Nature's Poultice: Healing
Beds of moss absorb and retain moisture, and spread a healing poultice over the raw wounds of nature. They prevent erosion of the soil from slopes and open spaces, provide cover for germinating seeds in the natural reforestation of burned areas, cover stumps and fallen trees with their smothering blanket of decay, and provide a friendly environment for slugs and bugs, for moles and voles, and for the myriad forms of life active in the never-ending process of soil conversion and plant succession.
In preparing specimens for my herbarium, I select individual plants and attempt to wash them free of dirt. Strangely, this is almost impossible to do. In spite of the most diligent effort, the rhizoids stubbornly retain a thick blob of mud. The reason for this is that the cell walls of the rhizoids are believed to secrete a mucilaginous substance that literally sticks them to soil particles and insures the plant a secure footing wherever it grows - on earth, rock or wood. This ability to anchor so effectively makes moss difficult to dislodge and most effective in its earth binding role.
Moss also acts like a furnace filter, trapping dust and debris from the circulating air currents to become part of its contribution to the soil. Considering that mosses are so small and inhabit some of the most secluded recesses of nature, it is a rude awakening to find in the privacy of a microscope such vulgar intrusions as hairs, fabric fibres and tiny bits of paper and plastic - all firm evidence of our own inter-relationship with the whole of nature.
The retreat of lichens in advance of industrially polluted air is well known. But mosses, perhaps because of their filtering abilities, are also considered good indicators of even mild air pollution. Cities, for instance, have sometimes been called "bryophyte deserts." This claim is not entirely true, however, though the number of species may be substantially reduced. Even for those of us who live in the city, mosses are literally within arm's reach - on wet shady shingle roofs, in clogged eavestroughs, on concrete, brick or stone walls, in sidewalk cracks, between patio stones and in flower pots. Cities, after all, are not noted for rolling stones! As many as half a dozen kinds of moss may be growing in any shady backyard, even in the heart of a big city.
Pollution probably does play a role in making city parks disappointing places to find mosses. But even more important are the same factors that have eliminated so many wildflowers from these places. Most city parks are well-trodden and so well groomed there is little undergrowth to prevent hillside erosion and no chance for even mosses to get a foothold. Yet there are still secluded and less accessible marshy areas of our parks where numerous mosses may be found in abundance, especially in early spring.
The delicate beauty of mosses belies their toughness and ability to survive. Several factors undoubtedly contribute to this survival:
Their low-lying habit of growth diminishes the risks that most taller plant forms have to contend with. But this under-foot, earth-covering habit of mosses, itself a certain liability, is compensated by a tough and wiry nature like the resilient carpet pile they are, erasing our footsteps as we pass. This habit also places a moss in the zone of richest concentration of plant nutrients, within the first 15 centimeters from the forest floor. Their need for this moisture-laden and nutritionally-rich environment keeps their low profile within its bounds.
Mosses have few enemies to deplete their numbers. Being generally unpalatable to the taste, they form an insignificant part of the diet of any of the mammals. An exception would certainly be the now-extinct Hairy Mammoth, one of which was dug out of the ice in northern Siberia in the late 1800s and found to have three species of moss in its stomach contents.
Little has been done on the chemistry of mosses, but drop a handful of fresh green moss of any kind into a basin of warm water and enjoy the pleasantly medicinal fragrance that is released. Most mosses are believed to have some antibiotic quality. Very rarely do insects of any species feed on them, except some of the spider mites. The Sphagnum moss of bogs is especially noted for its antibiotic value. The Indians and Inuit used the moss for dressing wounds, and the natives of northern Alaska still make a salve from Sphagnum leaves and animal fat for this purpose.
During the first World War, thousands of tons of Sphagnum were used by both sides as surgical dressing. It was found to be far more efficient than cotton for this purpose, absorbing 10 to 20 times its dry weight in moisture. And whereas cotton absorbs moisture only locally to the point of saturation, Sphagnum moss, by its peculiar cellular structure, absorbs the moisture into every cell of its mass.
Although often severely restricted ecologically in habitat, mosses generally have the ability to survive extended periods of drought, and even though apparently dead, revive quickly after the return of moisture. Mosses can be preserved as dried herbarium specimens almost indefinitely and relaxed with water to return them to a life-like state for study. Howard Crum in his excellent book
Mosses of the Great Lakes Forest discusses some laboratory experiments in which several species of moss were revived after periods of herbarium storage from 8 months to 19 years! Spore germination has been reported for some species after a record 50 years from maturity.