PARENT SESSION
Thursday, August 10, 1:30-5:00 pm
COS 102 - Arid ecosystem ecology
L-14, Lobby Level, Cook Convention Center
Presiders: J Fehmi
Net N2O consumption is observed following precipitation events in some semi-arid soils.
Hymus, Graham *,1, Grimm, Kirsten 2, Dijkstra, Paul1, Hungate, Bruce 1, 1 Northern Arizona University, Flagstaff, AZ2 LeTourneau University, Longview, TX
ABSTRACT- Nitrous oxide emission from soils accounts for 75% of annual global N2O production. Consequently, understanding controls on N2O production and consumption by soils is a research priority. For the semi-arid ecosystems of northern Arizona precipitation events are thought to trigger important emissions of N2O from the soil. We found soil wetup elicits idiosyncratic responses of N2O flux in grassland and ponderosa pine forest soils. As soil water content increased above 60%, net N2O production increased in the desert grassland soil. However, in the ponderosa pine soil the same increase in soil water content decreased net N2O production to the point where net N2O consumption was observed. 15N labeling of the NH4+ or NO3- pool showed the expected increases in the proportion of N2O derived from denitrification as soil water content increased. Pool dilutions showed continued nitrification and consumption of NO3- at 90% soil water content for both soils, evidence that gross N2O production was maintained. Consequently, the net N2O consumption observed in the ponderosa pine soil was most likely the result of continued N2O reductase activity following an almost complete depletion of the soil NO3- pool. These findings suggest that N2O consumption is variable between soil types and an important constraint on N2O emissions from certain semi-arid soils.
Key words: Semi-arid ecosystems, N2O production