Climbing kauri in the name of science

New Zealand's ancient kauri trees are helping scientists better understand how our forests might fare in droughts as the planet warms.

The University of Auckland's Dr Cate Macinnis-Ng and her team have been studying how kauri adapt to climate change by measuring the carbon uptake and water consumption of the trees.

Kauri remain the longest-lived and largest of New Zealand's tree species, and to last for 1500 years or more, they need to be resilient.

Yet, by measuring their year to year growth rates, scientists have been able to discover that these forest giants are responsive to climate fluctuations.

These environmental changes can be measured in the size of the trees' annual rings, and researchers have found this pattern correlates well with the El Nino Southern Oscillation, or ENSO, cycle.

The team are also interested in how drought - something increasing killing trees around the world - might have an impact.

For plants generally, climate change could cause some plants shift into higher elevations as temperatures changed, or threaten their survival with increasingly severe and frequent droughts.

To study the effect of drought on kauri, Macinnis-Ng and her team climb high into kauri canopies, where they insert probes to measure sap flow.

They use this data to calculate the amount of water used by the trees.

Kauri appear to have shallow root systems, potentially making them more susceptible to droughts than trees with deep roots and access to deeper water reservoirs.

While kauri trees can tolerate our mild droughts relatively well, whether these trees will survive longer droughts was unknown, Macinnis-Ng said.

"We don't know what the limits are. When will mortality happen and how often will it be?"

To answer that question, the researchers are capturing rainfall before it hits the forest floor, to see how the kauri trees respond to the lack of water.

This would inform how Kauri forests were cared for, if severe droughts came as a result of climate change.

The research comes as kauri are under growing threat from tree-killing dieback disease, which has spread across Auckland, Coromandel and Northland.