The emerald kingdom: the realm of moss

If mosses dream, I suspect they dream of rain.
~ Robin Wall Kimmerer ~

The wildly abundant, even overwhelming rain that has been falling on California this season has turned my neighborhood into a world of emerald fluff. In the woods, I walk through a green so pervasive that it’s palpable, almost breathable, both delicious and disorienting. The trail where I took the photo above leads into a redwood forest in a canyon. The combination of the needles and leaves overhead, ferns at my feet, and moss running up the trunks gives me a feeling of being suspended, unearthed, as one does in a fog. But here, it’s green. 

Moss and woody shelf fungus on a tree trunk

When, unable to resist the lush softness of a bed of moss, you run your hand over its springy surface, you are joining one of the oldest and youngest of Earth’s terrestrial creations. Mosses were the first plants to differentiate themselves from bacterial and algal life and take their place on land, sometime during the Ordovician Era, 485 to 444 million years ago. They were the forerunners of the towering trees they live among.

Bryophyta cousins moss and liverwort are the oldest land plants on Earth. Photo by Betsey Crawford
Bryophyta cousins moss and liverwort are the oldest land plants on Earth

The softness and lack of structure that characterize moss to this day make it a poor candidate for fossil creation in such ancient rock. Most species of moss have leaves that consist of a single layer of cells. But their spores have hard cases. So we can find fossil spores from the Ordovician indicating that the earliest plants were the Bryophyta cousins, liverworts and mosses. It wasn’t until 2020 that geologist Greg Retallack identified the first fossils of the plants from that era, dating them to 460 million years ago.

Ferns and moss growing along the Hoo-Koo-E-Koo Trail, Kentfield, California. Photo by Betsey Crawford.
The long survivors: ferns growing with moss

For all that time they have been slowly evolving to fit one niche after another since braving their first foray onto land. They have seen continents form and meet, crashing mountains into existence. Seen volcanoes cover the earth in ash. Watched as rivers carved canyons. They have been buried in ice, waited out years of dryness, welcomed eons of damp warmth. Survived all five mass extinctions. Meeting challenge after challenge until they mastered living on every continent amid all conditions.

Delicate moss fronds grow on the cut surface of a fallen tree trunk.

If you have ever watered a plant that got too dry and watched the drooping stems turn upright again you’ve seen the work of the plant’s vascular tissue. These are transport structures that run the length of the stem. They bring the water upwards, often at a surprising speed, and hold the plant upright. Mosses don’t possess that tissue, so, except for those species that grow in water or rainforests, they stay small and low to whatever ground they are growing on. Nor do they have water-absorbing roots. Instead, they use delicate threads called rhizoids to anchor them to their substrate. They depend on their tiny leaves to absorb moisture, nutrients, and the carbon dioxide they need for photosynthesis.

Moss draped tree in the Hoh Rain Forest, Olympic Peninsula, Washington by Betsey Crawford
Moss-draped tree in the Hoh Rain Forest, Olympic Peninsula

Though some mosses can take sunnier environments, those minute leaves love shady, cool places. Which is why they carpet the temperate coastal forests I live among.  Mosses and moisture are inextricably bound. They do survive dry spells; a few even live in the desert. In this Mediterranean climate, the rains drenching my backyard mountain will give way to months of complete dryness. Mosses survive those stretches and can make it through years when the rainy season is sparse and fleeting. They dry, curl into themselves, stop photosynthesizing and reproducing, and wait. As soon as the first rain comes, they will fluff out, expanding to absorb water through every cell in their leaves. Water resting on the leaf allows a path for carbon dioxide to enter the cells, which immediately start photosynthesizing. 

Capsules holding moss spores rise above the mat of moss leaves. Photo by Betsey Crawford

They then begin the process of reproducing, forming spores that will be contained in a small capsule lifted a couple of inches above the base mat by fine stems. When the capsules open, the powdery spores are borne off by wind. This reproductive strategy passes on the genes of only one parent. Thus with moss, as with other ancient plant families like ferns and horsetails, little has fundamentally changed in their 460 million-year history. Depending on whom you ask, mosses have differentiated enough to create 12,000 to 22,000 species. But compared to the wild abandon of sexual reproduction, which has produced 300,000 named species of flowering angiosperms, spore reproduction creates a close-knit family.

Moss and silvery lichen growing together on a tree trunk. Photo by. Betsey Crawford.
Moss and lichen growing together on a tree trunk

They have a few other reproductive tricks. Microarthropods like mites live in moss and can foster fertilization by moving sperm to egg, which usually depends on enough water for the sperm to swim. There is evidence that scents play a role in attracting these tiny arthropods, similar to one of the attractors of pollinators in flowers. Cloning is common and, with some species, the only method of reproduction. Branchlets, gemmae, and other specialized growths break off when it rains and establish themselves nearby. 

