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

Abstract

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 970965 ha, was about 5944 tons N2O-N per year.