Forest ecologists have long wondered why forests decline in the absence of catastrophic disturbances. A new study, in part funded by the British Ecological Society, and published in this week’s Science, has shed new light on this problem.
This study investigated natural forested stands across each of six ’chronosequences’ or sequences of soils of different ages since the most recent major disturbance. These sequences were located in a range of climatic zones, including northern Sweden (a series of forested islands near Arjeplog), Alaska, Hawaii, eastern Australia and two locations in southern New Zealand. All sequences consisted of forest stands on soils ranging in age from those formed very recently to those at least several thousand years old; the oldest soils studied were 4.1 million years old in Hawaii.
For all six sequences, forest biomass (mass of trees per unit area) increased initially as soil fertility increased. However, after thousands to tens of thousands of years, forest biomass declined sharply for all sequences, to a level where some sites could no longer support trees. The researchers found that this decline in all cases was due to reduced levels of plant-available phosphorus relative to nitrogen in the soil. As soils age, phosphorus becomes increasingly limiting for trees because it is not biologically renewable in the ecosystem. Conversely, nitrogen is biologically renewable (because atmospheric nitrogen can be converted by soil bacteria into forms of nitrogen that trees can use), so nitrogen limitation does not contribute to forest decline in these systems, contrary to popular views. There was also evidence from this study that phosphorous limitation during stage of forest decline negatively affected soil organisms, and therefore reduced their potential to release nutrients from the soil for maintaining tree growth.
Becky Allen | alfa
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An international research team including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has combined radio telescopes from five continents to prove the existence of a narrow stream of material, a so-called jet, emerging from the only gravitational wave event involving two neutron stars observed so far. With its high sensitivity and excellent performance, the 100-m radio telescope in Effelsberg played an important role in the observations.
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Up to now, OLEDs have been used exclusively as a novel lighting technology for use in luminaires and lamps. However, flexible organic technology can offer much more: as an active lighting surface, it can be combined with a wide variety of materials, not just to modify but to revolutionize the functionality and design of countless existing products. To exemplify this, the Fraunhofer FEP together with the company EMDE development of light GmbH will be presenting hybrid flexible OLEDs integrated into textile designs within the EU-funded project PI-SCALE for the first time at LOPEC (March 19-21, 2019 in Munich, Germany) as examples of some of the many possible applications.
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For the first time, an international team of scientists based in Regensburg, Germany, has recorded the orbitals of single molecules in different charge states in a novel type of microscopy. The research findings are published under the title “Mapping orbital changes upon electron transfer with tunneling microscopy on insulators” in the prestigious journal “Nature”.
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Scientists at the University of Konstanz identify fierce competition between the human immune system and bacterial pathogens
Cell biologists from the University of Konstanz shed light on a recent evolutionary process in the human immune system and publish their findings in the...
Laser physicists have taken snapshots of carbon molecules C₆₀ showing how they transform in intense infrared light
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