Seasonal controls on net branch CO2 assimilation in sub-Arctic Mountain Birch (Betula pubescens ssp. czerepanovii (Orlova) Hamet-Ahti)

Forests at northern high latitudes are experiencing climate-induced changes in growth and productivity, but our knowledge on the underlying mechanisms driving seasonal CO2 fluxes in northern boreal trees comes almost exclusively from ecosystem-level studies on evergreen conifers. In this study, we measured growing season whole-branch CO2 exchange in a deciduous tree species of the tundra-taiga ecotone, Mountain Birch (Betula pubescens ssp. czerepanovii (Orlova) Hamet-Ahti), at two locations in northern Fennoscandia: Abisko (Sweden) and Kevo (Finland). We identified strong seasonal and environmental controls on both photosynthesis and respiration by analysing the parameters of light response curves. Branch-level photosynthetic parameters showed a delayed response to temperature, and, at Kevo, they were well described by sigmoid functions of the state of acclimation (S). Temperature acclimation was slower (time constant, τ = 7 days) for maximum photosynthesis (βbr) than for quantum efficiency (αbr) (τ = 5 days). High temperature-independent values of the respiration parameter (γbr) during leaf and shoot expansion were consistent with associated higher growth respiration rates. The ratio γbr/βbr was positively related to temperature, a result consistent with substrate-induced variations in leaf respiration rates at the branch level. Differences in stand structure and within-site variation in the active period of C uptake determined the spatiotemporal patterns in net assimilation amongst branches. Growing season CO2 uptake of individual branches on a leaf area basis did not show a significant relationship with total incident photosynthetically active radiation, and did not differ across sites, averaging ca. 640 g CO2 m−2

Plant perfomance across latitude: the role of plasticity and local adaltation in aquatic plant

Geographic variation can lead to the evolution of different local varieties within a given species, therefore influencing its distribution and genetic structure. We investigated the contribution of plasticity and local adaptation to the performance of a common aquatic plant (Potamogeton pectinatus) in contrasting climates, using reciprocal transplants at three experimental sites across a latitudinal cline in Europe. Plants from 54 genets, originally collected from 14 populations situated within four climatic regions (sub- arctic, cold temperate, mild temperate, and mediterranean) were grown in three different localities within three of these regions (cold temperate, Nor way; mild temperate, The Netherlands; mediterranean, Spain). Tuber production was highest for the mild-temperate genets, irrespective of locality where the genets were grown. Selection coefficients indicated that populations at the European center of the species distribution perform better than all other populations, at all sites. However, marginal populations showed changes in life-histor y traits, such as compressed life cycles in the north and true perenniality in the south, that may allow them to perform better locally, at the limits of their distribution range. Our results thus suggest that local adaptation may overlap spatially with center–peripher y gra- dients in performance caused by genetic factors (such as genetic drift and inbreeding in range-marginal populations).Peer reviewe

Studies towards the exploitation of sonochemically formed microelectrode arrays for the development of electrochemical sensors

