Nitrogen forms affect root structure and water uptake in the hybrid poplar

The study analyses the effects of two different forms of nitrogen fertilisation (nitrate and ammonium) on root structure and water uptake of two hybrid poplar (Populus maximowiczii x P. balsamifera) clones in a field experiment. Water uptake was studied using sap flow gauges on individual proximal roots and coarse root structure was examined by excavating 18 whole-root systems. Finer roots were scanned and analyzed for architecture. Nitrogen forms did not affect coarse-root system development, but had a significant effect on fine-root development. Nitrate-treated trees presented higher fine:coarse root ratios and higher specific root lengths than control or ammonium treated trees. These allocation differences affected the water uptake capacity of the plants as reflected by the higher sapflow rate in the nitrate treatment. The diameter of proximal roots at the tree base predicted well the total root biomass and length. The diameter of smaller lateral roots also predicted the lateral root mass, length, surface area and the number of tips. The effect of nitrogen fertilisation on the fine root structure translated into an effect on the functioning of the fine roots forming a link between form (architecture) and function (water uptake)

Spatio‐temporal patterns of tree growth as related to carbon isotope fractionation in European forests under changing climate

Aim To decipher Europe-wide spatiotemporal patterns of forest growth dynamics and their associations with carbon isotope fractionation processes inferred from tree rings as modulated by climate warming. Location Europe and North Africa (30‒70°N, 10°W‒35°E). Time period 1901‒2003. Major taxa studied Temperate and Euro-Siberian trees. Methods We characterize changes in the relationship between tree growth and carbon isotope fractionation over the 20th century using a European network consisting of 20 site chronologies. Using indexed tree-ring widths (TRWi), we assess shifts in the temporal coherence of radial growth across sites (synchrony) for five forest ecosystems (Atlantic, Boreal, cold continental, Mediterranean and temperate). We also examine whether TRWi shows variable coupling with leaf-level gas exchange, inferred from indexed carbon isotope discrimination of tree-ring cellulose (Δ13Ci). Results We find spatial autocorrelation for TRWi and Δ13Ci extending over up to 1,000 km among forest stands. However, growth synchrony is not uniform across Europe, but increases along a latitudinal gradient concurrent with decreasing temperature and evapotranspiration. Latitudinal relationships between TRWi and Δ13Ci (changing from negative to positive southwards) point to drought impairing carbon uptake via stomatal regulation for water saving occurring at forests below 60°N in continental Europe. A rise in forest growth synchrony over the 20th century together with increasingly positive relationships between TRWi and Δ13Ci indicate intensifying drought impacts on tree performance. These effects are noticeable in drought-prone biomes (Mediterranean, temperate and cold continental). Main conclusions At the turn of this century, convergence in growth synchrony across European forest ecosystems is coupled with coordinated warming-induced drought effects on leaf physiology and tree growth spreading northwards. Such a tendency towards exacerbated moisture-sensitive growth and physiology could override positive effects of enhanced leaf intercellular CO2 concentrations, possibly resulting in Europe-wide declines of forest carbon gain in the coming decades

Pharmaceuticals and personal care products in the environment: What are the big questions?

Background: Over the past 10-15 years, a substantial amount of work has been done by the scientific, regulatory, and business communities to elucidate the effects and risks of pharmaceuticals and personal care products (PPCPs) in the environment. Objective: This review was undertaken to identify key outstanding issues regarding the effects of PPCPs on human and ecological health in order to ensure that future resources will be focused on the most important areas. Data sources: To better understand and manage the risks of PPCPs in the environment, we used the "key question" approach to identify the principle issues that need to be addressed. Initially, questions were solicited from academic, government, and business communities around the world. A list of 101 questions was then discussed at an international expert workshop, and a top-20 list was developed. Following the workshop, workshop attendees ranked the 20 questions by importance. Data synthesis: The top 20 priority questions fell into seven categories: a) prioritization of substances for assessment, b) pathways of exposure, c) bioavailability and uptake, d) effects characterization, e) risk and relative risk, f) antibiotic resistance, and g) risk management. Conclusions: A large body of information is now available on PPCPs in the environment. This exercise prioritized the most critical questions to aid in development of future research programs on the topic.Centro de Investigaciones del Medioambient

