Humans are social creatures; we thrive when connected to strong social networks. Turns out, trees aren’t all that different.
A new study from researchers at the Universities of Alberta and British Columbia is the first to show that adult trees grow faster when linked to other trees by networks of soil fungi.
Just like human support networks, these fungal networks allow trees to share resources and even send messages between neighbours. As well as drawing resources for themselves, the fungi act as a sort of highway. These links allow water, nutrients and chemical messengers, such as insect defence signals, to flow back and forth between trees. In hard times, the network supports those most in need.
These ectomycorrhizal fungal networks are known to support the growth of seedlings. But until now, relatively little was known about their impact on adult trees.
As a starting point, the team used a 2008 survey that mapped Rhizopogon vesiculosus and Rhizopogon vinicolor fungal connections between trees in 10×10 m plots near Kamloops, British Columbia. From this, they used core samples to construct continuous growth records for 350 adult Douglas fir trees.
The rings from these cores showed that annual growth was related to both tree-to-tree connections, and the number of unique fungi associated with a tree.
“We found that the more connected an adult tree is, the more it has significant growth advantages, which means the network could really influence large-scale important interactions in the forest, like carbon storage,” explains Joseph Birch, who led the study for his PhD thesis in the University of Alberta Faculty of Agricultural, Life & Environmental Sciences.
“If you have this network that is helping trees grow faster, that helps sequester more carbon year after year.”
The researchers suggest that these connections may dramatically improve growth and promote survival in extreme conditions such as drought.
“These networks may help them grow more steadily even as conditions become more stressful, and could even help buffer trees against death,” Birch explains.
Older trees contribute more to the surrounding forest in terms of capturing carbon and stabilizing soil erosion. So understanding how and why they thrive is important.
Birch hopes his findings inspire further research in different kinds of forests in other geographical areas. While connections change over time, more detailed knowledge about fungal networks could help reforestation efforts and resistance to climate change.