Grass-dominated vegetation, not species-diverse natural savanna, replaces degraded tropical forests on the southern edge of the Amazon Basin

Changes in land-uses, fire regimes, and climate are expected to promote savanna expansion in the Amazon Basin, but most studies that come to this conclusion fail to define “savanna” clearly or imply that natural savannas of native species will spread at the expense of forest. Given their different conservation values, we sought to differentiate between species-diverse natural savannas and other types of fire-maintained grass-dominated vegetation that replaced tropical forests between 1986 and 2005 in 22,500 km² of eastern lowland Bolivia. Analysis of Landsat TM and CBERS-2 satellite imagery revealed that, in addition to 1200 km² (7.1%) of deforestation for agriculture and planted pastures, 1420 km² (8.4%) of forest was replaced by derived savannas. Sampling in 2008 showed that natural savannas differed from forest-replacing derived savannas floristically, in soil fertility, and in fuel loads. Natural savannas typically occurred on sandy, acidic, nutrient-poor soils whereas most derived savannas were on comparatively fertile soils. Fuel loads in derived savannas were twice those of natural savannas. Natural savannas supported a diversity of grass species, whereas derived savannas were usually dominated by Guadua paniculata (native bamboo), Urochloa spp. (exotic forages), Imperata brasiliensis (native invasive), Digitaria insularis (native ruderal), or the native fire-adapted herb Hyptis suaveolens (Lamiaceae). Trees in derived savannas were forest species (e.g., Anadenanthera colubrina) and fire-tolerant palms (Attalea spp.), not thick-barked species characteristic of savanna environments (e.g., Curatella americana). In addressing tropical vegetation transitions it is clearly important to distinguish between native species-diverse ecosystems and novel derived vegetation of similar structure.     

Vegetation Response to a One-Time Spent Drilling Mud Application to Semiarid,Mixed-Grass Prairie

Landspraying while drilling (LWD) is an approved disposal method for water-based drilling mud (WBM) systems in western Canada. The mud is applied either on cultivated land, where it is incorporated by cultivation, or on vegetated land where it is not incorporated. This study examined the effects of summer WBM application (0, 15, 20, 40, and 80 m³ · ha^?1) on native vegetation properties. Our results indicated that LWD increased bare ground but decreased lichen cover at the 80 m³ · ha^?1 rate relative to the untreated control. Nitrogen (N), sulfur (S), and magnesium (Mg) concentrations in aboveground plant tissue increased with increasing LWD rate in samples taken 45 d after WBM application, but these differences disappeared 1 yr after treatment. Increase in tissue concentration of phosphorus (P) with LWD rate, however, was only detected 3 yr after LWD. Nonetheless, these changes in tissue chemistry were not associated with significant changes in biomass yield or species composition. Overall, our results suggest that single WBM applications at rates (≤ 20 m³ · ha^?1) commonly used in western Canada, if properly managed, are unlikely to adversely affect native prairie vegetation.     

Diversity of laccase genes from basidiomycetes in a forest soil

Fungal oxidative exo-enzymes lacking substrate specificity play a central role in the cycling of soil organic matter. Due to their broad ecological impact and available knowledge of their gene structure, laccases appeared to be appropriate markers to monitor fungi with this kind of oxidative potential in soils. A degenerate PCR-primer pair Cu1F/Cu2R, specific for basidiomycetes, was designed to assess directly the diversity of laccase genes in soils. PCR amplification of mycelial cultures and fruit-bodies of a wide spectrum of basidiomycetes, covering all functional groups (saprophytes, symbionts, and pathogens), produced multiple DNA fragments around 200 bp. A neighbor-joining tree analysis of the PCR-amplified laccase sequences showed a clear species-specificity, but also revealed that most fungal taxa possess several laccase genes showing a large sequence divergence. This sequence diversity precluded the systematic attribution of amplified laccase of unknown origin to specific taxa. Amplification of laccase sequences from DNA, extracted from a brown (moder) forest soil, showed a specific distribution of laccase genes and of the corresponding fungal species in the various soil horizons (O_h, A_h, B_v). The most organic O_h-horizon displayed the highest gene diversity. Saprophytic fungi appeared to be less widespread through the soil horizons and displayed a higher diversity of laccase genes than the mycorrhizal ones.     

Microparticle dispensers for the controlled release of insect pheromones

The potential utility of micrometer-sized particles as controlled-release devices for the volatilization of insect pheromones for mating disruption applications is evaluated in this study for two pheromone/model compound systems (codlemone/1-dodecanol and disparlure/1,2-epoxyoctadecane). To expedite the measurement of release rates from these particle devices, two techniques based on thermogravimetric analysis (TGA) have been exploited: isothermal TGA (I-TGA) at elevated temperatures (40-80 degrees C) with N(2) convection and volatilization temperature (VT) by dynamic TGA. A correlation between these two methods has been established. Samples that exhibit a higher VT provide a lower release rate from a particle substrate. Using these techniques, it has been demonstrated that chemical interactions between adsorbed liquids and particle surfaces may play a small role in defining release characteristics under conditions of low surface area, whereas parameters associated with total surface area and micropore structure appear to be much more significant in retarding evaporation for uncoated particles containing an adsorbed liquid. Additional regulation of release rates was achieved by coating the particle systems with water-soluble or water-dispersible polymers. By careful selection of particle porosity and coating composition, it is envisioned that the evaporation rate of pheromones can be tailored to specific insect control applications.     

