vendredi 30 mars 2018

126- The soil -5- About the importance of fungi


How fungi helped create life as we know it

Under the title "How fungi helped create life as we know it", a team of scientists from the University of Leeds (United Kingdom) published in December 2017, an exciting article on the role of fungi in the development of our planet.

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I found this article on a Facebook page that I like very much and from time to time I use publications, "Sols Vivant Québec" (Living Soils Quebec). I recommend that anyone interested in these issues follow it. The publications are usually in French or English.
This remark is also valid for my previous article on GMOs, part of an exchange on the French Facebook page "Agroécologie, agronomie et actualité agricole" (Agroecology, agronomy and agricultural actuality).

Here is the article, in its entirety.

“Today our world is visually dominated by animals and plants, but this world would not have been possible without fungi, say University of Leeds scientists.

Researchers have carried out experiments where plants and fungi are grown in atmospheres resembling the ancient Earth and, by incorporating their results into computer models, have shown that fungi were essential in the creation of an oxygen-rich atmosphere.

Humans and other mammals require high levels of oxygen to function, and it is generally thought that the planet developed an oxygen-rich atmosphere around 500 to 400 million years ago, as carbon dioxide was gradually photosynthesised by the first land plants.

The research team: Dr. Katie Field from the Centre for Plant Sciences, Dr. Sarah Batterman from the School of Geography and Dr. Benjamin Mills from the School of Earth and Environment, show that fungi played a critical part in establishing the breathable atmosphere on Earth by "mining" the nutrient phosphorus from rocks and transferring it to plants to power photosynthesis.

The new research shows that the amount of phosphorus transferred could have been very large under the ancient atmospheric conditions, and, using an "Earth system" computer model, the team show that fungi had the power to dramatically alter the ancient atmosphere.

Vital relationship

While many modern plants can gather their nutrients direct from soils through their roots, the earliest forms of plant life faced an entirely different climate, did not have roots and were non-vascular, meaning they could not hold water or move it around their system.

The "soil" they came into contact with was a mineral product lacking in organic matter, which is why their relationships with fungi were so important.

Fungi have the ability to extract minerals from the rocks they grow on through a process known as biological weathering. The fungi express organic acids which help to dissolve the rocks and mineral grains they grow across.

By extracting these minerals and passing them on to plants to aid the plants' growth, the fungi in return received the carbon the plants produced as they photosynthesised carbon dioxide from the atmosphere.

Gas exchange

Lab experiments undertaken by the Leeds team have shown that different ancient fungi, which still exist today, conducted these exchanges at different rates, which influenced the varied speeds at which plants produced oxygen.

In turn this affected the speed at which the atmosphere changed from being much more rich in carbon dioxide to becoming similar to the air we breathe today.

Dr. Field said: "We used a computer model to simulate what might have happened to the climate throughout the Palaeozoic era if the different types of early plant-fungal symbioses were included in the global phosphorus and carbon cycles.

"We found the effect was potentially dramatic, with the differences in plant-fungal carbon-for-nutrient exchange greatly altering Earth's climate through plant-powered drawdown of CO2 for photosynthesis, substantially changing the timing of the rise of oxygen in the atmosphere."

Dr. Mills said: "Photosynthesis by land plants is ultimately responsible for about half of the oxygen generation on Earth, and requires phosphorus, but we currently have a poor understanding of how the global supply of this nutrient to plants works.

"The results of including data on fungal interactions present a significant advance in our understanding of the Earth's early development. Our work clearly shows the importance of fungi in the creation of an oxygenated atmosphere."

Dr. Batterman added: "Our study shows tiny organisms such as fungi can have major effects on the global environment. Our critical finding was that the nature of the relationship between fungi and plants could have transformed the atmospheric carbon dioxide, oxygen and ultimately global climate in very different ways, depending on the type of fungi present."

The full paper, "Nutrient acquisition by symbiotic fungi governs Palaeozoic climate transition," is published in Philosophical Transactions of the Royal Society B.

This work shows the critical importance of soil fungi, these microscopic organisms, still poorly known by scientists, little known to professionals and totally unknown to the general public.

Our farming practices have very direct consequences for their lives and their actions.
They must continue to evolve and take into account, each day greater, their environmental consequences.

We can talk about tillage, which acts directly on soils life and on the biodiversity they shelter. All production techniques aimed at reducing plowing are favorable. And whatever some people think, the use of herbicides is not at all an ecological nonsense. It is almost always preferable to use an adjusted dose of a judiciously placed herbicide, rather than systematic plowing that is sometimes extremely degrading.

We can also talk about chemical fertilizers, which can act against soils. But we must not forget that certain natural fertilizers, such as liquid or fresh manure, also have detrimental effects. Again, it is not the fertilization itself that is problematic, it is usually the dosage and periodicity of inputs that can cause environmental damage. As almost always, it's a question of balance.

Finally, we can talk about pesticides, whose excessive concentration also affects the life of soils. It should be noted here that the worst pesticides are not only synthetic pesticides. I mean that the way pesticides are produced has no relation with their dangerousness to the life of soils. It is their persistence, their slowness to decomposition, and of course their direct toxicity, which will have an undesirable effect. Some synthetic pesticides are harmful, but also some pesticides authorized in organic farming. Thus the worst pesticide in relation to life of soils is a fungicide very widely used in organic, as in conventional farming, copper, which does not break down and accumulates inexorably.

Our soils are the basis of our present and especially of our food future. We must all be aware of their importance and especially their fragility.

But let's stop placing everything on the ideological plan. Organic is not an end in itself. This is one of the ways that will allow preservation and even restoration of degraded soils. But it is not the only way. We can talk about conservation agriculture and integrated production.
Agroecology, as it is currently being developed in France thanks to an ambitious political and societal project, can reconcile in a common objective, most forms of agriculture.
Provided that ideology does not prevail over reason and pragmatism.


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