Tree stumps that should be dead can be kept alive by nearby trees

Root grafting is a normal process and like the article suggest, it can be problematic for the trees. In Texas and others states affected by oak wilt one of the main defenses against it is to trench between healthy and sick stands of oaks. This can be extremely expensive especially in the hill country where trenching involves using a rock saw to cut through the surface limestone.

Oak wilt is a fungal disease that is spread through the root systems of interconnected trees and by actions of a specific beetle that is most active between end of February and late July. TAMU recommends no pruning of anything larger than a pencil between those dates if I remember correctly.

I had the misfortune of learning about this affliction after buying a home in north Texas that had mature live oaks, some more than a hundred years old, and watching those live oaks die suddenly. Live oaks are evergreen and when they suddenly started browning the second spring after buying the property I had already lost more than 10 trees.

Once it began affecting the 3 signature trees out front I called in an arborist and had many of them treated with a chemical fungicide. That was expensive. I also rented a backhoe and trenched between the sick and healthy stands on my place and between my property and my neighbor's. He had some beautiful oaks on his place too and I didn't want his trees to go down simply because they were root grafted across the fence to mine.

The end result is that I lost more than a dozen mature live oaks and the three trees out front that were treated once they started showing signs of oak wilt are still alive, albeit with greatly reduced canopy. The fungus usually kills 95% of the trees it afflicts and if the tree survives it never has a full canopy.

It can take a full year for the fungus to kill a mature live oak due to the small size of the pores which transport nutrients from leaves to roots and vice versa. A mature red oak on the other hand can be killed in a week since the pore sizes are much larger. I lost a perfect specimen tree that survived the initial affliction more than 15 years prior. It suddenly died four or five years ago. Many other red oaks in the area are dying too.

I rambled a bit there but overall an informative article that brought back unpleasant memories of my own battle with and experience with root grafted trees and some of the problems you may face.

The original study is available here: https://www.cell.com/iscience/fulltext/S2589-0042(19)30146-4

Abstract:

> Trees are commonly regarded as distinct entities, but the roots of many species fuse to form natural root grafts allowing the exchange of water, carbon, mineral nutrients, and microorganisms between individuals. Exploiting the phenomenon of leafless (photosynthetically inactive) tree remnants being kept alive by conspecifics, we show tight physiological coupling of a living kauri (Agathis australis) stump to conspecific neighbors. The trunk remnant displayed greatly reduced, inverted daily sap flow patterns compared with intact kauri trees. Its stem water potential showed strong diel variation with minima during daytime and maxima at night, coinciding with peak and minimal sap flow rates in neighbors, respectively. Sudden atmospherically driven changes in water relations in adjacent kauri trees were very rapidly and inversely mirrored in the living stump's water status. Such intimate hydrological coupling suggests a “communal physiology” among (conspecific) trees with far-reaching implications for our understanding of forest functioning, particularly under water shortage.

The stump acts as a biological cistern for the neighboring trees. In return for nutrients, it stores water when demand is low (night) and supplies water when demand is high (day). I imagine that the main survival advantage is that the neighboring trees get to grow leaves and branches into the stump's canopy void much faster than if they had to expand their own root system. This should give the trees a big advantage over other nearby species competing for the newly available sunlight.

Learned this in "The Hidden Life of Trees". Great book.

https://www.amazon.com/Hidden-Life-Trees-Communicate_Discove...

I have always wondered about that...when I was little I noticed that tree stumps would sometimes end up greying out and wither away when my dad cut them, and sometimes wouldn't. This explains everything!

This article (below) covers the same story. I like some of the photos it has.

https://gizmodo.com/undead-tree-stump-is-being-kept-alive-by...

I have seen the effect of neighboring trees on cut trees in the campgrounds of British Columbia. Tree stumps left when a tree was removed and then fully covered in bark as if it were a tree with no branches. No cut surface to be seen.

A stand of leafy tees who were shaded yet appeared mysteriously healthy was discovered after years of effort, including radioactive isotope tracing of underground nutrient flow, where being fed from a vast mycelium network which was transferring nutrients from a distant stand of leafy trees of a different species - Paul Stamets who is a fungi expert was part of the investigative team

Interesting. I was in the Paradise Camp Fire, and tens of thousands of trees have since been cutdown. Most of the trees (pines) survived because they evolved with fire, but I doubt any are still alive because they're rarely allowed to grow next to other trees in urban-rural interface areas. Maybe some would survive, which might be cool in some situations.

Isn't this just coppicing, where a percentage of trees are harvested for timber and stumps are left to regrow?

https://renconforestry.com.au/managing-coppice-in-eucalypt-p...

Fascinating. But why? If the "dead" tree can't contribute what is the (evolutionary) advantage of keeping it alive? As natural selection goes, how does being so "generous" benefit the living trees?

Every so often someone finds an albino sequoia sapling and post pictures. For it to have gotten that big with no chlorophyll it is taking sugars from from one of the adult trees via root grafting.