Plant-soil feedbacks (PSFs) are crucial ecological processes that influence how plant communities form and grow. In these processes, mycorrhizal fungi which form partnerships with plant roots play a key role. However, how these feedbacks differ globally between plants that associate with different types of mycorrhizal fungi remain unclear.

In a study published in Global Ecology and Biogeography, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and their collaborators investigated how mycorrhizal types affect plant-soil feedbacks through a comprehensive global meta-analysis.

The analysis included data published between 1994 and 2022 from all climate zones worldwide. It focused on woody plants (both flowering plants and conifers) to compare PSFs between two main mycorrhizal types: arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) fungi.

Researchers found a clear and consistent pattern. The host tree species of EcM generally experienced positive PSFs (growth promotion), meaning that they performed better in soil conditioned by their own kind. In contrast, the host tree species of AM predominantly showed negative PSFs (growth suppression), meaning that they performed poorly in its own soil conditions.

“This contrast is consistent across both flowering plants and conifers,” said SONG Xiaoyang of XTBG. “It suggests that the type of fungal partnership a tree forms fundamentally shapes its relationship with the soil and with neighboring plants.”

Moreover, there were notable regional differences. The strong contrast between AM and EcM trees was most evident in studies conducted in North America and Asia, but was not statistically significant in studies conducted in Europe and Oceania. In addition, climate played a role for AM trees. AM woody plants showed stronger negative PSFs in humid, cold environments, while the PSF intensity for EcM hosts did not change significantly across different latitudes or climates.

Researchers noted that the way PSFs are measured can be influenced by experimental conditions such as whether tests are done in a greenhouse or in the field. This points to a need for more standardized methods in future research to improve the reliability.

“Our study shows that mycorrhizal type is a strong predictor of plant-soil feedbacks on a global scale. To better understand these feedbacks, future studies should aim to standardize the experimental design and take into account the complex interactions between mycorrhizal fungi and the soil microbiome,” said SONG Xiaoyang, the corresponding author of the study.