Tree Mycorrhizal Type Determines the Storage and Distribution of Soil Organic Matter

Tree mycorrhizal type predicts within‐site variability in the storage and distribution of soil organic matter.

The Science

Researchers measured carbon and nitrogen soil organic matter (SOM) levels along with other soil composition metrics for trees with varying symbiotic root fungi dominance and at different sample depths down to one meter. The goal was to determine how fungus type affects the soil composition of forests and what implications this may have for forest longevity and stability.

The Impact

The findings of this study allow for a better understanding of the production and storage of SOM by the different tree fungus types. The results also provide insight into the long-term storage and stability of SOM based on fungus type. These insights will lead to a better understanding of SOM dynamics and support the use of fungus type as an important measurable biotic factor that can be used to improve land surface models.


The two primary root fungus types associated with trees are arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM). AM dominated trees were found to have higher levels of SOM at lower depths than ECM dominated trees while ECM soils had higher levels of SOM in upper surface soils. These findings, combined with the fact that carbon has a slower turnover time at lower depths in the soil, implies greater long-term storage and greater SOM stability in AM-dominated soils. Auxiliary measurements of soil composition reveal these patterns were driven by an accumulation of microbial residues in AM-dominated soils, which supports emerging theory on SOM formation and plant/mycorrhizal effects on soil.

Principal Investigator

Joshua B. Fisher

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science


DOE BER Environmental System Science (formerly Terrestrial Ecosystem Science) program and the  NSF Ecosystem Science program.


Craig, M. E., et al. "Tree Mycorrhizal Type Predicts Within‐Site Variability in the Storage and Distribution of Soil Organic Matter." Global Change Biology 24 (8), 3317-3330  (2018).