Microelectrodes offer a number of advantages for exploitation as electrochemical sensors such as imparting stir-independence to sensor responses and allowing lower limits of detection to be minimised. Microelectrode arrays offer an attractive route for increasing the current responses of microelectrodes, whilst still retaining their advantageous properties. Despite this, no commercial sensors, to date, have successfully employed microelectrode arrays, largely due to conventional fabrication routes proving too costly to be economically viable for the production of disposable sensing devices. Previous work carried out by this research group has described a novel and patented procedure for the fabrication of microelectrode arrays via the sonochemical ablation of insulating polymer films electrochemically deposited upon conductive surfaces. This format lends itself to mass fabrication due to the simplicity and inexpensiveness of the approach. This thesis describes work focussed towards the optimisation of each of the individual components involved in the formation of sonochemically fabricated microelectrode arrays. In particular, factors and techniques that may facilitate the commercial exploitation and mass fabrication of such arrays as generic sensing templates are described. Screen printed carbon has been investigated for its suitability as a host electrode. The comparative use of a number of possible activation methods to increase amperometric current responses at such electrodes is also described. Homogeneous poly(o-phenylenediamine) films of -40 nm thickness formed at the surfaces of screen printed carbon electrodes via the anodic electropolymerisation of o-phenylenediamine are shown to serve as effective diffusional barriers, thus insulating the underlying carbon electrodes. Microelectrode arrays formed by the sonochemical ablation of such films to expose microscopic areas of the underlying conductive substrates are seen to possess electrode element populations of -7.3 x 104 cm 2. Over 400 such sensors are shown to be able to be fabricated simultaneously with reproducibility of responses <4% relative standard deviation. Amperometric and cyclic voltammetric characterisations of the thus produced microelectrode arrays performed in model redox systems are shown to agree with accepted theoretical microelectrode behaviour, demonstrating sigmoidal shaped voltammograms, fluctuations in steady-state current responses of <10% with convection, scan rate independence and fast attainment (<20 seconds) of steady-state responses. Arrays of this type are also demonstrated to be suitable for exploitation within aqueous chlorine sensing devices, offering detection limits of <0.005 mg/l free chlorine, representing an order of magnitude lower than those obtainable via contemporary optical wet chemistry based approaches. In order to demonstrate further the applicability of this approach to the mass fabrication of disposable devices, methods for the deposition of a chemical modifying layer are also investigated, to avoid the need for additional reagents.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Slow recovery of High Arctic heath communities from nitrogen enrichment

Acknowledgements We are indebted to Ian Alexander who initiated the fertilisation experiment with SJW; to successive researchers involved in the experiment, John Baddeley, Nanette Madan, Lars Hogbom, Bernard Moyersen, Carmen Gordon; and to field assistants, Alison Horsburgh, Andrew Coughlan, Jo Wynn, Lora Crabtree. We thank Hans Kruijer and Michael Stech for assistance with bryophyte species identification in 2011. Funding for the initial experiment was provided by the NERC Arctic Terrestrial Ecology Special Topic Programme (GR3/9424, GR9/3433) with additional support from the CEC TMR Programme, Ny-Ålesund LSF and the British Ecological Society. This recovery study was funded by NERC (NE/I016899/1). The research was made possible by use of NERC facilities at Harland Huset; special thanks to Nick Cox and colleagues for their unfailing hospitality and support.Peer reviewedPostprintPostprin

Night optimised care technology for users needing assisted lifestyles

There is growing interest in the development of ambient assisted living services to increase the quality of life of the increasing proportion of the older population. We report on the Night Optimised Care Technology for UseRs Needing Assisted Lifestyles project, which provides specialised night time support to people at early stages of dementia. This article explains the technical infrastructure, the intelligent software behind the decision-making driving the system, the software development process followed, the interfaces used to interact with the user, and the findings and lessons of our user-centred approach

Calibrating soybean parameters in JULES 5.0 from the US-Ne2/3 FLUXNET sites and the SoyFACE-O3 experiment

