Fungi in boreal forests are sensitive to climate change

In the expansive and chilly territories of North America, northern Europe, and Russia, a vast expanse of boreal forests stretches as the world’s largest terrestrial ecosystem and the most northerly forest belt. Boreal forests, dominated by a canopy of spruce, pine, and fir, play a crucial role in the Earth’s environmental systems.

Hidden within the green fabric of these trees, alongside the lush layers of ground-covering lichens and mosses, resides a diverse community of fungi. Known as endophytes, these fungi reside within the plant tissues, often establishing symbiotic relationships that are beneficial for their plant hosts.

Living in a fungal world 

Senior author Elizabeth Arnold, a distinguished professor affiliated with multiple departments and institutes at the University of Arizona, emphasizes the integral role of these fungal partners in plant life.

“To be a plant is to live in a fungal world. Endophytic fungi are vital to the health of plants in ways that aren’t yet totally understood, but what we do know from endophytes in general is that they’re very good at protecting plants against disease and helping plants be more resilient to environmental stressors, like heat. They’ve been part of an important revolution in our thinking about plants.”

“Boreal forests are central to our planet’s carbon and water cycles. And our work highlights that they are home to some of the most evolutionarily diverse fungal endophytes in the world – endophytes that are found nowhere else,” she added.

Adaptive strategies of fungi

Motivated by a desire to delve deeper into the adaptive strategies of these fungi within varying microhabitats and their potential responses to climate shifts, Arnold and her team embarked on an adventurous field study in the remote wilderness of northeastern Canada over ten years ago.

The research unveiled a rich diversity within the boreal forest fungi, with species finely tuned to their local environments. This specialization suggests a vulnerability to the rapid climatic changes our planet is experiencing, posing implications for the future well-being of boreal forests and, by extension, global ecological health.

Boreal biome diversity 

“Our collaborative study shed light on the diversity in the boreal biome of newly discovered endophytic fungi and their sensitivity to climate,” said co-lead author Shuzo Oita, who completed his PhD in Arnold’s lab and is now a research scientist at Sumitomo Chemical Co., Ltd. “Endophytes are often overlooked because they occur in healthy plant tissues, but their importance in biodiversity and ecosystems has been revealed recently.”

The expedition to collect these invaluable data was a formidable task, demanding intense fieldwork that ranks among Arnold’s most challenging experiences. In the summer of 2011, the team, equipped with an expert pilot, ventured into areas unreachable by road, covering a vast stretch from southern boreal forests to the fringes of the Arctic tundra.

Complexities of fungal biodiversity 

During their month-long journey, the experts meticulously collected samples, conducted analyses, and traversed nearly 1,500 miles, all while marveling at the natural wonders above, such as the aurora borealis. Their efforts revealed not just the complexities of fungal biodiversity but also its intricate relationship with climate, plant hosts, and the broader ecosystem.

According to Arnold, previous studies have examined the link between biodiversity and latitude, which is frequently used as a proxy for climate. These studies found that life becomes more diverse closer to the equator. For instance, for many groups of organisms, those living in tropical rainforests are more biodiverse than those found in the Arctic tundra. However, when it comes to fungi living in boreal forests, the situation seems to be more complicated.

Broader implications 

“We show that boreal fungal communities don’t necessarily change with climate in the same predictable way as plant communities. Instead, the effect of climate on these fungi is highly dependent on both the fungal species and the host,” said co-lead author Jana U’Ren, who completed her PhD and conducted the laboratory analysis for this study as a postdoctoral scientist with Arnold before moving to Washington State University. “This means that we need to protect plants and their fungal endophytes across the boreal biome, and not just in one location, or we risk losing vital biodiversity and protective fungi in these important forests.”

Therefore, this research highlights the need for a holistic approach to conservation, recognizing the intricate web of interactions that sustain boreal forests. Arnold envisions building on these insights to harness the potential of local endophytes in Arizona, aiming to enhance crop resilience in the face of escalating environmental challenges. 

“Just like boreal forests harbor an unexpected diversity of endophytes, so too do plants here in Arizona. Our next steps are to tap these rich and ancient endophytes as tools for helping plants thrive. Ultimately, we hope that by understanding these fungi at a global scale, we can not only chart the past and future of a key element of our planet’s biodiversity, but we also can harness those in our local areas to make crops thrive with limited water and rising temperatures. You might say that the future is fungal,” she concluded.

The study is published in the journal Current Biology.

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