Their forest neighbors also play a role. Robin Wall Kimmerer is a bryologist, a specialist in moss. In Gathering Moss, her poetic ode to her favorite plant, she describes the summer she and a student spent trying to figure out why one moss was common on the top of felled trees while another was common on the sides. They found that the dynamics of the side moss are mediated by fungi. But only after hot, humid weeks spent being bitten by one bloodthirsty bug after another did they discover that the top moss is spread by chipmunks. Who, using those handy trunk runways to travel through the forest, pick up and drop moss branchlets on the way.

A chipmunk eats at the opening of his nest in a tree, carpeted in moss. Photo by Betsey Crawford

There are a lot of other beings — hundreds of thousands of them — living in and with moss in addition to chipmunks. Bacteria break down dead moss cells, helping to create a soil layer under the moss. One-celled cilia in turn break down the bacteria. As do multicellular nematodes, rotifers, and the minute, bear-like tardigraves who also eat moss cells and other microbes. This breaking down of organic matter adds to the nutrients available to both moss and its surroundings. Varieties of symbiotic, variously protective or parasitic bryophilous (moss-loving) fungi inhabit mosses. Cyanobacteria living in the leaves take the crucial nutrient nitrogen from the air, making it available to both themselves and the moss, which in turns enriches the soil with it.

Black mushrooms in the leptonia genus rise above the moss they live among. Photo by Betsey Crawford
Black mushrooms in the leptonia genus rise above the moss they live among

They lead a busy life, these small, quiet plants. Often the first colonizers of disturbed sites, they stabilize exposed ground. They add water on the one hand and absorb it to prevent erosion on the other, filtering toxins along the way. As they break down the detritus left by the disturbance and cleave minerals from rocks, they form soil and add nutrients to the ecosystem, inviting colonizing seeds to take root. Once the neighborhood is established, mosses continue to be an integral part, carrying on their soil formation and water management. Small animals like chipmunks and squirrels, along with various species of birds use moss in their nests. Insects nest among the branchlets. Lichen share boulders, tree trunks, and branches with them. Ferns and forest wildflowers grow from the soil they produce, often growing out of the moss itself. 

Fetid adders tongue (Scoliopis bigelovii) is one of the wildflower neighbors of moss on the King Mountain Loop, Larkspur, California. Photo by Betsey Crawford.
Fetid adders tongue (Scoliopis bigelovii)

These vibrant beings are the ancestors of the trees they carpet and they remain, in so many ways, the parents of the forest they inhabit. Large and preoccupied, we humans tend to give little heed to the tiny entities that really make life possible. We are awed by the redwoods, the rugged boulders, the cluster of wildflowers, the carpet of ferns. As we should be! But the charismatic features of the forest exist because the smallest members are doing the work of creating the ground on which the entire ecosystem stands.

In the green haze of the early spring woods, we walk among ancient intelligences. The more we pay attention to these ageless miracles, the further they pull us in. The surface jangle recedes. For a while, we dwell among the deepest life forces on our planet, connected to everything that has gone before and everything present now. Renewing, as Thomas Berry said, our participation in the grand liturgy of the universe. Powerful relationships that nourish our energies to protect the world we cherish, the beings we live among.

Moss and turkey tail fungus (Trametes versicolor) with its bright stripes of orange and brown on a log. Photo by Betsey Crawford.
Moss and turkey tail fungus (Trametes versicolor) on a log

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THE SOLACE OF DEEP TIME

If the 4.5 billion year timeline of Earth’s history ran from your nose to the tip of your finger, a swipe of a nail file would wipe out human history. A lot of wild things happened before that! Utah is a perfect showcase. Standing on ancient stone, I can find both the history of Earth and my soul’s bedrock.

ATTENTION IS REVERENCE

Attention is devotion, the poet Mary Oliver said. It is the gift we give back to the amazement of living, as well as a gift we give ourselves. As we step into the moment — awake, aware, moved, interested, curious — we bring vivid aliveness to days that can slip by in a blur of activity and reaction.

Vivid green fern leaves filling the picture. Black background. Photo by Betsey Crawford

THE SURVIVORS: THE LONG CONSOLATION OF FERNS

For all their delicacy, ferns are a hardy bunch. As we would be, too, if we had survived for 360 million years, outlasting two major extinctions, feeding dinosaurs along the way. Such ancient lineage, now dwelling peacefully in the forest, gives our own existence depth to depend on. Plus…a surprise.

THE INTIMATE BOND: HUMANS AND DIRT

Although dirt is one of the most crucial — and threatened — systems on our planet, it doesn’t have a reputation for excitement. Until we see our bare feet standing on dirt, and realize we are looking at different aspects of the same cosmic elements.

THE DRAMA OF DEEP TIME: JOGGINS FOSSIL CLIFFS

At Joggins you stand ankle-deep in fossils. Here were once vast forests of the ancestors of ferns and horsetails. Tree-sized relatives of mosses. As you walk the beach you can hold these ancient plants in your hand, stone after stone. It’s thrilling! And, as ever, profoundly moving to feel embedded in the deepest of time.

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