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
Sinking groundwater levels threaten the vitality of riverine ecosystems
04.10.2019 | Albert-Ludwigs-Universität Freiburg im Breisgau
A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.
The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...
Superconductivity has fascinated scientists for many years since it offers the potential to revolutionize current technologies. Materials only become superconductors - meaning that electrons can travel in them with no resistance - at very low temperatures. These days, this unique zero resistance superconductivity is commonly found in a number of technologies, such as magnetic resonance imaging (MRI).
Future technologies, however, will harness the total synchrony of electronic behavior in superconductors - a property called the phase. There is currently a...
How do some neutron stars become the strongest magnets in the Universe? A German-British team of astrophysicists has found a possible answer to the question of how these so-called magnetars form. Researchers from Heidelberg, Garching, and Oxford used large computer simulations to demonstrate how the merger of two stars creates strong magnetic fields. If such stars explode in supernovae, magnetars could result.
How Do the Strongest Magnets in the Universe Form?
A hot, molten Earth would be around 5% larger than its solid counterpart. This is the result of a study led by researchers at the University of Bern. The difference between molten and solid rocky planets is important for the search of Earth-like worlds beyond our Solar System and the understanding of Earth itself.
Rocky exoplanets that are around Earth-size are comparatively small, which makes them incredibly difficult to detect and characterise using telescopes. What...
Scientists at the Max Planck Institute for Chemical Physics of Solids in Dresden, Princeton University, the University of Illinois at Urbana-Champaign, and the University of the Chinese Academy of Sciences have spotted a famously elusive particle: The axion – first predicted 42 years ago as an elementary particle in extensions of the standard model of particle physics.
The team found signatures of axion particles composed of Weyl-type electrons (Weyl fermions) in the correlated Weyl semimetal (TaSe₄)₂I. At room temperature,...
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