MYCORRHIZAL CONUNDRUM

There has been much in the ecological mainstream and not-so-mainstream media about the connectivity and communication between trees in woods and forests. This has grown to the extent that there is now a widespread belief that trees form communicating and interdependent communities, a sort of “wood wide web”, but what does the science really say?

It all started with the findings of a symbiotic (usually mutualistic but sometime parasitic) relationship between fungi and tree roots to form mycorrhizae. These have a vital role in capturing nutrients for the plant from the soil. Over time, common mycorrhizal networks form, connecting the trees in woodlands but this has been expanded in popular belief to woods and forests being supra-organisms where trees communicate with each other through the fungal hyphae, protecting their offspring and sending nutrients to them preferentially in kin relationships, warning connected trees of threats and danger, and that there are “Mother Trees”, the largest and oldest trees with the most mycorrhizal connections. These ideas have entered common literature, but some scientists question such extrapolations.

A 2023 paper in the journal Nature, Ecology and Evolution by Karst, Jones and Hoeksema (Volume 7, pages 501–11) has expressed concerns about the above. They found that there was bias that had developed in citing the positive from the scientific papers and that, for example, there was significant variation in the results of field studies and that did not support generalisations that, for example, mature trees send resources through the mycorrhizal network to support the performance of conspecific seedlings. There were also concerns about the conclusion that defence signals were sent through the network. Much more fieldwork and scientific investigation is needed to support all the claims being made. This has, predictably, started something of a battle between those interested in this topic, especially where the attractive (to humans) ideas of the “wood wide web” are concerned. I would therefore suggest caution in that idea however emotionally attractive. I end with an apposite and amusing quote from the author Julie Karst who said, “less hype, more hyphae”.

We must all remember that science is not based on how we would like things to be, but on theories and observations tested by carefully controlled experiment and evidence.

Betts Ecology have much wooded land on the sites we manage. We apply the best science we can to protect the trees and the woodland ecosystem, promoting biodiversity and the preservation of Natural Capital.