This is why it’s much easier to reforest a clear-cut than a pasture. Most saplings planted in a clear-cut live, and most will be two to three times bigger than seedlings planted in a meadow at the same time—if the little trees in the grassland survive at all.
〜
Much of our planting has been focused on the old pasture just east of the creek and in the floodplain beside the newly meandered stream. But we’ve also been planting in the wooded uplands at our place, where all the big western redcedars and firs were logged off. There we’re replanting among broad cedar stumps, in the shade of tall bigleaf maples that were spared. The maples were damaged in the recent logging operation, however—by soil compaction, blows from falling cedars, and collisions with the skidders and other logging machinery. So they are not thriving. Large branches in their crowns are dying, rotting in place, and then snapping off in winter winds. The branch ends often plunge straight down and plant themselves a foot or more deep in the ground—as if they grew there. We’ve never seen this happen—we’ve only observed the aftermath—but I imagine the branches humming like tuning forks when their ends strike the ground.
When we underplant in the woods, there is no grass to scalp. Instead, the challenge is to find a root-free zone that can take a sapling. Stick a shovel in the ground in the Northwest woods and you’ll appreciate why it’s rare to see a young tree growing in the soil. Just under the surface of the forest floor is a mat of fine, tightly woven tree roots. The mat is in the black-soil zone, where roots are recycling nutrients released from recently fallen leaves and branches. The depth and density of this surface-root layer rivals what you find in a grassy pasture. If you hack through this mat and keep digging, you find stout root cords crisscrossing the deeper soil layers, branching into any pocket of soil that holds water and nutrients. In comparison, a sapling’s roots are slender and tender. In an arm wrestle over water, they don’t stand a chance.
The saplings find a way, though. In old forests, seeds germinate and start growing on nurse logs—downed, rotting trunks with upper surfaces 3 feet or more above the root mat. Once an old tree has been down for a decade or two, it’s common to see a row of 4-foot-tall hemlock or cedar saplings lined up along its back, like schoolchildren waiting for the bell.
The trees that emerge from the row and shade the others out will send their roots careening down the length of the nurse log, following the rotting cambium layer that held the old tree’s vascular tissue. This is where the lion’s share of the nutrients lie in the log. But some will head down, strike the soil, and take root there as well, straddling the log like a cowboy in the saddle.
The same thing happened when the early loggers left 6-to 8-foot-tall stumps. Seeds germinated on the flat surface of the cut, and the saplings that survived sent roots down the sides of the flaring column. When the carcass rotted away underneath, the great tree that remained would be perched on a web of roots—standing on tiptoe.
So when we carry a bucket of seedlings through the uplands, we have to look for open patches. Spaces a few feet from stumps are good, because the roots from trees felled five years before are rotting and roots from nearby trees haven’t yet taken their place. If you look up and see sky, you have checked both boxes: there is space for the roots and space for the stem. Then you can dig.
〜
Planting can bring pleasure or pain, depending on the soil you’re working in and the tool you’re working with. A planting tool should be chosen carefully. You want a shovel with a long, narrow blade. Depending on your preference and the soil involved, you may even want a hoedad: an implement with a stout wooden handle and a tonguelike steel blade making an L. If you choose a shovel, you want it to have a long throat—a metal tube that hugs the wooden handle. You never mean to pry, but sometimes you can’t help yourself when you’re planting. The handle of a tool with a long throat is less likely to snap if you get careless and use the shovel like a lever.
Saplings that are intended for replanting clear-cuts are grown and sold as plugs. Plugs have compact root systems and can be planted with a hoedad without digging a hole. Crews of professional tree planters work through clear-cuts carrying hundreds of saplings in a cloth bag—to keep the roots moist—slung over one shoulder. They plant a Douglas-fir plug every five paces or so by swinging their hoedad’s blade into the ground, prying open a vertical slit in the soil, pushing the plug in, stomping the opening closed, and moving ahead another five paces. The sequence takes ten to fifteen seconds; a good hand can plant three or four thousand trees in a day. Some professionals have planted a million trees this way.
