A research team led by Prof. LI Lei from the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences has found that nitrogen deposition promotes carbon sinks in terrestrial ecosystems, while changes in rainfall patterns increase the risk of these carbon sinks declining. The findings were published in Advanced Science and Catena on March 25, 2026 and May 23, 2025 respectively.

Nitrogen deposition is a key external source of nutrients that eases nitrogen limits in ecosystems. It plays an important role in building carbon sinks. To reliably estimate its contribution to the global carbon sink, scientists need to accurately track where deposited nitrogen goes.

To understand how changing rainfall patterns affect nitrogen retention and the resulting carbon sink, to estimate deposited nitrogen's contribution to global carbon sinks, and to improve the accuracy of future carbon sink predictions under climate change, the researchers carried out a series of experiments and analysis.

In the alpine grasslands of the Kunlun Mountains, the team used dual-isotope (¹⁵N) tracer experiments combined with controlled rainfall patterns. They then used stoichiometric methods to measure how changing rainfall affects the retention of deposited nitrogen and the region's carbon sink.

In addition, the team compiled and analyzed 829 global ¹⁵N isotope tracer observations. This allowed them to quantify how much reduced nitrogen (NHₓ) and oxidized nitrogen (NOᵧ) are retained in terrestrial ecosystems worldwide. They also distinguished where deposited nitrogen ends up—whether in woody tissues (stems, coarse roots, branches) or non-woody tissues (leaves, fine roots, bark). Finally, they revealed global patterns of nitrogen retention and the spatial distribution of the resulting carbon sink across terrestrial ecosystems.

The study shows that changes in rainfall patterns raise the risk that nitrogen-deposition-driven carbon sinks will decline. This suggests that current estimates, which are based on long-term average climate conditions, may be too high.

On a global scale, distinguishing nitrogen allocation between woody and non-woody plant tissues reduces uncertainty in estimating the nitrogen-driven carbon sink. It also establishes the spatial pattern of terrestrial carbon sinks boosted by nitrogen deposition, providing a key scientific foundation for global carbon sink assessments.