“Desert soils are unusual because the sand grains at the surface are bound together into a crust by bacteria, reducing wind erosion and adding nutrients to the soil. Deserts cover over one third of the world’s land surface and yet our understanding of their contribution to the atmospheric carbon dioxide balance is poor”, says Dr Andrew Thomas of Manchester Metropolitan University.
Sands like those in the Kalahari Desert of Botswana are full of cyanobacteria. These drought resistant bacteria can fix atmospheric carbon dioxide, and together they add significant quantities of organic matter to the nutrient deficient sands.
“We know that globally there is a huge exchange of carbon between the atmosphere and the soil. As average global temperatures rise, scientists are concerned that bacteria will break down organic matter in soils more rapidly, releasing more carbon dioxide into the atmosphere”, says Dr Thomas. “However, there have been very few actual field studies of this carbon exchange through world soils and little information on how they respond to temperature and moisture changes. This is particularly true for deserts. Here the bacteria have to be able to cope with long periods without rain and extreme temperatures, so they lie dormant in the desert soil only springing to life when there is enough moisture”.
The exchange or flux of carbon between the soils and the atmosphere is much smaller over deserts than for areas with more organically rich soils, but the sheer size of deserts makes it globally significant. Even small changes in the carbon balance of desert soils will also be important locally, where soil organic matter underpins fragile ecosystems currently supporting millions of poor pastoral farmers.
“We discovered that even after light rainfall, the gains and losses of carbon dioxide through the sands of the Kalahari Desert were similar in size to those reported for more organic rich grassland soils. Despite being short lived, these raised pulses of activity are a significant and previously unreported contributor to atmospheric carbon dioxide” says Dr Thomas. “Global climate change models have forgotten them”.
Dr Thomas with his colleagues, Dr Stephen Hoon and Dr Patricia Linton also of Manchester Metropolitan University, found that in some conditions, the cyanobacteria in the surface crust were taking net amounts of carbon dioxide out of the atmosphere as they photosynthesised. But after heavy rainfall other types of bacteria deeper in the subsoil became active and their activity masked the uptake of carbon by the surface cyanobacteria by consuming the organic matter in the soil, releasing large quantities of carbon dioxide.
“We also discovered that the fluxes of carbon dioxide from the soil were highly sensitive to temperature. Warmer air but similar soil moisture levels caused greater losses of carbon from the desert soils to the atmosphere”, says Dr Thomas. “These desert soils are contributing significantly to the global carbon dioxide budget. Until recently they have been ignored”.
“We need to know exactly what is happening as a better understanding of the factors controlling activity of the surface living soil cyanobacteria could help inform grazing policy. Millions of poor semi-subsistence pastoral farmers rely on the soils of the Kalahari to provide nutrients for grazing. The carbon produced by the cyanobacteria is a major contributor to the fertility of the soil and it is essential we understand how their metabolism is affected by environmental conditions”, says Dr Thomas.
Lucy Goodchild | EurekAlert!
Hidden river once flowed beneath Antarctic ice
22.08.2017 | Rice University
Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter
17.08.2017 | Swansea University
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
23.08.2017 | Materials Sciences
23.08.2017 | Automotive Engineering
23.08.2017 | Life Sciences