Saplings intended for underplanting in existing woods, or for reforesting pastures or hayfields, are a different animal entirely. They are field grown for two years, so they can be 1 or 2 feet high aboveground with roots a foot or more long. They compete against grass much better than plugs or younger bare-root stock, but the downside is that they are labor intensive to plant—they take a lot of digging. We’re usually planting big bare-root stock in the pasture or cutover uplands at Tarboo Creek, so we do a lot of digging. And we learn a great deal in the process.
Some holes turn out to be archaeological sites. I’ve found shards of glass and crockery, pieces of brick or sheet metal, and cogs or rings from old logging or farming machinery. Every hole has a geologic record, too. It’s actually rare for us to see a classic black-then-brown-then-tan layering of soil horizons, in part because of the extent of human disturbance and in part because we have so many clay or gravel pockets—gifts from the glaciers that scoured Puget Sound. When the grade school students planted at our place with their families, we’d find necklacelike rings of cobbles at the base of saplings that had been planted in particularly gravelly holes—shrines to the pain their shovels had just endured.
In winter, the soil in the Dead Zone is saturated with water and sticky enough to put on a potting wheel and throw. Just 6 to 8 inches under the surface, the gray clay is often flecked and streaked with reddish orange. The color is from iron, deposited by bacteria that live in waterlogged, oxygen-free soil. But in the same spot in late August, the clay will have dried out and been fired by the summer sun—baked hard enough to dull the blade of a shovel or even throw sparks when struck by a hoedad.
We also have muck soils—blackened dirt that’s rich in waterlogged organic matter. This is a favorite spot for western redcedar trees. They grow pancaked roots in sites like this, as the occasional windblown stem, or tip-up, will attest. Tree roots flatten out and stay near the surface if the deeper layers of the soil are waterlogged year-round. The problem is that saturated soils become oxygen free unless they’re exposed to flowing water or some other aerating process. Crumbly soils with good structure, or tilth, have air pockets that maintain an oxygen supply for plant roots. But in muck and peat and clay soils, water fills those pockets and prevents air from penetrating. Once the bacteria and fungi that decompose dead leaves and roots have used up all the available oxygen in these soils, there is no mechanism to replace it. Roots can’t grow in these oxygen-free zones. They suffocate. So instead they spread into a pancake at the surface, where they can breathe.
A planting hole can also present small mysteries. For example, I’ve struck pockets of rich organic matter beneath several layers of brown sands and gravels. Where did the black soil come from? Is it the decayed roots of gigantic old-growth trees, or surface soil that was buried recently by a bulldozer or plow? I’ve also unearthed little patches of bright rust-red soil, far uphill from the orange-flecked clays of the Dead Zone. For all I know, I could be excavating either the remains of a rusted bucket or an iron-laden rock that was transported from the far north and dumped by the glacier. Some holes reveal buried chunks of charcoal, possibly from one of the settlement-era fires or possibly from a forest that burned a thousand years ago.
〜
Perhaps the most important aspect of the soil we plant in, though, is invisible to us. All of the trees in a Pacific Northwest forest—indeed, virt
ually all of the world’s trees—live in association with fungi. Most of us know fungi only as baker’s and brewer’s yeast, the mushrooms on pizza, the mold on bread, and the cause of athlete’s foot. But there are millions of different species. Many are decomposers that make a living from the dead bodies of plants and animals, recycling nutrients that would otherwise be tied up in carcasses. The most important of these decomposers are members of the mushroom-making lineage. Together with a handful of bacteria, the mushroom-forming fungi are the only organisms in the world that can digest lignin—the molecule that gives tree trunks much of their strength. Without these decomposers, the world would be carpeted with dead wood.
