Spin-transfer switching and low-field precession in exchange-biased spin valve nano-pillars

Using a three-dimensional focused-ion beam lithography process we have fabricated nanopillar devices which show spin transfer torque switching at zero external magnetic fields. Under a small in-plane external bias field, a field-dependent peak in the differential resistance versus current is observed similar to that reported in asymmetrical nanopillar devices. This is interpreted as evidence for the low-field excitation of spin waves which in our case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange bias layer coupled to a relatively thin CoFe fixed layer.Comment: 11 pages, 4 figures. To appear in APL, April 200

Relationships between tree growth and weather extremes: spatial and interspecific comparisons in a temperate broadleaf forest

Three years of monthly growth increment data identified large interannual differences in growth rate across six contrasting species in a broadleaved, temperate forest with minimum management intervention (Wytham Woods, UK). Growth rates varied by species and canopy position, and were higher in canopy species. Growth rate in 2010 was up to 40% lower than in 2011 and 2012. This can best be explained as an effect of low temperature, which delayed the start of spring and the growing season. This had a greater impact on the growth of sub-canopy trees than that of canopy species. In temperate systems, late spring and summer is an important component of the whole growing season carbon balance because of long day length. In 2010 there were also periods of lower-than-average rainfall, which may additionally have constrained growth during the growing season. Fluctuations and seasonal changes in both temperature and rainfall are projected to continue, so we may expect to see increasing differences in growth and growth rates. A small effect of location relative to the nearest edge was also detected, with higher growth rates only found >50. m from the forest edge. The findings have implications for forest structure and productivity under climate change, and may thus inform current and future forest management

Nature-based Solutions for Climate Change in the UK

Nature-based solutions (NbS) address societal problems in ways that benefit both people and nature. The main focus of this report is the joint role of NbS for addressing the climate and biodiversity crises we currently face. Natural habitats act as NbS for climate if they sequester carbon (contributing to Net Zero targets) or provide adaptation to climate change effects (for example, reducing flooding, protecting coastline against sea-level rise or creating cool spaces in cities). As well as these climate benefits, they can enhance biodiversity, create improved and more resilient ecosystem functioning, enhance human wellbeing and provide economic benefits, in terms of monetary value and job creation. Despite the huge range of benefits NbS have, they should be seen as complementary to other climate and conservation actions, not as a replacement to them. NbS have great potential to tackle the two defining crises of our age. The BES report provides examples of opportunities for NbS across a range of habitats, as well as discussion of some of the complexities involved in planning for NbS. The report also outlines a detailed analysis of the tools, financial mechanisms and policies required for effective delivery in a UK context. Policy change will be necessary to overcome some of the challenges associated with NbS and to ensure that they fulfil their potential, yet the rewards are vital in meeting national climate change and biodiversity targets. The Executive Summary provides five key themes which emerge across the report, across the multiple habitats and multiple NbS studied. Six ‘priority’ habitats for NbS are given at the end of the summary. However, we emphasise that all habitats covered in the report can act as NbS and all can play a role in addressing the climate and biodiversity crises

Impacts of climate change on national biodiversity population trends

Lepidoptera are sensitive to climate change, with documented impacts on their phenology, distribution and communities. However, there remains considerable uncertainty over which species are most vulnerable, and which have been most affected so far. To address this, we analyse 35-year UK or English population trends of 55 butterfly and 265 moth species to model the impacts of variation in temperature and precipitation upon population growth rates. We identify the weather variables and periods that species are most sensitive to, the long-term impacts of climate change, and the characteristics of species which show the greatest responses. Positive impacts of summer temperature on both butterflies and moths were partly offset by negative impacts of temperature in other seasons, particularly winter. Precipitation tended to have negative impacts on population growth rates, particularly for moths. Annual population fluctuations were strongly driven by inter-annual variation in weather conditions. Over 40% of a significant decline in mean moth abundance from the 1990s to 2000s was consistent with a weather-driven decline predicted by our models, which also explained up to 19% of the decadal variation in abundance between species. Species overwintering as larvae and multivoltine species were most sensitive to the effects of weather, whilst southerly-distributed species, species associated with woodland and unimproved grassland habitats, and pest species, showed the most positive long-term responses to climate change. Combined, these results show how climate change is already having significant impacts on the abundance of particular butterfly and moth species, with likely future consequences for ecosystem function and services

Interacting effects of climate change and habitat fragmentation on drought-sensitive butterflies

Climate change is expected to increase the frequency of some climatic extremes. These may have drastic impacts on biodiversity, particularly if meteorological thresholds are crossed, leading to population collapses. Should this occur repeatedly, populations may be unable to recover, resulting in local extinctions. Comprehensive time series data on butterflies in Great Britain provide a rare opportunity to quantify population responses to both past severe drought and the interaction with habitat area and fragmentation. Here, we combine this knowledge with future projections from multiple climate models, for different Representative Concentration Pathways (RCPs), and for simultaneous modelled responses to different landscape characteristics. Under RCP8.5, which is associated with ‘business as usual’ emissions, widespread drought-sensitive butterfly population extinctions could occur as early as 2050. However, by managing landscapes and particularly reducing habitat fragmentation, the probability of persistence until mid-century improves from around zero to between 6 and 42% (95% confidence interval). Achieving persistence with a greater than 50% chance and right through to 2100 is possible only under both low climate change (RCP2.6) and semi-natural habitat restoration. Our data show that, for these drought-sensitive butterflies, persistence is achieved more effectively by restoring semi-natural landscapes to reduce fragmentation, rather than simply focusing on increasing habitat area, but this will only be successful in combination with substantial emission reductions

