Nitrous oxide (N₂O) is one of the most important greenhouse gases, with a global warming potential that is 280 times higher than that of CO₂. Tropical forests are important contributors for N₂O emissions from soil to the atmosphere; however, the microbial processes responsible for soil N₂O production in tropical forest soils remain unclear. 

In a study published in CATENA, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) employed a 40-day-long in situ ¹⁵NO₃^？ labeling experiment to determine the microbial processes that are responsible for N₂O production in an undisturbed tropical rainforest in Xishuangbanna, southwest China. 

The researchers distinguished the contributions of nitrification, denitrification, and co-denitrification to N₂O emissions based on the random isotope pairing principle in a ¹⁵N-labeled nitrate field experiment.

The field experiment certified that nitrification is the most important microbial processes underlying the N₂O emissions in the transition period between the dry and the rainy season. 

The results indicate that denitrification resulted in more N₂O emissions than co-denitrification via the higher consumption of both organic nitrogen and inherent NO₃^？. When extra N was added, soil N₂O emissions increased. Deposited ¹⁵NO₃^？ contributed 3.1% to the ¹⁵N₂O produced, whereas the added NH₄⁺ and native soil N contributed 48.6%. 

“To the best of our knowledge, this is the first study where the microbial processes involved in N₂O emissions have been measured in situ,” said Prof. ZHANG Yiping of XTBG. 

Contact 

ZHANG Yiping Ph.D  

Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail: yipingzh@xtbg.ac.cn