Their findings, to be published next week (27 November – 1 December) in the journal Proceedings of the National Academy of Sciences USA, summarizes key findings from the world’s largest and longest-running experimental study of habitat fragmentation.
The Amazon contains the planet’s most biologically diverse tree communities, with up to three hundred species occurring in an area the size of just two football fields. These forests are being rapidly felled and fragmented for timber operations, cattle ranches and industrial soy farms.
The team, led by William Laurance of the Smithsonian Tropical Research Institute in Panama, has been studying the fates of nearly 32,000 Amazonian trees since 1980. The most striking finding, say the authors, is the remarkable speed at which tree communities are changing in forest fragments.
“Rainforest trees can live for centuries, even millennia,” said Laurance, “so none of us expected things to change too fast. But in just two decades—a wink of time for a thousand year-old tree—the ecosystem has been seriously degraded.”
The main driver of these changes, say the authors, is ecological changes near the margins of forest fragments. “When you fragment the rainforest, hot winds from the surrounding pastures blow into the forest and kill many trees, which just can’t handle the stress,” said Henrique Nascimento, a team member from Brazil’s National Institute for Amazonian Research in Manaus. “Also, winds build up around the fragment and knock down a lot of trees.”
The trees that regenerate in their place are very different from the trees that died. “When you fragment a forest, the winners are common pioneer and generalist species that like forest disturbance,” said Laurance. “The losers are rare, slow-growing tree species that provide fruit, nectar, and homes for a diversity of rainforest animals.”
To understand how fragmentation is affecting the trees, the team studied 22 different characteristics of the increasing and declining species. “Our results show that tree communities in fragments are being completely restructured,” said Nascimento. “Most vulnerable are trees specialized for living in the dark forest understory that need animals such as birds or bats to disperse their seeds and pollen.”
Fragmentation is also changing the dynamics and structure of the forest. Tree communities in fragments are highly unstable, losing and gaining species at a high rate. Fragments also tend to lose many of their large trees and become dominated by small, fast-growing species.
Forest fragmentation may even increase global warming. The authors demonstrate that the small, fast-growing trees that proliferate in fragments contain less biomass, and hence store less carbon, than do the original rainforest trees they replaced. The carbon from the dead rainforest trees is broken down by microbes and fungi to become carbon dioxide, the most important greenhouse gas.
“Fragmentation is affecting the forest in a lot of ways,” said Laurance. “These changes occur remarkably fast, and when you completely alter something as basic as the trees, the other species that live in the rainforest will surely be affected too.”
Kakao in Monokultur verträgt Trockenheit besser als Kakao in Mischsystemen
18.09.2017 | Georg-August-Universität Göttingen
Ultrasound sensors make forage harvesters more reliable
28.08.2017 | Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren IZFP
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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