[fc417fc802]

I don't understand how osmosis enters into this? Capillary action is sufficient to explain water traveling up the roots to a point where it was removed. Evaporation from leaves is sufficient to explain removal during the day. You'd need some other explanation for extraction by fungi or etc at night.

As a largely unrelated aside, there will still be a chemical potential across a membrane that doesn't permit a solute to cross. So water can diffuse into a concentrated solution without the solute flowing backwards into the reservoir. Alternatively, small solutes can leave while larger solutes are retained. This is the basis of dialysis.

[hinkley]

In retrospect what I wrote became a bit more of a non sequitur than I meant.

Trees aren't even accessing water at ground level most times but pulling it up from 5-30 feet down. Fungal distribution is also a capillary action network (with asterisks) and ends up making some of that pumping more horizontal, but at the expense that if a tree's root sap is high in sugar due to dehydration, then the fungal network both introduces water to those roots but also exports sugar at the same time. Simard tries to anthropomorphize this process. It's my only real complaint with her work.

The asterisks are that fungal networks can react to information faster than the documented transport mechanisms work so we don't really know how the heck they do their thing yet. So it's possible that they're also maintaining nutrient gradients to feed themselves beyond the straight arbitrage that osmosis represents.