Quantum interference effects in p-Si1−xGex quantum wells

Quantum interference effects, such as weak localization and electronelectron interaction (EEI), have been investigated in magnetic fields up to 11 T for hole gases in a set of Si1−xGex quantum wells with 0.13 < x < 0.95. The temperature dependence of the hole phase relaxation time has been extracted from the magneto-resistance between 35 mK and 10 K. The spin-orbit effects that can be described within the Rashba model were observed in low magnetic fields. A quadratic negative magneto-resistance was observed in strong magnetic fields, due to the EEI effect. The hole-phonon scattering time was determined from hole overheating in a strong magnetic field

Atmospheric CO2 elevation has little effect on nitrifying and denitrifying enzyme activity in four European grasslands.

International audienceThe objective of this study was to determine what patterns, if any, existed in the response of nitrifying enzyme activity (NEA), denitrifying enzyme activity (DEA), soil microbial N and soil inorganic N to elevated CO2 across a broad range of grassland environments. We studied the response of these N pools and microbial activities in four CO2-enrichment sites of the MEGARICH project (Managing European Grasslands as a Sustainable Resource in a Changing Climate). CO2 treatment was studied in factorial combination with a cutting frequency treatment at two sites and with a temperature treatment at one site. Our study showed that microbial biomass N, NEA, DEA and extractable soil [NH4+] and [NO3-] were generally not affected by elevated CO2 in these grassland ecosystems after several years of treatment, nor by cutting frequency or temperature at the sites that included these treatments. Exceptions to this were that DEA and soil [NO3-] decreased by 22% and 45%, respectively, at the French site at elevated CO2. We discuss the possible explanations for this lack of respons

A framework to identify enabling and urgent actions for the 2020 Aichi Targets

In 2010, the parties of the Convention on Biological Diversity (CBD) adopted the Strategic Plan for Biodiversity 2011–2020 with the mission of halting biodiversity loss and enhance the benefits it provides to people. The 20 Aichi Biodiversity Targets (Aichi Targets), which are included in the Strategic Plan, are organized under five Strategic Goals, and provide coherent guidance on how to achieve it. Halfway through the Strategic Plan, it is time to prioritize actions in order to achieve the best possible outcomes for the Aichi Targets in 2020. Actions to achieve one target may influence other targets (downstream interactions);in turn a target may be influenced by actions taken to attain other targets (upstream interactions). We explore the interactions among targets and the time-lags between implemented measures and desired outcomes to develop a framework that can reduce the overall burden associated with the implementation of the Strategic Plan. We identified the targets addressing the underlying drivers of biodiversity loss and the targets aimed at enhancing the implementation of the Strategic Plan as having the highest level of downstream interactions. Targets aimed at improving the status of biodiversity and safeguarding ecosystems followed by targets aimed at reducing the direct pressures on biodiversity and enhancing the benefits to all from biodiversity and ecosystem services, were identified as having the highest levels of upstream interactions. Perhaps one of the most challenging aspects of the Strategic Plan is the need to balance actions for its long-term sustainability with the need for urgent actions to halt biodiversity loss

Species-level effects more important than functional group-level responses to elevated CO2: evidence from simulated turves

Using mixtures of 14 calcareous grassland plant species drawn from three functional groups, we looked at the effects of elevated atmospheric CO2 on contrasting levels of ecosystem performance (species, functional group and community). Experimental communities were subjected to ambient (?350 µmol mol?1) or elevated CO2 (?600 µmol mol?1) in controlled environments, with grazing simulated by clipping at monthly intervals for 546 days.We assessed the effect of elevated CO2 on plant performance by quantifying the productivity (biomass) and cover of component species. We also examined the effect of elevated CO2 on the vertical structure of the plant canopy. Elevated CO2 resulted in a significant increase in total community biomass only following nutrient addition. Within functional groups, non-leguminous forb species had significantly greater biomass and cover in elevated CO2 both before and after nutrient addition, although the effect was mainly due to the influence of one species (Centaurea nigra). Grasses, in contrast, responded negatively to elevated CO2, although again significant reductions in biomass and cover could mainly be ascribed to a single species (Brachypodium pinnatum). Legumes exhibited increased biomass and cover in elevated CO2 (the effects being particularly marked for Anthyllis vulneraria and Lotus corniculatus), but this response disappeared following nutrient addition. Vertical structure was little affected by CO2 treatment.We conclude that due to the idiosyncratic responses of individual species, the categorization of plants into broad functional groups is of limited use in guiding our understanding of the impacts of elevated atmospheric CO2 on plant communities.<br/