A tree stump that should be dead is still alive; here's why

A tree stump that should be dead is still alive; here's why
The Kauri tree stump in the study. Credit: Sebastian Leuzinger / iScience

Within a shrouded New Zealand forest, a tree stump keeps itself alive by holding onto the roots of its neighboring trees, exchanging water and resources through the grafted root system. New research, publishing July 25 in iScience, details how surrounding trees keep tree stumps alive, possibly in exchange for access to larger root systems. The findings suggest a shift from the perception of trees as individuals towards understanding forest ecosystems as "superorganisms."

"My colleague Martin Bader and I stumbled upon this kauri tree stump while we were hiking in West Auckland," says corresponding author Sebastian Leuzinger, an associate professor at the Auckland University of Technology (AUT). "It was odd, because even though the stump didn't have any foliage, it was alive."

Leuzinger and Bader, first author and an AUT senior lecturer, decided to investigate how the nearby were keeping the tree stump alive by measuring in both the stump and the surrounding trees belonging to the same species. What they found is that the movement in the tree stump was strongly negatively correlated with that in the other trees.

These measurements suggest that the roots of the stump and surrounding conspecific trees were grafted together, Leuzinger says. Root grafts can form between trees once a tree recognizes that a nearby root tissue, although genetically different, is similar enough to allow for the exchange of resources.

"This is different from how normal trees operate, where the water flow is driven by the water potential of the atmosphere," Leuzinger says. "In this case, the stump has to follow what the rest of the trees do, because since it lacks transpiring leaves, it escapes the atmospheric pull."

But while root grafts are common between living trees of the same species, Leuzinger and Bader were interested in why a living kauri tree would want to keep a nearby stump alive.

"For the stump, the advantages are obvious—it would be dead without the grafts, because it doesn't have any green tissue of its own," Leuzinger says. "But why would the green trees keep their grandpa tree alive on the while it doesn't seem to provide anything for its host trees?"

One explanation, Leuzinger says, is that the root grafts formed before one of the trees lost its leaves and became a stump. The grafted roots expand the root systems of the trees, allowing them to access more resources such as water and nutrients, as well as increase the stability of the trees on the steep forest slope. As one of the trees stops providing carbohydrates, this may go unnoticed and thus allow the "pensioner" to continue its life on the backs of surrounding, intact trees.

"This has far-reaching consequences for our perception of trees—possibly we are not really dealing with trees as individuals, but with the as a superorganism," Leuzinger says.

During a drought, for example, trees with less access to water might be connected to those with more access to water, allowing them to share the water and increase their chances of survival. However, this interconnectivity could also allow for the rapid spread of diseases such as kauri dieback, Leuzinger says.

To better understand how root systems are formed between kauri stumps and living trees, Leuzinger says he hopes to find more instances of these types of stumps and to explore root grafting in intact trees, which will help expand their scope of research.

"This is a call for more research in this area, particularly in a changing climate and a risk of more frequent and more severe droughts," Leuzinger says. "This changes the way we look at the survival of trees and the ecology of forests."


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More information: M.K.-F. Bader et al, Hydraulic Coupling of a Leafless Kauri Tree Remnant to Conspecific Hosts, iScience (2019). DOI: 10.1016/j.isci.2019.05.009
Provided by Cell Press
Citation: A tree stump that should be dead is still alive; here's why (2019, July 25) retrieved 23 October 2019 from https://phys.org/news/2019-07-tree-stump-dead-alive.html
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Jul 25, 2019
Four years ago P Wohlleben wrote "The Hidden Life of Trees" explaining just this

Jul 25, 2019
There is also likely to be fungal-root interactions that may be supporting the stump's life.

Jul 25, 2019
The Aspen tree Pando occupies 100 acres and is 80K years old.

Jul 25, 2019
Four years ago P Wohlleben wrote "The Hidden Life of Trees" explaining just this

Well, I gave a tree stump new life as an infinity symbol with my chainsaw...

Jul 25, 2019
The Aspen tree Pando occupies 100 acres and is 80K years old.


That one is unique in that every tree is a clone of the master tree and it does not reproduce in the usual way.

Jul 25, 2019
Four years ago P Wohlleben wrote "The Hidden Life of Trees" explaining just this


This website published a blurb about this 8 years ago too. Re-examining things and coming to the same or similar conclusions from different angles reinforces scientific study.

https://phys.org/...ior.html

Jul 26, 2019
The Aspen tree Pando occupies 100 acres and is 80K years old.


That one is unique in that every tree is a clone of the master tree and it does not reproduce in the usual way.


""Clonal groups of P. tremuloides in eastern North America are very common, but generally less than 0.1 ha in size, while in areas of Utah, groups as large as 80 ha have been observed (Kemperman and Barnes 1976)." ... "Despite enormous crops of viable seeds, successful seedling establishment appears to be a rare event in the semi-arid West, but the establishment of new trees from seeds appears to be common in the moist, humid forests of New England... aspen establishment from seeds probably has not occurred in the western United States since the last glaciation, some 10,000 years ago... sexual reproduction is effectively frustrated ...""

[ https://en.wikipe...o_(tree) ]

Jul 29, 2019
there is a tree in my garden I cut it down to that size poured kerosene over it then lit afire it in now growing back and has no trees near it only grass

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