Earthquakes can actually help trees grow, new evidence shows

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Once the tremors subside, the strongest evidence of an earthquake is seeing the changing landscapes it left behind. But there are less visible signs of seismic shifts, and not in the geological record.

In a new study, scientists have discovered a surprising consequence of earthquakes, one that remains after the earthquake’s aftershocks: a marked increase in tree growth, driven by earthquake-induced changes in groundwater availability.

It has long been known that earthquakes can change the fortunes of trees, but there is still much we don’t know about how tree growth is affected by earthquakes, and about how much is recorded in the living biological archive of their stumps.

In simple terms, thinking is basically this.

Explains the team of researchers led by first author and hydrologist Christian Mohr from the University of Potsdam in Germany.

“If tree growth is primarily limited by water, trees should, in theory, record hydrologic responses to earthquakes by altering their growth rates.”

To explore these ideas and test their hypothesis that seismic changes in groundwater supplies would promote tree growth when trees are close to valley currents—but impede their growth if they are higher on hillsides—researchers studied Pinus radiata pine trees in Chile, looking to measure the effects of The strong 8.8-magnitude earthquake that severely affected the Mule district in 2010.

Analysis of tree cores taken in 2014, extracted from trees at the valley floor as well as ridge slopes, showed that some trees in the valley experienced increased transient growth after the earthquake, based on tree ring evidence (increased cavity area), and in the ratio of carbon isotopes in Tree cells, giving a cellular-level perspective on aspects of tree health, growth, and water availability.

By contrast, some trees on the slopes did not do well in the same period, which provides some support for the researchers’ hypothesis, although the team acknowledged that the overall impact of the quake was slight, and seemed to only last temporarily – for weeks.

However, as a case study showing how these techniques can be used in the field, the researchers say their results show that seismic subsequent changes in the bore region and carbon isotope ratios can be used to study tree growth and photosynthesis responses to earthquakes.

And with that, we may have a new tool for studying earthquakes in the past.

“Details in wood and isotope anatomy may offer a tree-based approach to palaeontology that goes beyond simply looking at the presentation,” the researchers wrote.

The results are reported in JGR Biogeosciences.

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