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Tree hydraulics and water relations : Why trees die as a result of drought

Phys.org/news (Apr 13, 2021)

Titre : Tree hydraulics and water relations : Why trees die as a result of drought

When trees die during a period of drought, they die of thirst. Researchers from the University of Basel have demonstrated in a field study that a rapid collapse in the hydraulic system is responsible for tree death. And they found out that the trees possibly die more rapidly than previously thought.

Phys.org/news (Apr 13, 2021)

Présentation
The heatwave of summer 2018 was an exceptional situation—both for nature and for research. Although admittedly hard on our native woods, it also presented an opportunity for researchers at the University of Basel to closely study the reaction of trees to this weather phenomenon.

The research group led by Professor Ansgar Kahmen had already set up a research area in the Basel-Landschaft municipality of Hölstein the previous year. Their aim was to study the tree canopy 30 meters above ground using a crane to determine how native tree species such as the Norway spruce respond to climate change.

Arend emphasizes that the observation that trees suffer during drought is not new. What is much more important, he says, is to understand the processes that lead to this tree death, and this is exactly what the researchers have achieved in the study published in the scientific journal PNAS. "This is the only way for us to ensure better modeling processes in future," explains Arend.

The study also made a surprising finding : "The hydraulic system collapses extremely quickly," he says. The researchers assume that this critical point is reached when a large proportion of the roots in the drying soil lose contact with the soil moisture. "Forecasts are very difficult, because it is not a slow, linear process, but one that happens very suddenly, with the system of water uptake and transport failing in the space of just a few days."

The new results diverge from the previous mortality threshold values identified in the lab, which means that the hydraulic system of a tree collapses much sooner than previously thought. This happens because dehydration does not progress linearly and the tree cannot recover from the hydraulic collapse, and dies as a result.

Source  : University of Basel

Annonce (Phys.org/news)

Page publiée le 4 juillet 2021