Mats and Nets – Patterns from the Dunes

December 22, 2015

NOTE: Images in this archived article have been removed.

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“I reckon you know what you got into,” Hank says. . . .

“A devil’s stovepipe, I guess.”

“Yeah. . . . You see, bub, this here was a pine forest a long, long time ago. These dunes didn’t useta be here, just trees. But the winds kept bankin’ the sand higher and higher and finally covered up the forest. Clean to the top of the trees. And the trees eventually rotted out, leaving these hollows where they useta be, maybe just barely covered at the top. An’ you stepped into one. . . . Most people who fall into a devil’s stovepipe pull the stovepipe in after ’em. . . .”
(From Ken Kesey’s Sometimes a Great Notion.)

Smothered beneath the dunes that blanket 150 miles of the Oregon coast are ancient, dead forests. Yet on these same dunes, the crumbling of delicate mosses and lichens on naked sand builds new soil, launching new forests. Ecologists love sand dunes. Patches of just-sprouted pioneer plants dip fingers into ancient forests, and all the many stages of ecological succession form their own patches depending on how long ago they emerged from their last sand-drowning. Sand-dune ecology offers vivid examples of the shifting patterns that time weaves with plants and earth. It should be no surprise, then, that we can use the ecological patterns of the dunes in permaculture. After all, in many ways, permaculture is applied ecology.

On the dunes, all the many phases of ecological succession—the journey from pioneer species to forest, which normally takes centuries to unfold—have been stacked together and shuffled by the disrupting forces of sand and wind. Sand drowns a whole forest here, while over there its scouring etches out a plate-sized circle of moisture for a beak-full of clover seeds to take root. The result is a rich fractal patchwork. On every scale pioneer species, shrublands, and old forests are blended together. Patterns that usually occur in time have been transformed into patterns in space, and these patterns tell a story.

In twenty years of exploring ecology on the Oregon dunes, I’ve never seen a devil’s stovepipe; never ended up, like Hank Stamper’s brother in Kesey’s novel, at the bottom of a bark-lined tunnel in the sand left by a rotted tree. But I have stepped through other transitions on the dunes that were almost as abrupt as Lee Stamper’s fall. I’ve walked from shrieking wind and ripping sand on a naked winter beach into, just a few feet away, a tall shrub thicket that was calm and cool and quiet. Here, on sand that’s been stilled and enriched by plants, a dense wall of evergreen huckleberry, western rhododendron, Oregon waxmyrtle, salal, and manzanita forms impenetrable tangles that will reduce a howling Pacific gale to a whisper. These thickets flicker with birds, rustle with scampering lizards, are drilled with dark trails of small mammals, and offer a sweet harvest of flowers and berries to hikers.

How has the force of raw, blasting sand been gentled into rich soil and diverse habitat? What patterns can we see here, and how can we transfer these patterns to our own designs to create a thriving ecosystem?

Pioneers in the Sand

Dry sand habitats are tough places for plants to colonize. These dessicated environments come in two types: those with actively blowing sand, or with stable sand. Nature uses different tactics to co-opt each. But behind the dissimilar tactics lies the same strategy: To damp down wildly fluctuating, erratic processes and energies, like rainstorms, wind, or temperature extremes, and convert them into regulated, reliable sources of food and habitat. For example, rain pounding onto dry sand is fiercely erosive and quickly saturates the beach. But the water quickly drains away through the notoriously non-absorptive sand. Then in the first minutes of sun, the sand dries out completely. That’s a violent flood/drought cycle. But the situation changes when plants protect the sand with a leafy cover, and humus binds the rocky grains into spongy soil. Now, life has filtered and smoothed the wild oscillations of eroding flood and searing drought into a gentle rhythm of moist to not-quite-dry. The battering energy of rain has been turned, via biological aikido, into a useful, dependable source of plant growth.

On my dune walks, I often linger in the windless shelter that lies behind dunes or forests. This is the dry stable sand environment, the first of the two mentioned above. Here, protected from the constant ocean wind, I gladly stop to eat lunch or take notes. In these quiet patches, ecological succession begins with clumps of red fescue grass that colonize bare sand. The grass mounds create miniature windbreaks, stopping air movement near the ground. This offers a welcoming environment for a type of moss that loves sunny, dry sites. Incoming spores sprout quickly. When I picnic or write in these sheltered spots, I’m often surrounded by thick crusty mats of these ancient organisms.

The growing moss, in the pattern of ungratefulness familiar to ecologists and parents everywhere, eventually crowds out its older benefactor—the fescue nets that nurtured it. As the seasons pass, the carpet of moss alternately dries and renews, crumbling nutrients into the sand. Lichens move in next, and add their crop of organic matter. The resulting patch of shelter and soil tailors an ideal habitat for the subsequent occupant: kinnikinnik, a creeping evergreen shrub with red berries.

