Simard’s inquiries confirmed that beneath her forest floor there did indeed exist what she called an “underground social network,” a “bustling community of mycorrhizal fungal species” that linked sapling to sapling. She also discovered that the hyphae made connections between species: joining not only paper birch to paper birch and Douglas fir to Douglas fir, but also fir to birch and far beyond—forming a non-hierarchical network between numerous kinds of plants.
Simard had established a structure of connection between the saplings. But the hyphae provided only the means of mutualism. Its existence did not explain why the fir saplings faltered when the birch saplings were weeded out, or details as to what—if anything—might be transmitted via this collaborative system. So Simard and her team devised an experiment that could let them track possible biochemical movements along this invisible buried lattice. They decided to inject fir trees with radioactive carbon isotopes. Using mass spectrometers and scintillation counters, they were then able to track the flow of carbon isotopes from tree to tree.
What this tracking revealed was astonishing. The carbon isotopes did not stay confined to the individual trees into which they were injected. Instead, they moved down the trees’ vascular systems to their root tips, where they passed into the fungal hyphae that wove with those tips. Once in the hyphae they traveled along the network to the root tips of another tree, where they entered the vascular system of that new tree. Along the way, the fungi drew off and metabolized some of the photosynthesized resources that were moving along their hyphae; this was their benefit from the mutualism.
Here was proof that trees could move resources around between one another using the mycorrhizal network. The isotope tracking also demonstrated the unexpected intricacy of the interrelations. In a research plot thirty meters square, every single tree was connected to the fungal system, and some trees—the oldest—were connected to as many as forty-seven others. The results also solved the puzzle of the fir–birch mutualism: the Douglas firs were receiving more photosynthetic carbon from paper birches than they were transmitting. When paper birches were weeded out, the nutrient intake of the fir saplings was thus—counterintuitively—reduced rather than increased, and so the firs weakened and died.
The fungi and the trees had “forged their duality into a oneness, thereby making a forest,” wrote Simard in a bold summary of her findings. Instead of seeing trees as individual agents competing for resources, she proposed the forest as a “cooperative system,” in which trees “talk” to one another, producing a collaborative intelligence she described as “forest wisdom.” Some older trees even “nurture” smaller trees that they recognize as their “kin,” acting as “mothers.” Seen in the light of Simard’s research, the whole vision of a forest ecology shimmered and shifted—from a fierce free market to something more like a community with a socialist system of resource redistribution.
- The Understory by Robert Macfarlane excerpts from his book, Underland: A Deep Time Journey
Simard had established a structure of connection between the saplings. But the hyphae provided only the means of mutualism. Its existence did not explain why the fir saplings faltered when the birch saplings were weeded out, or details as to what—if anything—might be transmitted via this collaborative system. So Simard and her team devised an experiment that could let them track possible biochemical movements along this invisible buried lattice. They decided to inject fir trees with radioactive carbon isotopes. Using mass spectrometers and scintillation counters, they were then able to track the flow of carbon isotopes from tree to tree.
What this tracking revealed was astonishing. The carbon isotopes did not stay confined to the individual trees into which they were injected. Instead, they moved down the trees’ vascular systems to their root tips, where they passed into the fungal hyphae that wove with those tips. Once in the hyphae they traveled along the network to the root tips of another tree, where they entered the vascular system of that new tree. Along the way, the fungi drew off and metabolized some of the photosynthesized resources that were moving along their hyphae; this was their benefit from the mutualism.
Here was proof that trees could move resources around between one another using the mycorrhizal network. The isotope tracking also demonstrated the unexpected intricacy of the interrelations. In a research plot thirty meters square, every single tree was connected to the fungal system, and some trees—the oldest—were connected to as many as forty-seven others. The results also solved the puzzle of the fir–birch mutualism: the Douglas firs were receiving more photosynthetic carbon from paper birches than they were transmitting. When paper birches were weeded out, the nutrient intake of the fir saplings was thus—counterintuitively—reduced rather than increased, and so the firs weakened and died.
The fungi and the trees had “forged their duality into a oneness, thereby making a forest,” wrote Simard in a bold summary of her findings. Instead of seeing trees as individual agents competing for resources, she proposed the forest as a “cooperative system,” in which trees “talk” to one another, producing a collaborative intelligence she described as “forest wisdom.” Some older trees even “nurture” smaller trees that they recognize as their “kin,” acting as “mothers.” Seen in the light of Simard’s research, the whole vision of a forest ecology shimmered and shifted—from a fierce free market to something more like a community with a socialist system of resource redistribution.
- The Understory by Robert Macfarlane excerpts from his book, Underland: A Deep Time Journey
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