Surplus Carbon Drives Allocation and Plant-Soil Interactions

Plant growth is usually constrained by the availability of nutrients, water, or temperature, rather than photosynthetic carbon (C) fixation. Under these conditions leaf growth is curtailed more than C fixation, and the surplus photosynthates are exported from the leaf. In plants limited by nitrogen (N) or phosphorus (P), photosynthates are converted into sugars and secondary metabolites. Some surplus C is translocated to roots and released as root exudates or transferred to root-associated microorganisms. Surplus C is also produced under low moisture availability, low temperature, and high atmospheric CO2 concentrations, with similar below-ground effects. Many interactions among above- and below-ground ecosystem components can be parsimoniously explained by the production, distribution, and release of surplus C under conditions that limit plant growth.Non peer reviewe

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

Influence of moisture, nutrients, and distance from stream on early-stage mass loss of western red cedar leaf litter in headwater riparian forests

Western red cedar (Thuja plicata Donn ex D.Don) is a dominant species in forests of the Pacific Northwest in North America, but little is known about its decomposition in riparian habitat. We experimentally tested how early-stage mass loss of cedar leaf litter varied with distance from the stream (five distances from 1 to 40 m away) and responded to nutrient and water additions near four headwater streams in southwestern British Columbia. We ran three coarse-mesh litterbag trials in durations between five months to one year from January 2013 and January 2014. Litterbags were either untreated or given the following treatments: water additions during dry summer months, nitrogen and phosphorus additions, or additions of both. Control litterbags lost 21% initial mass over 12 months (January 2013 – January 2014), 20% over five months (January 2013 – June 2013), and 15% over eight months (June 2013 – January 2014). Rates of mass loss did not increase with water in any trial but did increase with nutrients in the 12-month trial. Litter located 40 m from the stream lost 7% more mass than that located 1 m away in this same trial. Our study indicates that cedar leaf litter mass loss responded primarily to nutrient additions.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author