Once a powerful kauri tree, this low, leafless strain has now been dead for a long time. But that's all but the case. Do not be fooled by appearances ... Credits: Sebastian Leuzinger / iScience

During the day, while healthy trees are busy carrying water up and down to the roots, the stump is dormant. Then at night, when the host trees rest, the strain wakes up and circulates the water and nutrients in what remains of his body. According to the researchers, it is as if these trees take turns and operate as separate pumps in a single hydraulic network. Credits: iScience

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Hydraulic Coupling of a Leafless Kauri Tree Remnant to Conspecific Hosts

M.K.-F. Bader S. Leuzinger 2

Published:July 25, 2019

DOI:https://doi.org/10.1016/j.isci.2019.05.009

In a New Zealand forest, a "vampire tree" clings to life. Formerly a powerful kauri tree (a kind of conifer that can grow up to 50 meters high), this low and leafless strain seems dead for a long time now. But, as a new study published this week shows ... we must not trust appearances.According to the authors of the study, this strain is part of a " superorganism " forest: a network of interlaced roots that share resources. Note that this true community can include dozens or even hundreds of trees. Indeed, by grafting its roots on those of its neighbors, this strain of kauri can feed during the night water and other nutrients collected by other trees during the day, allowing it to survive through hard work of his comrades.For the strain, the benefits are obvious: she would be dead without these transplants, because she no longer has green tissue per se ," said Sebastian Leuzinger, co-author of the study, and associate professor at the Auckland University of Technology of New Zealand. " But why would the trees keep this stump on the ground alive, when it does not seem to provide anything to its host trees? "Asks Leuzinger.Leuzinger and his colleagues attempted to answer this question by studying the flow of nutrients between the vampire strain and its two closest host trees. Using several sensors to measure the movement of water and sap through the three trees, the team noted a curious trend: the strain and its neighbors seemed to drink water, the whole time at opposite times.But in this case, why add an almost dead tree to a real underground nutrient highway? According to the researchers, although the stump has no leaves, it is possible that its roots still have value for the surrounding trees, as a bridge to other trees in the network. It is also highly possible that the strain reached its neighbors a long time ago, even before it became a stump.Also to know that the roots under these trees are very intertwined and therefore, according to the research team, it might be necessary to rethink the very concept of what a forest really is. " Maybe we do not really have to do trees as individual elements, but to the forest as a superorganism, " Leuzinger said.According to the researchers, these forest superorganisms could also create some kind of additional protection against drought, by providing water to trees that have less access to it.It is therefore extremely valuable information and resource for the future, as the frequency and intensity of droughts are about to increase in the face of changing global climate change. .There is one element that the researchers wanted to highlight. All the positive elements of this real network, there is potentially a great disadvantage to everything being linked: in the same way that nutrients can be shared between individuals, pathogens could be transmitted as easily infected tree to another. It should also be noted that kauri trees in particular are threatened by a disease called kauri dieback , which is spread by a soil pathogen.Researchers now want to continue their research on these forest superorganisms to learn more about their functioning and role.