Climate models need deeper roots, scientists say

By soaking up moisture with their roots and later releasing it from their leaves, plants play an active role in regulating the climate. In fact, in vegetated ecosystems, plants are the primary channels that connect the soil to the atmosphere, with plant roots controlling the below-ground dynamics.

“Most climate models assume that roots are shallow – usually within 6 feet of the surface – and that only the soil moisture near the surface can significantly impact the climate,” said Praveen Kumar, a professor of civil and environmental engineering at the University of Illinois at Urbana-Champaign. “Our research shows that it is not just the near surface, but also the deep reservoir of soil moisture that affect terrestrial heat and moisture processes in land-atmosphere interaction.”

A better understanding of this interaction, Kumar said, could lead to more accurate climate models and better predictability.

Using a land surface model, Kumar and graduate student Geremew Amenu are assessing the effects of deep roots on soil moisture and temperature redistribution. Three sites with different vegetation, soil and climate characteristics are being studied: the Mogollon Rim in Arizona, the Edwards Plateau in Texas and the Southern Piedmont in Georgia. Soil depths of up to 30 feet are being investigated.

There are two primary mechanisms by which deep-layer moisture affects the soil surface, Kumar said. First, its temporal variability sets the lower boundary for the transfer of moisture and heat from the surface. And second, this temporal variability influences the uptake of moisture by the plant roots, resulting in the variability of the transpiration and therefore the entire energy balance.

“Our initial results suggest that this second mechanism is predominant, indicating that accurate specification of rooting depth in climate models will play a crucial role in improving predictability,” Kumar said.

Through the process of transpiration, plants remove heat from their immediate environment. The evaporated moisture is carried elsewhere, eventually to fall as precipitation, releasing heat in the process. Through this ongoing energy cycle, plants can influence the climate.

“The variation of soil moisture in the deeper layers is a long term variation that we believe will be highly correlated with long term variations produced by climate models,” Kumar said. “If we are right, we will have better predictability of climate over a longer period of time, to the extent that plants impact the climate system.”

Kumar and Amenu will present the latest results of their modeling efforts, and the implications for climate modeling, at the American Geophysical Union meeting in San Francisco, Dec. 5-9. Their work was funded by the National Oceanic and Atmospheric Administration.

Source: University of Illinois at Urbana-Champaign

Related stories:

High mountain meadows are disappearing as trees move higher
Nothing lures visitors to Paradise like the transitory displays of wildflowers that populate Mount Rainier's high mountain meadows.
Water table depth tied to droughts in Great Plains
(PhysOrg.com) -- Will there be another “dust bowl” in the Great Plains similar to the one that swept the region in the 1930s? It depends on water storage underground. Groundwater depth has a significant effect on whether the Great Plains will have a drought or bountiful year.
Researchers examine impact of beetle kill on Rocky Mountain weather, air quality
Mountain pine beetles appear to be doing more than killing large swaths of forests in the Rocky Mountains. Scientists suspect they are also altering local weather patterns and air quality.
Global warming's ecosystem double whammy
Plants and soils act like sponges for atmospheric carbon dioxide, but new research finds that one abnormally warm year can suppress the amount of carbon dioxide taken up by some grassland ecosystems for up to two years. The findings, which followed an unprecedented four-year study of sealed, 12-ton containerized grassland plots at DRI is the cover story in this week's issue (September 18) of the journal Nature.
International experts collect alpine fungi in Beartooth Mountains of Montana
Armed guards once kept polar bears away while Cathy Cripps collected mushrooms and fungi on the island of Svalbard between Norway and the North Pole. Another time, Cripps encountered musk-oxen while gathering fungi in Greenland.
GOCE Earth explorer satellite to look at the Earth's surface and core
The European Space Agency is about to launch the most sophisticated mission ever to investigate the Earth's gravitational field and to map the reference shape of our planet – the geoid - with unprecedented resolution and accuracy.
New climate record shows century-long droughts in eastern North America
A stalagmite in a West Virginia cave has yielded the most detailed geological record to date on climate cycles in eastern North America over the past 7,000 years. The new study confirms that during periods when Earth received less solar radiation, the Atlantic Ocean cooled, icebergs increased and precipitation fell, creating a series of century-long droughts.
Crop Residue May Be Too Valuable to Harvest for Biofuels
(PhysOrg.com) -- In the rush to develop renewable fuels from plants, converting crop residues into cellulosic ethanol would seem to be a slam dunk.

News discussion:

Space & Earth science news