AUTHOR=Qiu Qingyan , Mgelwa Abubakari Said , Jin Shaofei , Hu Yalin 

TITLE=Nitrogen-Induced Changes in Soil Environmental Factors Are More Important Than Nitrification and Denitrification Gene Abundance in Regulating N2O Emissions in Subtropical Forest Soils

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.950367

DOI=10.3389/fpls.2022.950367

ISSN=1664-462X

ABSTRACT=<p>Subtropical regions are currently experiencing a dramatic increase in nitrogen (N) deposition; however, the contributions of nitrification and denitrification processes to soil N<sub>2</sub>O emissions and the underlying mechanisms under increasing N deposition remain unclear. Therefore, a <sup>15</sup>N-tracing laboratory experiment with four N application rates (0, 12.5, 25, and 50 μg <sup>15</sup>N g<sup>–1</sup> soil) was conducted to investigate the response of nitrification- and denitrification-derived N<sub>2</sub>O to N additions in an evergreen broad-leaved forest (BF) and a <italic>Pinus</italic> forest (PF) in the Wuyi Mountains in southeastern China. Moreover, the abundance of functional genes related to nitrification (<italic>amoA</italic>), denitrification (<italic>nirK</italic>, <italic>nirS</italic>, and <italic>nosZ</italic>), and soil properties were measured to clarify the underlying mechanisms. Results showed that nitrification-derived N<sub>2</sub>O emissions were generally decreased with increasing N input. However, denitrification-derived N<sub>2</sub>O emissions were a non-linear response to N additions, with maximum N<sub>2</sub>O emissions at the middle N application rate. Denitrification-derived N<sub>2</sub>O was the dominant pathway of N<sub>2</sub>O production, accounting for 64 to 100% of the total N<sub>2</sub>O fluxes. Soil NH<sub>4</sub><sup>+</sup>-N content and pH were the predominant factors in regulating nitrification-derived N<sub>2</sub>O emissions in BF and PF, respectively. Soil pH and the <italic>nirS</italic> abundance contributed the most to the variations of denitrification-derived N<sub>2</sub>O emissions in BF and PF, respectively. Our results suggest that N application has the potential to increase the contribution of denitrification to N<sub>2</sub>O production in subtropical forest soils. Changes in soil chemical properties induced by N addition are more important than the abundance of nitrification and denitrification functional genes in regulating soil nitrification- and denitrification-derived N<sub>2</sub>O emissions.</p>