Fungi Supply Plant Communities With Underground Nutrient Pipeline
Dig up a cubic yard of soil, and you may have disturbed 12,000 miles of an extensive network of passageways that supply plant roots with carbon, nitrogen, and phosphorus. This highway is made of fungi. Their secret lives in the soil rarely see the light of day, but down in their cryptic, dark, subsurface world, they support most of the thriving plant communities above ground, writes Elizabeth Pennisi in the June 11 issue of Science.1 “Once considered pathogens,” she begins, “microscopic fungi that live in soil are shaping plant communities and aiding efforts in environmental restoration.”
She tells how scientists are beginning to understand that the above-ground and underground biotas form a network of symbiotic relationships. The thin mycelia (hair-like threads) of fungi, being 1/60th the diameter of roots, are able to wiggle between soil particles and extract minerals; they supply these to the plant roots, which in turn, reward their fungal partners with sugars. Usually these relationships are beneficial to both parties, although some fungi are parasitic (and some plants become freeloaders on underground welfare). Most plants, however, depend on their underground partners in a mutually beneficial way. Long difficult to study because of their “cryptic environment” and fragility, underground fungi called mycorrhizae are providing scientists with a new paradigm about the complex web of plant life. Pennisi lists some of the new realizations about mycorrhizae:
- Pioneer infrastructure: “when the first plants colonized land, mycorrhizal fungi were there,“ helping plants survive a harsh, dry landscape. “Often the first plants to repopulate polluted or highly disturbed sites are weeds that don’t form mycorrhizae. Only when mycorrhizal fungi move in … does diversity blossom.”
- Cultivation: “By hindering water loss and erosion, they improve the soil.”
- Toxic cleanup: “They also protect against pathogens and dampen harm from toxic wastes—talents that researchers exploit to reduce fertilizer use and remake damaged ecosystems.” One of her illustrations is captioned, “Mycorrhizal fungi can enable plants such as this rare flower (right) to live in polluted wastelands.” Another study showed that “when fungi are present, they can modify a heavy metal, such as cadmium, making that toxin unavailable for uptake by the plant.” In this way, they “sequester toxins and make soils more amenable to diverse growth.”
- Damage repair: “They help plants settle into damaged areas, such as those destroyed by fire.” In fact, “some fungi build up a ‘bank’ of stored spores that become active after fires and help rejuvenate the mycorrhizae network.”
- Pollution control: “Mycorrhizae also cause soil particles to clump, enabling them to hold on to nutrients. At waste sites, these clumps keep toxins from becoming airborne and dangerous to people,” noted one soil ecologist.
- Community lifeblood: “In addition, new studies are showing that these fungal threads link one plant to another, transferring nutrients not only among fungi but from plant to plant as well, shaping the biological makeup of whole communities.” All the species in a community are thus tapped into a common pipeline: “The mycelia pipeline can extend well beyond the immediate partners; it also provides for two-way traffic of carbon resources through the tangled maze of plant roots and fungal threads. In this way, a large oak tree may be feeding not just its fungal partner but also other plants in its neighborhood.” For new seedlings, this pipeline may actually be a lifeline, letting it get a foothold in the community.
In other words, fungi form an “underground highway” that links plants into a community. DNA sampling of soil is revealing that these fungi are more diverse and widespread than previously believed.
Furthermore, “in contrast to a widely held view—soil microorganisms aren’t always harmful.” The world of mycorrhizal fungi is “cracking wide open,” leading ecologists to envision practical benefits that could be gained from understanding these relationships. Scientists are finding, for instance, that adding mycorrhizae to strip mines and toxic waste dumps allows plants to become established again, without the need for polluting fertilizers. Others are working to find the right mycorrhizal mix that will allow endangered species to become reestablished in their native environments.
The discovery of this “underground highway“ is “changing the way people think about plant ecology.” Results of recent investigations that portray fungi as pioneers, providers and protectors “are solidifying the idea that the fungi are movers and shakers in the plant world.”
1Elizabeth Pennisi, “The Secret Life of Fungi,” Science, Vol 304, Issue 5677, 1620-1622, 11 June 2004 [DOI: 10.1126/science.304.5677.1620].
The old Darwinian/Malthusian picture of a dog-eat-dog world, nature red in tooth and claw, each species fighting over limited resources for survival of the fittest, just took a beating with this story. This complex web of beneficial interactions looks mighty friendly. You can almost picture the scouts exploring the new territory, the carpenters following behind to build the town and string the telegraph lines and railroad tracks, the sheriff and firefighters setting up headquarters and the settlers moving in to form a thriving, interactive, responsive community — all in the silent world of plants. Where Darwinists used to see selfish, harmful microorganisms trying to steal from the land plants, they now see pioneers, providers and protectors.
So how does evolutionary theory deal with these new realizations? There are only three references to evolution in this paper:
- Once upon a time: “Four hundred million years ago, ’when the first plants colonized land, mycorrhizal fungi were there,’ helping newcomers survive in a harsh, dry landscape, [John] Klironomos explains. Since then, the support system has grown, says Katarzyna Turnau, an ecologist at Jagiellonian University in Krakow, Poland. ‘Mycorrhizae [gave] the plants the ability to use different areas and to explore new niches,’ making possible the incredible diversity of modern flora.”
This statement has no explanatory power; it merely assumes evolution. It fails to answer how the mycorrhizae survived in sterile dirt without the sugars that land plants provide. It assumes that resources are sufficient to create diversity, which begs the question of how that might occur.
- Fictitious force: One ecologist who studied the relationships between orchids and truffles remarked that the truffles “appear to be evolution drivers.” Sorry, truffles don’t qualify for a driver’s license.
- Job prospecting: Klironomos says in conclusion, “when it comes to ecology and evolutionary biology, the [mycorrhizal] field is cracking wide open.” I.e., here is an opening for unemployed storytellers (see 12/22/2003 headline).
In short, evolutionary theory adds nothing to these findings. On the contrary; evolutionists appear surprised by them, because they ran counter to their expectations. In light of the sophistication of the observed underground pipeline, its many specialized functions, and its many beneficial effects, it appears instead that the mycorrhizal field is cracking wide open for the intelligent design movement.