Receiving less than 10 inches of rain a year, arid areas run in a wide band at 30 degrees north and south latitude. Along with semi-arid areas, which receive less than 20 inches of rain a year, they account for nearly half the earth's land surface.
Forest soils have more organic matter and, square foot for square foot, hold much more carbon. But because arid soils cover so much area, they can have an outsize role in the earth's carbon budget and in how much the earth warms as heat-trapping gases accumulate in the atmosphere.
Working on the Nevada National Security Site, the researchers marked off nine octagonal plots about 75 feet in diameter. Air with 380 parts-per-million concentrations of CO2, the current CO2 levels, was blown over three plots. Three received no extra air. Three were exposed to concentrations of 550 parts per million, the CO2 levels expected in 2050.
The CO2 was fed through PVC pipes ringing the plots and had a specific chemical fingerprint that could be detected when the soil, plants and other biomass were analyzed.
The analysis, done by Benjamin Harlow in WSU's Stable Isotope Core Laboratory, suggests that arid lands may increase their carbon uptake enough in the future to account for 15 to 28 percent of the amount currently being absorbed by land surfaces.
Overall, said Evans, rising CO2 levels may increase the uptake by arid lands enough to account for 4 to 8 percent of current emissions.
The experiment did not account for other possible changes stemming from climate change, like varying precipitation and warming temperatures.
Still, said Evans, "I was surprised at the magnitude of the carbon gain, that we were able to detect it after 10 years, because 10 years isn't very long in the life of an ecosystem."
While forest ecosystems tend to store carbon in plant matter, the Mojave researc
|Contact: R. Dave Evans|
Washington State University