In a shrouded New Zealand forest, a tree stump keeps alive by clinging to the roots of neighboring trees and exchanging water and resources through the grafted root system. New research published in iScience on July 25 describes how surrounding trees keep tree stumps alive, possibly in exchange for access to larger root systems. The results indicate a shift from the perception of trees as individuals to the understanding of forest ecosystems as "superorganisms".
"My colleague Martin Bader and I stumbled upon this kauri tree stump while hiking in West Auckland," says associate author Sebastian Leuzinger, associate professor at Auckland University of Technology (AUT). "It was strange because even though the tree stump had no foliage, he lived."
Leuzinger and Bader, first author and AUT lecturer, decided to investigate how the trees near the tree stump kept alive by measuring the water flow both in the stump and in the surrounding trees of the same species. They found that the Water movement in the stump was strongly negatively correlated with that in the other trees.
These measurements suggest that the roots of the tree stump and the surrounding tree species have been planted together, says Leuzinger. Root grafts can form between trees when a tree recognizes that a nearby root tissue, although genetically diverse, is similar enough to exchange resources.
"This differs from the functioning of normal trees, where the water flow is driven by the water potential of the atmosphere," says Leuzinger. "In this case, the tree stump must follow what the rest of the trees do, because it lacks transpiring leaves, it eludes the atmospheric attraction." and Bader were interested in why a living kauri tree wants to keep a nearby tree stump alive its own, "says Leuzinger." But why would the green trees keep their grandpa alive on the forest floor while he seems to offer nothing for his host trees ? "
One explanation, says Leuzinger, is that the root grafts formed in front of one of the two trees lost their leaves and became a tree stump.The grafted roots extend the root systems of the trees and allow them access to more resources such as Water and nutrients as well as the stability of the trees on the steep forest slope, as one of the trees no longer supplies carbohydrates can go unnoticed and allow the "retiree" to continue his life on the backs of surrounding, intact trees.
"This has far-reaching consequences for our perception of trees ̵
To better understand how root systems are formed between kauri stumps and living trees, Leuzinger hopes to find more cases of this kind from tree stumps and to research on root transplantation in intact trees, which will help expand their scope of research.
"says Leuzinger," This changes our view on the survival of trees and the ecology of forests. "
US. Forest changes are double-edged sword for the environment
M.K.-F. Bader et al., Hydraulic Coupling of a Leafless Kauri Tree Residue to Certain Hosts, iScience (2019). DOI: 10.1016 / j.isci.2019.05.009
A stump that should be dead is still alive; here is the reason (2019, 25th of July)
retrieved on July 26, 2019
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