Trees have a microbiome inside them? This is both obvious and profound

A few years ago, I spent a pleasant afternoon in an old forest near London by discovering the old trees and their vital importance for biodiversity. My host, the mycologist at the University of Cardiff, Lynne Boddy, told me that once a tree has been living for a few hundred years, the inner part of her trunk begins to rot because she is slowly consumed by mushrooms. This “heart rot” is a natural part of the life cycle of a tree and provides irreplaceable habitat for insects, birds and mammals. But the heart rots itself is dying, because there are no longer enough old trees to pick up the coat when the ancients die. Boddy and others have the mission of saving the rot of the heart as you get young trees prematurely.

It did not come to my mind at the time, but the mushrooms for the heart rot are part of the microbiome of a tree, analogous to the rich assembly of bacteria, archaea, mushrooms, protists and viruses that live inside our body cavities. Indeed, at the time, no one really thought in these terms. But thanks to new revolutionary research in NatureWe now know that trees have a microbiome as diverse and fascinating as ours, and which is probably just as essential to their biology.

We already knew that the areas of trees – trunks, roots, leaves, etc. – host a diversified microbiome. But what the new research shows is that their interiors do too. Inside the wood of each tree on earth are a large number of microorganisms, many of them are new in science.

It is one of those discoveries that is both obvious and deep. Obviously because microbiomas are everywhere in nature, including inside small plants, so why not in trees? Deep because it reveals a microbial ecosystem previously unknown sitting just under our nose, and also because it redesign trees – undoubtedly the most important living beings on earth – in a new light: not as discreet organisms, but as Holobiontes.

In other words, like us, they are a collective entity made up of the host and its microorganisms. And if the microbiomas of the trees are in fact as an integral part of their biology as the case with human microbiomas, we can be able to transform this to our advantage in the battle to save biodiversity and repair the climate.

The researchers behind the new works have sampered wood, branches and roots of 150 living trees representing 16 species in the forests of the northeast of the United States. They did what they call a microbial census and found that wood inside a tree hosts a large number of microorganisms, included not only mushrooms for heart rot, but also many other microorganisms, including other mushrooms, bacteria and archaea, some of which live only inside the trees. In addition, each tree species houses a distinct microbiome inside.

Or do these two microbiomas. The tree trunks are made up of two different types of wood, exterior sapwood and inner heart wood. The sapwood is alive and its main function is to drive water from the roots to the leaves; Heart wood is dead and mainly provides structural support (this is the part finally eaten away by heart rot). The researchers found that microbial communities in both types of wood are clearly different from each other.

Even if they have sampled only a small number of species, it is likely that all the trees, everywhere, host these microbiomas in their wood. The 16 species of their study represent 11 genres, all with global distribution.

What do the microbes do there? For the moment, we do not know, but the researchers say that they are probably playing a role in supporting the health of trees and that of the larger forest. They probably also contribute to some of the critical ecosystem services that trees provide, as habitats for other plants and animals, as clean water producers and as a carbon storage. Wood in the trees in the world contains approximately 600 carbon gigatons, says the new document, around 60 years of current global emissions. They could hold more and have a chance to limit global warming to 2 ° C above pre-industrial levels, we need healthy and expanding forests. A more in -depth understanding of the microbiomas of the trees could help to deliver this, say the researchers.

This is also more generally true. Microorganisms are often neglected elements of biodiversity, but they are the basic stone of global ecosystems. They are the main decomposers of organic matter and keep critical biogeochemical cycles that turn, providing the biosphere of carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. They also form symbiosis with the vast majority of plant species. It is not for nothing that they were called the planet’s survival system. However, there are disturbing signs that the Earth’s microbiome is in decline.

It is too early to say if this is also true for trees microbiobs. But now we know that they have one, we must make sure they keep it.