A new addition to the terrestrial nitrogen cycle

This post contributed by Lindsay Deel, a Ph.D. student in geography at West Virginia University and Intern with ESA’s journal Frontiers in Ecology and the Environment Memorizing diagrams of the nitrogen cycle – complete with all the little arrows flowing between atmospheric sources to uptake by vegetation – is a rite of passage for most undergraduate ecology students.  Now, following a new study published in the journal Nature, the diagrams will need to include a new little arrow flowing from bedrock sources to vegetation.  This could have dramatic implications for understanding the growth potential – and therefore, the carbon sequestration potential – of forested ecosystems. Nitrogen is often cited as the most limiting nutrient for the growth of trees, so if forests can access more nitrogen, there is greater growth potential – and more growth means more carbon storage. “We were really shocked; everything we’ve ever thought about the nitrogen cycle and all of the textbook theories have been turned on their heads by these data,” said Benjamin Houlton, Assistant Professor of Terrestrial Biogeochemistry, in a UC Davis press release about the study.  “Findings from this study suggest that our climate-change models should not only consider the importance of nitrogen from the atmosphere, but now we also have to start thinking about how rocks may affect climate change.” Scientists have long thought that nitrogen could only enter forest ecosystems through the atmosphere – by deposition or biological fixation.  Based on this assumption, the UC Davis scientists expected to find, at most, the same nitrogen contribution from rocks. “To put it in perspective, there is enough nitrogen contained in one inch of the rocks at our study site to completely support the growth of a typical coniferous forest for about 25 years,” explained Randy Dahlgren, a biogeochemist and study co-author, in the UC Davis press release.  “This nitrogen is released slowly over time and helps to maintain the long-term fertility of many California forests. It is also interesting to consider that the nitrogen in the rocks from our study site originates from the time of the dinosaurs, when plant and animal remains were incorporated into the sediments that eventually formed the rocks.” The discovery of such a substantial pool of stored nitrogen that is directly accessible to plants also sheds new light on the infamous “missing carbon sink,” which is assumed to be terrestrial.  Indeed, research related to nitrogen cycling will change because of this finding – as will the diagrams of nitrogen cycling in undergraduate ecology textbooks.   Photo: Mountain deep forest by Paolo...

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An ant’s eye view of sand

To an ant, a piece of garnet or a shark’s tooth is merely another boulder to excavate for the expansion of the nest. And for humans, these bits of treasure would largely go unnoticed as just another grain in an anthill. But, as the blog Neatorama pointed out this week, every inch of sand is a world of discovery to photographers and sand collectors. Specifically, Flickr user Mouser Williams captures the history and biological connections of each location through his macro lens. For example, the pointy star sand from beaches in southern Japan—such as on Iriomote Island in Okinawa—was formed from the death of Foraminifera. In this case, these organisms are marine protists with calcium-based skeletons that wash ashore to create the “sand.” Williams also described how the hard work of ants creates unique sand compositions: “…Ant sand from a site near Taos, New Mexico…has a remarkably high concentration of garnets. The reddish faceted spheres are garnets hauled up to the surface by the ants. Because they are roughly spherical, they tend to roll down the slopes of the ant hills and collect in an annulus around the base of the ant hill.” Using a magnet, Williams extracted some of the garnets and photographed them separately. “These garnets range in size from 1mm to 5mm in diameter,” he explained. “There are presumably larger garnets in the soil in this area, but with ant sand you are limited to things ants can lift and carry.” In another photo, ants excavated fossil bits from their nest in the Morrison Formation of New Mexico, a location that at one point supported dinosaurs, reptiles, termites, conifers, ginkgos, tree ferns and more along the area’s rivers. The site also had a diverse group of sauropod species at one time. Photo Credit for Star Sand Naked Eye (sand on a finger): Geomr Photo Credit for all other sand photos: Mouser...

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When habitat destruction is extremely subtle

When it comes to habitat destruction, startling events like oil spills and deforestation are certain to grab the headlines. Yet as a new study in the journal Animal Conservation shows, sometimes habitat destruction can be so subtle that it passes under the eyes of all but the most astute scientists. David Pike and fellow researchers from the University of Sydney look at the case of reptiles in outcrops and find that people moving rocks less than 30 centimeters out of place can ruin the habitat for species like the endangered broad-headed snake that shelter in narrow crevices.

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