Lately I have been re- reading Robin Wall Kimmerer’s book Gathering Moss trying to conjure up the southwestern face of trillium rock, which is presently buried under two feet of snow below my house. For three seasons of the year this large nubbly granite boulder is glowing with emerald mosses and sage green lichens. For many years I have been watching both spread over the stone’s surface creating a perfect environment for pine and hemlock seedlings, trailing arbutus, partridgeberry and trillium that are now also thriving on this glacial boulder that lies within a foot of the brook.
I learned from Kimmerer’s book that any rock must first be weathered by wind and water and then etched with acids produced by a lichen crust. Only then will the moss rhizoids begin to attach. So the lichens were there first, although by the time I moved here the stone was growing both. During most of the year I visit this spot daily, especially in the late afternoons when the light turns golden. Even in February beneath the snow on relatively mild days mosses and lichens are photosynthesizing. An amazing thought. I love the lowlands for many reasons but one of the most important is that because these are the places where diminutive beings grow. I never tire of running my hand over silken coats of a clump of hair cap moss or the prickly surface of a pincushion. Whenever I examine lichens I am drawn into a magical Lilliputian land or forest…
To digress for a moment… I cannot write about mosses without thinking about my favorite forest, some distance from here. There I am surrounded by so many varieties of moss that I cannot name them all. This naming is a project I intend to engage in this summer having already bathed myself in the wonder that such places still exist. I observe first, falling under the spell of the forest. Only later will I return to do some fieldwork and research…I am impatient for a change in season. White is monotonous and I am tired of the glaring snow crust that separates me from the earth, stilling her song.
Moss not only grows on glacial rocks, but on old stone -walls, trees, clay pots, brick, roofs and even in the in cracks of city pavement, to give the reader just a few examples. Mosses reproduce in two ways, sexually by producing spores that the wind disperses, and by branching or fragmentation, which is what happens when a small piece of moss is broken away from another and begins a new life. Mosses have the ability to clone themselves.
Because mosses have amazing capacities to adapt these tiny plants find ways to thrive in deserts, dark caves, rocky ledges, and frigid mountains; they are capable of surviving very extreme conditions. They can continue to photosynthesize until temperatures dip below zero. In fiercely hot environments like prairies or deserts, mosses become dormant. Desiccated mosses can survive temperatures up to about 200 degrees F.
Mosses and their cousins, liverworts and hornworts, the latter live in water, are classified as bryophytes.
These are very ancient plants. Kimmerer says they date back to about 450 million years ago and have survived earth’s five major extinction periods. There are about 1500 to 2500 species of moss and they occur on every continent and in every ecosystem. There is some controversy around whether lichens or mosses were the first organisms to populate the earth but for me, either way the point is the same. Plants in some form were around 400 plus million years ago and we share approximately 50 percent of our DNA with them. Now that we are contending with a sixth extinction, mosses are becoming threatened for the first time because of habitat loss, water/air pollution and overharvesting.
Mosses are non-flowering plants that produce spores and have stems and leaves. However, unlike most plants mosses do not have roots. They do have rhizoids that are small hair-like structures whose function is to anchor the plant to rocks, tree bark, soil etc. Some mosses absorb nutrients through rhizoids and all draw in moisture and minerals from rain. Water is distributed evenly throughout the highly absorbent surface that acts like a sponge. Mosses soak up rainfall and maintain moisture in the substrate below keeping conditions around them very humid. This ability to hold moisture attracts other plants to moss covered areas. This is one reason we often see mosses and seedlings growing together. These plants create their own miniature microclimates, and all around them other plants thrive.
Mosses also play a critical role in the development of new ecosystems. They’re among the first plants to colonize disturbed sites after fires or when an area has been stripped of its forest. Mosses stabilize the soil and retain water, practices that contribute to the growth of other plant species.
Mosses also impact the temperature of the soil, both warming it up and cooling it down depending on the environment.
In hot places, they can protect tree roots by shading and insulating the soil from high temperatures. In the Arctic they have an opposite effect on temperature. They can prevent the warmth of the sun from reaching the ground and reduce the speed at which ice thaws, keeping it cooler for longer.
Some mosses are luminous. The ones that grow in caves have adapted to lower light conditions. One of the most well known cave mosses is dragons gold (Schistostega pennata) that apparently glows an unearthly luminescent emerald green. Inside the threadlike structures (protonema) chloroplasts gather together to receive the maximum amount of light. Lens shaped cells help focus the light and the reflection from these chloroplasts is what creates the luminous glow.
Not surprisingly, mosses are responsible for biodiversity in moist forests, wetlands, mountains and tundra ecosystems because they offer microhabitats that are critical to the survival of many organisms. Moss communities provide valuable shelter for insects to live, lay their eggs and hunt for food. Turtles frogs, toads and salamanders benefit from mosses ability to regulate temperatures. In Canada turtles spend the winter under sphagnum moss, and around here small frogs burrow in the sphagnum that surrounds my little amphibian pond. Even on a day when it is well below freezing mosses living on a rock may be bathed in liquid water. Sphagnum mosses form spongy carpets on the ground in the lowlands like the ones in my forest stretching across tree roots that might otherwise dry out. They inhabit the edge of marshes, and make up the bulk of heaths playing a vital role in the creation of peat bogs. Mosses have an exceptional ability to remove toxins from the water. And whenever you see moss growing on living (not decaying) trees they are healthy.
Kimmerer also writes that looking at any moss.
community is uncannily similar to the experience she had as a researcher in the Amazon because the sheer volume of living beings in the jungle matched what she sees when she studies moss colonies under her microscope! The structure and function of both is the same.
One very curious note is that although we know that mosses liverworts and lichen all interact we don’t know how these relationships work.
In Maine we have a multitude of different kinds of mosses. For those just beginning to look for moss visit the edge of a swamp or pond and you will greeted with the acidic loving sphagnum moss along with pitcher plants, sundews, small pink orchids, and cranberries (depending on the season). Follow a stream and you will find feather and silver moss, red stem moss, brown fork moss, and two of my favorites, brocade and hair cap moss. There are so many to choose from. I could go on and on here.
As I already mentioned, in the early spring after the snow is gone and before the leaves begin to unfurl, the sight of the burgeoning emerald green moss and lichen colony below my house is a siren’s call that I can seldom resist. Yesterday we had a mild day and I gingerly snow – shoed down to the brook thinking I might uncover a little of the snow – capped rock to see some moss. Much to my surprise, a strip about three feet in length on the southwest corner of this granite boulder was clear of snow and oh, the largest clump of hair cap moss was a brilliant emerald. As I stood there enchanted by both a myriad of mosses and tiny lichen forests, joy surged through me. Winter will not last forever!