How a ‘dead’ tree stump in New Zealand has kept itself alive by grafting onto other roots to get nutrients and water
- Tree stump keeps itself alive by holding onto the roots of its neighbouring trees
- It exchanges water and resources through access to the grafted root system
- Team measured water in the stump and surrounding trees from same species
- The findings suggest a shift from the perception of trees as individuals towards understanding forest ecosystems as ‘superorganisms’
- Root grafts can form once a tree recognises that a nearby root tissue, although genetically different, is similar enough to allow for the exchange of resources
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.
A ‘dead’ tree trunk in a New Zealand woodland keeps itself alive by holding onto the roots of its neighbouring trees, researchers have said. The stump exchanges water and resources through the grafted root system of its surrounding trees which, apparently, keeps it alive
WHY WOULD A LIVE TREE KEEP A ‘DEAD’ ONE ALIVE?
One explanation, Leuzinger says, is that the root grafts formed before one of the trees lost its leaves and became a stump.
The grafted roots expand the root systems of the trees, allowing them to access more resources such as water and nutrients, as well as increase the stability of the trees on the steep forest slope.
As one of the trees stops providing carbohydrates, this may go unnoticed and thus allow the ‘pensioner’ to continue its life on the backs of surrounding, intact trees.
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.
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
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’.