Certain landscapes show resistance to the withering away of ashes



Biosecurity concern is about to become increasingly essential to prevent invasive alien pathogens from entering UK habitats

A review means that certain types of environments help block the development of the ash dieback disease, which threatens thousands upon thousands of ash trees in the UK.

Landscapes with hedges and woods made from a number of trees are more resistant to the pathogen than areas with predominant ash.

The deadly fungus had been present in Europe long before it arrived in the UK in 2012.

The results were published in the Journal of Ecology.

Ash wood is one of the UK’s most abundant tree species. And it is estimated that the withering away of ashes could cost the British economic system billions of pounds.

The fungus that causes the withering of the ashes causes the lack of leaves and leads to the death of parts of the tree.

Researchers examined the disease’s progress in a space in northeastern France, monitoring the preliminary levels of its spread throughout 2012, about two years after the mushroom’s first record in space.

They then reassessed the identical space between 2016 and 2018 as soon as the disease had the opportunity to settle in the countryside.

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Media captionHow does the decline of ashes develop?

Benoit Marcais, director of analysis at the French National Institute of Agriculture, Food and the Environment (INRAE) defined that understanding how the panorama affected the course and severity of the disease trees was essential from a scientific and sensible point of view.

“(The arrival of the dieback of ashes near my laboratory in a diverse landscape, with ashes in contrasting situations, offered a good opportunity to progress in the matter,” he said.

Reborn from the ashes

Called because the common or European ash, the tree – the only native species of ash in the UK – is scientifically often known as Fraxinus excelsior.

In the UK, it is the third most abundant hardwood species (after oak and birch), masking 129,000 hectares of wood.

Ash is an extremely essential species in all hedgerows in the UK and accounts for around 10% of the country’s 123 million “non-timber” woods.

The dieback of ashes again arrived on the British coast in March 2012, when it was discovered on ash wood in a nursery. In October of this year, the worst fears of tree lovers had been realized when it was discovered in the wild, inside a Norfolk forest.

Since then, the disease has spread to all parts of the UK. According to a current estimate, the decline of the ashes would cost the British economic system 15 billion pounds sterling. This estimate results from the price of deforestation of dead and dying wood and consists of misplaced benefits provided by the wood; by purifying water and air and locking down carbon from the atmosphere.

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Peter Stenzel / Flickr


There had been fears that ash, as a species, might have been wiped from our landscapes due to dieback

Dr. Marcais and his staff monitored a community of plots in northeastern France, looking for evidence of dieback on the wood, in addition to the presence of the fungus that causes the disease – Hymenoscyphus fraxineus – in forest litter (combination of leaves and different natural materials on the forest floor).

He informed BBC News that the microorganism deployed quickly and efficiently throughout the examination space within a number of years of recording.

Manna of science?

The examination revealed shocking results, as Dr Marcais defined it: “The withering of the ashes, however, shows a very contrasted gravity according to the environment, remaining soft on the trees in open canopies (hedges, isolated trees ) or on trees in the forest with a mixture of tree species and just a few ashes, ”remarked Dr. Marcais.

However, areas that had excessive density of ash wood, similar to ash wood, showed the results of being severely affected by dieback.

Sick saplings usually show lifeless tops and appearance shoots. Lesions are sometimes found at the base of lifeless looking shoots. Meanwhile, lesions on the department or stem can cause the foliage above to wilt. The disease affects mature wood by killing new developments.

Dr. Marcais mentioned that it was shocking to document an excessive amount of the fungal pathogen in the forest litter, but that it looked like a distinction between areas with excessive density of ash wood and populated areas, such as hedges, with a reduced density of wood.

Image copyright
Forestry Commission


Young and vulnerable ash wood quickly succumbs to the pathogen

Reassuringly, the results of the review seemed to support the growing scientific view that the disease will not erase the ash wood from the panorama in Europe.

But he added: “The work identifies situations where the ashes are little affected by the withering away of the ashes.

“In particular, we establish that under a safe ash density, the disease will remain mild. “

The results will be welcomed by foresters and policy makers, who have been “keen to have additional ash density thresholds to improve administration, as ash is already common in mixed stands”.

However, the silver lining provided by this study still surrounds a very dark cloud, which tells us that the forests of pure ash are “very badly affected by the disease”.


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