Nitrogen and phosphorus addition impact soil N(2)O emission in a secondary tropical forest of South China

Nutrient availability greatly regulates ecosystem processes and functions of tropical forests. However, few studies have explored impacts of N addition (aN), P addition (aP) and N×P interaction on tropical forests N(2)O fluxes. We established an N and P addition experiment in a tropical forest to test whether: (1) N addition would increase N(2)O emission and nitrification, and (2) P addition would increase N(2)O emission and N transformations. Nitrogen and P addition had no effect on N mineralization and nitrification. Soil microbial biomass was increased following P addition in wet seasons. aN increased 39% N(2)O emission as compared to control (43.3 μgN(2)O-N m(−2)h(−1)). aP did not increase N(2)O emission. Overall, N(2)O emission was 60% greater for aNP relative to the control, but significant difference was observed only in wet seasons, when N(2)O emission was 78% greater for aNP relative to the control. Our results suggested that increasing N deposition will enhance soil N(2)O emission, and there would be N×P interaction on N(2)O emission in wet seasons. Given elevated N deposition in future, P addition in this tropical soil will stimulate soil microbial activities in wet seasons, which will further enhance soil N(2)O emission.