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Recently a considerable amount of effort has been put into quantifying how interactions of the carbon and nitrogen cycle affect future terrestrial carbon sinks. Dynamic vegetation models, representing the nitrogen cycle with varying degree of complexity, have shown diverging constraints of nitrogen dynamics on future carbon sequestration. In this study, we use the dynamic vegetation model LPJ-GUESS to evaluate how population dynamics and resource competition between plant functional types, combined with nitrogen dynamics, have influenced the terrestrial carbon storage in the past and to investigate how terrestrial carbon and nitrogen dynamics might change in the future (1850 to 2100; one exemplary "business-as-usual" climate scenario). Single factor model experiments of CO2 fertilisation and climate change show generally similar directions of the responses of C–N interactions, compared to the C-only version of the model, as documented in previous studies. Under a RCP 8.5 scenario, nitrogen limitation suppresses potential CO2 fertilisation, reducing the cumulative net ecosystem carbon uptake between 1850 and 2100 by 61%, and soil warming-induced increase in nitrogen mineralisation reduces terrestrial carbon loss by 31%. When environmental changes are considered conjointly, carbon sequestration is limited by nitrogen dynamics until present. However, during the 21st century nitrogen dynamics induce a net increase in carbon sequestration, resulting in an overall larger carbon uptake of 17% over the full period. This contradicts earlier model results that showed an 8 to 37% decrease in carbon uptake, questioning the often stated assumption that projections of future terrestrial C dynamics from C-only models are too optimistic.
Recently a considerable amount of effort has been put into quantifying how interactions of the carbon and nitrogen cycle affect future terrestrial carbon sinks. Dynamic vegetation models, representing the nitrogen cycle with varying degree of complexity, have shown diverging constraints of nitrogen dynamics on future carbon sequestration. In this study, we use LPJ-GUESS, a dynamic vegetation model employing a detailed individual- and patch-based representation of vegetation dynamics, to evaluate how population dynamics and resource competition between plant functional types, combined with nitrogen dynamics, have influenced the terrestrial carbon storage in the past and to investigate how terrestrial carbon and nitrogen dynamics might change in the future (1850 to 2100; one representative "business-as-usual" climate scenario). Single-factor model experiments of CO2 fertilisation and climate change show generally similar directions of the responses of C–N interactions, compared to the C-only version of the model as documented in previous studies using other global models. Under an RCP 8.5 scenario, nitrogen limitation suppresses potential CO2 fertilisation, reducing the cumulative net ecosystem carbon uptake between 1850 and 2100 by 61%, and soil warming-induced increase in nitrogen mineralisation reduces terrestrial carbon loss by 31%. When environmental changes are considered conjointly, carbon sequestration is limited by nitrogen dynamics up to the present. However, during the 21st century, nitrogen dynamics induce a net increase in carbon sequestration, resulting in an overall larger carbon uptake of 17% over the full period. This contrasts with previous results with other global models that have shown an 8 to 37% decrease in carbon uptake relative to modern baseline conditions. Implications for the plausibility of earlier projections of future terrestrial C dynamics based on C-only models are discussed.
Increased oxidative stress and reduced nitric oxide (NO) bioavailability play a causal role in endothelial cell dysfunction occurring in the vasculature of diabetic patients. In this review, we summarized the molecular mechanisms underpinning diabetic endothelial and vascular dysfunction. In particular, we focused our attention on the complex interplay existing among NO, reactive oxygen species (ROS), and one crucial regulator of intracellular ROS production, p66Shc protein.
Nigeria at 100: What Next?
(2014)
pH and Na+ homeostasis in all cells requires Na+/H+ antiporters. The crystal structure, obtained at pH 4, of NhaA, the main antiporter of Escherichia coli, has provided general insights into an antiporter mechanism and its unique pH regulation. Here, we describe a general method to select various NhaA mutants from a library of randomly mutagenized NhaA. The selected mutants, A167P and F267C are described in detail. Both mutants are expressed in Escherichia coli EP432 cells at 70–95% of the wild type but grow on selective medium only at neutral pH, A167P on Li+ (0.1 M) and F267C on Na+ (0.6 M). Surprising for an electrogenic secondary transporter, and opposed to wild type NhaA, the rates of A167P and F267C are almost indifferent to membrane potential. Detailed kinetic analysis reveals that in both mutants the rate limiting step of the cation exchange cycle is changed from an electrogenic to an electroneutral reaction.
This paper investigates the impact of news media sentiment on financial market returns and volatility in the long-term. We hypothesize that the way the media formulate and present news to the public produces different perceptions and, thus, incurs different investor behavior. To analyze such framing effects we distinguish between optimistic and pessimistic news frames. We construct a monthly media sentiment indicator by taking the ratio of the number of newspaper articles that contain predetermined negative words to the number of newspaper articles that contain predetermined positive words in the headline and/or the lead paragraph. Our results indicate that pessimistic news media sentiment is positively related to global market volatility and negatively related to global market returns 12 to 24 months in advance. We show that our media sentiment indicator reflects very well the financial market crises and pricing bubbles over the past 20 years.
Four new species and one new genus of Cerambycinae are described from French Guiana: Sphagoeme premarginata sp. nov. and Atenizus apicalis sp. nov. (Oemini); Paraniophis signatipes gen. nov., sp. nov., and Niophis brusteli sp. nov. (Ectenessini). Three new country records for French Guiana are provided: Sphagoeme paraensis Martins, 1977, Atenizus simplex Bates, 1884, and Macroeme vittipennis (Melzer, 1934). All taxa are illustrated.
In 2012, two articles were published describing new species of the genus Chelotrupes Jekel, 1866 (Coleoptera: Geotrupidae); the fi rst one included fi ve new species and the second a single species. However, the species described in the second article, Chelotrupes annamariae Byk 2012, is identical to Chelotrupes algarvicus Hillert, Král and Schneider 2012 and should be considered a junior synonym: Chelotrupes algarvicus Hillert, Král and Schneider 2012 = Chelotrupes annamariae Byk 2012, syn. nov.