Kinnikinnik sprouts from bird-dropped seed or from dormant tendrils left over from earlier colonizations. Like the moss, this trailing shrub grows in a mat shape, but on a larger scale, and eventually smothers the shade-intolerant moss. The moss is now relegated to the margins of the expanding kinnikinnik mat, and creeps outward into the sunny, protected edge, transforming more sand into soil. The growing kinnikinnik cover deflects the wind upward enough for new, taller shrubs—evergreen huckleberry and salal—to sprout and thrive in the ensemble. Through these succeeding stages, a patch of bare sand has become an expanding island of fertile, densely vegetated soil.

In a few years the loamy center of the moss and shrub island is rich and protected enough to germinate shore-pine seeds, shat out by birds lured to the tangled shelter and to the fruit of kinnikinnik, salal, and huckleberry. The young pines grow upward into the ocean wind, which buffets and squashes them into another layer of bonsaied, mat-like vegetation. This largest rosette, ringed by an advance guard of habitat-preparing kinnikinnik and moss, advances into an ever-expanding circle of ground. Inside the circle, the wind-flattened trees eventually shoulder upward as the surrounding shrubs generate an expanding windbreak. The more protected vegetation in the middle grows taller, giving the island a domed profile. Finally, straight and tall pines, completely sheltered from the wind, stand at the center. A forest island has been born.

Here, the first tactic in nature’s strategy for building habitat has been to reduce the most disruptive force—the wind. After the initial grass windbreak forms, an ever-enlarging series of mat-forming plants follows. As the pattern proceeds from moss to shrub to pine, each succeeding plant community needs more nutrients and milder conditions to prosper. Both are provided by the earlier stages. Supplied with these, each succeeding community can wrest a larger territory from the once-raw and fitful environment. The new inhabitants enfold this space, quiet it, transform it into a nurturing home. Each generation uses the litter and habitat bestowed by the earlier occupants as a pump-priming, an investment to be wisely applied and increased. The fuel for this work is freely supplied sun, water, and air. As succession proceeds, organic matter, biomass, and nutrient recycling increase. Roots drive deeper, stems thrust higher. Increasingly, the plants regulate their environment’s temperature, water, and nutrient levels. Influences on the community shift from being elemental—wind, drought, high heat—to biological in origin. Enticing habitats form, and a dense web of connections links the many species.

This rich tapestry—a whole forest—began with a tuft of grass and a tiny crust of moss.

Stay with me for a second sand-dune survival strategy, and then I’ll tie both examples more explicitly into permaculture.

Networking on the Dunes

The most hostile habitat on the Oregon dunes is dry, blowing sand. Few plants can survive this environment’s combination of alternating burial and exposure, scouring sand, desiccating salt air, and lack of moisture and nutrients. I don’t linger in these inhospitable places, but usually huddle with my jacket flapping and billowing around me, squinting to shield my eyes from stinging sand, staying just long enough to list the species growing here. Some of the hardy plants that manage to colonize these howling bare dunes are seashore bluegrass, large-headed sedge, gray beach pea, and beach silver-top. These plants all use the same set of survival gimmicks: deep, spreading roots that don’t mind exposure to air when shifting sand lays them bare, and large seeds that are easily carried by wind and that hold enough nutrients to give the seedlings a good start in poor soil. These species are also unfazed by burial—they respond by happily putting out tillers to the surface.

Instead of forming mats the way stable-sand pioneers do, pioneers in active sand grow as single plants, randomly established wherever the wind’s vagaries drop a germinating seed. The shape of these plants—either a clump of grass or a mound of tightly clustered leaves—creates a small sheltered zone around each individual. The plant forms its own microclimate, a wind-sheltered ring of unmoving sand that holds moisture and litter. Once again, life has moderated high wind, extreme dryness, and sterile ground into a more tolerable range. Thus bolstered, the plant builds enough reserve energy to send out runners, and constructs a network of clump-forming clones, each spaced one to three feet apart.

This network sets the stage for the community’s jump to a new level of self-organization. Picture each plant with its small zone of benign microclimate. Each sheltered zone nearly touches the ones around it, creating a network of protection that covers a few hundred square feet. The individual plants have coalesced into an interconnected region of reduced wind, more stable sand, higher fertility, and increased moisture. Yet the plant density is very low: There’s plenty of unoccupied ground that can be colonized by new species. A second-generation community now moves into the gaps in this friendly environment, and soon, seaside tansy, coast angelica, seashore lupine, bracken fern, and pearly everlasting are thriving amidst the pioneers. These new nectar flows beckon to pollinating insects, while birds and seed-eating rodents are enticed by the food and shelter. Diversity builds.

