Abstract:
Hurricane activity is predicted to increase over the mid-Atlantic as global temperatures
rise. Nitrous oxide (N2O), a greenhouse gas with a substantial source from tropical soils,
may increase after hurricanes yet this effect has been insufficiently documented. On
September 21, 1998, Hurricane Georges crossed Puerto Rico causing extensive
defoliation. We used a before–after design to assess the effect of Georges on N2O
emissions, and factors likely influencing N2O fluxes including soil inorganic nitrogen
pools and soil water content in a humid tropical forest at El Verde, Puerto Rico.
Emissions of N2O up to 7 months post-Georges ranged from 5.92 to 4.26 ng cm2 h1 and
averaged five times greater than fluxes previously measured at the site. N2O emissions 27
months after the hurricane remained over two times greater than previously measured
fluxes. Soil ammonium pools decreased after Georges and remained low. The first year
after the hurricane, nitrate pools increased, but not significantly when compared against
a single measurement made before the hurricane. Soil moisture and temperature did not
differ significantly in the two sampling periods. These results suggest that hurricanes
increase N2O fluxes in these forests by altering soil N transformations and the relative
availabilities of inorganic nitrogen.