Nitrogen-rich tropical/subtropical forest soil acts as a terrestrial
source of nitrous oxide (N2O) emissions, a greenhouse gas commonly
affected by soil nitrogen availability and soil moisture. However, in
tropical and subtropical regions experiencing both elevated nitrogen
deposition and altered precipitation regimes, it is unclear whether
nitrogen deposition and precipitation regimes have interactive effects
on forest soil N2O emissions and what roles N2O-associated
nitrifiers/denitrifiers play in these interactions. We conducted a
two-year field study in a subtropical evergreen broadleaf forest in
southern China by applying four treatments: nitrogen addition (N),
seasonal precipitation distribution change (P), both nitrogen addition
and seasonal precipitation distribution change (NP) and a control (C).
The Results showed that N2O efflux from the forest soil was
significantly greater in the wet season than in the dry season, but was
promoted by the NP treatment only in the dry season. Soil moisture and
pH decreased in the P and N treatments, respectively. The abundances of
the nitrifying gene AOA-amoA and denitrifying gene nosZ in the wet
season and the abundance of the denitrifying gene nirK in the dry season
differed significantly among the four treatments. A structural equation
model showed that precipitation change was more important than nitrogen
addition in affecting soil properties (e.g. moisture and pH) and
N2O-associated nitrifiers/denitrifiers, while soil nirK- and
nosZ-denitrifiers were the dominant functional microbes in regulating
N2O emissions. The results support predictions of future nitrogen losses
(N2O) in subtropical forests in the context of interactions between
elevated nitrogen deposition and altered precipitation regimes.