Peter C. Hartsough | Search USGS

USGS2004

Response to comment on "A reservoir of nitrate beneath desert soils"

We appreciate the comment by Jackson et al. ( 1 ), which underscores two points made in our recent paper ( 2 ): (i) that desert subsoil nitrate (NO – 3 ) inventories are spatially highly variable, and thereby warrant substantial measurement efforts to reduce uncertainty in global extrapolations, and (ii) that Chihuahuan Desert subsoil NO – 3 inventories tend to be much smaller than inventories in other western U.S. deserts.

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USGS2003

A reservoir of nitrate beneath desert soils

A large reservoir of bioavailable nitrogen (up to ∼10 4 kilograms of nitrogen per hectare, as nitrate) has been previously overlooked in studies of global nitrogen distribution. The reservoir has been accumulating in subsoil zones of arid regions throughout the Holocene. Consideration of the subsoil reservoir raises estimates of vadose-zone nitrogen inventories by 14 to 71% for warm deserts and arid shrublands worldwide and by 3 to 16% globally. Subsoil nitrate accumulation indicates long-term leaching from desert soils, impelling further evaluation of nutrient dynamics in xeric ecosystems. Evidence that subsoil accumulations are readily mobilized raises concern about groundwater contamination after land-use or climate change.

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