Does a vast network of fungi connect forests? Here’s what we know. : ScienceAlert

The possibility of fungal communication networks connecting forest ecosystems in a ‘wooden web’ has gained increasing attention among researchers in recent decades.

However, it may be more hyphae than hyphae, according to one perspective recently published in Nature Ecology and Evolution.

Three biologists at the University of Alberta and the University of British Columbia in Canada and the University of Mississippi in the United States argue that other scientists have unintentionally exaggerated evidence supporting highly complex models. mycorrhizal networks ignoring the limitations of previous studies.

Biologists analyzed more than 1,500 scientific articles and counted the number of claims based on weak or absent evidence. They found that the percentage of unsupported claims had doubled over the past 25 years, with a tendency to cite the positive effects of fungus networks.

“Some of the unsupported quotes came from our own previous publications,” biologists Jason Hoeksema, Melanie Jones, and Justine Karst to write.

“These types of unsubstantiated claims are a problem because we scientists have, probably unintentionally, become vectors of unsubstantiated claims.”

‘Wood webs’ models argue symbiotic networks of fungi and trees provide resources such as water and nitrogen to other plants, while also “whispering” warn each other and their offspring about predatory insects.

The fact that fungi form interdependent relationships with trees by living within plant roots (known as mycorrhiza) or living in nearby soil (known as ectomycorrhiza) is not disputed. However, the architecture and complexity of vast resource-sharing systems known as common mycorrhizal networks (CMN) are much more difficult to define. And evidence for something vast and complex is still lacking, biologists say.

“Arguments are now being made to change forest management and policy based on this information,” write Hoeksema, Jones and Karst.

“(Scientists) may be shaping the public narrative with increasingly inaccurate characterization.”

Mapping fungi and trees in a forest is an arduous task and only five studies have been carried out in two forest types; just two tree species out of an estimated 73,300 worldwide.

These studies also cannot show that fungal connections are permanent.

“Hyphae and mycorrhizal roots change rapidly and are scratched – processes that break connections,” the biologists write.

Experiments were done using potted plants with various mesh arrangements to prevent roots or fungus (or both) from growing in certain zones. This enabled scientists to examine the impact of denying a plant access to the fungal network.

However, even when these experiments produce positive results (perhaps when observing stunted growth of a plant due to CMN isolation), it is difficult to rule out alternative explanations that could also explain the results. For example, adding a mesh around a plant’s root system is a very artificial intervention and can change the composition of pathogens or fungi in the soil, which can influence a plant’s growth.

These potential confounders are not properly controlled for in many experiments, the researchers argue. And, even when experimental limitations are pointed out by the authors, they are often overlooked by researchers who cite the original studies. This gives the impression that the evidence supporting fungal networks is much stronger than it actually is.

Hoeksema, Jones, and Karst make several recommendations for experiments that can determine the existence of fungal networks, including mapping the fungi in a wide range of forests around the world, using dyes to track water flowing through the network, and collecting additional data. on possible confounding factors. factors.

“Let’s design new experiments, demand better evidence, think critically about alternative explanations for results, and become more selective with the claims we disseminate,” urges the trio.

“If not, we run the risk of turning the web of the forest into a fantasy under our feet.”

This perspective article was published in Nature Ecology & Evolution.

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