2023-08-25 18:55:58
The panther amenite, the lemon strip fungus, the fringe amenite, the common witch bolete, the hare’s foot, the sticky coral fungus and the common porcini mushroom. The forest floor seemed to be lulled to sleep for a while, but following a few soaking wet weeks there is plenty of life once more. In all shapes and sizes, the mushroom caps bounce above their flexible stems.
Anyone who went out in recent weeks to see the cheerfully colored fungi might not believe their luck. So is Martijn Oud of the Dutch Mycological Association. “Last Sunday I went out and found, really, over a hundred red net boletes. The red net bolete is actually a very rare species. It was first observed 25 years ago. Now the species has grown into what I saw on Sunday. It’s really absurd.”
Where mushrooms are normally a synonym for autumn, this year the summer period was a fungus mecca. It is the result, it seems, of a few weeks of downpours that finally replaced the exceptionally dry spring and summer.
Rainy July months
Climate change causes a rise in temperature and makes weather extremes such as drought and heavy rainfall much more common. For plants, we know that climate change is causing an earlier growing season and for most animals it is known that the optimal habitat is slowly moving north. For both plants and animals, heat and drought lead to increased mortality. For fungi, the story seems a lot less clear.
Thomas Kuyper, emeritus professor of mycology at Wageningen University and Research, acknowledges that it was a dry spring and a wet summer. “But historically it is not very special. We have been used to dry summers lately. Rainy July months used to be no exception. And when you have that much rain, it is to be expected that the mushrooms will come up.”
That does not immediately mean that autumn has started earlier, on the contrary. The mushrooms that mycologist Oud encountered during his Sunday walk are typical summer varieties. Many of these are boletes, a mushroom genus that includes, for example, porcini mushrooms. These fleshy mushrooms are easy to recognize by the tubes under the cap, where other mushrooms often have pictures.
Barter
A mushroom is the above-ground part of a fungus. The largest part is underground and is called the mycelium (also known as mycelium). The underground part of boletes becomes intertwined with the roots of trees and enters into a partnership: a mycorrhiza. A mushroom supplies nutrients and water to the tree and grabs some sugar in return.
“The mycorrhiza-formers dive into the ground and only emerge when the sap flow from trees gets going once more,” Oud continues. In the wet weeks in July, the boletes and other mycorrhizing fungi were able to tap sugars from trees once more. Good timing, because at the end of the growing season a tree stores a lot of sugar in the roots. After all, he no longer needs it in the leaves. Mushrooms use the sugar to build new tissue. The result: a mushroom that allows them to spread their spores.
Rising and shrinking
Rise like mushrooms following a rainy day. This old Dutch saying proved its truth this summer. Although the weather is not decisive for all mushrooms. Some mushrooms need the nutrients from dead leaves, says Kuyper. “The best time is of course autumn.” The so-called saprotrophic mushrooms clean up the dead plant material. The oyster mushroom, with dead wood as a food source, is also such a cleaner. “Because wood retains moisture relatively well, you can find these mushrooms as early as March. They do follow a seasonal pattern, but are much less fluctuating in size and growth habit than mushrooms on the ground.”
The close cooperation between trees and boletes also entails risks. If the sap flow stops once more due to a dry period, the mushrooms that have just been created are likely to shrivel up. “A number of mushrooms will dry out before they have shed their ripe spores,” explains Kuyper. “Then they have relatively few spores to spread and it seems like a lost year. But because the underground organism can live for decades, that does not necessarily have to be a problem.” Other mushrooms escape drought through a very short life cycle and have turned rapid shrivelling into an art. “You can almost only see small ink fungi and some broken stems when it dews in the morning. At the end of the day they are already gone.”
Not the climate, but the environment
ClimFun is a large European research project that has investigated the effect of climate change on mushrooms. Kuyper was one of the researchers. “It turned out that the mushroom season is much longer. Nowadays you can find many more mushrooms in November than sixty years ago. Some summer species that used to mushroom once, now sometimes do so twice. Once in the summer and once in the fall.
Drought, heavy rainfall, temperature rise. It doesn’t seem to bother fungi. The environment is much more important, says Oud, referring to the biggest divisive issue of recent years: nitrogen. “When I was little I sat on the back of my eldest brother’s bicycle. It was the early fifties. Then the woods were completely full of fine-scaly boletes. The species used to grow in pine forests by the thousands and has now disappeared everywhere. If you go to the same pine forests, you won’t find anything anymore, because the soil under the pine forests has acidified.”
All colors of the rainbow
“I’m not too worried regarding climate change. Mushrooms always seem to find a way,” Oud explains delightedly. The mycologist keeps a close eye on mushroom sightings in the Netherlands and has seen the arrival of up to six new species per month in recent years. Especially species that used to occur further south are now doing well in the Netherlands. Other species are similarly slowly disappearing to more northerly areas.
“Compared to plants, mushrooms have a larger distribution area and greater tolerance to temperature differences. Their tracks can travel a greater distance and move faster to suitable places,” says Kuyper. For example, the beloved summer truffle is already growing in some places in the Netherlands. Other species will certainly follow in the coming years.
This is good news for a mushroom lover like Oud. “Those southern boletes are very beautiful. It’s not normal: they are all the colors of the rainbow. Scarlet is in it, yellow, slate gray, blood red. They have beautiful networks on the stem. What more do you want from the forest?”
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Prescription
Baby potatoes with asparagus, oyster mushroom and pangrattato
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