Soil Carbon Fractions and Aggregation Regulate N 2 O Emissions and Microbial N‐Cycling Genes: A Case Study Across Tropical Paddy Soils With Contrasting Organic Matter Levels
Yunxing Wan, Di Feng, Qiqian Lu, Lijun Liu, Shuirong Tang, Yanzheng Wu, Jing Hu, Xiaoqian Dan, Qilin Zhu, Lei Meng, Ahmed S. Elrys, Jinbo ZhangABSTRACT
Background : Nitrous oxide (N 2 O) is a major greenhouse gas, and its production is shaped by soil organic matter (SOM). Yet, how different SOM‐derived labile carbon fractions regulate N 2 O remains unclear, especially in tropical paddy soils where weak SOM stabilization leads to low fertility and high nitrogen loss.
Results : By collecting and analyzing soil samples from 16 tropical paddy soil sites with varying SOM contents (6–10 g kg −1 , 10–20 g kg −1 , 20–30 g kg −1 , and 30–40 g kg −1 ), we found that N 2 O emissions were twice as high in soils with higher SOM content compared to those with lower SOM content and that N 2 O emissions increased significantly with increasing SOM content. This stimulation of N 2 O emissions was accompanied by increases in soil easily oxidizable organic carbon (EOC), particulate organic carbon (POC), total nitrogen, microbial biomass carbon (MBC), and the abundances of nitrification and denitrification genes as SOM content increased. Moreover, increasing SOM above 20 g kg −1 increased the proportion of small soil aggregates (<0.053 mm), creating more anaerobic microsites that favored denitrify gene proliferation and ultimately led to higher N 2 O emissions.
Conclusion : Our results highlight the critical roles of organic carbon fractions and soil aggregates in controlling N 2 O emissions in tropical soils.