to the climatic changes at present. Regarding the future, the relative development of the uptake and release of CO₂ and CH₄ by northern ecosystems is fundamental to the overall GHG status of the Arctic under scenarios of continued climate change.     

Serological studies on Corynebacterium pseudotuberculosis infections in goats in Baden-Wuerttemberg (Germany) and seroreactions on antigens used for newly developed enzyme-linked immunosorbent assays (ELISA)

In the present study, comprehensive data on the seroprevalence of Corynebacterium (C.) pseudotuberculosis infections in goats are presented for Baden-Wuerttemberg, a Federal State of Germany, for the first time. As a prerequisite, ELISAs based on a recombinant phospholipase D (rPLD) and whole cell antigens (WCA) were designed and validated yielding sensitivity values of 81% and 97% and specificity values of 98% and 99%, respectively. Immunisation trials in goats demonstrated a significant production of antibodies to rPLD but an evidently lower antibody production to WCA as determined in the corresponding ELISA. Moreover, immunisation with rPLD resulted in the formation of antibodies, which were also detected in the WCA ELISA. In contrast, this phenomenon was not observed with the rPLD ELISA after immunisation with WCA. Implementation of the rPLD and WCA ELISAs in a broad-based seroprevalence study in Baden-Wuerttemberg revealed positive reactions in both ELISAs in 13.2% of the 1771 goat sera tested. In 53.7% of 121 herds of which five or more animals were tested per herd there was at least one animal that showed a positive reaction in both tests.     

Comparative analysis of neonicotinoid binding to insect membranes: I. A structure-activity study of the mode of [3H]imidacloprid displacement in Myzus persicae and Aphis craccivora

Neonicotinoids bind selectively to insect nicotinic acetylcholine receptors with nanomolar affinity to act as potent insecticides. While the members of the neonicotinoid class have many structural features in common, it is not known whether they also share the same mode of binding to the target receptor. Previous competition studies with [3H]imidacloprid, the first commercialised neonicotinoid, indicated that thiamethoxam, representing a novel structural sub-class, may bind in a different way from that of other neonicotinoids. In the present work we analysed the mode of [3H]imidacloprid displacement by established neonicotinoids and newly synthesized analogues in the aphids Myzus persicae Sulzer and Aphis craccivora Koch. We found two classes of neonicotinoids with distinct modes of interference with [3H]imidacloprid, described as direct competitive inhibition and non-competitive inhibition, respectively. Competitive neonicotinoids were acetamiprid, nitenpyram, thiacloprid, clothianidin and nithiazine, whereas thiamethoxam and the N-methyl analogues of imidacloprid and clothianidin showed non-competitive inhibition. The chloropyridine or chlorothiazole heterocycles, the polar pharmacophore parts, such as nitroimino, cyanoimino and nitromethylene, and the cyclic or acyclic structure of the pharmacophore were not relevant for the mode of inhibition. Consensus structural features of the neonicotinoids were defined for the two mechanisms of interaction with [3H]imidacloprid binding. Furthermore, two sub-classes of non-competitive inhibitors can be discriminated on the basis of their Hill coefficients for imidacloprid displacement. We conclude from the present data that the direct competitors share the binding site with imidacloprid, whereas non-competitive compounds, like thiamethoxam, bind to a different site or in a different mode.     

Assessment of ultrasound imaging as a noninvasive measure of blubber thickness in pinnipeds.

Portable ultrasound imaging was examined as a noninvasive measure of skin including blubber thickness in captive subadult Steller sea lions (Eumetopias jubatus) and adult harbor seals (Phoca vitulina). This method was validated through comparison with blubber biopsy. Ultrasound images provided depth measurements that were accurate to 99.8% of the actual. This method allowed clear images of the epidermis, dermis, and blubber layer to be rapidly obtained, with minimal animal restraint, and allowed differentiation of phocid and otariid blubber structure.     

RADIOGRAPHIC, ULTRASONOGRAPHIC, AND COMPUTED TOMOGRAPHIC APPEARANCE OF ALVEOLAR ECHINOCOCCOSIS IN DOGS

Alveolar echinococcosis is a rare metacestodal infection of humans and domestic animals with Echinococcus multilocularis and predominantly affects the liver. In humans, diagnosis is based on serology, ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI), techniques that have not yet been validated for the diagnosis of alveolar echinococcosis in dogs. Therefore, the purpose of this retrospective study was to describe the radiographic, ultrasonographic, and CT appearance of canine alveolar echinococcosis. Eleven dogs with confirmed alveolar echinococcosis (PCR or histology from biopsy material of metacestode tissue) diagnosed between 1995 and 2003 were included in the study. The age of the dogs at initial presentation ranged from 7 months to 10.5 years. Abdominal radiographs were made in nine animals, abdominal ultrasonography was performed in 10 dogs, and two CT studies in one dog, respectively. The history, clinical presentation, and laboratory findings for the 11 dogs were unspecific, the most frequent clinical finding being nonpainful progressive abdominal distention. All radiographed dogs had large liver masses; they contained small mineralizations in five. The most frequent ultrasonographic finding was multiple large cavitary masses with or without wall mineralizations. Seven animals received surgical and subsequent medical therapy with albendazole (10mg/kg) and all went into clinical remission. This study reviewed for the first time imaging findings associated with alveolar echinococcosis. The disease has to be included in the list of differential diagnoses in dogs with large, cavitary liver masses, particularly when mineralization is noted.