It’s not long before some familiar shrubs show up: evergreen huckleberry and salal, along with western rhododendron. The pioneering grasses and sedges begin to disappear, driven out by shade, resource competition, and lack of sand deposition. The pioneers have unselfishly programmed their own obsolescence. Soon the shrub community progresses toward forest.

Patterns for Permaculture

The two patterns of colonization that I’ve noticed on stable and unstable sand—mat and net—illustrate two strategies for converting poor habitat to good. On stable sand, plants form a stack of overlapping mats, each layer on a larger scale than the previous. This creates a continuous, densely populated cover that radiates out from a secure beginning. On unstable ground, where a young mat might be quickly and totally buried, the wiser strategy is a more open net of plants, cast over a wider area. This net is less dense than a mat, but also less prone to catastrophic disruption. A net can be torn and still function—and nature builds self-repairing nets. If sand buries a section of a plant network, vigorously growing rhizomes will quickly stitch together the gap.

Permaculture already employs the mat and net strategies, though I’ve never seen them formally identified as such. By recognizing when we are using mats and nets, and applying our observations from the dunes, we can fine-tune our strategies and increase our chances of success.

When we plant in zone one, we’re essentially using a mat technique. First, we blanket any weeds and build soil with a continuous, deep sheet-mulch. Then we colonize the entire terrain with dense planting. Presto, we’ve built a mat. The mat technique works best where we can keep tight control over the area, in zones one and two. There, we’ll quickly notice and evaluate any new species moving in.

One technique for permaculture, inspired by the dune’s mat pattern, is the use of mat-forming plants of ever-increasing scales to quickly colonize new ground. Let’s say there is a spot we want to cover with plants, but we don’t want to spend a lot of time tending it. First, put down a small, tight mat of sheet mulch, and fill it with low-growing, spreading plants such as strawberry, clover, purslane, Nepalese raspberry, or others of your own choice. In the center of the mat place prostrate shrubs, like lowbush blueberry, gooseberry, currant, or bushy willows. To speed spreading, we can pin down a branch or two to encourage layering. As the mat spreads, or at the beginning, add trees or tall shrubs that sucker and sprawl, such as figs, bamboo, or black locust. We’ll have a forest in no time. We could also interrupt the mat-forming process anytime after the first low-growing plants have colonized the zone, using non-spreading plants in the next phase. Maybe we ought to—Several layers of madly sprawling plants might uncork unstoppable rampancy.

In more distant zones and over larger areas, a mat technique is too labor-intensive—we don’t have the time or the plants to control a big space. For planting larger areas, permaculturists often use a scattering of mulched circles: disks of mulch and small plants, each centered around a tree or shrub. This creates individual clumps of controlled space. If we design our pattern of mulched circles with the knowledge that we’re linking them into a network, we can optimize the spaces between circles. Remember that each mulched circle is surrounded by a ring of benign microclimate (high humidity, small temperature fluctuations) and improved soil (more organic matter, soil life, and moisture retention) that diminishes with distance from the circle’s center. If we space our mulched circles so that each ring of influence almost (but not quite) touches its neighbors, we maximize the “edge” and the number of different niches and microclimates in our net. The circles should be distant enough to avoid producing too much shade or root competition for new plants to thrive between them. But the circles should be spaced close enough to include the raw ground between circles in the “network effect.” Proper spacing is what binds the separate mulched circles into a network: The area behaves as a unit and has qualities that are more life-welcoming than those of unlinked plantings. The benign habitat between each networked circle will quickly fill with planted or opportunistic flora and with wildlife.

In permaculture, we’re often trying to accelerate succession and rapidly create mature ecosystems. By observing places such as sand dunes, where many different stages of succession are visible at once, we can see what patterns nature uses to quickly colonize difficult environments, as well as observe the phases and endpoint of the successionary process. Our design can then incorporate the species, patterns, and communities that will speed us to a productive, diverse, and mature landscape. With a little creative modification, we can use nature’s lessons to help us restore and enrich our world.


Botanical Names of Dune Species Mentioned in Text

Red fescue Festuca rubra

Moss Rhacomitrium canescens

Lichen Cladonia spp.

Kinnikinnik Arctostaphylos uva-ursi

Seashore bluegrass Poa macrantha

Large-headed sedge Carex macrocephela

Gray beach pea Lathyrus littoralis

Beach silver-top Glehnia leiocarpa

Seaside tansy Tanacetum camphoratum

Coast angelica Angelica hendersonii

Seashore lupine Lupinus littoralis

Bracken fern Pteridium aquilinum

Pearly everlasting Anaphalis margaritacea

Evergreen huckleberry Vaccinium ovatum

Salal Gaultheria shallon

Oregon waxmyrtle Myrica californica

Manzanita Arctostaphylos columbiana

Western rhododendron Rhododendron macrophyllum

Shore pine Pinus contorta

"Star-dune". Licensed under CC BY-SA 2.5 via Commons

Tags: pattern language, permaculture