Short-lived isotopic method to measure nitrous oxide emissions from a soil under four low-fertility management systems
1999
Speir, T.W. | Townsend, J.A. | More, R.D. | Hill, L.F.
Aerobic production of N(2)O and N(2) from denitrification in four low-fertility ecosystems was measured using the short-lived radioisotope (13)N. The ecosystems, comprising two pastures, native beech (Nothofagus truncata) forest and exotic pine (Pinus radiata) forest, all had the same soil and the same slope and aspect. There was no consistent seasonal pattern of emissions, although the soils were dry on all three occasions (summer, autumn and spring) that samples were taken. Emission rates and N(2)O-to-N(2) ratios were generally highest in the surface 0-2 cm in the pasture soils, but not as frequently in the forest soils. Some of the forest soil samples produced a third gas, tentatively identified as NO. Emissions of N(2)O, but not of N(2), appeared to be generally greater from the forest than from the pasture sites, although only a limited number of samples were studied. Nitrate-N concentrations were generally low (ranging from 0.36 to 57.4 mg kg(-1), mean 3.27 mg kg(-1)) in these samples. Production of N(2)O, estimated from the relativity between (13)NO3(-)-N added and NO3(-)-N present in the soil, placed these ecosystems at the lower end of emission rates for undisturbed ecosystems, with rates ranging from 0.02 to 6.38 ng N(2)O-N g(-1) soil h(-1) (mean 0.65 ng N(2)O-N g(-1) soil h(-1)).
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