Acceleration of soil N2O flux and nitrogen transformation during tropical secondary forest succession after slash-and-burn agriculture

Abstract

Abstract The responses of soil nitrous oxide (N2O) fluxes to tropical forest development are not well documented. We linked the characteristics of N2O fluxes with community composition, N cycling, inorganic nitrogen (N) pools, as well as other soil variables during tropical secondary forest succession after slash-and-burn agriculture in Xishuangbanna, Yunnan, China. During succession, from Mallotus paniculatus to Syzygium oblatum communities, N2O emissions increased from 390.8 ug N m−2 h−1 to 671.6 ug N m−2 h−1, where the greatest value occurred during the wet season. The increased soil water content following forest succession explained 71–90 % of the N2O emissions, while decreased soil temperature only contributed 66–70 % to the emissions. Net N mineralization and nitrification increased along the secondary succession of tropical forests, which was positively and nonlinearly correlated with variations in the inorganic nitrogen pool. The variations in N2O fluxes were positively correlated with net N mineralization and nitrification, ammonia and nitrate N, and microbial biomass, but negatively associated with bulk density of soils and C:N ratio of the litter and soil. Our data suggested that a substantial acceleration of soil N2O flux was mainly determined by the increasing availability of inorganic N stimulated by the improved litter quality (low C:N ratio), as well as elevated gravimetric water content, and net N mineralization and nitrification during the spontaneous succession of secondary tropical forests after slash-and-burn agriculture.