Daily and seasonal nitrous oxide fluxes in soils from hardwood forest and different agroecosystems of Taiwan

Fluxes of N₂O from four paddy soils, two upland soils, two orchard soils, and two hardwood forest soils located at central and southern parts of Taiwan were measured between 1994 and 1997 using a static close chamber technique. Daily emissions and variations in rate of N₂O fluxes from paddy and orchard soils were larger than those from fallow upland and hardwood forest soils. Daily coefficients of variation of these measurements ranged from 4% to 350%. The range of daily N₂O fluxes were listed in the following order : the highest amount observed in upland soils, paddy soils, orchard soils, and hardwood forest soils. The largest N₂O flux was detected from upland soil collected at Chishan which was 324.6 g N₂O-N ha⁻¹ day⁻¹ with a daily mean flux around 57.7 g N₂O-N ha⁻¹. In all test soils, based on annual measurements, the mean temporal coefficients of variation ranged from 14.8 to 130.9%, and the largest was detected in paddy soils. The results also indicate that the mean annual amounts of N₂O released into the atmosphere was 11.3, 5.6, 4.5 and 3.4 kg N₂O-N ha⁻¹ yr⁻¹ from upland, paddy, orchard, and hardwood forest soils, respectively. It was calculated that the total amounts of emission of N₂O from those agroecosystems and hardwood forest soils of central and southern parts of Taiwan, together having a total area of 970 965 ha, was about 5944 tons N₂O-N per year.