Warming will disturb balance of soil nutrients in drylands

Oct 30, 2013
A dryland ecosystem in Peru that was one of the sites sampled by researchers in their global study of sites in 16 countries. Credit: David Eldridge et al.

An increase in aridity due to global warming will disturb the balance of nutrients in the soil and reduce productivity of the world's drylands, which support millions of people, a landmark study predicts.

The research was conducted by a of scientists who carried out the same studies of 224 dryland sites in 16 countries on every continent except Antarctica.

In Australia, woodland sites near Mildura in NSW were studied by UNSW's Adjunct Professor David Eldridge, of the School of Biological, Earth and Environmental Sciences, who is a member of the international research team.

Other sites included areas of the Negev Desert in Israel, the Pampas lowlands in Argentina and the Altiplano highlands of Peru. Rainfall at the sites ranged from 100 to 800 mm per year, and all soil samples were analysed in the same laboratory in Spain.

The research shows that increasing aridity is associated with a reduction in carbon and nitrogen in the soil and an increase in phosphorus.

The results are published in the journal Nature.

"Drylands cover about 41 per cent of Earth's land surface and support more than 38 per cent of the world's population," says Professor Eldridge, who also works for the NSW Office of Environment & Heritage.

Maasai giraffe (Giraffa camelopardalis tippelskirchi) in Samburu National Reserve (Kenya). Credit: Vicente Polo

"As the world's population grows, people will increasingly rely on marginal lands – particularly drylands - for production of food, wood and biofuels. But these ecosystems will be severely affected by imbalances in the cycle of carbon, nitrogen and phosphorus."

A worldwide decrease in soil moisture ranging from 5-15 per cent has been predicted for the 2080-2099 period.

Phosphorus in rocks and sediments is released into the soil by weathering, and levels are expected to increase as soils become drier and erode more.

This increase in phosphorus will be accompanied by reductions in carbon and nitrogen, which are more dependent on biological processes such as litter decomposition, photosynthesis and nitrogen fixation. Reduced plant cover will also exacerbate this effect.

"Plants need all of these elements, in the correct amounts and at the right times, but increasing aridity will upset this balance, leading to a breakdown in essential processes," says Professor Eldridge.

Explore further: Team suggests complex relationship between phosphorus levels and nitrogen removal in lakes

More information: dx.doi.org/10.1038/nature12670

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jyro
1.2 / 5 (17) Oct 30, 2013
The next global warning prediction that comes true will be the first.
Neal Asher
1.2 / 5 (17) Oct 31, 2013
Meanwhile, in the real world, the increased CO2 in the atmosphere is greening desert regions like the Sahel, while the minimal increase in warming has increased rainfall. Only inside perpetually failing computer models do you find disaster.
NikFromNYC
1.2 / 5 (18) Oct 31, 2013
"The research shows that increasing aridity is associated with a reduction in carbon and nitrogen in the soil and an increase in phosphorus."

James Hansen noted in a recent paper the fertilization effects of carbon and nitrogen molecule emissions as an explanation of why carbon dioxide not ramping up as fast as emissions are:

"We suggest that the surge of fossil fuel use, mainly coal, since 2000 is a basic cause of the large increase of carbon uptake by the combined terrestrial and ocean carbon sinks. One mechanism by which fossil fuel emissions increase carbon uptake is by fertilizing the biosphere via provision of nutrients essential for tissue building, especially nitrogen, which plays a critical role in controlling net primary productivity and is limited in many ecosystems and field studies confirm a major role of nitrogen deposition, working in concert with CO2 fertilization, in causing a large increase in net primary productivity of temperate and boreal forests."
NikFromNYC
1.2 / 5 (18) Oct 31, 2013
This study appears twice on Phys.org:
http://phys.org/n...oil.html

Though paywalled, this computer model study does have reference 26 that is another computer model study that addresses fertilization effects along with nitrogen:

"Thornton, P. E. et al. Influence of carbon–nitrogen cycle coupling on land model response to CO2 fertilization and climate variability. Glob. Biogeochem. Cycles 21, GB4018 (2007)"

http://onlinelibr...F.f03t03

"Nutrient cycling affects carbon uptake by the terrestrial biosphere and imposes controls on carbon cycle response to variation in temperature and precipitation, but nutrient cycling is ignored in most global coupled models of the carbon cycle and climate system."
Howhot
4 / 5 (4) Nov 02, 2013
Acid rains from vaporized carbolic-acid and coal burning sulfur have an devastating impact on soil nutrients Add drought conditions and extreme heat from global warming effects and long term soil nutrients could vanish in under a decade. Farmers could see their entire acreage turned to desert. That doesn't sound like a very good thing to the terrestrial biosphere.

Still, the most important aspect of farming remains freshwater. Freshwater has to be there at the right time for the environment to live. Drought conditions, heat waves, flooding rainfall excesses due to global warming will upend natural balances and damage the vital bio-cycles farmers rely on.