Break Down: How Wood Decay Drives Carbon Cycle

Biology’s Amy Zanne and a team of researchers are linking wood decomposition rates among fungi to a better understanding of the global carbon cycle and its effect on climate change.

fungi decay measurements
The rate of fungi decay experiment conducted by Associate Professor of Biology Amy Zanne and a team of researchers is shedding light on the global carbon cycle.
June 09, 2020

Through a combination of lab and field experiments, Associate Professor of Biology Amy Zanne and a team of researchers have developed a better understanding of the factors accounting for different wood decomposition rates among fungi. Their findings, published in the Proceedings of the National Academy of Sciences, reveal how deciphering fungal trait variation can improve the predictive ability of early and mid-stage wood decay, a key driver of the global carbon cycle.

“Fungi are largely hidden players. We know they are critical for cycling carbon but it has been difficult to determine the effects of different decomposers in causing fast or slow decomposition,” Zanne said. ”As we identify who fungal decomposers are in rotting logs and what allows a particular species to affect these rates, we can better predict carbon cycling around the globe under current and future climates.”

As the main decomposers of litter and wood, fungi play an important role in the global carbon cycle—the process that helps regulate the planet's global temperature and climate by controlling the amount of carbon dioxide in the atmosphere. While current Earth system models represent little of the functional variation in microbial groups, fungi differ greatly in their decomposing ability. Zanne and her fellow researchers set out to find which traits best explain fungal decomposition ability to help improve the current models.

They found that the hyphal extension rate—or fungal growth rate—is the strongest single predictor of fungal-mediated wood decomposition. The decomposing ability of fungi varies along a spectrum: Slow-growing, stress-tolerant fungi are poor decomposers; fast-growing, highly competitive fungi have fast decomposition rates. The slow growing fungi are more likely to exist in drier forests with high precipitation seasonality. In contrast, the fast-growing fungi tend to be found in more favorable environments and decompose wood more quickly, regardless of the local microclimate.

“Fungi differ massively in how quickly they decompose wood, releasing carbon back into the ecosystem. Our study identifies different fungal traits that explain this variation, which has great potential to improve predictions of the carbon cycle in forests,” said lead author Nicky Lustenhouwer, a postdoctoral scholar at the University of California, Santa Cruz.

Their findings show that the same processes that determine where a fungus lives—its ability to displace other fungi and survive in stressful environments—closely aligns with its decomposition ability. “This connection allows us to translate an ecological mechanism into broad-scale patterns in microbial decomposition rates, helping to address a key uncertainty in earth system models,” said co-author Daniel Maynard, a postdoctoral researcher at Crowther Lab, ETH Zurich.