Direct measurement of denitrification in a Prosopis (Mesquite) dominated Sonoran Desert ecosystem

Denitrification was directly measured using the acetylene inhibition technique in a Sonoran Desert ecosystem dominated by Prosopis glandulosa. Soil under Prosopis and from the unvegetated area between Prosopis was wetted with 50 mm of water and denitrification measured for 48 hours. The mean denitrification rate under Prosopis was 11.6 g N ha^-1h^-1 compared to only 0.2 g N ha^-1h^-1 away from Prosopis. The denitrification response to wetting was rapid and rates peaked about 24 h after water application.The much higher denitrification under Prosopis probably results from high available organic C under Prosopis, but other soil chemical and physical changes effected by Prosopis may influence denitrification rates. About 0.5 kg N ha^-1 of Prosopis cover may be lost from this ecosystem by denitrification after infrequent major rainfalls.