how pollution and landscaping affect urban fungi


As I walked through a local estate, on one of those steel gray November mornings that have characterized so much this fall, I was interested to see a few late mushrooms growing among the Hebe in a cluster of shrubs.

They were eaten up a lot by slugs but still recognizable as false chanterelles. You may know the real chanterelle; the ‘chanterelle’. With its beautiful egg yolk and apricot scent, it is one of the most popular edible mushrooms.

False chanterelle is unrelated but gets its name from its superficial similarities. It is also yellow, although darker and more orange in tone, and both mushrooms have what are known as “decurrent” gills, which descend partly along the stem to give them a tree-like appearance. funnel. The false chanterelle also has, in my opinion, a rather pleasant and slightly fragrant smell, but not as marked as the chanterelle.

According to my beloved Roger Phillips book on mushrooms, false chanterelle is “said to be edible but is known to cause alarming symptoms, such as hallucinations, in some cases.” I have, in the spirit of science, tried it only once, and with no ill effects, but I have always refrained from giving it to my family.

Since it is primarily a fungus of the coniferous woods, the surprise was not only that it grew in November, but that it grew on a border of urban shrubs. The answer was quite simple, as it grew from a mulch of wood chips, presumably from pine or other softwood.

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The growth in the horticultural use of wood chips has brought a number of new species to our cities and I have fond memories of many times collecting the deliciously edible morel, a highly prized mushroom that resembles a brain on a stick. I not only found it in parks and gardens, but once in an Islington school playground where I made it for the staff. Due to the increasing importation of exotic plants, these woodchip fungi even include species that are completely new to the country. The ‘redlead roundhead’, for example, a very distinctive species with a bright red-orange hat, arrived here from New Zealand, and I remember once finding it in a large pot inside the branch. of Finsbury Park from City and Islington College.

Larger mushrooms like these get their nutrients through one of three methods. Fungi on wood chips clearly act as saprophytes; feeding on and breaking down non-living organic matter.

Fungi can also function as parasites, but the majority of them feed by a process of symbiosis, sending networks of subterranean wires that penetrate the roots of trees and then participate in mutual sharing of nutrients.

I mention all of this because it affects the type of fungi you might encounter in an urban area. Trees and shrubs use their relationship with fungi to help break down organic nitrogen-containing compounds, which might otherwise be difficult to obtain. In cities like ours, however, there is a very high level of nitrogen deposition in the soil from car exhaust fumes and other sources. This means that urban trees allocate more nitrogen for growth – in leaves and shoots – and have to store less in their roots. Which in turn means that the fungi have less nitrogen to feed themselves and that we see less fungi forming their fruiting bodies.

There is another estate near my house, bordered by a lawn where I surreptitiously pick up shaggy ink plugs every year. They first appeared, in large quantities, when the area was backfilled.

Year by year, however, they have decreased. I suspect that having arrived with the imported soil, they fell prey to this nitrogen problem and are unable to form a mycorrhizal relationship with the surrounding trees.

What he illustrates is the fabulous and fragile network of living beings and the complexity of the invisible relationships between them. It also demonstrates the unforeseen environmental impacts of our actions and how far we must go if we are to establish a truly biodiverse city. Frankly if things get worse maybe I should start eating the fake chanterelles.


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