Roles of glial cells in synapse development

Brain function relies on communication among neurons via highly specialized contacts, the synapses, and synaptic dysfunction lies at the heart of age-, disease-, and injury-induced defects of the nervous system. For these reasons, the formation—and repair—of synaptic connections is a major focus of neuroscience research. In this review, I summarize recent evidence that synapse development is not a cell-autonomous process and that its distinct phases depend on assistance from the so-called glial cells. The results supporting this view concern synapses in the central nervous system as well as neuromuscular junctions and originate from experimental models ranging from cell cultures to living flies, worms, and mice. Peeking at the future, I will highlight recent technical advances that are likely to revolutionize our views on synapse–glia interactions in the developing, adult and diseased brain

Ecologically implausible carbon response? Reply

International audienc

Europos izotopų tinklas ISONET: pirmieji rezultatai

Within the EU-Project ISONET (co-ordinator: G. Schleser, http//www.isonet-online.de), 13 partner institutions collaborate to develop the first large-scale network of stable isotopes (C, O and H), integrating 25 European tree sites reaching from the Iberian Peninsula to Fennoscandia. Key species are oak and pine. The sampling design considers not only ecologically “extreme” sites, with mostly a single climate factor dominating tree growth, as supportive for ring width and wood density analyses (Bräuning & Mantwill 2005; Briffa et al. 2001, 2002; Frank & Esper 2005a, b), but also temperate regions with diffuse climate signals recorded in the ‘traditional’ tree ring parameters. Within the project we aim to estimate temperature, humidity and precipitation variations with annual resolution, to reconstruct local to European scale climate variability over the last 400 years. Climate variability is addressed on three timescales, namely decade-century, interannual and intra-annual. This strategy allows understanding of both, high frequency (high resolution exploration of seasonality signals, and extreme events) and longer-term trends (source water/air mass dominance, baseline variability) in site specific and synoptic climate across Europe. Here we present results from initial network analyses considering first data of carbon (δ13C) and oxygen (δ18O) isotopes, to evaluate (a) common patterns in these networks and (b) their potential for detailed climate reconstruction beyond the information commonly achieved from ring width and density analysesVytauto Didžiojo universiteta

Signal strength and climate calibration of a European tree-ring isotope network

We present the first European network of tree ring δ 13C and δ 18O, containing 23 sites from Finland to Morocco. Common climate signals are found over broad climatic-ecological ranges. In temperate regions we find positive correlations with summer maximum temperatures and negative correlations with summer precipitation and Palmer Drought Severity Indices (PDSI) with no obvious species-specific differences. Regional δ 13C and δ 18O chronologies share high common variance in year-to-year variations. Long-term variations, however, exhibit differences that may reflect spatial variability in environmental forcings, age trends and/or plant physiological responses to increasing atmospheric CO2 concentration. Rotated principal component analysis (RPCA) and climate field correlations enable the identification of four sub-regions in the δ 18O network - northern and eastern Central Europe, Scandinavia and the western Mediterranean. Regional patterns in the δ 13C network are less clear and are timescale dependent. Our results indicate that future reconstruction efforts should concentrate on δ 18O data in the identified European regions

Klimato signalai Europos izotopų tnkle ISONET

Over the last three years, 16 European isotope labs collaborated in the EU project ISONET (co-ordinator: G. Schleser, http//www.isonet-online.de) on developing the first large-scale network of 13C, 18O and 2H in from oak, pine and cedar tree-rings, covering sites from Fennoscandia to the Mediterranean region. The sampling design considered not only ecologically “extreme” sites, with a single climate factor predominantly determining tree growth, as required for ring width and wood density analyses (Bräuning & Mantwill 2005, Briffa et al. 2001, 2002, Frank & Esper 2005a, b), but also temperate regions with diffuse climate signals recorded in the ‘traditional’ tree ring parameters. This strategy, however, may enable expanding climatic reconstructions into regions not yet well covered. As reported earlier (Treydte et al. 2005), the aim is to estimate temperature, humidity and precipitation variations with annual resolution, to reconstruct local to European scale climate variability over the last 400 years. Climate variability is addressed on intra-annual to century timescales. This strategy should allow understanding both, high frequency variations including the exploration of seasonality signals and extreme events, and longer-term trends including source water/air mass changes and baseline variability across Europe. Here we present first climate calibration results for the 20th century, using 13C and 18O data from up to 25 sites currently available in the networkVytauto Didžiojo universiteta

Pharmaceuticals and personal care products in the environment: What are the big questions?

