hydraulic descent

I am reading - http://creating-a-new-earth.blogspot.se/2015/12/building-healthy-soils-with-not-so.html - which has a section about hydraulic descent of water through root action of dormant plants.

Does anyone know more about this phenomenon? The only permies thread I found that referred to it was https://permies.com/t/18164/organic/Deep-Pipe-Irrigation from 3 years ago.

Does anyone know if there are trees or shrubs that fill this role in the Pacific North Wet Coast?

I have a friend with a very old orchard that has not really had significant care or abuse but appears to have very clay soil and he feels the soil isn't allowing the water to infiltrate well and he's looking for a number of things that would help this. The soil is covered with grass, but clippings are left where they drop, so although the soil probably has more of a bacterial tilt than mycorrhizal-loving trees would prefer, nothing nasty has been done to make matters worse. We have no way of knowing how badly the soil was abused before the orchard was planted approximately 80 years ago, but 80 years seems long enough that if we're going to do something to help the symptoms he's seeing, we need to know more. It's a mixed orchard of apple and pear varieties of full size with their crowns close to touching. In last summer's drought, the grass went totally dormant. There is a history of irrigation but they've been doing less of that in recent years.

All suggestions welcome!
Thanks J.

Jay Angler : See link below :

https://permies.com/t/32725/sepp-holzer/Sepp-Spring-Terrace


It certainly appears that there is a common thread in these 3 posts. It will take me more than a little time to find the common links !

I hope this was timely and helpful, for the Good of the Crafts ! Big AL

Thanks Allen, I've read through the thread you posted.

The orchard in question is down-slope of a ditched, paved road, is about 3/4 acre and has minimal slope. This area of Vancouver Island is known for its past glacial disturbance, so the soil can change rapidly and abruptly with little warning and is known for its rocks. This is why as a first approach I thought I'd ask for suggestions of trees/shrubs that could be interplanted to help.

That being said, an important concept I'm taking from the thread is that it would be good if my friend at least tried to dig some test pits to see what the layers look like. It seems that a key part of Sepp's success was not just the clay, but importantly the tree cover. Also, from the pictures, the understory is mostly forb and leaf litter rather than grass. There is lots to think about!