Chinese Researchers Uncover Stagnation in Carbon Absorption by Arid Zone Vegetation Globally

Information from the Institute of Grassland Research of the Chinese Academy of Agricultural Sciences (CAAS) shows that the Innovative Team of Grassland Remote Sensing Intelligent Perception and Disaster Prevention and Mitigation, led by Researcher Li Fei from the institute, has achieved a major original breakthrough in the field of global terrestrial ecosystem carbon cycle research. The relevant results were recently published online in the international journal Nature Geoscience, systematically revealing for the first time that the growth of vegetation photosynthetic carbon absorption in global arid zones has shown an obvious "stagnation" phenomenon.

For a long time, the "fertilization effect" brought by the continuous increase of carbon dioxide concentration in the atmosphere has been generally considered to continuously improve the photosynthetic carbon sequestration capacity of vegetation, becoming the core driving force for the growth of terrestrial ecosystem carbon sinks. However, against the background of global warming, how the carbon sink capacity of different climate zones evolves and whether there is a growth inflection point have long been major scientific problems in the international ecological and environmental field.

To address this cutting-edge issue, Li Fei’s team rose to the challenge. Relying on the global FLUXNET flux observation network and satellite remote sensing data, they built a framework of multi-source data integration and machine learning methods, reconstructed the long-term carbon-water exchange dynamics on a global scale, and accurately depicted the real changes of global vegetation carbon absorption with scientific data.

The research results clearly show that since 2001, the growth rate of vegetation photosynthetic carbon absorption in global arid zones has slowed down significantly. In sharp contrast, humid zones have maintained a continuous growth trend over the past 40 years, eventually forming an asymmetric change pattern of "stagnation in arid zones and acceleration in humid zones".

The team further analyzed the mechanism and found that the core reason for this pattern is the increase of atmospheric vapor pressure deficit (VPD), which intensifies water constraints and offsets the positive fertilization effect brought by the increase of carbon dioxide concentration. China Science Daily reported that this discovery breaks the traditional cognitive limitations and sounds the alarm for the ecological protection of global arid zones.

Arid zones account for more than 40% of the global land area, nurturing and maintaining unique biodiversity while supporting the survival and development of about a quarter of the global population. The study confirms that water constraints are expanding outward from arid zones, which directly affects the ecological stability of grasslands in northern China, the effectiveness of desertification control and the sustainable development of animal husbandry.

This achievement is another landmark progress of Li Fei’s team in grassland ecosystem research under climate change. After returning to China in 2020, Li Fei, who once conducted research at the University of Tennessee, Michigan State University and the Chinese Academy of Sciences, took root in the Inner Mongolia grassland and led the team to make a series of important achievements, including revealing the saturation phenomenon of water use efficiency in global terrestrial ecosystems in Science.