In Praise of Snags

Snags are standing dead or dying trees. In natural forests in the Pacific Northwest, there are usually a number of trees that have died from lack of light, overcrowding, competition and whatnot. Forests older than 150 years are heading into old growth status and by then some trees in these forests have been killed by fungi infecting the roots or trunk (the diseases they cause go by colorful names like stringy butt rot or laminated root rot). Wind is a big creator of snags. There may be some broken tops in trees with sound roots but weak trunks (windsnap) or if the roots are rotten or the ground soft from rain and snow, blow downs (windthrow).

In an old-growth west side conifer forest (250 – 1000+ yrs) diversity abounds: openings where giants have fallen let in light to allow shrubs and seedlings to grow better, there is wood on the ground, standing dead snags, trees growing out of nurse logs, a mossy zone with perennials and groundcovers, a shrub layer, a lower understory tree layer, intermediate to very tall trees. This is all great from an ecologist’s perspective.

An oak woodland has a different character. If a woodland or savanna was burned, it might have an open character. If no fire killed the young trees and brush, it will be crowded with skinny trees reaching over each other for the light, maybe one or two legacy giants that were seedlings 150 to 300 years ago, overtopped by douglas firs; dappled shade, poison oak shrubs, and vines climbing the trees, grasses, a few shrubs (serviceberry, snowberry) and flowering bulbs (camas) and perennials (checkermallow, strawberries) persist in the low light. There will be dead standing oaks in either case, many with dead branches and brittle broken limbs among the live ones. And lichens: many species and a great biomass of lichens.

In a managed forest, the forester does the thinning in order to grow fatter trees for market, like a row crop. When these trees – all the same age – are eventually cut, like giant broccoli, there will be some green trees left and some dead standing snags because the Oregon Department of Forestry requires it.

Why? Why do we value snags enough to write them – however few and inadequate in number – into the forestry regulations? Life. And diversity. A dead tree has arguably more life in it than a live tree. The diversity of fungi, bacteria, and wood decay organisms is enormous. Beetles, termites, ants, and others feed on the dead wood and fungi. These are the base of the food web, the decomposers and recyclers that return nutrients stored over decades or centuries, to the forest.

There are plenty of birds (woodpeckers, chickadees, nuthatches) who visit the snag to find food, and excavate nest cavities in the softening wood. Others (owls, bats) who can’t excavate a hole, use those made by woodpeckers, in a grand circle of beneficial re-use and mutual aid. A dead tree is a great place for a raptor like a hawk or osprey to nest or sit and watch for prey, possibly a douglas or flying squirrel. Snags are so important to wildlife that getting rid of them endangers species that rely on old growth and dead wood.

Next time you drive through the Oregon Coast Range on the way to the beach, observe the difference between a national forest and adjacent tree farms owned privately or by the BLM. Instantly the trees get bigger in the national forest, the ground level cooler and more diverse, the depth of the canopy is higher and the light changes. Streams look like real streams. This you can tell at 55 miles per hour.

We had a tree next to the house made into a snag. A dougfir that needed to be removed for safety. Our arborist Brian French (that’s him up the tree in photo below) took off the limbs, topped it and crafted a new jagged top – an outstanding fake lightning strike to accelerate fungal invasion. (Final touch was a birdhouse built by birdman Tom Brewster, volunteer with the Yamhill Conservation District, local woodworker, and possessor of the best Willamette Valley accent/drawl ever.) Brian also hollowed out a section of trunk behind a carefully cut piece of bark, then replaced the bark so the birds could move in right away without waiting for the snag to soften up.

Just in time for nesting season, a tree swallow pair scouted it and pronounced it livable. The rest of the flock looks on in envy. For the first time we have tree swallows careening over the house grabbing insects in the new, more sunny and open space. Yay snag.

Link

Closeup on Forests of the Pacific Northwest : Image of the Day.

Had to share something I stumbled on while looking for a satellite image of the vast Eastern Oregon wetland that is the Malheur National Wildlife refuge. The accompanying text is very important. These carbon sinks are old growth conifer forests, not white oak woodlands, so a little departure from this blog’s theme.

Another feature not mentioned in the text is that “checkerboard lands” are very clearly defined on this map. These are our legacy from US government donation of the spoils of conquest to the railroad barons more than a century ago.

Scotch Broom, Scourge of the Northwest

There is a class of weeds that are legally defined as NOXIOUS. This is a special term applied to weeds that are so aggressive as to be considered economic and ecological dangers. They can completely alter an ecosystem by changing the soil nutrients, pH, or forming a monoculture that excludes other plants. Dandelions may be weeds (a weed control specialist once termed them obnoxious), but they are not designated as noxious because they are not capable of destroying crop value or ecosystems. They and many others are “background weeds” we live with.

