Forest ecosystems are vital to the global carbon (C) cycle. Although the importance of tree mycorrhizal fungi in this process is known, how different tree mycorrhizal types affect forest C storage, especially in species-rich subtropical forests, remains poorly understood. 

A research team from the Wuhan Botanical Garden of the Chinese Academy of Sciences conducted a systematic investigation in the Badagongshan subtropical mountainous forest. Along a gradient of ectomycorrhizal (ECM) tree dominance, they established 58 plots to examine the effects of ECM dominance on forest C stocks, including tree biomass C, forest floor C, and soil C.

The results revealed that total forest C stocks increased with higher ECM dominance. Specifically, both tree biomass C and forest floor C were positively associated with ECM dominance, whereas soil C storage showed no significant relationship. The increase in tree biomass C was mainly attributed to the higher density of large-size trees in ECM-dominated stands, while the accumulation of forest floor C was primarily due to the lower litter quality (higher C : Nitrogen ratio) of ECM trees. 

Notably, although ECM-dominated plots contained larger vegetation and litter C pools, this did not translate into greater soil C storage. This may be related to the peroxidase activity of ECM fungi and the relatively low microbial C use efficiency in these stands.

These findings underscore the critical role of tree mycorrhizal types in determining forest C stock, particularly in subtropical regions. This knowledge is a vital piece of the puzzle for scientists and policymakers working to enhance C sequestration and address the growing challenge of climate change.

The findings were published in Forest Ecology and Management entitled "Effects of tree mycorrhizal type on ecosystem carbon stock in a subtropical mountainous forest". Professor LIU Feng is the corresponding author, with LU mengzhen as the first author.

 Location of the 58 plots along a gradient of ECM tree dominance (ECM%) in the subtropical mountainous forest (Image by WBG)

The effect of ECM tree dominance on different components of forest C stock (Image by WBG)

Diagram showing the results of PLS-PM for the effects of measured factors on tree biomass C stock and forest floor C stock (Image by WBG)