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headspace-hotel:

An attempt at summarizing the controversies that embroil mycorrhizal network research:
a bunch of scientists are miffed at how the media has taken “plants communicate and distribute nutrients through the mycorrhizal network” and run with it, finding the “mother tree” thing too anthropomorphizing and too presumptive about something very poorly understood
unfortunately all of the major models for understanding the mycorrhizal network are anthropomorphizing, even the more competition-centered ones…to the point that papers discuss whether the network is a “capitalist” or a “socialist” system
other researchers, screaming STOP USING LOADED TERMS THAT PROMOTE AN ANTHROPOCENTRIC INTERPRETATION
But, setting aside the question of whether trees can “intentionally” do something or be altruistic…how do we know the plant is the one in control? Are the trees “sending” nutrients or is the fungus taking the nutrients and sending them to other trees? Wait, how do we assign agency in a system like this at all? Isn’t it unscientific to assume that any part of the system, fungus or plant, is consciously acting? Wait…are they actually separate organisms with their own interests, or is it more accurate to view all the members of a mycorrhizal network as one big super-organism? (Wait, is it anthropomorphizing to consider organisms as having interests? If yes, how do we describe what’s happening using language?)
Basically, yes we have demonstrated and established that nutrients move from one plant to another plant in the mycorrhizal network, including from fully grown trees to saplings, plants in sunlight to shaded plants, and other things that are definitely fun to interpret as one plant “helping” the weaker plant. However, we don’t actually know the intentions of plants, so for all we know, the fungus could be doing everything. Or it could be completely stupid to describe any of it as “one individual organism in the network Intentionally Does A Thing.”
Big Problem: Although a shit ton of research is being done, most research in the mycorrhizal network is done on very simple networks of 1 or 2 plant species with a handful of selected fungal inoculants in otherwise sterile laboratory settings. These conditions do not reflect the natural world at all.
in fact, experimental conditions used to study mycorrhizal networks are mostly completely unlike anything that would ever exist…you know, Outside,
most of the research pertains to agriculture and there are many demonstrated benefits, and many farmers are ALREADY using methods to promote mycorrhizal networks, but my guess is that it’s not as simple as matching crops up to fungal inoculants that help them for instant 20% yield increase, at least in Real Outdoor Soil with an existing microbiome and seed bank.
Roughly speaking, 50% of mycorrhizal associations benefit seedling establishment, and the remaining 50% are themselves split halfway between “no effect” and “negative effect.” Doesn’t this mean that the mycorrhizal network is not always chill and altruistic?
Well, those findings might mean absolutely nothing either way, since in a field-setting plant community, there are dozens if not hundreds of fungi species (the diversity and number of specialists increases in later-successional communities) that are part of the mycorrhizal network, and through them any given seedling might be linked to a thousand different plants.
Some researchers find it puzzling how so many mycorrhizal partnerships seem to have no effect. Maybe the effect only comes online in certain conditions?
Parasitism, mutualism and commensalism aren’t fixed types of relationship, and two partners in the mycorrhizal network can and do switch between the three constantly. This is another problem: the experiments don’t usually follow both partners in a plant-fungal pairing to the end of their natural lives, and it’s been shown that a fungus can be mutualistic early in a plant’s life and later on become more parasitic (for example). Or that a fungus can be beneficial in poor soil conditions and become parasitic in rich soil conditions.
But…is this really best understood as a situational switch between types of symbiosis, or can we judge it by the net effect on both partners throughout their life spans, or…my brain is breaking
Like, a fungus that mostly decreases the fitness of the host plant, BUT becomes very helpful in the presence of extreme drought…is it a parasite or mutualistic partner?
Some researchers lean toward a source-sink model where nutrients tend to flow toward plants that are most lacking and away from plants with most abundance. This is a rough approximation of something ridiculously complicated
Plants can and do select fungal partners to pair with and reject fungi that contribute fewer benefits.
Fungi also appear capable of selectively distributing resources based on the fitness of the host, or at least they did this one experiment where the fungus was connected to two different trees and researchers ripped all the leaves off one of the trees. This caused the fungus to divert its nutrient flow to the undamaged tree (throwing in its lot with the tree most likely to survive). However, we’re not sure if this would happen in a forest or other natural plant community, since in the lab, the fungus was totally dependent on the two trees for survival and there were no other participants in the network. So basically, it’s kinda like those behavior studies on captive wolves?