How a ‘dead’ tree stump in New Zealand has kept itself alive


Trees can ‘reach out’ with their roots to help old and damaged trees, scientists have found.

The discovery was triggered by an old tree stump in Australia that was found to be still alive – despite having no leaves.

Scientists found that it was receiving sugars produced by another tree’s roots connecting to its own.

The discovery has led scientists to suggest that rather than seeing trees as individuals, the may form a ‘superorganism’ – sharing root systems over a wide area.

Sebastian Leuzinger, an associate professor Auckland University of Technology, said of the discovery: ‘My colleague Martin Bader and I stumbled upon this kauri tree stump while we were hiking in West Auckland.

‘It was odd, because even though the stump didn’t have any foliage, it was alive.’ The scientists measured water flow in the stump – of a type of tree called a Kauri – and the surrounding trees and found that it was receiving water from neighbouring trees.

Digging down, they found that the old stump’s roots were grafted together with neighbouring trees.

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’ Professor Leuzinger said.

‘But why would the green trees keep their grandpa tree alive on the forest floor while it doesn’t seem to provide anything for its host trees?’

It is possible that the root grafts happened before one of the trees lost its leaves and became a stump – and the grafted roots expand the root systems of the trees, allowing them to get more resources such as water and nutrients.

Grafting on to the stump’s roots also could give more stability on the steep forest slope.

If one of the trees stops providing sugars through the roots, this may go unnoticed and what the researchers call the ‘pensioner’ stump continues its life on the backs of surrounding, intact trees.

Professor Leuzinger said: ‘This has far-reaching consequences for our perception of trees – possibly we are not really dealing with trees as individuals, but with the forest as a superorganism.’ 

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 said.

German forestry researcher Peter Wohlleben writing in the Daily Mail three years ago goes even further – and claims trees can think.

They keep dying trees alive because ‘they are even reluctant, like elephants, to abandon their dead’.


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