There is a black walnut tree in the backyard of our house here in Spartanburg. Every September, it drops its fruit, and the thick green husks split open, staining the ground (and the fingers of our children) dark. The squirrels know the timing better than we do. The tree has been doing this longer than anyone on the street has been alive.
But according to a growing body of research, it has been doing something else during that time too… something largely invisible and harder to name. Beneath the soil, networks of fungal threads connect the roots of the walnut to other plants and organisms in ways scientists are still working to describe. And the question those networks keep raising is not simply biological. It is perceptual. It is asking us whether we know how to pay attention to what is right beneath us.
Earlier this year, a team of researchers at Princeton University working across institutions in the United States and Europe published new findings on mycorrhizal fungi (the microscopic threads that link plant roots underground). Using imaging techniques refined over several years, they mapped not only how the architecture of these underground networks forms, but also the fluid motions occurring inside fungal tubes roughly one-tenth the diameter of a human hair, through which nutrients flow back and forth throughout the organism. These networks move carbon, nitrogen, and phosphorus across remarkable distances through the soil, allowing plants and fungi to exchange resources through a shared infrastructure that predates our street, our city, and the entire textile economy that built it.
As one researcher put it simply, there are all these things happening underground that no one ever thinks about because they cannot see them.
That invisibility is part of what makes this hard to talk about in practical terms. We tend to extend moral consideration to what we can perceive… and the soil beneath the tulip poplars and white oaks lining the creek corridors through Spartanburg is not legible to us in ordinary ways. But legibility is not the same as presence.
The forests surrounding Greenville and Spartanburg sit at a remarkable ecological threshold. The southern Appalachians are considered one of the most biologically diverse regions of the temperate world, according to the South Carolina Native Plant Society, and the Piedmont foothills carry that diversity into the clay-heavy, iron-stained soils that anyone who has gardened here knows immediately. Those soils formed over millions of years as the ancient Appalachians weathered and eroded, leaving behind a mineral complexity that still shapes which species grow where, which fungi partner with which roots, which relationships persist, and which collapse under pressure.
The forests here also carry a complicated history. The mid-twentieth-century abandonment of row crops allowed forests to return to the Piedmont, though not the oak and hickory that typified earlier centuries. Loblolly pine colonized the abandoned cotton fields first. Sweetgum, tulip poplar, and red maple followed. The visible forest changed, but the deeper processes in the soil continued shaping recovery in ways the canopy did not reveal. Seedbanks persisted underground while fungal communities survived in fragments. Mycorrhizal networks that had supported older forests were interrupted but not entirely erased. When we walk through Croft State Park today, or along the Pacolet River corridor, we are moving through forests still rebuilding themselves after those earlier disturbances. The soil carries those histories in its structure and microbial communities. In that sense, the forest remembers… not through anything like human memory, but through ecological processes unfolding across decades.
Plants and fungi developed a partnership lasting over 400 million years, one that may have enabled plants to colonize dry landmasses and transform them into prolific habitats for terrestrial life (Springer). The relationship is not incidental to the forest, but is constitutional. Mycorrhizal fungal networks linking the roots of trees facilitate inter-tree communication via resource sharing, defense signaling, and kin recognition, influencing what researchers describe as sophisticated behavior among neighboring plants (ResearchGate). Some researchers have gone further, exploring what a recent paper in Symbiosis called “extended plant cognition” and the possibility that plants benefit from the cognition and behavior of mycorrhizal fungi to enhance their own survival, including foraging complementarity, expanded perception of the below-ground environment, and shaping the mycorrhizal community to meet survival needs.
The language here is careful and contested, and it should be. This is not the same as saying trees think in the way we do. But the underlying ecological picture is not nothing. Responsiveness within a forest does not appear to reside solely within individual organisms. It emerges through relationships linking plants, fungi, and soil communities in ways that begin to look less like isolated biological transactions and more like what phenomenologists might call a field of distributed perception… awareness that is not located anywhere in particular but present throughout the whole.
I have been exploring this idea in my own writing as ecological intentionality (the practice of attentive presence that recognizes humans as participants in, not observers of, the living world). What the mycorrhizal research keeps returning me to is how thoroughly that participatory logic runs through the forest itself. The sweetgums and beeches, the stands of loblolly along the old field margins, the black walnut in the backyard… each of these participates in a network of exchange that extends through the soil and across time in ways that our usual categories of “individual” and “organism” struggle to hold.
This matters for more than philosophical reasons here in the Upstate. As I wrote earlier this year about Project Spero (the proposed AI data center at the Tyger River Industrial Park), the questions it raised were ultimately about more than megawatts and gallons of water. They were about what kinds of relationships between land, water, and intelligence we are willing to normalize in this place. The project was eventually withdrawn after months of community opposition (a moment of civic attention worth studying carefully). But the broader pressure it represented has not disappeared. Proposals like it will keep arriving in communities like ours, asking us to decide how much of the landscape’s capacity (including its soil capacity, its fungal capacity, its slow-built ecological memory) should be redirected toward sustaining planetary-scale computation whose primary benefits flow elsewhere.
The question for a forest, if we can ask it that way, is not whether development will come. It is whether the networks beneath the soil can persist through what arrives. Those networks are not infinitely resilient. Mycorrhizal interactions play a foundational role in global patterns and structures of forest diversity, with mycorrhizal tree type systematically mediating the strength of competitive and cooperative dynamics within communities (Nature). What that means at the scale of a particular watershed is that the diversity and responsiveness of a forest depend not only on which species are present aboveground, but on the web of relationships in the soil (many of which are species-specific, many of which take decades to establish, and all of which can be severed quickly).
Donna Haraway has a word I keep returning to in this context, one I thought about recently when writing about the first signs of spring… composting. The idea that life continues through processes of breakdown, recombination, and transformation. Nothing simply disappears. Things are continually folded back into the living systems that surround them. The brown leaves underfoot right now on the trails at Croft carry last year’s sunlight and last year’s rain into the soil that is already shaping what grows next spring. The forest floor is composting memory into future life.
The black walnut in our backyard does not need me to make this argument. It has been making its own version of it for longer than the street has had a name, through a language of carbon, phosphorus, and fungal exchange that we are only beginning to have instruments sensitive enough to partially read.
The question is not whether that language is happening. The question is whether we are willing to develop the kind of attention it requires… and whether we can build that attention into the civic and ecological decisions we are already making about this place.
More Reading…
Simard, Suzanne W., Ryan, Teresa L., and Perry, David A. “Response to Questions About Common Mycorrhizal Networks.” Frontiers in Forests and Global Change (January 2025). https://www.frontiersin.org/journals/forests-and-global-change/articles/10.3389/ffgc.2024.1512518/full
Ma, Xiaofan and Limpens, Erik. “Networking via Mycorrhizae.” Frontiers in Agricultural Science and Engineering 12, no. 1 (2025): 37–46. https://journal.hep.com.cn/fase/EN/10.15302/J-FASE-2024578
“Research Reveals the Underground Traffic Between Fungi and Plants.” Princeton University, March 25, 2025. https://www.princeton.edu/news/2025/03/25/research-reveals-underground-traffic-between-fungi-and-plants
Leyval, C. et al. “How Mycorrhizal Fungi Could Extend Plant Cognitive Processes.” Symbiosis (2025). https://link.springer.com/article/10.1007/s13199-025-01065-y
Society for the Protection of Underground Networks (SPUN) — Global Mycorrhizal Mapping Initiative: https://spun.earth
South Carolina Native Plant Society — Upstate Chapter https://scnps.org/upstate
