Manchester Metropolitan University

About: Manchester Metropolitan University is a education organization based out in Manchester, Manchester, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 5435 authors who have published 16202 publications receiving 442561 citations. The organization is also known as: Manchester Polytechnic & MMU.

Loss of forb diversity in relation to nitrogen deposition in the UK: regional trends and potential controls

Abstract: In this study we investigate the impact of nitrogen (N) deposition on the diversity of three different vegetation functional groups – forbs, grasses and mosses – using a field survey of acid grasslands across Great Britain. Our aim is to identify the vegetation types that are most vulnerable to enhanced N deposition, and to shed light on the mechanisms that may be driving N-initiated species changes in the UK. Sixty-eight randomly selected grasslands belonging to the UK National Vegetation Classification group U4 (Festuca ovina–Agrostis capillaris–Galium saxatile grassland) were studied along a gradient of atmospheric N deposition ranging from 6 to 36 kg N ha−1 yr−1. At each site, vegetation was surveyed and samples were taken from the topsoil and subsoil. Aboveground plant material was collected from three species: a forb, grass and moss. Both the species richness and cover of forbs declined strongly with increasing N deposition, from greater than eight species/20% cover per m2 quadrat at low levels of N to fewer than two species/5% cover at the highest N deposition levels. Grasses showed a weak but significant decline in species richness, and a trend toward increasing cover with increasing N input. Mosses showed no trends in either species richness or cover. Most of the decline in plant species richness could be accounted for by the level of ammonium deposition. Soil KCl-extractable ammonium concentration showed a significant positive correlation with N input, but there was no relationship between N deposition and extractable nitrate. In the soil O/A horizon, there was no relationship between N deposition and %N, and only a very weak positive relationship between the level of N deposition and the C : N ratio. Finally, in the vegetation, there was no relationship between N deposition and either shoot tissue N concentration or N : P ratio for any of the three reference species. Combining our regional survey with the results of published N-addition experiments provides compelling evidence that there has been a significant decline in the species richness and cover of forbs across Great Britain, and that the primary cause is competition due to an increase in the cover of grasses in response to enhanced deposition of reactive N, primarily NH4+.

Electrochemistry of graphene : not such a beneficial electrode material?

Abstract: We critically evaluate the reported electro-catalysis of graphene using inner-sphere and outer-sphere electrochemical redox probes, namely potassium ferrocyanide (II) and hexaammine-ruthenium(III) chloride, in addition to L-ascorbic acid and β-nicotinamide adenine dinucleotide. Well characterised commercially available graphene is utilised which has not been chemically treated, is free from surfactants, and as a result of its fabrication has an extremely low oxygen content allowing the electronic properties to be properly de-convoluted. Surprisingly we observe that graphene exhibits slow electron transfer towards the electrochemical probes studied, effectively blocking underlying electron transfer of the supporting electrode substrate likely due to its large basal and low edge plane content. Such observations, never reported before, suggest that graphene may not be such a beneficial electrode material as widely reported in the literature. Density Functional Theory is conducted on symmetric graphene flakes of varying sizes indicating that the HOMO and LUMO energies are concentrated around the edge of the graphene sheet, at the edge plane sites, rather than the central basal plane region, consistent with experimental observations. We define differentiating coverage-based working regions for the electrochemical utilisation of graphene: ‘Zone I’, where graphene additions do not result in complete coverage of the underlying electrode and thus increasing basal contribution from graphene modification leads to increasingly reduced electron transfer and electrochemical activity; ‘Zone II’, once complete single-layer coverage is achieved, layered graphenevizgraphite materialises with increased edge plane content and thus an increase in heterogeneous electron transfer is observed with increased layering. We offer insight into the electrochemical properties of these carbon materials, invaluable where electrode design for electrochemical sensing applications is sought.

The implications of grassland and heathland management for the conservation of spider communities: a review

Abstract: Both intensity and type of habitat management in grasslands and heathlands affect spider communities. With high intensity management, spider communities often lack diversity and are dominated by a few r -selected species affiliated with bare ground. Low intensity management produces more complex communities introducing more niches for aerial web spinners and climbing spiders. The preferred management will be site-dependent and may not be appropriate for all spiders in all situations, particularly for some rare or threatened species. Providing natural cover is recommended when using extreme forms of management or intensive grazing (particularly by sheep). In extreme cases, or where trampling is heavy, the litter layer should be conserved. We advocate research and survey before and after major management implementation. Habitat management for spiders should not be considered alone, but integrated into a holistic plan. Management for spiders may conflict with rare plant conservation and small reserves should examine the viability of providing two contrasting regimes.