National Research Program
Studies of Nitrogen and Carbon
Deserts have long been thought to be nutrient poor, but most traditional studies of nitrogen cycling in terrestrial ecosystems have examined the biologically active soil zone, which is considered to extend to about one meter below the surface. Then, in 2003, a report by USGS and other scientists on the Amargosa and other deserts noted that substantial quantities of nitrogen as nitrate have accumulated below the soil zone over millennial time frames and that arid regions in the southwestern United States contain a large reservoir of bioavailable nitrogen that had been previously overlooked continues to generate considerable interest. As a result of this discovery, it is believed that the earth's global reservoir of soil nitrate is up to 16% greater than previously estimated. Because the desert subsoils contain oxygen and are low in organic matter, microbial populations, and water content, denitrification is inhibited and nitrate accumulates. However, there is evidence that climate change or the irrigation of arid areas could result in the percolation of this newly discovered nitrate into and the subsequent contamination of ground-water aquifers.
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