Image curtesy of National Geographic and Eye of Science through Sue Grayston
In forest management, we spend a lot of time on the things we can see; charismatic megafauna, trees, pests and plants. But what about the things we can’t see? What if I told you there was an entirely unexplored ecosystem below our feet? One that has more biodiversity than we can imagine. This community is responsible for half of the carbon sequestration of the forest, and the maintenance of ecosystem function for above ground species. This life beneath our feet is as much responsible for the forests we love as the biggest trees and the cutest caribou. Let’s show it some love.
Resources
Sponsors
Quotes
28.35 - 28.48: “It’s so important for us to be able to appreciate it, to be able to visualize it, and so that’s always been the problem in getting people interested and concerned perhaps about life below ground… you can’t see most of it.”
Takeaways
The hidden living ecosystem (05.58)
Growing up in England, Sue spent time with her mother tending their garden and became fascinated with the tiny creatures of the soil. She earned degrees in microbiology and the rest is history. As a child, Cindy loved spending time in the forests and had the opportunity to work in forests in Alberta after her undergrad. She delved into forest ecology in her master’s program and got in touch with Sue through her research and they now work on below-ground processes.
New microscopic frontiers (10.17)
Sue marvels at the new processes that allow faster research results to become available now compared to when they first started researching. Culturing species in a lab allows a different growth process which wouldn’t be possible in the soil. Cindy highlights that they found archaea populations in forest soil, a different type of organism which can also carry out nitrification of the soil.
Unseen but not the least (14.41)
Sue points out that tree species can be identified by morphology, but not microbes. Cindy adds that it is difficult to advocate for the importance and inclusion in forest management of organisms that can’t be seen. They have been studying microbes which degrade plant organic matter and release their nutrients, thereby nourishing the soil, as well as those that live on the surfaces of roots.
A whole world in a spoon of soil (19.52)
Cindy explains that from the 70s to the 90s, litter decomposer microbes were the focus of studies. Carbon tracing studies showed that up to half of the carbon that is fixed in the leaves of the trees is sent below ground, taken in by mycorrhizal fungi and quickly comes out of the soil as carbon dioxide and into the food web, not just being respired out of plants. Next-generation sequencing techniques help us understand the workings of organisms in the soil.
Techniques that reveal microbial processes (24.51)
Sue describes the labelling techniques through which they label trees with heavy isotopes of carbon sources similar to the carbon from trees, allowing them to identify groups of organisms that are important in using that carbon and following them till they are consumed by animals. Cindy shares how such studies helped clarify how carbon flows through the ecosystem. She uses electron micrographs of tree roots and fungal hyphae to see the bacteria on them.
Soil microbes saving the world (30.20)
Sue spotlights the fact that many organisms spend all or some of their lives in the soil creating a link between organisms above and below. Fungi developed enzymes evolutionarily to help decompose the accumulated plant litter and release its nutrients to allow the continuity of terrestrial ecosystems. Forest soil microbes remove methane and nitrous oxide from the atmosphere and clean water waste. Many antibiotics are also developed from soil organisms.
Knowledge of microbial processes is power (34.41)
Cindy believes that understanding the workings of soil organisms is better than using chemicals for biological controls. She explains the process by which they get nitrogen moving through the ecosystem and by which they replenish the persistent organic matter and sequester carbon in the soil. Microbes process organic matter and help lock it into the soil. The amount of carbon that reaches the microbial community is important for nutrient cycling and carbon sequestering.
How forest harvest affects microbial communities (48.40)
Sue explains the process of conducting research through which they found that dispersed retention in clear cuts has a better function in retaining microbial diversity and its functioning across the cut block. Cindy adds that mycorrhizal fungi communities depend on the dynamic flux created by trees, which is taken away after forest harvest. She urges listeners to visualize these processes even if they are unseen, to relate to them better.
Below-ground diversity leads to a resilient ecosystem (56.32)
Cindy emphasizes that every plant is important for carbon sequestration, with each species having different mycorrhizal fungi that associate with them, which impacts the diversity of soil microbes. Every plant species has its temperature range of comfort which is being affected due to climate change. Recent wildfires have also been devastating for the soil biome. Sue adds that severe wildfires that burn the forest floor wipe out the soil microbes.
Inoculant seed zones (1.06.59)
Sue and Cindy talk about how unaffected forests can act as seed zones after a wildfire. The University of Alberta is conducting research in the oil sands on recreating soil substrates with forest floors from surrounding forests. Research on mine sites shows that after about 30 years, soil organic matter builds up again with the help of nitrogen-fixing species. Nitrogen fixers prevent the soil from declining if there is a wildfire again.
Resilient and productive ecosystems (1.15.12)
Cindy stresses the need to “think about restoring and rehabilitating regardless of the disturbance” and making “a more resilient and possibly productive ecosystem” by including the diversity of trees in forest management plans. Sue lists examples of different mycorrhizal fungi that depend on the diversity of living tree species. Cindy urges listeners to evaluate the effect different species have on different parts of the ecosystem.
What’s below is as important as what’s above ground (1.22.33)
Cindy offers a different way of thinking about forest management - that sites can not only be saved but also improved using the understanding of below-ground ecosystems. She laments the lack of care with which soil is currently viewed. She advises that “a significant amount of cutover needs to have the influence of living trees” for regeneration to take place. She explains how nitrogen affects the carbon flux and the below-ground system of fine root production.
Stand and landscape level diversity (1.36.21)
Cindy shares an example of nitrogen-deficient sites on Vancouver Island where adding nitrogen and phosphorus promoted both above-ground growth and below-ground diversity and function. When there is a diversity of tree and plant species, there will also be below-ground diversity. Built into that maintenance of stand productivity is using improved genetic stocks that are programmed to grow faster as well as silviculture techniques, she opines.
Ongoing monitoring (1.41.45)
Cindy talks about the need to monitor soil biodiversity and measure key processes and the amount of soil organic matter, especially mineral-associated organic matter. If mineral-associated organic matter is being regenerated at least at the rate at which it is degrading, then the soil will be healthy. She reinforces the need to develop resilient forests, and the first step would be to update forestry policies to make them fit for the 21st century.
If you liked this podcast, please rate and review it, share it on Instagram, Twitter and Facebook and tag a friend, and send your feedback and comments to yourforestpodcast@gmail.com.