According to a study by researchers from the Institute of Applied Ecology (IAE) of the Chinese Academy of Sciences (CAS) and their domestic and international collaborators, forest recovery on land affected by fires, harvesting, and other disturbances has been the main contributor to China's forest carbon sink over the past three decades.

The study was published in Nature Geoscience on August 17.

A carbon sink is an ecosystem that absorbs more carbon from the atmosphere than it releases over a given period. Forests are a major component of the global terrestrial carbon sink. Their net carbon sink is determined by the balance between carbon uptake as trees grow and emissions from processes including biomass burning from fires and fuelwood and the decomposition of coarse woody debris and harvested wood products following fires and harvesting.

China's forest carbon sink has generally increased in recent decades as forest area and biomass have expanded. However, estimates have differed substantially, and the relative contributions of forest recovery after disturbances, new forest establishment, and disturbance-induced carbon emissions remain insufficiently quantified.

Using high-resolution data on forest disturbances and biomass, the researchers, including XU Wenru, LIU Zhihua and ZHU Jiaojun, developed a spatially explicit forest carbon accounting model. This model tracked annual carbon uptake and emissions across China with 30-meter spatial resolution from 1986 to 2019.

They found that forests recovering from disturbances accumulated carbon faster than newly established forests. This makes reforestation the dominant contributor to China's forest carbon sink over the past three decades.

In this study, "reforestation" refers to the recovery of forests on land that was previously forested but affected by disturbances such as fire or harvesting. "Afforestation" refers to the establishment of forests on land that was not previously forested.

These findings help distinguish the contributions of reforestation and afforestation to China's forest carbon sink.