Invited review: climate change impacts in polar regions: lessons from Antarctic moss bank archives.

Mosses are the dominant plants in polar and boreal regions, areas which are experiencing rapid impacts of regional warming. Long-term monitoring programmes provide some records of the rate of recent climate change, but moss peat banks contain an unrivalled temporal record of past climate change on terrestrial plant Antarctic systems. We summarise the current understanding of climatic proxies and determinants of moss growth for contrasting continental and maritime Antarctic regions, as informed by 13C and 18O signals in organic material. Rates of moss accumulation are more than three times higher in the maritime Antarctic than continental Antarctica with growing season length being a critical determinant of growth rate, and high carbon isotope discrimination values reflecting optimal hydration conditions. Correlation plots of 13C and 18O values show that species (Chorisodontium aciphyllum / Polytrichum strictum) and growth form (hummock / bank) are the major determinants of measured isotope ratios. The interplay between moss growth form, photosynthetic physiology, water status and isotope composition are compared with developments of secondary proxies, such as chlorophyll fluorescence. These approaches provide a framework to consider the potential impact of climate change on terrestrial Antarctic habitats as well as having implications for future studies of temperate, boreal and Arctic peatlands. There are many urgent ecological and environmental problems in the Arctic related to mosses in a changing climate, but the geographical ranges of species and life-forms are difficult to track individually. Our goal was to translate what we have learned from the more simple systems in Antarctica, for application to Arctic habitats.JR is funded by Natural Environment Research Council grant NE/H014896/1.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/gcb.1277

Bill Hillier, Christopher Alexander and the representation of urban complexity: their concepts of ‘pervasive centrality’ and ‘field of centres’ brought into dialogue

This paper draws attention to what we propose as a shared sensibility towards the life of cities in the work of Christopher Alexander and Bill Hillier. Specifically, it reflects on some similarities in their conceptions of urban centrality, while also acknowledging their very different intellectual trajectories. A consideration is how both men grounded their theoretical and analytical insights in their personal experience of cities. Alexander’s emphasis on detailed multimodal observation and awareness as a source of design understanding is writ large throughout his many publications. The same could hardly be said of Hillier who consistently prioritized the configurational modelling of urban form. Yet those familiar with Hillier’s teaching and design practice know how his analytical understanding drew on a deep knowledge of cities worldwide. For Hillier space syntax models were not simply outputs of a computational process but a stage in his ongoing dialogue with real places. Direct points of contact between Alexander and Hillier are few. Hillier’s engagement with Alexander in Space is the Machine (1996) takes issue with the inductive epistemology in Notes on the Synthesis of Form (1964), while Hillier (2009) refers approvingly to Alexander’s critique of the modernist city in ‘A city is not a tree’ (1965). Conversely, in The Nature of Order, Alexander makes brief but positive reference to Hillier and Hanson’s analysis of ‘G’ in The Social Logic of Space (1984). This paper concludes by explaining why the connection of Alexander and Hillier, two of the great urban thinkers of last half-century, is worth developing further

Stability of a bi-layer free film: simultaneous or individual rupture events?

We consider the stability of a long free film of liquid composed of two immiscible layers of differing viscosities, where each layer experiences a van der Waals force between its interfaces. We analyse the different ways the system can exhibit interfacial instability when the liquid layers are sufficiently thin. For an excess of surfactant on one gas–liquid interface the coupling between the layers is relatively weak and the instability manifests as temporally separated rupture events in each layer. Conversely, in the absence of surfactant the coupling between the layers is much stronger and the instability manifests as rupture of both layers simultaneously. These features are consistent with recent experimental observations

Evaluation of older people\u27s knowledge, awareness, motivation and perceptions about falls and falls prevention in residential aged care homes: A tale of two cities

