[Lee Jong-gil's Autumn Return] The World of Moss Resembling Humans

Ecologist Robin Wall Kimmerer 'With Moss'

Polytrichum Swallows the Sphagnum... Unable to Survive 24 Hours Underwater, Dominates Only at the Top

Ten Species with Weak Survival Fix Themselves in the Middle Zone... Stratification and Rational Patterns Highlight the 'Value of Coexistence'

The Kickapoo River in Wisconsin, USA, frequently floods. Due to its small volume, it cannot handle heavy rains. When the weather clears, various shades of moss form horizontal bands below the cliff. Plant communities naturally vary with altitude, and moss vegetation is no exception. A consistent pattern emerges as you move away from the water surface. However, a slightly different phenomenon is observed here.

The 30 cm space from the water surface upward is marked by a black band of Polytrichum moss. Its above-ground part is only 8 mm but is a tough and stiff species. It appears flat at first glance. A smooth, thin blade-like leaf tip is covered by another leaf. The rhizoids look like fine threads. It firmly adheres even to sandstone mixed with gravel. This is the secret to forming a single colony near the water surface.

Above the Polytrichum moss, various mosses such as Calcarea moss, Wire moss, and Lantern moss are distributed. In some empty spaces, the yellowish-brown surface of the sandstone is exposed. The highest area within reach from the water surface is densely covered by Paenggae Usan moss. Paenggae Usan moss is also called "Snake grass" because it resembles green viper scales. It is a thin thallus without distinction between leaves and stems. Its blunt triangular shape resembles the triangular head of a venomous snake. Paenggae Usan moss loosely attaches to the ground with sparse rhizoids. It spreads its territory flat on rocks or soil.

The ecological researcher Robin Wall Kimmerer’s book Gathering Moss is the first popular science book introducing moss ecology in Korea. It lists insights gained from observing the diverse lives of mosses, prompting reflection on our own lives. The mosses of the Kickapoo River point to the value of coexistence. This is because the Polytrichum moss below the cliff, the Paenggae Usan moss at the top, and the various mosses mixed in between show clear stratification.

Just as one tree casts shade over another species, unexpected patterns often occur in ecosystems. The author assumes the boundary space between Paenggae Usan moss and Polytrichum moss results from competition. The two species do well separately, but when placed side by side, they engage in a power struggle. Victory always belongs to Paenggae Usan moss. The snake-like thallus swallows the smaller Polytrichum moss from top to bottom. Polytrichum moss must flee from Paenggae Usan moss to survive. However, Paenggae Usan moss does not extend its territory near the water surface.

To solve this curiosity, the author experiments on how long each moss species can endure underwater. Moss samples are placed in shallow dishes filled with water, and changes are observed by species. Polytrichum moss and Calcarea moss remained vigorous even after three days. In contrast, Paenggae Usan moss turned black and sticky in less than 24 hours. It could not withstand being underwater, which explains why it settles only in high cliff areas.

The author confirmed this phenomenon in the flood-prone Kickapoo River. The results matched the experiment. Polytrichum moss thrived despite overflowing water. Its streamlined, stiff stems could withstand water flow. Paenggae Usan moss dominated only areas rarely touched by water. It safely spread much higher than the water surface, covering rocks densely like a green blanket.

What about the middle zone between the two mosses? Between bare rocks exposing the yellowish-brown sandstone surface, as many as ten moss species coexisted. In areas with average flood frequency, no species monopolized the habitat.

This aligns with the findings of ecologist Robert Paine, who studied differences in disturbance cycles of organisms on the Washington coast. He observed wave patterns and changes in mussels and barnacles in the intertidal zone made of rocks. Mussels and barnacles are sessile organisms that compete for space, similar to mosses.

Paine discovered an interesting pattern. Few species inhabited areas where waves consistently hit or where waves never reached. In contrast, species diversity was high in zones with intermediate disturbance frequency. The author highlights this species diversity to explain the "Intermediate Disturbance Hypothesis" (the hypothesis that biodiversity is maximized in habitats experiencing moderate levels of disturbance).

"Ecologists have proven that without any disturbance, dominant competitors like Paenggae Usan moss gradually invade and completely exclude other species through competitive superiority. If disturbances occur too frequently, only species resilient to the environment survive the chaos. However, in intermediate zones with moderate disturbance frequency, a wide variety of species coexist in balance. Periodic disturbances prevent any one species from monopolizing, but stable periods are long enough for multiple species to establish themselves consecutively. The greater the age diversity within communities, the greater the biodiversity."

The Intermediate Disturbance Hypothesis has already been validated in various ecosystems such as grasslands and forests. Based on this, the U.S. Forest Service (USFS) implements wildfire prevention policies. After wildfire prevention campaigns, forests became monocultures. The disturbance cycle became too low, increasing the risk of fire spread. When wildfire frequency was too high, only short shrubs remained. However, with an optimal wildfire cycle maximizing diversity, empty spaces formed like mosaics, creating wildlife habitats and maintaining forest health.

The rational consistency observed in the lives of mosses also applies to our lives. If every day were clear and sunny, the world would become a desert. Rain, snow, and wind are necessary to maintain a rich environment. As long as balance is maintained, disturbance or alteration is not destruction but regeneration.

This content was produced with the assistance of AI translation services.