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Fertilization reshapes the tree-fungi relationship in boreal forests

Fertilization reshapes tree-fungus relationship in boreal forest

Fertilization promotes plant growth, but alters the plant’s interaction with their mycorrhizal fungal partners. Credit: Dalibor Perina, Unsplash

How do nutritional changes affect the interaction between trees and soil microorganisms? This has long been a black box, but a new study has shed light on this cryptic association. It shows that increased soil nutrition alters the communication between trees and their associated fungi, thereby restructuring the root-associated fungal community with major consequences for the forest carbon cycle.

The study was published today in Proceedings of the National Academy of Sciences† Researchers from the Umeå Plant Science Center, a collaboration between the Swedish University of Agricultural Sciences and Umeå University, led the study and were supported by Science for Life Laboratory researchers from Stockholm University and Uppsala University.

Advances in sequencing techniques have made it possible to capture the dynamics of how tree roots and their fungal partners interact. The researchers from the Swedish University of Agricultural Sciences, Umeå University and Science for Life Laboratory compared a forest that was continuously fertilized for 25 years with a non-fertilized forest. They analyzed gene activity in tree roots and in more than 350 fungal species over the course of a growing season and revealed that the fertilized trees changed their communication strategy and became more hostile to their fungal partners. As a result, the fungal community shifted from dominated by specialist to more versatile species.

“In nutrient-poor boreal forests, trees depend on root-associated myccorhyzal fungi for their nutrient supply and maintain this partnership through the exchange of valuable sugars,” said Simon Law, lead author of the study and former postdoctoral fellow in Vaughan Haast’s group. the University of Amsterdam. Umeå Plant Science Center. “Soil fertilization disrupts this sensitive trade relationship, causing trees to divert these sugars to their own growth and defense, with profound implications for the fungal community.”

Stress-tolerant fungi are promoted in fertilized soils

The researchers showed that fertilized trees reduce the activity of genes encoding the information for sugar-exporting proteins, while enhancing defense processes. The specialized myccorhyzal fungi that rely heavily on the carbonaceous sugars from the trees were hit the hardest. By ramping up their defense processes, the plants made root colonization by these specialized fungi even more difficult and became less abundant.

In contrast, metabolically versatile fungal species that were less dependent on the trees in the fertilized forests thrived. These myccorhyzal fungi are characterized by dark-colored, resilient cell walls that make the fungi more resistant to stress, but also allow the cell walls to break down more slowly. This shift in the fungal community also affects the carbon cycle in the soil, as the specialized fungi play an important role in breaking down plant litter. In other studies, fertilization of the northern coniferous forests has been shown to increase carbon storage, both in the above-ground plant tissues and in the soil. This new study provides insight into the underlying mechanisms of soil storage processes.

“It is well known that fertilization leads to an increase in carbon storage in the above-ground tissues of the trees at the expense of the underground root and fungal network,” explains Vaughan Haast, a professor at the Swedish University of Agricultural Sciences. “But what this study shows is the complexity of the communication between the tree and its associated fungal community — and it highlights the importance of the tree’s voice in that interaction.”

Dietary Changes Affect Carbon Cycles in Boreal Forests

The conifer-dominated boreal forest encircles the Northern Hemisphere and contains the largest terrestrial carbon store on Earth, which may play a critical role in mitigating climate change. Warming temperatures will increase the decomposition of dead material in the soil and thus increase the nutrient cycle. This affects the nutritional status of the trees and their associated fungal partners.

The researchers show that the complex relationship between trees and their associated microorganisms needs to be better understood to improve predictive models of how changing environmental conditions affect the carbon and nutrient cycle in boreal forests.

Starting point for many more studies

“The relationship between the different organisms in the soil is hugely complex and has been largely inaccessible. The sequencing approach we’ve used allows us to examine these complex interactions at the molecular level, telling us who’s there and what they’re doing.” do,” said Nathaniel Street, the study’s second corresponding author and associate professor at Umeå University. “The approach we took in this study opens up many new possibilities, and we think in the long run it will allow us to better understand the functional mechanisms driving ecosystem dynamics.”

The vast amount of data the researchers have collected in their research on plant roots and soil microorganisms is made public through an online tool, the Boreal Rhizospheric Atlas, hosted by the Science for Life Laboratory. Researchers have free access to this tool and can explore the data further. The future plan is to include data from additional studies in the tool to shed more light on the complex relationship between plants and soil microorganisms.

Fungi: The Missing Link in Tree Planting Schedules

More information:
Simon R. Law et al, Metatranscriptomics records dynamic shifts in mycorrhizal coordination in boreal forests, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2118852119

Provided by Umea University

Quote: Fertilization reshapes the tree-fungal relationship in boreal forests (2022, June 22) Retrieved June 22, 2022 from https://phys.org/news/2022-06-fertilization-reshapes-tree-fungi-relationship-boreal.html

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