Falls prevention strategies can only be effective in reducing falls amongst older people if they are adopted and enacted in their daily lives. There is limited evidence identifying what older people in residential aged care (RAC) homes understand about falls and falls prevention, or what may limit or enable their adoption of strategies. This study was conducted in two countries and explored older people’s knowledge and awareness of falls and their preferences, opportunities and motivation to undertake falls prevention strategies. A cross-sectional survey was administered to participants (N = 70) aged 65 years and over, living in six RAC homes in Perth, Australia and six RAC homes in Swansea, Wales, United Kingdom. Participants had limited knowledge about intrinsic falls risk factors and strategies to address these and frequently expressed self-blame regarding falling. Almost all (N = 67, 95.7%) participants felt highly motivated to maintain their current functional mobility and independence in everyday tasks. Key preferences for receiving falls prevention messages favoured a positive approach promoting wellness and independence (N = 41, 58.6%) via pictorial posters or brochures (N = 37, 52.9%) and small group discussions preferably with demonstrations (N = 18, 25.7%). Findings from this study may assist organisations and staff to more effectively engage with older people living in RAC about falls prevention and design targeted resources to address the motivations and preferences of this population

Stable isotope signals provide seasonal climatic markers for moss functional groups.

Living moss biomass and archival peat deposits represent key indicators of present and past climatic conditions, but prediction of future climatic impacts requires appropriate marker species to be characterized under a range of contemporary conditions. Stable isotope signals in high latitude moss deposits offer potential climatic proxies. Seasonal changes in δ13C and δ18O of organic material (cellulose) in representative functional groups, and associated photosynthetic activity (as chlorophyll fluorescence) have been compared across East Anglia, UK, as a function of tissue water content. Representative species from contrasting acid bog, heathland, and fen woodland habitats were selected for monthly sampling of recent growth tissues between spring 2017 and autumn 2018, with isotopic signals in purified cellulose compared with tissue water, precipitation, and nearby groundwater signals. Sphagnum and Polytrichum groups, which tend to dominate peat formation, provided contrasting and complementary indicators of seasonal variations in carbon assimilation. Cellulose δ18O signals from Sphagnum spp. demonstrate seasonal variations in source precipitation inputs; carbon isotope signals in Polytrichum spp. indicate evaporative demand and photosynthetic limitation

Interpreting bryophyte stable carbon isotope composition: Plants as temporal and spatial climate recorders

Bryophytes are unable to control tissue water content although physiological adaptations allow growth in a wide range of habitats. Carbon isotope signals in two mosses (Syntrichia ruralis and Chorisodontium aciphyllum) and two liverworts (Conocephalum conicum and Marchantia polymorpha), whether instantaneous (real-time, Δ13C), or organic matter (as δ13COM), provide an assimilation-weighted summary of bryophyte environmental adaptations. In mosses, δ13COM is within the measured range of Δ13C values, which suggests that other proxies, such as compound specific organic signals will be representative of historical photosynthetic and growth conditions. The liverworts were photosynthetically active over a wider range of relative water contents (RWC) than the mosses. There was a consistent 5‰ offset between Δ13C values in C. conicum and M. polymorpha, suggestive of greater diffusion limitation in the latter. Analysis of a C. aciphyllum moss-peat core showed the isotopic composition over the past 200 years reflects recent anthropogenic CO2 emissions. Once corrected for source-CO2 inputs, the seasonally integrated ∆13COM between 1350 and 2000 AD varied by 1.5‰ compared with potential range of the 12‰ measured experimentally, demonstrating the relatively narrow range of conditions under which the majority of net assimilation takes place. Carbon isotope discrimination also varies spatially, with a 4‰ shift in epiphytic bryophyte organic matter found between lowland Amazonia and upper montane tropical cloud forest in the Peruvian Andes; associated with increased diffusion limitation

The algal pyrenoid: key unanswered questions.

The confinement of Rubisco in a chloroplast microcompartment, or pyrenoid, is a distinctive feature of most microalgae, and contributes to perhaps ~30 Pg of carbon fixed each year, yet our understanding of pyrenoid composition, regulation, and function remains fragmentary. Recently, significant progress in understanding the pyrenoid has arisen from studies using mutant lines, mass spectrometric analysis of isolated pyrenoids, and advanced ultrastructural imaging of the microcompartment in the model alga Chlamydomonas. The emergence of molecular details in other lineages provides a comparative framework for this review, and evidence that most pyrenoids function similarly, even in the absence of a common ancestry. The objective of this review is to explore pyrenoid diversity throughout key algal lineages and discuss whether common ultrastructural and cellular features are indicative of common functional processes. By characterizing pyrenoid origins in terms of mechanistic and structural parallels, we hope to provide key unanswered questions which will inform future research directions