Classification of Dutch and German avian reoviruses by sequencing the sigma C protein

We have amplified, cloned and sequenced (part of) the open reading frame of the S1 segment encoding the sigma C protein of avian reoviruses isolated from chickens with different disease conditions in Germany and The Netherlands during 1980 up to 2000. These avian reoviruses were analysed phylogenetically and compared with sequences of avian reoviruses in the Genbank database. The avian reoviruses could be grouped in 5 different genotyping clusters and this classification was identical when the sequences were compared of the 5' end, the 3' end or the whole open reading frame of the sigma C protein. Therefore sequencing of either part of the gene encoding the sigma C protein seems to be reliable for classification. We were unable to identify a correlation between sigma C sequences of the avian reoviruses and the disease condition they were isolated from. The sequences found in The Netherlands and in Germany are, like those in Taiwan, more dispersed than the known avian reovirus sigma C sequences in the USA and Australia. We did not establish temporal or geographic differences in the avian reoviruses studied.     

Reproducibility and Repeatability of Equine Muscle Thickness Measurements with Ultrasound

This study examined the reproducibility and repeatability of muscle thickness (MT) measurements with ultrasound for the following muscles: extensor carpi radialis, extensor digitorum longus (both flexed and extended), gluteus medius, longissimus lumborum, semitendinosus, and supraspinatus. Three examiners measured thickness of these muscles in five Thoroughbreds on 3 consecutive days. The day of measurement did not have any effect on the mean MT value of the muscles examined (P > .05). The left longissimus lumborum muscle was the only muscle for which the second measurement varied from the first and third (P < .05). The examiners had an effect on the mean coefficient of variation (CV) of the thickness of the flexed left extensor carpi radialis and flexed left extensor digitorum longus. The daily measurements varied more in the case of one of the examiners. Mean CVs higher or close to 10% were reported for both sides of the flexed extensor digitorum longus and for the supraspinatus muscles. The lowest CV was calculated for the longissimus lumborum and the extended semitendinosus (<5%). The largest disagreements between the examiners were observed for both sides of the flexed extensor digitorum longus and the supraspinatus (>10%–<20%). The best agreement was measured for the extended extensor carpi radialis and the longissimus lumborum (>3%–<7%). The results showed that for some muscles, it was difficult to locate the exact anatomical site for taking the MT measurements. To reduce CV, it was suggested that only one examiner should take all the measurements and the whole procedure must be such that it is as comfortable as possible for this particular examiner.     

番茄疮痂病病原菌分类、抗性遗传和分子标记辅助选择进展

番茄疮痂病是世界上所有番茄种植地区主要的细菌性病害之一，该病能引起严重的产量损失和品质下降，几十年来一直受到育种界的关注。由于该病病原菌存在多个种和小种以及对该病的抗性呈数量性状遗传，因此通过育种途径来改良抗性进展缓慢。分子标记辅助选择为育种家筛选、聚合或累加对多个小种的抗性提供了一种工具。以前的综述对1997年以前在病害的发生、症状、危害、综合防治、遗传分析和育种等方面的研究进行了较为详尽的总结。近年来，在病原菌种与小种的鉴定、抗源的发掘、抗性遗传的分子定位和分子标记辅助选择方面的研究取得了很大进展，传统育种与分子生物学方法有机结合的策略也初见成效。本文将对这些进展进行总结，并对分子标记在番茄疮痂病抗性育种中的应用前景进行讨论。     

Making Asian students,making students Asian: The racialisation of export education in Auckland,New Zealand

Abstract: In recent years, international education has become a source of considerable political, academic and media debate in New Zealand. This is nowhere more the case than with regards to Auckland, the New Zealand city that has hosted the greatest number of international students. This paper focuses on the media debates around international students in Auckland with particular emphasis on the representations of the largest group of international students, those who originate from countries within the North‐East Asian region. The media representations of these students have fixed a diverse group of individuals within a singular racial identity that is known by stereotypical economic, cultural and social characteristics. As a result, these representations have further problematised the interaction between international students and the host population in Auckland while simultaneously implicating a cohort of young New Zealand citizens and permanent residents who are of similar descent within the same discourses. This process of othering the Asian student, regardless of citizenship, has consequences not simply for the practice of exporting education in this city but also for the future of a multicultural Auckland and New Zealand.