This is the final version. Available on open access from the European Geosciences Union via the DOI in this record.Code availability. This study uses JULES version 5.0 releases. The code and configuration for the SoyFACE runs can be downloaded via the Met Office Science Repository Service (MOSRS) at https://code.metoffice.gov.uk/trac/roses-u/browser/a/r/8/6/6/trunk (JULES Collaboration, 2018) (registration required) and are freely available subject to accepting the terms of the software licence. The Leaf Simulator can be downloaded from https://code.metoffice.gov.uk/trac/utils (Williams et al., 2018) (login required).Data availability. Unless otherwise noted, all site observations discussed in this paper were obtained from the site information pages of the AmeriFlux website hosted by the Oak Ridge National Laboratory (http://fluxnet.fluxdata.org/, AmeriFlux collaboration, 2018) or by personal communication with the Mead site research technologist. The longwave radiation, diffuse radiation, and air pressure from Bondville, Illinois, site can be obtained by the SURFRAD (surface radiation) network from ftp://aftp.cmdl.noaa.gov/data/radiation/surfrad/Bondville_IL/ (NOAA, 2018). The SoyFACE data used for the run are available on MOSRS at https://code.metoffice.gov.uk/trac/roses-u/browser/a/r/8/6/6/trunk/driving_data (Ainsoworth, 2017a), https://code.metoffice.gov.uk/trac/roses-u/browser/a/r/8/6/6/trunk/bin/SoyFACE_gas_exchange_data_2009.csv (Ainsoworth, 2017b), and https://code.metoffice.gov.uk/trac/roses-u/browser/a/r/8/6/6/trunk/ancil_data (Ainsoworth, 2017c).Tropospheric ozone (O3) is the third most important anthropogenic greenhouse gas. O3 is detrimental to plant productivity, and it has a significant impact on crop yield. Currently, the Joint UK Land Environment Simulator (JULES) land surface model includes a representation of global crops (JULES-crop) but does not have crop-specific O3 damage parameters and applies default C3 grass O3 parameters for soybean that underestimate O3 damage. Physiological parameters for O3 damage in soybean in JULES-crop were calibrated against leaf gas-exchange measurements from the Soybean Free Air Concentration Enrichment (SoyFACE) with O3 experiment in Illinois, USA. Other plant parameters were calibrated using an extensive array of soybean observations such as crop height and leaf carbon and meteorological data from FLUXNET sites near Mead, Nebraska, USA. The yield, aboveground carbon, and leaf area index (LAI) of soybean from the SoyFACE experiment were used to evaluate the newly calibrated parameters. The result shows good performance for yield, with the modelled yield being within the spread of the SoyFACE observations. Although JULES-crop is able to reproduce observed LAI seasonality, its magnitude is underestimated. The newly calibrated version of JULES will be applied regionally and globally in future JULES simulations. This study helps to build a state-of-the-art impact assessment model and contribute to a more complete understanding of the impacts of climate change on food production.Natural Environment Research Council (NERC)European Commissio

Implications of climate change for agricultural productivity in the early twenty-first century

This paper reviews recent literature concerning a wide range of processes through which climate change could potentially impact global-scale agricultural productivity, and presents projections of changes in relevant meteorological, hydrological and plant physiological quantities from a climate model ensemble to illustrate key areas of uncertainty. Few global-scale assessments have been carried out, and these are limited in their ability to capture the uncertainty in climate projections, and omit potentially important aspects such as extreme events and changes in pests and diseases. There is a lack of clarity on how climate change impacts on drought are best quantified from an agricultural perspective, with different metrics giving very different impressions of future risk. The dependence of some regional agriculture on remote rainfall, snowmelt and glaciers adds to the complexity. Indirect impacts via sea-level rise, storms and diseases have not been quantified. Perhaps most seriously, there is high uncertainty in the extent to which the direct effects of CO2 rise on plant physiology will interact with climate change in affecting productivity. At present, the aggregate impacts of climate change on global-scale agricultural productivity cannot be reliably quantified

Secure referee selection for fair and responsive peer-to-peer gaming

Peer-to-Peer (P2P) architectures for Massively Multiplayer Online Games (MMOG) provide better scalability than Client/Server (C/S); however, they increase the possibility of cheating. Recently proposed P2P protocols use trusted referees that simulate/validate the game to provide security equivalent to C/S. When selecting referees from untrusted peers, selecting non-colluding referees becomes critical. Further, referees should be selected such that the range and length of delays to players is minimised (maximising game fairness and responsiveness). In this paper we formally define the referee selection problem and propose two secure referee selection algorithms, SRS-1 and SRS-2, to solve it. Both algorithms ensure the probability of corrupt referees controlling a zone/region is below a predefined limit, while attempting to maximise responsiveness and fairness. The trade-off between responsiveness and fairness is adjustable for both algorithms. Simulations of three different scenarios show the effectiveness of our algorithms