Rising nitrogen and rainfall could supercharge greenhouse gas emissions from the world’s largest grasslands

As the planet warms and rainfall patterns shift, new research suggests that the world’s largest grassland region may become a growing source of nitrous oxide, a greenhouse gas nearly 300 times more potent than carbon dioxide.

A team of scientists led by Dr. Shuping Qin from the Chinese Academy of Sciences examined how soil and climate conditions control the process of denitrification, a key microbial pathway that converts nitrogen compounds in soil into gases including nitrous oxide (N₂O) and nitrogen gas (N₂). Their study, recently published in Environmental and Biogeochemical Processes, is the first to map how denitrification responds to environmental changes across the Loess Plateau, Inner Mongolian Plateau, and Xizang Plateau of the Eurasian steppe.

“Understanding what drives soil denitrification helps us predict how grasslands will respond to climate change and rising nitrogen inputs,” said Dr. Qin. “These ecosystems play a crucial role in the global nitrogen cycle, yet their emissions remain poorly quantified.”

The researchers collected 150 soil samples from 30 undisturbed grassland sites across northern and western China. They measured the potential for nitrous oxide and nitrogen gas release under controlled laboratory conditions and compared results across regions with different soil types, rainfall levels, and temperatures. The team also simulated nitrogen deposition by adding small amounts of nitrate to each sample.

Their findings show that nitrogen addition significantly boosted nitrous oxide emissions across nearly all steppe soils, increasing average emission rates by about 65 percent. The Inner Mongolian and Xizang Plateau sites were identified as major “hotspots,” with nitrous oxide release roughly twice as high as in soils from the Loess Plateau.

At a broad regional scale, the total amount of nitrogen in soil emerged as the dominant factor controlling denitrification potential. In more localized analyses, total carbon, mean annual precipitation, and total nitrogen worked together to explain differences in emission rates. The study highlights how both nutrient availability and climate conditions can amplify the release of nitrous oxide.

“As rainfall and nitrogen deposition increase globally, steppe regions that are already sensitive to nitrogen, such as the Tibetan Plateau, may see a disproportionate surge in greenhouse gas emissions,” said co-author Dr. Xiaodong He. “This underscores the urgent need for targeted mitigation strategies in vulnerable ecosystems.”

The study also found that soil carbon and pH levels influence how efficiently microbes convert nitrous oxide into harmless nitrogen gas. In areas with higher carbon content or moderate soil acidity, microbial activity favored more complete reduction of nitrous oxide, helping limit its release to the atmosphere.

These findings provide valuable insights for improving greenhouse gas models and guiding sustainable grassland management. The researchers suggest that predictive models should account for local climate and soil characteristics to better estimate nitrous oxide fluxes under future environmental conditions.

“Our results reveal that grassland soils are not uniform in their response to nitrogen and climate change,” Dr. Qin said. “Recognizing these regional differences will be critical for designing effective strategies to reduce emissions and protect the ecological health of these vital ecosystems.”

The research was supported by the Natural Science Foundation of Hebei Province, the China Postdoctoral Science Foundation, and related programs aimed at advancing environmental science and technology in China.

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Journal reference: Yuan D, He X, Clough TJ, Hu C, Li X, et al. 2025. Patterns and drivers of soil denitrification and its responses to nitrogen addition in steppe ecosystems. Environmental and Biogeochemical Processes 1: e008  

https://www.maxapress.com/article/doi/10.48130/ebp-0025-0007  

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About the Journal:

Environmental and Biogeochemical Processes is a multidisciplinary platform for communicating advances in fundamental and applied research on the interactions and processes involving the cycling of elements and compounds between the biological, geological, and chemical components of the environment. 

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