Trees that resist wildfires

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More than 20,000 hectares of forest were charred. But in the middle of the devastation, a group of cypresses was still standing tall and green.

When a fire swept through an experimental plot in Andilla, in the Spanish province of Valencia in 2012, it gave researchers the perfect opportunity.

The plot, which was part of CypFire, a project financed by the European Union, was established during the 1980s to test the resistance of more than 50 varieties of Mediterranean cypress to a pathogenic fungus.

After the fire event of 2012, it also provided further anecdotal evidence of the peculiar resilience of the species in the face of fire.

Botanist Bernabé Moya and his brother, environmental engineer José Moya, both from the department of monumental trees in Valencia, had been involved in the project for several years.

“On our way to what we knew would be a Dante-esque scene during that tragic summer, we felt deep sadness at the thought of losing a plot of such value to the conservation of biodiversity,” Bernabé Moya told BBC Mundo.

“But we had hope that perhaps some of the cypresses had survived.”

“When we got there we saw that all the common oaks, holm oaks, pines and junipers had completely burnt. But only 1.27% of the Mediterranean cypresses had ignited.”

The fire in Valencia led to a three-year international study to find the reasons behind the resilience of the species and discover if it could provide buffer zones to hinder or prevent the rapid spread of wildfires…The study was published in this month’s issue of the Journal of Environmental Management…

The lab tests were performed by scientists from the Forest Fire Laboratory at INIA-CIFOR in Spain, and the Institute for Sustainable Plant Protection in Florence, Italy…

A crucial difference of the new tests is that they were performed not only on dead dry samples but also on live fine twigs with leaves taken from different crown heights, which revealed one of the key traits of the species: its high water content.

“We observed that the Mediterranean cypress, because of the particular structure of its leaves, is able to maintain a high water content even in situations of extreme heat and drought, and this is a very favourable starting point concerning fire risk,” explains Gianni Della Rocca.

“The cuticle is thick and the stomata are arranged on the inside and protected side of the scale-like leaves and therefore less subject to high water loss”…

The litter on the forest floor, made up of small fragments of leaves, also forms an intricate and compact layer and is slow to decompose.

“The thick and dense litter layer acts as a ‘sponge’ and retains water, and the space for air circulation is reduced”, says Della Rocca.

Plantations with selections of cypresses have already been made in Valencia, Spain, and Siena, Italy, to further research the role of crown structure.

“In a few years, we will have cypress barriers and observations at real scale,” Mr Della Rocca says.

Bravo! RTFA for more details, explanation of factors operating as a fire barrier.

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