While hiking in the New Zealand wilderness, Sebastian Leuzinger of the Auckland University of Technology and a colleague made an astonishing discovery: a tree stump that should have died was being kept alive by neighboring trees. After conducting an experiment, the researchers concluded that nearby trees were funneling water and nutrients to the stump through an interconnected root system. The revelation supports the understanding that trees and other organisms work together for the benefit of a forest.
For the study, Leuzinger and his teammate decided to put continuous water monitors in the kauri (Agathis australis) stump and in two nearby adult trees of the same species. Then, they waited. After several weeks, they discovered a relationship between the water flow in the trees and the stump.
When nearby trees evaporated water through their leaves during the day, the water movement in the stump remained low. But, when the trees were dormant during the evening, the water would begin circulating through the stump. Furthermore, when it was overcast or rainy and the water flow dropped in the trees, the stump picked it up.
As NewScientistreports, water flow is largely driven by evaporation in healthy trees. But, without leaves, the stump's water flow was dependent on the movement of its neighbors.
The finding, which was published in iScience, undermines the notion of trees as individual or separate entities. We've long known the symbiotic relationship between fungi and tree roots, but the new information "dramatically changes our view of forest ecosystems as ‘superorganisms'," said Leuzinger.
He added that the networking of water makes the trees more resistant to water scarcity. However, it also increases the risk of disease spreading. This could be problematic for Kauri trees which are affected by a deadly disease called kauri dieback.
Living stumps have been reported as far back as the 1800s. But, this is one of the first studies ever on how they survive. There are several theories as to why trees help each other out. The most probable of which suggests that a leafless stump simply becomes part of the host tree's broader root system.
According to Greg Moore at the University of Melbourne, Australia, trees are "ruthlessly efficient" in maximizing their resources. "So the fact that this stump is being supported by nearby trees tells you they are getting a benefit," he said.
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