Tree of Life?

Every culture has a myth about the “tree of life” except the western one unless we include the Christmas tree which today is often made of plastic. As we approach the holiday season I am sickened by the thought of more live trees being cut down, only to be thrown out the door as soon as the presents are opened. I see the tree as a kind of backdrop for the human drama. The Christmas tree seems to be a symbol for excessive consumption for most.    

Nature no longer structures our collective reality in any meaningful way, and trees if they are noticed at all viewed as a kind of indoor or outdoor wallpaper.

It is my intent in this article to bring one tree to life…

  Eastern Hemlocks are one of my favorite woodland trees and have been since I was a child. During the years my brother was at Harvard I spent a lot of time at that institution because my brother trained in the Harvard Forest. Davey was an internationally known runner who held the steeplechase record until about 20 years ago. Not surprisingly, we always ended our time in Petersham relaxing and talking under the hemlocks.  

Every year in the late fall after all the leaves of deciduous trees have fallen the deep green needles and elegant curved shapes of hemlocks stand out like sentries bowing over my brook. Graceful evergreen boughs cascade over the water creating a canopy that stabilizes temperatures all year long. The first snows bow the young ones low, but they never break. In my small hemlock forest that borders both sides of the stream it is always cool and dark. Plant growth is sparse in the places where hemlocks overlap one another. In places where hemlock forests have been left to re-wild themselves many ground covers and other interesting plants can be found growing near hemlocks and their companions, oak and beech, including some rare species.

Animals thrive in hemlock territory; the red eft is one that appears regularly after a rain. Deer browse and seek cover under hemlock boughs. Red squirrels and mice feast on hemlock seeds. Hares like the foliage. Bears take cover under their boughs. Many insects inhabit the rich humus under hemlocks and in the branches of these trees songbirds flourish. Blue throated green warblers, Blackburnian warblers, Acadian flycatchers, hermit thrushes, winter wrens, nuthatches are just a few examples. The Blackburnian warbler nests nowhere else. Most of the warblers that I heard this summer were hiding in hemlocks! Ruffed grouse, barred, great horned owls, and saw whet owls like to roost in hemlocks branches.  Hawks like them too. Brook trout need hemlocks to keep the water pure and cool. 

Hemlocks are also one of the trees that have been spared by logging up until recently (now we take them to be ground up for pulp and garden mulch – spreading the wooly adelgid in the process of mulching gardens). This means that in most forests hemlocks may be older than other trees because their wood was not deemed valuable. All forests have been cut at least two or three times, usually sustainably until about 40 years ago when what I call ‘the industrial logging machine’ took over stripping forests, uprooting tree trunks, and ruining the soil.

 Hemlocks have both male and female reproductive structures on each tree and in the fall small cones adorn the tips of flat – needled branches. The tree’s ability to seed itself so close to a parent – within a hundred feet – allows the seedlings to be nourished through roots from the mother tree. Hemlock roots are attached to a complex underground mycelial network that stretches across the forest floor. Wherever hemlocks survive each is a living museum of the ecology of the woods in that particular region. Because these trees thrive in the lowlands hemlock pollen can also be studied because it has been preserved for millennia in the sediments of lakes, bogs, swamps and wetlands where these trees have grown. 

 Eastern Hemlocks returned after the last glacial period arriving in New England about 10,000 years ago from the south. They ‘migrated’ north about 900 miles in in 5000 years keeping up with changing climate conditions. Their range extends from Nova Scotia to Michigan. Today, of course, with  climate change upon us, these trees are under stresses they haven’t been before.

Curiously, hemlocks and the chestnut tree had a reciprocal relationship. There is no evidence of hemlock disturbance by Native peoples prior to the European invasion. For the last 5000 years hemlocks have been interspersed with white pine, beech, oak, maple and birch, cedar and spruce. Beech and oak are also very shade tolerant trees.

In addition to being shade tolerant, hemlocks are also the most patient of trees. When a space in the canopy opens even a tree that is already 75 – 100 years old will shoot up to the sky, branching ladders reaching for sun. A pencil thin hemlock can be 100 years old! Tiny flat forest green needles create and layer their own canopy in a patterned way that allows every stream of light to be maximized by the tree – an incredible strategy to make the most of low light. 

Hemlocks can also photosynthesize at very low temperatures – just above freezing. In the spring before leaf out the hemlocks absorb high light creating optimal conditions for growth.  Besides pine, beech and oak, in untrammeled forested areas hemlocks are also peppered with mountain laurel, hobblebush, and witch hazel, understory plants that can also tolerate lower light. A small plant called twisted stalk can also be found here. Indian pipes are a common sight in summer. Partridgeberry and wintergreen too.

When adult trees die their nutrients slowly seep into the ground because this tree decays very slowly nourishing the rest of the trees and plants of the forest. Mushrooms, fruiting bodies of fungi that belong the complex underground highway of the mycelial network, appear at their feet. There are 20,000 fruiting fungi in all. Hemlock varnished shelf mushrooms are my favorites. Morels and Chanterelles are editable mushrooms that I have found growing under hemlocks. Amanitas, giant Lactarius  (some reach the size of dinner plates) and blushing Russulas are also common around here, as are Boletes. Coral mushrooms are also familiar sights. Various Cortinaruis species abound…. Hemlocks seem to be a hotbed for so many species of fruiting fungi. 

