Large near-surface nitrate pools in soils capped by desert pavement in the Mojave Desert, California

We found exceptionally high nitrate levels (up to 12,750 kg ha(-1)) at shallow depths (<= 1m) in soils mantled by desert pavement, a common land-surface feature in and regions. Nearby soils without desert pavement had nitrate contents that were one to two orders of magnitude lower. The soil conditions coincident with desert pavement (i.e., stability, antiquity, and virtually no leaching) favor the retention and accumulation of nitrate delivered by atmospheric deposition or in situ fixation. The nitrate stored in soils under desert pavement is a previously unrecognized pool of nitrogen that has the potential to increase the global nitrogen inventory for near-surface desert soils to five times previous estimates. Its near-surface occurrence makes this labile nitrogen pool particularly susceptible to mobilization by climate change or human disturbance, risking contamination of surface and groundwaters.