Soil N2O and NO emissions from an arid, urban ecosystem in central Arizona-Phoenix

Soil nitrogen (N) cycling and fluxes of N2O and NO in three land-use types across
the metropolitan area of Phoenix, Arizona has been measured.Urbanization increased
N2O emissions compared to native landscapes, primarily due to the expansion of
fertilized and irrigated lawns. Fluxes of N2O from lawns ranged from 18 to 80 mg N
m^(-2) h^(-1) and were significantly larger than managed xeric landscapes (2.5-22 mg
N m^(-2) h^(-1)) and remnant desert sites within the urban core (3.7-14 mg N m^(-2)
h^(-1)). In contrast, average NO fluxes from lawns were not significantly different
from native desert when dry (6-80 mg N m^(-2) h^(-1); 5-16 mg N m^(-2) h^(-1)
desert) and were lower than fluxes from deserts after wetting events. Furthermore,
urbanization has significantly altered the temporal dynamics of NO emissions by
replacing pulse-driven desert ecosystems with year-round irrigated, managed lawns.
Short-term, pulse-driven emissions of NO from wetting of dry desert soils may reach
35% of anthropogenic emissions within a day after summer monsoon storms. If regional
O3 production is NOx-limited during the monsoon season, fluxes from warm, recently
wet arid soils may contribute to summer O3 episodes. .