Experimental evidence for the interacting effects of forest edge, moisture and soil macrofauna on leaf litter decomposition

a b s t r a c t Forest ecosystems have been widely fragmented by human land use. Fragmentation induces significant microclimatic and biological differences at the forest edge relative to the forest interior. Increased exposure to solar radiation and wind at forest edges reduces soil moisture, which in turn affects leaf litter decomposition. We investigate the effect of forest fragmentation, soil moisture, soil macrofauna and litter quality on leaf litter decomposition to test the hypothesis that decomposition will be slower at a forest edge relative to the interior and that this effect is driven by lower soil moisture at the forest edge. Experimental plots were established at Wytham Woods, UK, and an experimental watering treatment was applied in plots at the forest edge and interior. Decomposition rate was measured using litter bags of two different mesh sizes, to include or exclude invertebrate macrofauna, and containing leaf litter of two tree species: easily decomposing ash (Fraxinus excelsior L.) and recalcitrant oak (Quercus robur L.). The decomposition rate was moisture-limited at both sites. However, the soil was moister and decomposition for both species was faster in the forest interior than at the edge. The presence of macrofauna accelerated the decomposition rate regardless of moisture conditions, and was particularly important in the decomposition of the recalcitrant oak. However, there was no effect of the watering treatment on macrofauna species richness and abundance. This study demonstrates the effect of forest fragmentation on an important ecosystem process, providing new insights into the interacting effects of moisture conditions, litter quality, forest edge and soil macrofauna

The effectiveness of protected areas in the conservation of species with changing geographical ranges

A cornerstone of conservation is the designation and management of protected areas (PAs): locations often under conservation management containing species of conservation concern, where some development and other detrimental influences are prevented or mitigated. However, the value of PAs for conserving biodiversity in the long term has been questioned given that species are changing their distributions in response to climatic change. There is a concern that PAs may become climatically unsuitable for those species that they were designated to protect, and may not be located appropriately to receive newly-colonizing species for which the climate is improving. In the present study, we analyze fine-scale distribution data from detailed resurveys of seven butterfly and 11 bird species in Great Britain aiming to examine any effect of PA designation in preventing extinctions and promoting colonizations. We found a positive effect of PA designation on species' persistence at trailing-edge warm range margins, although with a decreased magnitude at higher latitudes and altitudes. In addition, colonizations by range expanding species were more likely to occur on PAs even after altitude and latitude were taken into account. PAs will therefore remain an important strategy for conservation. The potential for PA management to mitigate the effects of climatic change for retracting species deserves further investigation

Conducting robust ecological analyses with climate data

Although the number of studies discerning the impact of climate change on ecological systems continues to increase, there has been relatively little sharing of the lessons learnt when accumulating this evidence. At a recent workshop entitled ‘Using climate data in ecological research’ held at the UK Met Office, ecologists and climate scientists came together to discuss the robust analysis of climate data in ecology. The discussions identified three common pitfalls encountered by ecologists: 1) selection of inappropriate spatial resolutions for analysis; 2) improper use of publically available data or code; and 3) insufficient representation of the uncertainties behind the adopted approach. Here, we discuss how these pitfalls can be avoided, before suggesting ways that both ecology and climate science can move forward. Our main recommendation is that ecologists and climate scientists collaborate more closely, on grant proposals and scientific publications, and informally through online media and workshops. More sharing of data and code (e.g. via online repositories), lessons and guidance would help to reconcile differing approaches to the robust handling of data. We call on ecologists to think critically about which aspects of the climate are relevant to their study system, and to acknowledge and actively explore uncertainty in all types of climate data. And we call on climate scientists to make simple estimates of uncertainty available to the wider research community. Through steps such as these, we will improve our ability to robustly attribute observed ecological changes to climate or other factors, while providing the sort of influential, comprehensive analyses that efforts to mitigate and adapt to climate change so urgently require

The role of sex in the pathophysiology of pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease characterised by increased pulmonary vascular resistance and pulmonary artery remodelling as result of increased vascular tone and vascular cell proliferation, respectively. Eventually, this leads to right heart failure. Heritable PAH is caused by a mutation in the bone morphogenetic protein receptor-II (BMPR-II). Female susceptibility to PAH has been known for some time, and most recent figures show a female-to-male ratio of 4:1. Variations in the female sex hormone estrogen and estrogen metabolism modify FPAH risk, and penetrance of the disease in BMPR-II mutation carriers is increased in females. Several lines of evidence point towards estrogen being pathogenic in the pulmonary circulation, and thus increasing the risk of females developing PAH. Recent studies have also suggested that estrogen metabolism may be crucial in the development and progression of PAH with studies indicating that downstream metabolites such as 16α-hydroxyestrone are upregulated in several forms of experimental pulmonary hypertension (PH) and can cause pulmonary artery smooth muscle cell proliferation and subsequent vascular remodelling. Conversely, other estrogen metabolites such as 2-methoxyestradiol have been shown to be protective in the context of PAH. Estrogen may also upregulate the signalling pathways of other key mediators of PAH such as serotonin