Most if not all have a mycorrhizal relationship with hemlocks. Recall that mycorrhizal mushrooms are mutualistic fungi that form a symbiotic relationship with plants and trees. In the west a list of over 100 mycorrhizal fungi were associated with hemlocks. Mycorrhizal mushrooms can extend a plant’s root system up to a 1000 times, playing a critical role in forest ecosystems. The presence of so many plants and mushrooms under or around forests free of recent logging was what drew me to these magnificent trees in the first place aside from their size and beauty.

Hemlocks moderate temperatures, dropping them about 10 degrees in the canopy, and 5 to 10 degrees below on the forest floor. Feathery branches intercept rain or snow reducing the moisture that actually reaches the ground that helps control flooding. These trees also purify the waters beneath them allowing brook trout to thrive. If left alone hemlocks can live 800 years making them the longest – lived tree in the east.

 About 5000 years ago hemlocks almost disappeared and then resurrected themselves to become a “Foundational Tree” (Harvard Forest Hemlock Research) helping to structure the rest of our eastern forests. Although fewer trees and plants thrive directly under hemlocks the duff creates a very rich layer of humus (sometimes many feet deep) that stays moist even in drought and is capable of storing seeds hundreds, even thousands of years old making them a veritable seed bank.

Last spring when I was on the coast, I saw whole tracts totally stripped of what used to be hemlock forests. Harvard’s Hemlock project states that preemptive logging not only kills the trees but destroys any chance of the trees’ ability to develop a natural defense that might eventually help the species to survive. The second cause of death is the woolly adelgid. According to sources like fish and game the adelgid has spread as far west as Poland and Minot but is not yet here

in western Maine. I challenge this supposition because I have found the insects infesting hemlocks in heavily logged areas, although thankfully I have yet to find evidence of it on my property or that of protected forests that I visit. That’s not to say that I think our trees will be spared in the long run, because I don’t.

 It is easy to see this insect sucking the life out of needles simply by turning over a branch. Adelgids appear like fuzzy white clusters for most of the year. Another sign of a diseased hemlock is the loss of its crown or the raining down of dis –colored brown needles. This insect is impossible to eradicate although the use of pesticides and the introduction of would be predators have been tried and failed (we make same mistakes over and over – never learning).  

 Dr. Suzanne Simard’s work and that of other scientists and studies done by Harvard ecologists inform us that cutting trees preemptively doesn’t allow the hemlocks to develop natural defenses against insect invasion. My observations and senses also suggest that forests that are left to care for themselves may slow the spread of the wooly adelgid because forests are one living organism that already has many natural defenses against invasions of all kinds. Most have not yet been either identified or studied, or if they have (like Suzanne Simard’s groundbreaking work) the results are simply dismissed. 

 Maine’s Forestry folks are operating out of a severely outdated paradigm. Why? Because economy trumps nature every time. We could make changes but we won’t because we want to keep logging our trees instead of saving the trees we have left while focusing on developing healthy tree plantations to supply us with wood…

 Because I am aware that the loss of this tree is going to alter the character of what’s left of our fragmented forests I spend more time than ever before in hemlock peppered woodlands.  In fact it was my love for these trees and my need to be around them that first spoke to me of their antiquity in ways I cannot explain… And they did this before I ever did any research. 

I also have a beautiful four foot piece of smooth hemlock wood that was dredged up from a local pond that stands perpendicular like the tree it once was in front of some healthy young hemlocks. I see it as a natural sculpture with an ‘eye’ that opens to the future. Because of the resinous heartwood that preserves the wood even under water I find myself querying ‘what truths might the future hold for trees under siege’ every time I pass by this piece.

The Harvard Hemlock research team has been studying the hemlock and other trees since the early 1900’s. These scientists state that ecology is rarely a consideration in land management decisions. If the objective is to ‘manage’ in harmony with natural processes then the most efficient ecological approach to the slow dying of the hemlock is to DO NOTHING. 

 They go on to say that cutting or girdling, salvage logging as well as preemptive harvesting of declining trees interrupts forest continuity and recovery. Harvesting dying trees  compromises the ongoing capacity of the forest to take up nutrients and moisture damaging any surviving plants. No small points, these.

These folks also remind us that left alone the effects of dying hemlocks will remain for decades as important structural elements that support a diversity of organisms. Think of the seeds that remain in the soil for hundreds or thousands of years. The Hemlocks may be dying but if their forests are left to themselves in a relatively short time emerging trees, some will be hardwoods with canopy protection, will help create a very different but healthy woodland. And in today’s disappearing forested landscape that means life, carbon sequestration etc.

Unfortunately change is the only constant and warming temperatures, the logging machine, and the introduction of the Asian woolly adelgid is sucking the life out of these magnificent eastern trees.

 Harvard’s ecologists inform us that once infected a tree will succumb in four to twelve years. Harvard’s hemlock forests are dying and to honor this passage they have created the Hemlock Hospice project, bringing in international artists to highlight what is happening to these foundational trees by creating sculptures in the hemlock forest. 

I think it is so hopeful that an institution like Harvard is honoring the death of hemlocks as REAL trees whose loss is to be mourned.  

If, and this is a big IF we can cease industrial logging that uproots not only the trunks of trees (where new life begins immediately in the decaying trunk) and the soil beneath them, there is hope. 

Because under those dead hemlocks, seeds that are hundreds or thousands of years old may one day rise to repopulate the planet with this ‘Tree of Life’.

 In the meantime it might be prudent to spend a little time with these majestic denizens of our forests while we still have them.

Postscript: My life this year seems to have been dominated by hemlock trees because I spend so much time with them and this is the last and most complete post about the natural history of these trees.