The people who decide who gets noxious weeds status are the state and county noxious weed control boards. The Department of Agriculture is the supporting agency for these boards, because noxious weeds were recognized as an economic problem for agriculture. Controlling noxious weeds also protects ecosystem integrity in natural areas. Many weeds that don’t seem that bad to the average person can be very bad when they are unleashed in the countryside.

Scotch broom (or Scots broom) is a noxious weed. Its natural enemies are back in the homeland (Europe) so it can spread at will here. However some insects that eat seeds and vegetative parts of it have been introduced and may help control it.

We are dealing with the legacy of soil disturbance from grazing, logging, and trail blazing followed by Scotch broom invasion. When our restoration work was done, huge patches of it were mowed, and mowed again in subsequent years. But mostly just keeps the plants short. To kill it, one can cut large stems during summer drought, spray when it’s in bloom (highly effective), or pull small ones. Each method has its advantages and disadvantages. In an area where the seed has fallen and built up in the soil, it can take many decades to exhaust the seed bank. Pulling can bring seeds up to the surface and result in a whole new crop the following year.

Which brings me to my latest small project: due to weather and other circumstances, a couple of our scotch broom patches had not been mowed for one or two years, and it had grown taller. This actually makes is easier to spray, since when it’s short it is hard to kill because it doesn’t have enough leaf area and doesn’t bloom.

This winter I tried using a dormant spray on the evergreen stems which were more ‘alive’ due to the mild winter we had. It is more difficult to get all stems covered with a dormant spray, but easier to avoid killing the plants you want, as they have all died back. A combination of Triclopyr (Element 4A), and an oil/adjuvant (Mor-Act) seemed to do the trick, although it takes a heap-o-spray to get total coverage. I sprayed again during bloom, which was very effective.

IMG_0705

invaded area – previously sprayed broom is dead and dying. blooming plants are overtopping wildflowers in the nectar plots

IMG_0704-2One problem area was the nectar plots where we had planted wildflowers. The broom had invaded them over the years. Suddenly after a couple of years of no mowing, it was blooming. I couldn’t spray it without killing the wildflowers.

I hauled the weed wrench up the hill and brought along my spray bottle of herbicide and loppers. The ground was still soft from recent rain, so I thought perhaps I could minimize disturbing the seed bank by careful use of the weed wrench to pull the broom. It’s a satisfying plant for pulling – the taproot comes easily out of the ground with a ripping sound and not much fuss. But this was a rather slow operation. Actually weed wrenches are often more attractive as an idea than a tool. They are fun and easy to use, but the soil disturbance frequently outweighs their benefit.

IMG_0706

I thought perhaps I could test the effectiveness of various methods, and speed things up too, so I switched to cutting with loppers, spraying the ends immediately with a 1:3 mixture of triclopyr (Garlon) and water from a spray bottle with a little surfactant – a variation on the “cut and paint” method. The weather was hot, the broom plants numerous, and so I decided to also add a third treatment – just cutting. I am curious about how late in the season cutting alone will kill broom. Ideally, that’s a method for older large stems that have more trouble resprouting and it is supposed to be done in the hot dry summer to make it doubly difficult. Some of the stems I was cutting were smaller, and we subsequently had several weeks of cold damp rainy weather, so I don’t expect those to disappear. However, at least the wildflowers had some light to grow.

done at last

done at last

Same plot three weeks later - rose checkermallow in bloom. Others in foreground still struggling

same plot three weeks later – rose checkermallow in bloom. dead broom mulch

A Map Of Time, Time In Maps

This is a gallery of landscape changes in our little corner of the world. In a very short time (1994-2012), the local vegetation has been altered by land management quite dramatically. From our perspective (our 20-acre rectangle) it often seems overwhelming.

In 2005 we had a comfortable buffer of forest around us for the birds and wildlife we like to watch. We knew it was tree farm country, so logging was a given but, patchy as it was, it didn’t seem too traumatic. You can see the tree farms mostly blanketing the area in the earliest GoogleEarth map.

Then came a shift in land use – ‘conversion’ is the term – from timber to vineyards. Watch the photos as the trees begin to disappear. Vineyards and orchards sound like a sort of idyllic alteration, but think just a minute about what that entails. Conversion from old growth to tree farms is a step away from diverse, patchy habitat of a particular kind: spotted owls, flying squirrels, really big trees with a lot of carbon stored in their massive trunks, a lot of cavities for owls and other specialists. Old growth trees (250+ yrs) that store and hold – sequester – more carbon than any other type of forest. You can see that even in the earlier views, the connectivity between patches is important – those are corridors that allow wildlife and plants to move across the landscape either to escape the clearcutting or to find food or mates.

