Image of the Day: Tree Hugger

Water flows between a dead-looking stump and nearby trees on an alternating schedule.

Nicoletta Lanese
Jul 29, 2019
Researchers tracked water flow through a rotting kauri tree stump using heat-ratio sap flow sensors (pictured), confirming that it was very much alive.

Scientists happened upon an apparently lifeless tree stump while hiking in West Auckland, New Zealand, only to discover it is actually alive. The once robust kauri tree (Agathis australis) shares a fused root system with nearby trees, exchanging resources such as water and carbon, researchers reported July 25 in iScience. Measurements gathered with heat-ratio sap flow sensors revealed that the stump circulates water at night and during rains, swiping resources from its neighbors that have transpired throughout the day. 

The leaf-laden trees may benefit from the relationship by extending the reach of their root system, or the deal may have been struck long ago when the stump still stood tall.

“Possibly we are not really dealing with trees as individuals, but with the forest as a superorganism,” says coauthor Sebastian Leuzinger, an ecologist at the Auckland University of Technology, in an announcement.    

S. Leuzinger, M. Bader, “Tight hydraulic coupling via natural root grafts: are trees superorganisms?” doi:10.1016/j.isci.2019.05.009, iScience, 2019. 

Nicoletta Lanese is an intern at The Scientist. Email her at