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They solve the enigma of cypress trees that resist fires

They solve the enigma of cypress trees that resist fires


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More than 20,000 hectares of calcined forest. And in the midst of the devastation, a group of upright green cypress trees.

When fire destroyed an experimental plantation in Andilla, in the province of Valencia, in 2012, scientists set out to uncover the "mystery" of the cypress trees.

"When we moved to the dantesque scene in that tragic summer of 2012, we were assailed by great sadness and regret. We were shocked by the dimensions of the devastation," botanist Bernabé Moya, who arrived at the scene of the incident with his brother José, graduated in environmental sciences, both from the Department of Monumental Trees of the Diputación de Valencia.

But anecdotes and previous indications pointed to the peculiar resistance of the Mediterranean cypress.

"Observations accumulated over the years gave us hope that some cypress trees had survived."

"Upon arrival, we verified that all the surrounding vegetation formed by holm oaks, oaks, Aleppo pines, Rodenos pines, junipers etc, characteristic of the Mediterranean forest, was completely burned. But only 1.27% of Mediterranean cypresses had ignited".

Bernabé and José Moya are two of the authors of a new study that finally gives answer to the riddle of cypresses, after three years of research by scientists in Spain and Italy.

The study was just published in this month's issue of the journal Journal of Environmental Management.

Flammability tests

The new study demonstrates the resistance of the Mediterranean cypress (Cupressus sempervirens) to fire and its possible application as a fire barrier to the devastating disasters that affect the Mediterranean.

More than 269,000 fires, mostly the product of human activity, were reported between 2006 and 2010 in the region, with more than two million hectares of forest destroyed, according to the FAO.

The international work is the first to use laboratory tests with a variety of techniques not only on dead or dry vegetation, but on living fine green leaves and branches.

The tests were developed in two laboratories considered reference centers in fires and the study of cypress, the laboratory of the Department of Forestry and Management of Forest Systems of INIA-CIFOR in Spain, and the laboratory of the Institute for the Sustainable Protection of Plants, in Florence, Italy, (IPSP-CNR).

"In the past this species was not studied in depth or only a few parameters were used," Gianni de la Rocca, an IPSP researcher and another of the authors of the new study, told BBC Mundo.


Moisture content

The tests on live leaves and branches revealed a key element: its high moisture content (84-96%) during the summer period, which delays its entry into ignition.

"The higher the water content, the plants have greater resistance to flames," explained Bernabé Moya.

Bernabé Moya explained to BBC Mundo that "the ignition time of the living parts of the Mediterranean cypress is between 1.5 and 7 times higher, in laboratory tests, than that of other Mediterranean forest species such as the holm oak, the common juniper and the rodeno pine ".

Furthermore, due to the reduced dimensions of its leaves, "the litter generated by the cypress on the ground is very compact. The air circulation inside it is less than in other species, such as pine needles."

And this dense, compact layer of litter also "acts like a 'sponge' that locks in moisture," according to Della Rocca.

Cup architecture

The scientists used genotypes selected from a variety of Mediterranean cypress, Cupressus sempervirens var. horizontalis, which is resistant to a disease known as "cypress canker" caused by the fungus Seiridium cardinale.

"This pandemic is a very dangerous threat to the cypress. It causes large portions of the crown to die and there are exhudations of resin from the trunk and branches," he explained to BBC Mundo Della Rocca.

Unlike other varieties of Mediterranean cypress, in horizontalis "the branches are inserted into the trunk at angles between 45 and 90 degrees," said Bernabé Moya.

This means that dead vegetation is usually not trapped.

On the other hand, "the shape of the cypress crown is dense and homogeneous, which hinders air circulation, as evidenced by the recognized windbreak function of the Mediterranean cypress in agriculture."

Resins

"The chemical composition of the leaves is formed, in addition to cellulose and lignin as structural elements, by an organic mixture of resins, terpenes, etc., which when released into the atmosphere become part of the Volatile Organic Compounds, VOSs", he explained Bernabé Moya.

In highly resinous species such as pine trees, these substances are crucial in accelerating combustion.

Della Rocca pointed out that "from preliminary tests, we observed that under experimental conditions, in pines the process of gasification, volatilization, of these flammable compounds happens rapidly. The ignition starts from these gases and is then transmitted to the branches and leaves" .

"In the case of cypresses, perhaps flammable compounds gradually gasify during the temperature rise phase that precedes ignition, so they do not participate in the combustion process."

From Patagonia to California

Could the Mediterranean cypress help fight fires in other parts of the world, like Patagonia in Chile and Argentina, or California?

According to Bernabé Moya, the species "has great plasticity."

"It can live in all types of soils except in flooded ones, as well as on poor and degraded substrates, and it grows from sea level to more than 2,000 meters high."

Moya recalls that the species was introduced centuries ago in Latin America where it has adapted to many regions.

"It has no difficulty growing in the temperate and Mediterranean climate zones of California, Chile and Argentina."

"The first thing that should be done is to carry out studies to determine the degree of adaptability and suitability of the different varieties of Mediterranean cypress to local conditions and proceed to establish experimental plots."

First plantations

The European study concludes that plantations with selected varieties of cypress trees could be a new and alternative tool to counteract the risk of forest fires in places with higher risk, such as areas of contact between forests, agricultural areas or inhabited areas, where sources of fire occur. fire more frequently.

As a result of international work, the region

And in Spain, "from the Department of Monumental Trees and together with the Department of Forest Brigades for the prevention of forest fires of the Diputación de Valencia, IMELSA, we will carry out the first plantings of fire barriers of the Ciprés System in the country along this fall, "Moya said.

Another important application of the study, according to the researcher, is that citizens can contribute to increasing the protection of their properties against fire.

"It has to do with aspects related to proper maintenance and cleaning of the hedges and fences of urbanizations and villas, regardless of the species used."

"It is essential to remove all the dry and dead branches, which accumulate inside the hedges, as a result of repeated pruning."

Future generations

The resilience of the Mediterranean cypress shows for Moya that "nature has the answer to many of the problems we face."

But the study also points to the need for urgent action.

For the Spanish botanist, "the vulnerability of vegetation masses to fires is related to the lack of information for the population, support for research and the abandonment of the rural world, a situation that will worsen with climate change" .

Many problems such as desertification, forest fires, the loss of biodiversity and the abandonment of rural areas can be reversed with planting and caring for forests, according to Moya.

"It is urgent that humanity take these problems seriously."

"Fighting fires is everyone's effort. We owe it to the forest and to future generations."

from Tuscany in Italy included the Mediterranean cypress in the list of suitable forest species for use in fighting forest fires.

BBC


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