Timber farms, especially smaller ones cut in patches on a long rotation, (time between cuts), shelter many important organisms while they grow, and if those plants and animals are lucky, they can shift over to another patch when the clearcut begins. Technically, people are required to leave a certain number of trees and snags, but the rules about that are so lenient that it doesn’t really amount to anything ecologically important in most cases on private land. Federal forests are another story, as they are managed differently. The other thing about forestry is that there are relatively long periods between soil disturbance.

Now, step it up one notch with conversion from timber land to row crops, vineyards, or a hazelnut orchard. If you look, you can see that to the north and east of our 20 acres, all trees were removed, conifer, oak, even the ones that were formerly left by commercial forestry. Stumps were bulldozed, burned, and the land plowed. Two major changes that occur now are the absence of trees and shrubs, and soil disturbance on a regular schedule. Weed control and monoculture demand constant spraying, plowing, or both. All these activities restrict plant life and, importantly, affect the insects that can survive in disturbed habitat.

Unless a farm, orchard, or vineyard is conscientiously managed to leave patches of undisturbed habitat for native ground nesting bees, predatory insects, and other beneficials, the landscape is a depauperate one compared to a natural one.

In the gallery above, you can view the transition from 1) patchy timber harvest to 2) clearcuts on a larger scale (there is a large absentee landowner to the north and east of us who is progressively extracting all the monetary value from his timber, then selling off the land) then 3) conversion to vineyard to the east and north. Note the extremely clean patches and rows of plowed and planted crops. Oak trees that were left after cutting douglas firs were stripped off the land and sold for firewood. Thankfully, a few trees were left around a low spot on the east side, that is the source of a stream that flows across our property and down to Deer Creek. However, our hydrology is permanently altered. Erosion from the force of high water flows, and lower flows in summer are byproducts of vegetation stripped off the soil surface.

Next week – the closeup view of our patch before and after we acquired it.

Oh, the irony…

In April, NPR ran a story about shooting one species of owl to save another in Oregon. It just begs for commentary.

Although there aren’t any spotted owls on our place, this is an example – no, possibly THE example of the ethics and dilemma of ecological restoration and questions surrounding repair of damaged ecosystems:

  • Are the results of human-caused ecosystem change separable from change that occurs naturally?
  • If we are serious about saving species and habitat, how far do we have to go to change our own behavior that caused their decline?
  • Are we in a downward spiral – making the situation worse by reacting to the effects of our actions rather than addressing the true causes of extinction?
  • Is this whole endangered species recovery exercise going to work for some but not all species? Which species will be able to live with us?
  • Will that be enough to preserve the safety net we humans depend on to survive?

Okie doke, so in a nutshell here is the situation:

In the 1970’s, a biologist named Eric Forsman did groundbreaking research on the northern spotted owl (Strix occidentalis caurina). Forsman found that spotted owls depend on old-growth forest habitat. It was determined that they were endangered due to loss of old growth to widespread logging in the Pacific Northwest.

In 1990 the northern spotted owl was placed on the endangered species list. The Endangered Species Act (ESA) mandates protection for species if they are listed, plus a plan to bring them back from the brink. So in 1991 millions of acres of federal forestland were excluded from logging to save habitat for the northern spotted owl. All hell broke loose in the logging communities of the Pacific Northwest, because of their dependence on federal timber land. For an excellent account, see The Final Forest by William Dietrich.

So for the last 30+ years Eric Forsman and a lot of other biologists and managers have been working to bring the spotted owl numbers up by saving habitat. But in fact the numbers are sinking.

As early as 1998 reports about an aggressive cousin – the barred owl (Strix varia) – discussed it as a potentially game-changing threat to the spotted owl (The Owl: Spotted, Listed, Barred or Gone?). Now it has come to pass that yes, the barred owl is currently a big factor in the decline of the northern spotted owl. The biggest factor.

Where did barred owls come from? Apparently barred owls started moving west from the eastern US about the time settlers began plowing up the prairies and suppressing fire. They moved through Canada and Montana, and started expanding their range into the Pacific Northwest in the 1960’s. Was it because of us? Or would this have happened anyway? Impossible to say. The two species might have evolved from a common single species at the time of the last ice age – at least we can be reasonably sure humans didn’t have anything to do with that.

