Environmental controls on nitric oxide emission from northern Chihuahuan desert soils

Abstract

A survey of nitric oxide (NO) emission from Chihuahuan desert soils found mean NO fluxes <0.1 ng NO-N cm−2h−1 during the dry season. These fluxes were at thelower end of the range reported for temperate grassland and woodlandecosystems. NO fluxes from wet or watered soils were higher(0.1–35 ng NO-N cm−2 h−1).Watering of black grama grassland soils produced an initial pulse of 12ng cm−2 h−1 (12-h after 1-cm watering)with high fluxes sustained over 4 days with repeated watering. Initialpulses from shrubland soils were lower (maximum 5 ngcm−2 h−1), and fluxes declined withrepeated watering. Repeated watering of creosotebush soils depleted thesoil NH 4 + pool, and NO emissions weredirectly related to soil NH 4 + concentrationsat the end of the experiment. In watered andNH 4 + -fertilized creosotebush soils, NO fluxeswere positively related to potential net nitrification rates.NH 4 + -fertilization boosted the initial NOpulse 15 times in the shrubland and 5 times in black grama grasslandrelative to watered controls. These experimental results point towardgreater substrate limitation in shrublands. In this desert basin, NOemission averaged 0.12 kg N ha−1 y−1in untreated soil and 0.76 kg N ha−1y−1 in watered soil. We multiplied these averages bythe distribution of grassland and shrubland vegetation within a58,600-ha area of the Jornada del Muerto basin to estimate regionallosses of 0.15–0.38 kg NO-N ha−1y−1 for this area of the Chihuahuan desert.