Responses of Soil Nitrous Oxide Emission to Nitrogen Addition at Two Topographic Positions of a Subtropical Forest
Pengpeng Duan, Daobo Wang, Kongcao Xiao, Liang Zheng, Hao Chen, Kelin Wang, Dejun Li
Abstract
Abstract Topography can influence nitrous oxide (N 2 O) emission via its influences on soil nutrient availability, moisture, and microbial communities. Nevertheless, it is still unclear whether topography modulates the responses of soil N 2 O emissions to elevated N deposition. Here the N addition experiment was conducted in the valley and on the slope of a subtropical karst forest in southwest China. Nitrogen was applied as NH 4 NO 3 in two levels, that is, 50 (moderate N) and 100 (high N) kg N ha −1 yr −1 with no N addition plots as the control. Nitrogen addition consistently increased N 2 O emission in the valley, but only high N addition significantly increased N 2 O emission on the slope in 2017. The cumulative N 2 O fluxes across the 3 years were 1.16 ± 0.24 kg N ha −1 in the valley and 1.50 ± 0.06 kg N ha −1 on the slope under the control. Nitrogen addition stimulated N 2 O emission by 88.7%–113.3% in the valley due to increased ammonium, nitrate and dissolved organic carbon availabilities and ammonia‐oxidizing bacteria (AOB) amoA abundance. High N addition stimulated N 2 O emission by 84.3% on the slope owing to increased nitrate and carbon availabilities, AOB amoA, and nirK abundances. The stimulation of N 2 O emission by moderate N addition was more pronounced in the valley than on the slope largely owing to the lower N status in the valley. This work highlights the importance of N status in regulating the responses of soil N 2 O emissions to elevated N deposition.