This kauri tree-stump has stunned the science world because it refused to die

Friday, 26 July 2019

This new knowledge may have future advantages for disease management, including Kauri Dieback disease.

A kauri tree stump in the middle of an Auckland forest has offered new insights into tree communities, which could be harnessed to fight Kauri dieback, research suggests.

Essentially, kauri trees 'hold hands' beneath the ground, sharing water and nutrients through an interconnected root system.

Ecologists Dr Martin Bader and Dr Sebastian Leuzinger are the first to show this physiological link between trees, in their paper published online on Friday.

The two AUT ecologists came across the 50cm stump through 'perfect coincidence' while on a hike in the Waitakere Rangers.

**READ MORE:

Ecologists Dr Martin Bader and Dr Sebastian Leuzinger are the first scientists to show the very tight community network, or physiological link between trees

* Kauri dieback: National treasure on the brink of extinction

* Kauri dieback five-year survey under way: How far has it spread?

Essentially, kauri trees 'hold hands' beneath the ground, sharing water and nutrients through an interconnected root system.

* Five years on and diseased kauri injected with phosphite are growing strong**

While unremarkable looking to some, the ecologists were immediately intrigued.

For about three months they monitored the stump by installing senses senses into it and the surrounding trees, which were likely to be aged around 80 to 100 years old.

'It was still alive but technically it should be dead,' Bader said.

Trees stay alive by eating food through photosynthesis, getting carbohydrates and sugars through their leaves. Technically, a tree stump with no green foliage should not be able to survive, he said.

After investigation, they discovered it was the two surrounding trees that were feeding this little stump.

'The water had to cycle through the little stump like a radiator because the top has grown over by wound tissue,' Bader said. 'It's really cool.'

Unfortunately, this research has an alarming prognosis for kauri dieback disease.

If the pathogen is within the tree it could be distributed through the root connection without restriction, Bader said.

Kauri dieback has been known to travel uphill, and the common root network would explain that, he said.

'However, if the pathogen can be sent through the root's system, that might be something we can use to our advantage in the future,' he said.

'Trees have been injected with a phosphate to stop the trees from getting the disease.

'It's very expensive. So knowing where the communities of trees are sharing a root network could save money because the trees are sharing the remedy between themselves.'

Kauri dieback disease has spread rapidly through New Zealand's forests. Last year, iwi confirmed dieback had been discovered in a young tree less than 60 metres from T ā ne Mahuta.

The disease is 100 per cent fatal to trees and it is spread through soil movement, largely by human visitors to the bush who do not clean their boots properly.

This new discovery of root sharing is another component into how this is spreading so rapidly.

The pair got a research permit from Auckland Council and began their research at the beginning of 2017.

For about three months they monitored the stump by installing sensors into it and the surrounding trees, which were likely to be aged around 80 to 100 years old.

Bader said he has had an 'overwhelmingly positive response', since the paper was published.

Future research would delve into how big the root networks extend to below ground.

Hydraulic Coupling of a Leafless Kauri Tree Remnant to Conspecific Hosts was published on iScience on July 25.