Plant communities affect arbuscular mycorrhizal fungal diversity and community composition in grassland microcosms

The diversity of arbuscular mycorrhizal (AM) fungi was investigated in an unfertilized limestone grassland soil supporting different synthesized vascular plant assemblages that had developed for 3 yr. The experimental treatments comprised: bare soil; monocultures of the nonmycotrophic sedge Carex flacca; monocultures of the mycotrophic grass Festuca ovina; and a species-rich mixture of four forbs, four grasses and four sedges. The diversity of AM fungi was analysed in roots of Plantago lanceolata bioassay seedlings using terminal-restriction fragment length polymorphism (T-RFLP). The extent of AM colonization, shoot biomass and nitrogen and phosphorus concentrations were also measured. The AM diversity was affected significantly by the floristic composition of the microcosms and shoot phosphorus concentration was positively correlated with AM diversity. The diversity of AM fungi in P. lanceolata decreased in the order: bare soil > C. flacca > 12 species > F. ovina. The unexpectedly high diversity in the bare soil and sedge monoculture likely reflects differences in the modes of colonization and sources of inoculum in these treatments compared with the assemblages containing established AM-compatible plants

Drivers of vegetation change in grasslands of the Sheffield region, northern England, between 1965 and 2012/13

Questions: How has vegetation species diversity and species composition changed between 1965 and 2012/13 in acidic and calcareous grasslands? What has driven this change in vegetation? Location: A 2400-km2 area around Sheffield, northern England. Methods: In 1965 a survey was conducted to describe grassland vegetation of the Sheffield region. We repeated this survey in 2012/13, revisiting acidic and calcareous grassland sites (455 quadrats). Climate, N and sulphur deposition, cattle and sheep stocking rates, soil pH, altitude, aspect and slope were considered to be potential drivers of variation in vegetation. We analysed temporal changes in vegetation and examined relationships with spatial and temporal variation in driver variables. Results: Both acidic and calcareous grasslands showed clear changes in species composition between the two time periods. In acidic grasslands there was no significant change in richness but there were declines in diversity. There were significant increases in Ellenberg N. Nitrogen deposition and grazing were identified as potential drivers of spatial and temporal patterns but it was not possible to discriminate the respective impacts of potential drivers. In calcareous grasslands there were declines in species richness, diversity and appropriate diversity indices. Climate and soil pH were identified as potential drivers of spatial and temporal patterns. Conclusions: Despite only small site losses compared to other surveys in the UK, especially within the national park, both calcareous and acidic grasslands showed very clear changes in species composition. In acidic grasslands, high abundance of Pteridium aquilinum was a particular problem and had increased considerably between the two survey periods. Atmospheric N deposition and grazing were identified as drivers of species diversity. A number of calcareous grasslands showed signs of reduced management intensity leading to scrub invasion

On the idempotents of Hecke algebras

We give a new construction of primitive idempotents of the Hecke algebras associated with the symmetric groups. The idempotents are found as evaluated products of certain rational functions thus providing a new version of the fusion procedure for the Hecke algebras. We show that the normalization factors which occur in the procedure are related to the Ocneanu--Markov trace of the idempotents.Comment: 11 page

Do Alterations in the Rate of Gastric Emptying after Injection Sclerotherapy for Oesophageal Varices Play any Role in the Development of Portal Hypertensive Gastropathy?

Bleeding from portal hypertensive gastropathy (PHG) has been estimated to account for upto 30% of all upper gastrointestinal haemorrhage in patients with cirrhosis and portal hypertension. Although portal hypertension seems to be an essential prerequisite, the precise mechanisms responsible for the development of PHG are unknown. The aim of this study was to examine the role of injection sclerotherapy of oesophageal varices in the development of PHG. Gastric emptying was studied using a radionuclide test meal with the emptying characteristics of a slow liquid in 57 patients with cirrhosis and/or portal hypertension (median age 53 yrs), of whom 34 had received injection sclerotherapy for their oesophageal varices and 20 normal healthy volunteers (median age 42 yrs). As vagal damage is associated with more rapid emptying of liquids, despite hold up of solids, this technique might be expected to demonstrate such damage if gastric emptying was accelerated. The results indicated that there was no difference in the rate of gastric emptying between normal healthy volunteers and portal hypertensive patients. However, patients who had received injection sclerotherapy emptied their stomachs faster than those who had not (p<0.05). Furthermore, the speed of gastric emptying correlated directly with the number of injections (r=0.41; p=0.02) and the volume of sclerosant injected (r=0.39; p=0.03). These observations suggest that injection sclerotherapy for oesophageal varices results in disturbances of gastric emptying that may contribute to the pathogenesis of portal hypertensive gastropathy

A trait‐based approach to plant species selection to increase functionality of farmland vegetative strips

Farmland vegetative strips are a proven source of support for ecosystem services and are globally used to mitigate effects of agricultural intensification. However, increasing pressures on agricultural land require increases in their functionality, such as supporting multiple ecosystem services concurrently. The plant species sown in a vegetative strip seed mix determine the establishment, plant community, and ecosystem services that are supported. Currently, there is no clearly defined or structured method to select plant species for multifunctional vegetative strips. Plant traits determine how plants support ecosystem services. Also, the establishment and persistence of plant communities is influenced by key internal and external factors. We propose a novel, evidence‐informed method of multifunctional vegetative strip design based on these essential traits and factors. This study had three distinct stages. The first identified plant traits that support water quality protection, pollinators and/or crop pest natural enemies, using existing research evidence. We then identified key factors affecting plant community establishment and persistence. Finally, we applied these standardized methods to design a multifunctional vegetative strip for a specific case study (UK lowland farmland). Key plant traits identified, included floral display size, flower color, nectar content, leaf surface area, leaf trichome density, percentage fine roots, root length, rooting depth, and root density. Key internal and external establishment factors included life history, native status, distribution, established competitive strategy, associated floristic diversity, flowering time and duration, and preferred soil type and pH. In the United Kingdom case study, we used five different plant traits and all of the identified factors to design a seed mix for a multifunctional vegetative strip. We present a transferable method of vegetative strip design that can be adapted for other ecosystem services and climates. It provides landowners and advisors with an evidence‐informed approach to increase field margin functionality while supporting farmland biodiversity

Coarse-grained simulation reveals key features of HIV-1 capsid self-assembly

The maturation of HIV-1 viral particles is essential for viral infectivity. During maturation, many copies of the capsid protein (CA) self-assemble into a capsid shell to enclose the viral RNA. The mechanistic details of the initiation and early stages of capsid assembly remain to be delineated. We present coarse-grained simulations of capsid assembly under various conditions, considering not only capsid lattice self-assembly but also the potential disassembly of capsid upon delivery to the cytoplasm of a target cell. The effects of CA concentration, molecular crowding, and the conformational variability of CA are described, with results indicating that capsid nucleation and growth is a multi-stage process requiring well-defined metastable intermediates. Generation of the mature capsid lattice is sensitive to local conditions, with relatively subtle changes in CA concentration and molecular crowding influencing self-assembly and the ensemble of structural morphologies