Scientists at the University of Alberta have debunked the widely held myth that trees are able to signal each other through an underground fungal network or mycorrhizal network (CMN). According to their results, published in the journal Nature Ecology & Evolution, the popular view does not match current scientific evidence.

Although the existence of the CMN is not disputed by scientists, the authors criticized the hypothesis that this network is actively involved in the life of trees, bringing them benefits. The researchers analyzed the results of field studies and found that one of the claims that CMNs are widespread in forests is not supported by enough scientific evidence. There are no detailed data on the structure of networks and their functions.

Another claim that nutrients are transferred from mature trees to seedlings via CMN, and that they promote survival and growth, has also been questioned. Although resources can be transferred to fungi, mycorrhiza does not necessarily carry the flow of matter, and seedlings usually do not gain access to CMN. While the potential mycorrhizal network may have a beneficial effect, it may also have a negative effect, and neutral effects are most commonly reported.

The third claim, that mature trees preferentially send resources or "warning signals" of insect damage to young trees via CMN, is not supported by any peer-reviewed published field study.