But fungi are critical to plants in life as well as death. Healthy trees are coated with dozens of different fungal species, from the tips of their branches to the bottoms of their deepest roots. The situation parallels the human body, which hosts dozens or hundreds of species of bacteria. Our skin is coated with a layer of them, and they fill our guts. We are walking, talking habitats for these bacteria—much like trees with their resident fungi. Most of the bacteria on human skin are harmless hitchhikers; we’re merely a convenient place for them to live. But the bacteria in the human gut, like the fungi on plant roots, are crucial to nutrition. Bacteria in the small intestine synthesize vitamins we can’t live without and digest food molecules our own cells aren’t able to process; bacterial cells in the large intestine also help with water balance. Much of our feces consists of the dead bodies of these symbiotic cells. Change your diet—say, from one that emphasizes grains to one dominated by sugars and oils—and the composition of your gut flora will change in concert.
The diversity of fungi that live on tree leaves and stems was discovered recently, and research has yet to clarify whether most of these aboveground symbionts help their host plant, hurt it, or have no effect. Belowground, the picture is much clearer: most trees and other plants could not thrive without the fungi that live in and around their roots. In some cases, the fungi actually penetrate the interior of the roots, meaning that the partner organism is anchored inside the plant’s body. Whether one end coats the root exterior or enters the interior, the body of the fungus fans out from the point of contact with the root into the soil, creating a net that captures nutrients. Plants leak sugars and other photosynthetic products to the fungi at the point where the two partners touch; in exchange, the fungi seek out and transport nitrogen and phosphorus atoms from the soil to the plant. It’s an underground economy that benefits both parties.
The key to this system is that the branching network of thin filaments that make up a fungus’s body presents an enormous amount of surface area to the soil—much larger than the total surface area available in a plant’s roots. The exterior of each fungal filament is studded with proteins that secrete digestive enzymes; the enzymes break down rotting plant material in the soil, creating a slurry. Each filament also contains proteins that are specialized for importing the nutrients released by digesting dead plant tissues, so nitrogen, phosphorus, and other key substances can be transported into the fungus’s weblike body. When it comes to reclaiming and recycling nutrients, fungi are the most efficient organisms on Earth.
Trees barter for these atoms—especially the nitrogen and phosphorus. A significant fraction of the sugars manufactured in tree leaves is destined for export to the fungi that wrap the tree’s roots. The exchange is reminiscent of merchants who pull sacks of wheat and rice off the backs of camels, haul them into the dim interior of a bazaar, and trade them for a handful of diamonds. Even red alders and other species that house nitrogen-fixing bacteria in root nodules will take up with soil-dwelling fungi. Deny tree roots their fungal partners, and the entire plant will be stunted.
Fungal hyphae can even connect the roots of adjacent trees and facilitate a flow of sugars and other molecules between them. A tree that is in the sun giveth; a tree that is in the shade taketh away. How the sunlit, producer trees avoid donating sugars to nearby shaded trees indefinitely—in effect, getting parasitized—is a question biologists are still researching.
When we’re out planting trees, though, we assume that the roots will find the fungi they need somewhere in the soil. We don’t add them. A friend who is Washington’s leading expert on fungi tells me it’s safe to assume that spores from the appropriate root-living fungi are just about everywhere. But if I ever walk by a sapling that’s still struggling after several growing seasons, I sometimes wonder if its roots are naked instead of clothed in a sheath of fungi, and the plant malnourished as a result. Sometimes I even deposit a handful of forest soil at the base of small trees like these, hoping I’m introducing spores from the missing root-associated fungal species. It’s like eating yogurt or other probiotics if your gut gets upset and stays upset during a long course of antibiotics.
〜
Once a hole is dug deep enough and wide enough, success in tree planting hinges on the sapling’s roots. For the rest of its life, these will be hidden from us. Years later we may walk by and recall that the roots have become coated with fungal hyphae, or we might be dimly aware that the roots have become grafted to the roots of neighboring individuals, with sugars and nutrients passing between them like gossip. But the world of the soil, like the world of the deep sea, is mostly a mystery. We are out of our depth.