Background: Over the past 10-15 years, a substantial amount of work has been done by the scientific, regulatory, and business communities to elucidate the effects and risks of pharmaceuticals and personal care products (PPCPs) in the environment. Objective: This review was undertaken to identify key outstanding issues regarding the effects of PPCPs on human and ecological health in order to ensure that future resources will be focused on the most important areas. Data sources: To better understand and manage the risks of PPCPs in the environment, we used the "key question" approach to identify the principle issues that need to be addressed. Initially, questions were solicited from academic, government, and business communities around the world. A list of 101 questions was then discussed at an international expert workshop, and a top-20 list was developed. Following the workshop, workshop attendees ranked the 20 questions by importance. Data synthesis: The top 20 priority questions fell into seven categories: a) prioritization of substances for assessment, b) pathways of exposure, c) bioavailability and uptake, d) effects characterization, e) risk and relative risk, f) antibiotic resistance, and g) risk management. Conclusions: A large body of information is now available on PPCPs in the environment. This exercise prioritized the most critical questions to aid in development of future research programs on the topic.Fil: Boxall, Alistair B. A.. University of York; Reino UnidoFil: Rudd, Murray A.. University of York; Reino UnidoFil: Brooks, Bryan W.. Baylor University; Estados UnidosFil: Caldwell, Daniel J.. Johnson & Johnson; Estados UnidosFil: Choi, Kyungho. Seoul National University; Corea del SurFil: Hickmann, Silke. Umweltbundesamt; AlemaniaFil: Innes, Elizabeth. Health Canada; CanadáFil: Ostapyk, Kim. Health Canada; CanadáFil: Staveley, Jane P.. Exponent; Estados UnidosFil: Verslycke, Tim. Gradient; Estados UnidosFil: Ankley, Gerald T.. United States Environmental Protection Agency; Estados UnidosFil: Beazley, Karen F.. Dalhousie University Halifax; CanadáFil: Belanger, Scott E.. Procter And Gamble; Estados UnidosFil: Berninger, Jason P.. Baylor University; Estados UnidosFil: Carriquiriborde, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Química. Centro de Investigaciones del Medio Ambiente; ArgentinaFil: Coors, Anja. Ect Oekotoxikologie Gmbh; AlemaniaFil: DeLeo, Paul C.. American Cleaning Institute; Estados UnidosFil: Dyer, Scott D.. Procter And Gamble; Estados UnidosFil: Ericson, Jon F.. Pfizer Inc.; Estados UnidosFil: Gagné, François. Environment Canada; CanadáFil: Giesy, John P.. University of Saskatchewan; CanadáFil: Gouin, Todd. Unilever; Reino UnidoFil: Hallstrom, Lars. University of Alberta; CanadáFil: Karlsson, Maja V.. University of York; Reino UnidoFil: Joakim Larsson, D.G.. University of Göteborg; AlemaniaFil: Lazorchak, James M.. United States Environmental Protection Agency; Estados UnidosFil: Mastrocco, Frank. Pfizer Inc.; Estados UnidosFil: McLaughlin, Alison. Health Canada; CanadáFil: McMaster, Mark E.. Environment Canada; CanadáFil: Meyerhoff, Roger D.. Eli Lilly And Company; Estados UnidosFil: Moore, Roberta. Health Canada; CanadáFil: Parrott, Joanne L.. Environment Canada; CanadáFil: Snape, Jason R.. AstraZeneca UK Ltd.; Reino UnidoFil: Murray-Smith, Richard. AstraZeneca UK Ltd.; Reino UnidoFil: Servos, Mark R.. University of Waterloo; CanadáFil: Sibley, Paul K.. University of Guelph; CanadáFil: Straub, Jürg Oliver. F. Hoffmann-La Roche Ltd.; SuizaFil: Szabo, Nora D.. University of Ottawa; CanadáFil: Topp, Edward. Agriculture Et Agroalimentaire Canada; CanadáFil: Tetreault, Gerald R.. University of Waterloo; CanadáFil: Trudeau, Vance L.. University of Ottawa; CanadáFil: Van Der Kraak, Glen. University of Guelph; Canad