Global Patterns and Controls of Nutrient Immobilization On Decomposing Cellulose In Riverine Ecosystems

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

BENTHIC COMMUNITY STRUCTURE IN TWO ADJACENT STREAMS IN YELLOWSTONE NATIONAL PARK FIVE YEARS AFTER THE 1988 WILDFIRES

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Mean denitrification rate by treatment over time.

<p>No significant differences were detected. Error bars indicate +1 SE.</p

Statistical analysis of bacterial community structure in study streams.

<p>(A)Redundancy analysis of LWD 16S rRNA T-RFLP profiles by hydrologic conditions. Stream hydrologic condition explained 40.21% of community variation. (B) Redundancy analysis of LWD <i>nosZ</i> T-RFLP profiles by hydrologic conditions. Stream hydrologic condition explained 45.30% of denitrifier community variation.</p

Mean (±1 SE) percent benthic organic matter (% OM); other variables are from water samples: temperature (temp), pH, turbidity, dissolved oxygen (DO), specific conductivity, discharge, and soluble reactive phosphorus (SRP) by stream for each date.

<p>There was no standing water at the LWD site in Sept.</p><p>Mean (±1 SE) percent benthic organic matter (% OM); other variables are from water samples: temperature (temp), pH, turbidity, dissolved oxygen (DO), specific conductivity, discharge, and soluble reactive phosphorus (SRP) by stream for each date.</p