24-Jun-2018: Air pollution causes malnutrition in trees

Air pollution from farms, diesel engines and factories is leaving trees malnourished by killing off the fungi that feed them nutrients.

Trees across Britain and Europe have recently shown signs of illness, including discoloured leaves and sparse growth of leaves.

Toxic levels of nitrogen in rainwater also appear to be breaking up ancient fungal highways, known as the "wood-wide web," through which trees exchange essential compounds.

Between 15 and 90 percent of forests in the UK are thought to be stricken by pollutants that trickle down into the soil and disrupt the communities of microbes gathered around tree roots.

Now it has been found that the culprit is air pollution -- causing "malnutrition" in trees by harming beneficial fungi in the roots.

The roots rely on the mycorrhizal fungi to extract soil nutrients such as nitrogen, phosphorus and potassium. In return the roots pass carbon to the fungi, a mutually beneficial relationship crucial to the tree's health.

But tougher fungi, which return fewer nutrients, now thrive instead -- making the tree suffer from a lack of nutrition. As a result, researchers say legal limits on air pollution are set too high and need to be reduced.