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Terrestrial gross primary production (GPP) is the largest global C[O.sub.2] flux driving several ecosystem functions. We provide an observation-based estimate of this flux at 123 [+ or -] 8 petagrams of carbon per year (Pg C [year.sup.-1]) using eddy covariance flux data and various diagnostic models. Tropical forests and savannahs account for 60%. GPP over 40% of the vegetated Land is associated with precipitation. State-of-the-art process-oriented biosphere models used for climate predictions exhibit a large between-model variation of GPP's latitudinal patterns and show higher spatial correlations between GPP and precipitation, suggesting the existence of missing processes or feedback mechanisms which attenuate the vegetation response to climate. Our estimates of spatially distributed GPP and its covariation with climate can help improve coupled climate-carbon cycle process models. 10.1126/science.1184984

GROWING HUMAN PRESSURE ON EARTH'S biodiversity demands rapid development of a sound scientific and economic foundation for conservation. Andrew Balmford and co-authors, in their report 'Conservation conflicts across Africa' (30 [...]

The increasing concentration of carbon dioxide ([CO.sub.2]) in the atmosphere (1) is the surest evidence that humans are changing the global environment. Atmospheric [CO.sub.2] would accumulate even faster if the [...]

Models describing the evolution of the partial pressure of atmospheric oxygen over Phanerozoic time are constrained by the mass balances required between the inputs and outputs of carbon and sulfur to the oceans. This constraint has limited the applicability of proposed negative feedback mechanisms for maintaining levels of atmospheric [O.sub.2] at biologically permissable levels. Here we describe a modeling approach that incorporates [O.sub.2]-dependent carbon and sulfur isotope fractionation using data obtained from laboratory experiments on carbon-13 discrimination by vascular land plants and marine plankton. The model allows us to calculate a Phanerozoic [O.sub.2] history that agrees with independent models and with biological and physical constraints and supports the hypothesis of a high atmospheric [O.sub.2] content during the Carboniferous (300 million years ago), a time when insect gigantism was widespread., A dominant feature of Earth's atmosphere is the presence of abundant flee oxygen ([O.sub.2]), which signifies an active aerobic biosphere. Much attention has been directed toward understanding the rise of [...]

At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool., Because species differ in their ecological attributes, the loss of biodiversity from local communities may be detrimental to the ecosystem goods and services on which humans ultimately depend (1). This [...]

The Triassic-Jurassic boundary marks a major faunal mass extinction, but records of accompanying environmental changes are limited. Paleobotanical evidence indicates a fourfold increase in atmospheric carbon dioxide concentration and suggests an associated 3 ° to 4 ° C 'greenhouse' warming across the boundary. These environmental conditions are calculated to have raised leaf temperatures above a highly conserved lethal limit, perhaps contributing to the [is greater than] 95 percent species-level turnover of Triassic-Jurassic megaflora., The end-Triassic mass extinction event [205.7 ± 4 million years ago (Ma)] was the third largest in the Phanerozoic, resulting in the loss of over 30% of marine genera (1) [...]

Discusses a research on a modeling approach that incorporates oxygen-dependent carbon and sulfur isotope fractionation using data obtained from experiments on carbon-13 discrimination by vascular land plants and marine plankton. How calculation of changes in power of oxygen be achieved; Methodology used in the research; Findings of the research.