Multiple factors affect oxygen levels on Qinghai-Tibet Plateau

Altitude, vegetation and temperature collectively contribute to the variation in oxygen concentration on the Qinghai-Tibet Plateau, Chinese researchers have found.

The finding has challenged a view long held by researchers from home and abroad that altitude is the only factor that determines oxygen levels worldwide.

"At any given altitude, the oxygen concentration is higher in the summer than it is in the winter," said Shi Peijun, a geography professor at Beijing Normal University and president of Qinghai Normal University. "This is because temperatures are higher in the summer, and oxygen produced by photosynthesis in the ecosystem also increases oxygen concentration."

"Therefore, altitude is not the only factor influencing the near-surface oxygen content on the Qinghai-Tibet Plateau," said Shi, also the lead researcher of the study, which is a part of China's second scientific expedition on the plateau.

China in 2017 launched a major expedition to study changes in climate, biodiversity and environment on the plateau over the past decades.

"No one has systematically measured differences in oxygen content at different locations and in different seasons on the plateau, and this study fills that gap," said Chen Yanqiang, a doctoral student at Beijing Normal University and a member of the research team.

In previous studies, monitoring sites were established only in lower-elevation areas of the Pacific, the Arctic and the Antarctic, where interference from human activities is minimal, Chen said.

Over recent years, Shi's team has traveled more than 30,000 kilometers to 591 sampling sites on the Qinghai-Tibet Plateau to collect data on surface oxygen content, air temperature, altitude, atmospheric pressure, vegetation coverage and soil properties, and to study landforms and topographic features.

More specifically, the study has found that oxygen concentration shows strong spatial and seasonal differences on the plateau, generally decreasing from southeast to northwest, higher in warm seasons than in cold seasons, and higher at noon than in the early morning, even within a single day.

"The research will help reveal the mechanism of environmental changes on the Qinghai-Tibet Plateau and the human impact on the environment, and it will quantitatively assess the effects of hypoxia on the health of humans and animals," Shi said.

The results of the study have been published in the Chinese Science Bulletin, and in the internationally renowned journals Science Bulletin and Scientific Reports.

Based on the research, Ma Yonggui, a professor at Qinghai Normal University, and his team have found the linear relationship between the incidence of chronic altitude sickness and hypoxia – the lower the oxygen content, the higher the incidence of altitude sickness.

As the largest and highest plateau in the world, the Qinghai-Tibet Plateau is known as the "roof of the world" and the "third pole of Earth." It plays important roles in China's, as well as the planet's, climate system, water supply, biodiversity conservation and carbon balance.