Tree Communities Harness the Power of Interdependence

*AUTHOR BIO

Trees are known to compete for sunlight and soil resources, but forest researchers have discovered a deeper reality beneath the ground. Trees actually relate to one another in communities and even share essential nutrients through their roots.


Dr. Camille Defrenne, an ecologist specializing in plant-fungal symbioses at the Climate Change Science Institute and Environmental Sciences Division of Oak Ridge National Laboratory in Tennessee, is one such researcher who has studied the inner workings of this remarkable phenomenon.

Trees communicate and cooperate through their roots. ©cocoparisienne/Pixabay
Trees communicate and cooperate through their roots. ©cocoparisienne/Pixabay

Fungi Bridge the Gap Between Trees


During her Ph.D. studies at the University of British Columbia, Defrenne spent four years studying the fine roots of Douglas-fir trees at the side of Dr. Suzanne Simard, best-selling author and professor of forest and conservation sciences. Simard’s research on the observed ‘intelligence’ and communication between trees has sparked widespread interest in this increasingly popular field.


“In most forests around the world, trees share resources, such as carbon and nutrients, and information such as defense signals,” explains Defrenne. They are able to do so because they are interconnected below the ground thanks to mycorrhizal fungi. For 400 million years, these fungi physically associated with the tips of fine roots, creating exchange sites where a tree can trade the carbon it gets from photosynthesis for resources acquired from the soil by fungi.

Tiny fungi connect tree roots for mutual benefit. ©Camille Defrenne
Tiny fungi connect tree roots for mutual benefit. ©Camille Defrenne

Mycorrhizal fungi connect multiple trees beneath the soil surface through their microscopic filaments that grow out from the root tips. These filaments form the basic links of mycorrhizal networks, which were coined the “Wood Wide Web” in Suzanne Simard’s seminal 1997 research. Carbon and nutrients flow through mycorrhizal networks from where they are more abundant to where they are less abundant, a circumstance known as source-sink gradient.


“Research shows that these resource fluxes are sufficiently large in some cases to facilitate tree establishment and growth,” says Defrenne. “Highly connected hub trees, also named ‘Mother Trees,’ share their excess carbon and nitrogen with the understory seedlings, which can increase their survival.”


Humans and Nature Thrive in Balanced Ecosystems


Research led by Simard, Dr. Teresa Ryan of the Tsimshian Nation, and colleagues at the University of British Columbia has shown that in Pacific coastal rainforests, the salmon, trees, mycorrhizal fungi, and Aboriginal people are interdependent. “The Aboriginal people of the Pacific Coast are sustainably embedded in a complex system including forests, rivers, and the ocean,” adds Defrenne.


A large part of the nutrients that mycorrhizal fungi take up in these rainforests is from salmon origins—the salmon are caught by predators that leave the fish carcasses on the forest floor. “The salmon nutrients contribute to faster tree growth along salmon streams and mediate the high productivity of these ecosystems,” shares Defrenne, “In turn, trees modulate the water temperature of the rivers and transmit nutrients to the ebb tides through seepage.” As a result, a cycle is formed that promotes the health and productivity of the fish.


“Closing the circle, the Aboriginal people harvest tree bark and roots to make clothing and tools to catch salmon,” details Defrenne. “The integrity of this circle of life depends on what the Aboriginals call reciprocity—the trade of mutual respect.”

Bears leave salmon carcasses behind which in turn nourish trees. ©dailyshot/Pickupimage
Bears leave salmon carcasses behind which in turn nourish trees. ©dailyshot/Pickupimage

The benefits of interdependence in forest ecosystems speak to human ecosystems, as well. As Defrenne describes, “The idea that trees in forest ecosystems may interact in apparently similar ways to humans and animals is fascinating because it makes it easier to relate.”


If we look at examples of how trees, our bodies, and people coexist harmoniously, we can see that they communicate and engage in cooperative relationships. “For example, trees and mycorrhizal fungi depend on each other for survival in forest ecosystems; white blood cells and antibodies collaborate to fight infection in our immune system, and individuals are interconnected through institutions and social media in human societies,” shares Defrenne. All of these complex systems adapt to changing conditions in their efforts to survive, function, and thrive.


Rethinking Our Approach to Nature


The more we study forest ecosystems, the more we learn about managing them well: “Research in forest ecology provides invaluable quantitative information and tools for resource managers and policymakers,” details Defrenne. “Especially, experiments manipulating climate or forest practices are essential to predict and maintain the functioning of forest ecosystems in the future” Defrenne goes on to say.


The structure and function of forest ecosystems might even inspire design practices of the future. The 2019 Google's Annual Design and Technology Conference featured a workshop entitled ‘Towards Resilient Systems.’ Google’s Artificial Intelligence (AI) Strategy and Research team offered the idea that designers should rethink human-centric design in both discussion and practice. Workshop organizers encouraged designers to re-prioritize relationships between individuals, species, and the surrounding landscape in their designs.


How to Reconnect to Our Natural World


From plants to animals to ecosystems, there is a whole world out there of interdependent ecosystems to explore and enjoy. Defrenne shares her advice for making the most of it:

  • Bring yourself and your kids to the forest.

  • Educate yourself and others about our environment. For example, listen to and share good podcasts on the environment such as Science Friday, For the Wild, and TED.

  • Stay informed by engaging with the scientific community. You can Skype with a scientist. Learn more at: https://www.skypeascientist.com/for-families.html.

  • Engage with environmental organizations to protect vulnerable ecosystems.

  • Take a virtual tour of the SPRUCE experiment. The SPRUCE experiment assesses the response of northern peatland ecosystems to increases in temperature and exposures to elevated atmospheric CO2 concentrations.

An increasing number of people feel disconnected from the natural world. Being aware that trees are far more connected than previously thought can change our thinking about forests and ourselves. Adds Defrenne: “It also encourages people to educate themselves and others about their environment and to remain humble in front of the natural world and its mysteries.”

 

*Natasha Spencer-Jolliffe is a freelance journalist and editor. Over the past ten years, she has reported for a host of publications, exploring the wider world and industries from environmental, scientific, business, legal, and sociological perspectives.


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