Still, at planting time, roots are foremost, and it’s critical to keep them moist. The best planting weather occurs on classic Northwest winter days, when the temperature is 40°F and a gray mist is falling—the kind of weather that can settle in for weeks on end and send recent immigrants back to southern California, vowing never to return. On days like these, the humidity is 100 percent and the roots of planting stock are well satisfied. Even if it’s raining, though, we’re careful to keep the roots snug in a canvas or brown-paper planting bag, or surrounded by soil in a bucket. On dry days or in a wind, this precaution is urgent.
As a tree comes out of the bag or bucket, it’s important to look at the length of the roots and the depth of the hole, and judge whether the roots will fit. If the hole isn’t deep enough, the roots will lie on their side and the tree will be J-rooted—meaning the ends of the roots are headed to the side instead of down. If the roots continue to grow like this, the tree will be tippy. Even if the root tips succeed in turning down and spreading out, the tree has had to do extra work at the most vulnerable interval in its life. If you were transplanted to a new job in a foreign culture and were struggling with the food and language and housing situation, you’d rather not break your leg as well. If the soil really is impossible to dig deep enough, I’ve gotten a jackknife out as a last-ditch measure and trimmed the roots.
So the goal is to give the saplings every possible advantage. Little things count. Plant the tree so that it’s vertical and not leaning to one side—that way the stem won’t have to waste time and energy righting itself. Depth is another Goldilocks problem: don’t plant the stem so deep that part of it is buried or so shallow that the tops of the roots are exposed. And if the depth is off a little, things will probably work out. Plants are tough.
If possible, it’s good to spread the roots out in the hole so that they are separated and have a head start on finding soil with a fresh supply of oxygen, nutrients, and water. Then hold the top of the plant and start pulling or kicking soil into the hole to surround the roots. When the first third of the hole is filled, gently tamp the soil with your fingers or boot tip to make sure any large air pockets are filled—airy cavities can dry nearby roots and kill them. Finish filling the hole and press a boot around the base of the stem to pack the rest of the soil and remove any other air pockets. Hold the tip of the stem and pull on it gently as you do this—providing enough tension to prevent the roots from compressing along with the soil.
And with that, a tree is planted.
Before moving on, though, it can be important to protect the young thing. If the planting site is mousey, most planters will slip a plastic tube over each tree and secure the
sleeve with a thin stake. The plant protector will prevent mice from nibbling the bark when they’re hungry in winter. Tall plant protectors will also help with rabbits, who like to nip off tender shoot tips.
Susan’s cousin, who is reforesting an old pasture in the Baraboo Hills of central Wisconsin, has to protect her young oaks, hickories, and white pines from white-tailed deer, which are epidemic. She uses a technique favored by Swedish foresters: spraying the saplings with pig’s blood. She buys the stuff dry, mixes it up in water, and hoses the little trees down. It gives the saplings an odd reddish hue but puts the deer off their browse.
In the pasture we’re replanting, we also have to think about protecting the trees from grass that will inevitably encroach on the little patches that we’ve scalped and threaten to overwhelm the little saplings. Each summer nwi sends crews in to cut the grass around plant-a-thon saplings with gas-powered string trimmers. We tend to favor mulching the trees with wood chips or weed barrier cloth, or even with burlap—using landscape staples to pin an old coffee bag on either side of a sapling. We get free coffee bags by the pickup load from a roasting plant near Seattle. But when we can’t get a mulch down, we have to let the trees fend for themselves.
〜
Once a tree is planted and protected, you move on to the next. Planting in a clear-cut is all about rhythm—you’ll see crews moving as efficiently as dancers as they plant plug after plug, sometimes glancing up to monitor each other’s progress. But planting in grass is labor intensive. A plug can be in the ground in seconds, whereas planting and protecting a two-year-old bare-root sapling in grass can take five minutes or more—even in soil that’s easy to dig.
The work may be slow, but it’s also sociable. We usually work in teams of two or four—one or two people with shovels and the others with the plant bucket, plastic protectors, and coffee bags in a garden cart. We talk and work and work and talk: about our kids, the bald eagle passing overhead, the pileated woodpeckers yammering from the woods, the mouse tunnels in the grass.
Saving Tarboo Creek Page 9