Differences in nitrous oxide fluxes from red soil under different land uses in mid-subtropical China

Abstract

Red soil may play an important role in nitrous oxide (N 2O) emissions due to its recent land use change pattern. To predict the land use change effect on N 2O emissions, we examined the relationship between soil N 2O flux and environmental determinants in four different types of land uses in subtropical red soil. During two years of study (January 2005–January 2007), biweekly N 2O fluxes were measured from 09:00 to 11:00 a.m. using static closed chamber method. Objectives were to estimate the seasonal and annual N 2O flux differences from land use change and, reveal the controlling factors of soil N 2O emission by studying the relationship of dissolved organic carbon (DOC), microbial biomass carbon (MBC), water filled pore space (WFPS) and soil temperature with soil N 2O flux. Nitrous oxide fluxes were significantly higher in hot-humid season than in the cool-dry season. Significant differences in soil N 2O fluxes were observed among four land uses; 2.9, 1.9 and 1.7 times increased N 2O emissions were observed after conventional land use conversion from woodland to paddy, orchard and upland, respectively. The mean annual budgets of N 2O emission were 0.71–2.21 kg N 2O-N ha −1 year −1 from four land use types. The differences were partly attributed to increased fertilizer use in agriculture land uses. In all land uses, N 2O fluxes were positively related to soil temperature and DOC accounting for 22–48% and 30–46% of the seasonal N 2O flux variability, respectively. Nitrous oxide fluxes did significantly correlate with WFPS in orchard and upland only. Nitrous oxide fluxes responded positively to MBC in all land use types except orchard which had the lowest WFPS. We conclude that (1) land use conversion from woodland to agriculture land uses leads to increased soil N 2O fluxes, partly due increased fertilizer use, and (2) irrespective of land use, soil N 2O fluxes are under environmental controls, the main variables being soil temperature and DOC, both of which control the supply of nitrification and denitrification substrates.