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Variation in the stable carbon and oxygen isotope composition (δ13C, Δ18O) of co-occurring plant species may reflect the functional diversity of water use strategies present in natural plant communities., We investigated the patterns of water use among 10 coexisting plant species representing diverse taxonomic groups and life forms in semiarid southeast Spain by measuring their leaf δ13C and Δ18O, the oxygen isotope ratio of stem water and leaf gas exchange rates., Across species, Δ18O was tightly negatively correlated with stomatal conductance ( gs), whereas δ13C was positively correlated with intrinsic water use efficiency ( WUEi). Broad interspecific variation in Δ18O, δ13C and WUEi was largely determined by differences in gs, as indicated by a strong positive correlation between leaf δ13C and Δ18O across species, The 10 co-occurring species segregated along a continuous ecophysiological gradient defined by their leaf δ13C and Δ18O, thus revealing a wide spectrum of stomatal regulation intensity and contrasting water use strategies ranging from 'profligate/opportunistic' (high gs, low WUEi) to 'conservative' (low gs, high WUEi). Coexisting species maintained their relative isotopic rankings in 2 yr with contrasting rainfall, suggesting the existence of species-specific 'isotopic niches' that reflect ecophysiological niche segregation in dryland plant communities. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigated whether stand structure modulates the long-term physiological performance and growth of Pinus halepensis Mill. in a semiarid Mediterranean ecosystem. Tree radial growth and carbon and oxygen stable isotope composition of latewood ( δ13CLW and δ18OLW, respectively) from 1967 to 2007 were measured in P. halepensis trees from two sharply contrasting stand types: open woodlands with widely scattered trees versus dense afforested stands. In both stand types, tree radial growth, δ13CLW and δ18OLW were strongly correlated with annual rainfall, thus indicating that tree performance in this semiarid environment is largely determined by inter-annual changes in water availability. However, trees in dense afforested stands showed consistently higher δ18OLW and similar δ13CLW values compared with those in neighbouring open woodlands, indicating lower stomatal conductance and photosynthesis rates in the former, but little difference in water use efficiency between stand types. Trees in dense afforested stands were more water stressed and showed lower radial growth, overall suggesting greater vulnerability to drought and climate aridification compared with trees in open woodlands. In this semiarid ecosystem, the negative impacts of intense inter-tree competition for water on P. halepensis performance clearly outweigh potential benefits derived from enhanced infiltration and reduced run-off losses in dense afforested stands. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To assess the role of iron overload in type 2 diabetic men with hyperferritinemia. Methods: 150 men were recruited from a genetic screening programme for hereditary hemocromatosis (HH) and were tested for type 2 diabetes, other components of the metabolic syndrome, beta cell function (BCF), insulin sensitivity, high-sensitivity C-reactive protein and iron overload. Results: Fifty-one men had type 2 diabetes. They were older (p =0.017) and 99 had lower BCF (p <0.001) than non-diabetic men. None of the iron overload indexes was associated with diabetes. Conclusions: Our findings dispute a role of iron overload in the pathogenesis of type 2 diabetes. [Copyright &y& Elsevier]