Plant scientists are calling for a rethink of what a tree is

They’re not just big, woody creatures, say plant scientists, who want the planet’s trees to be rearranged into much more elaborate and complex organisms amid the challenges of climate change.

Environmental scientists have long predicted that living organisms will be challenged by global warming and the ecological shifts that result, and that trees in particular will be threatened.

They are long-lived and, unlike animals, which can move to new territory, have a fixed position, so adaptation to the changing climate must largely take place where they are.

Yet there is an article published by New Zealand, Australian and American plant scientists in the journal Trends in plant science, suggests that tree species can withstand climate pressures through their rapidly changing microbiome. This tree microbiome consists of a wide range of microorganisms that live in and on their tissues.

“Climate change has happened before, but the pace we are experiencing now is unprecedented in recent history,” said Sarah Addison, a tree root microbiome researcher at Western Sydney University and New Zealand forest research organization Scion.

“Because trees live long and cannot migrate easily, current plants may end up in an unsuitable climate. We need new tools to support trees that will face changes in the future.”

Over time, the relationship between host trees and microbial life can change in ways that promote adaptation to new conditions. Creating suitable microbial environments can also help.

Addison and her co-authors suggest that trees should no longer be viewed as separate entities, but rather as ‘holobionts’ – systems of both the tree and the symbiotic culture of bacteria, viruses, archaea, fungi and other microbes. That’s because the holobiont provides a more robust model to study climate change and its impact on trees and the environment.

“We need to shift our perspective from ‘trees and their microbiomes’ to a perspective of a single, co-evolved entity that interacts dynamically within and as part of the environment,” says Addison.

This ‘neo-Darwinian’ approach to evolution requires what the authors describe as a reinterpretation of a tree “from a single sessile organism with a limited capacity to respond to the environment, to a node within a holobiont network that interacts with other nodes ( trees) and interact collectively with the environment.

“Understanding the coevolution of trees and microbiomes linked to abiotic factors could be an area that creates a better understanding of microbiome assembly and their intricate relationships.

“There remain unexplored questions about what adaptations the plant-microbiome relationship provides to equip the tree for future growth; how the environment influences this mutualistic relationship for long-lived tree species; and how these microbiomes are transmitted from generation to generation.”