Interestingly, barred owl populations here did not explode until about 20 years ago – about the time the spotted owl was listed. Speculation about why this happened follows this line of reasoning: like many invasive species, at first there aren’t many of them, but gradually they become adapted to their surroundings, or perhaps their population builds to the point where they just produce a ton of offspring. Suddenly the population explodes – because they have few or no predators and parasites, or because they are just better at hogging resources.

In the case of the barred owl, not only are they more aggressive, they are omnivorous and voracious. Whereas the spotted owl is more retiring, and picky about what it will eat – which happens to be old growth-dependent species like flying squirrels and tree voles. Spotted owls are part of a wonderfully complex and delicate food web, involving truffles, arboreal mammals, and big tree cavities. Fat lot of good that did them.

Because barred owls scare off spotted owls (although not always – they also hybridise with them, meaning it is possible spotted owl genes could be lost or “swamped” by barred owl genes), and because they aren’t particular about what they eat, they have no problem supporting themselves at the expense of spotted owls. But when barred owls have been removed or shot, spotted owls show up again. This is where the idea of getting rid of the barred owls came from. But really, this is an idea that can’t get very far. If land managers could get past the outcry over shooting a sort-of native bird, according to Eric Forsman, “You could shoot barred owls until you’re blue in the face, but unless you’re willing to do it forever, it’s just not going to work.”

So were all those years of trying to save habitat wasted?

People who depend on timber for income, and who have suffered disproportionately during the recent economic recession are suggesting that okay, since you can’t save the spotted owl by setting aside habitat, it doesn’t matter. Let us start cutting timber in the reserves set aside during the 1990’s. This is the disadvantage to saving species instead of looking at the really big picture – people can argue that if we can’t save those species, we don’t need their habitats. But this would accelerate the degradation of ecosystems we all depend on.

…far from saying that the logging restrictions were a mistake, owl biologists largely insist that more forests must be spared, especially since heavy logging continues on state and private land.. .”If you start cutting habitat for either bird, you just increase competitive pressure.”

http://www.smithsonianmag.com/science-nature/The-Spotted-Owls-New-Nemesis.html#ixzz1ywI7txwy

Besides the barred owl, It appears that other changes in the larger landscape have caught up with efforts to conserve spotted owls. A recent review on spotted owl protection lists wildfire as a major threat to spotted owls in drier areas of the Cascades (remember the Biscuit fire?). That is a result of first, more than a century of fire suppression and second, climate change and normal weather patterns leading to conditions conducive to fire in forests loaded with fuel.

In a landscape before habitat became so scarce, if a fire burned one part of the forest, animals and plants could survive in refugia or recolonize from neighboring undamaged habitat. Now that there is so little intact high quality habitat left and it is fragmented, it is a dangerously fragile situation – organisms may not be able to find a place to wait out a wildfire or there may not be an adjoining area that can donate species to it later. With only 10% of high quality intact ecosystems remaining, on average, in the Northwest (e.g. old growth forest, Willamette Valley prairie and savannah, shrub-steppe in eastern Washington) it’s no wonder things are falling apart.

Lots of species are suffering the effects of practices that began during settlement and development of the west. Saving iconic wild salmon runs has been a priority for decades – at least people like to say it is. But how is spending time and resources shooting sea lions and relocating Caspian terns that eat salmon congregating below dams helping the situation? It’s stopgap emergency action, not a solution.

There are currently 11 dams on the Columbia River; “…32 dams in the land mass drained by the Columbia River system (including other rivers), an area roughly the size of France.” Does this not suggest that all the efforts to plant trees in riparian areas, shoot sea lions, and barge fish around dams is really just window dressing? If we want hydropower and irrigation, large scale agriculture and forestry, we will not have wild salmon.

Salmon and owls are two species that are indicators of a healthy ecosystem. We need to recognize that our ecosystems are at risk, and while it is the job of land managers and biologists to manage species, it requires an effort from all of us to look at the whole and make changes that affect how we build our cities, farm our food, allow ourselves to live with other species.

Many species have learned to live with us – coyotes and crows are two that come to mind. The barred owl can be a member of this club too (they live in suburban and even urban areas). We consider them pests or invasive, and think we have nothing to do with how they came to be so numerous. But they are adapting to us, we facilitated it, and it is in fact all about us. Don’t blame the messenger.

The thing is, if we don’t attend to these problems, we may lose the ecosystems that keep us alive. As with past mass extinctions though, the planet will keep on turning. New combinations of species will appear. Maybe humans will be among them.