Tag Archives: Trees

Let’s Pause to Consider…Trees and Other “Kin” on which Our Lives Depend

An old oak at the far eastern end of the Eastern Prairie at Charles Ilsley Park

Like many of you, I suspect, I have always had great admiration and even a special affection for trees. As a child in a sometimes chaotic family, I found peace and solace sitting high in a hundred year old sugar maple on Lake George Road with my book and a snack. But more recently, writing this blog has brought me time and again to startling new revelations about these giants of the plant world. So I thought in these lingering winter-ish days of early spring, we might take a few minutes to marvel at trees – and plants in general.

Cool Things about Trees that I’ve Explored Before

Mature oaks like the one at Bear Creek’s Center Pond can feed their saplings through the mycorrhizal fungi.

In February of 2017, I shared what I’d learned about the recent scientific work that shows how endless miles of mycorrhizal fungi create a “wood-wide web” beneath forests. Trees benefit from allowing these underground thread-like fungi to pierce or wrap around their roots because the fungi provide them with more nutrients and water than is available through their roots. In fact, the web created by these fungi can reach a soil area up to 700 times larger than a plant’s roots can reach on their own – a huge benefit!  Trees in turn feed these fungi the sugars created by photosynthesis that the fungi need to grow – symbiotic teamwork that benefits both species. Check out this short video for a visual representation of how this relationship takes place. Trees also use this web to feed other trees, including, it is now reported, their own saplings and other trees.

In March of 2017, I explored the many similarities between humans and trees. For example, I marveled that oak, hickory and other trees in a forest somehow coordinate their production of nuts by periodically but irregularly creating huge amounts of them. We call these abundant years “mast years.” One of the hypotheses on mast years is that predators like deer, blue jays, squirrels and such can only eat and store so many nuts in any season. So during mast years when trees produce an abundance, many more nuts are left to start young trees either through being left behind or being “planted” and forgotten by the animals that store them. Tree teamwork!  Scientists have several hypotheses about this phenomenon,  but have not yet reached a consensus on why and how mast years occur.

During a “mast year,” trees like this Bur Oak produce huge quantities of nuts, possibly so that more survive to produce saplings rather then being eaten or stored by birds and animals

Some New Insights on the Ancient History of Trees

Just lately, though, I’ve been exploring some other remarkable aspects of trees, their fungal partners beneath the soil and their relationship with us, the human population. I began by thinking about the evolution of plants in general. According to Scientific American, “The world’s lush profusion of photosynthesizers …owe their existence to a tiny alga eons ago that swallowed a cyanobacteria and turned it into an internal solar power plant.” Voilà, about one billion years ago, algae on the ocean surface could use sunlight and nutrients from the water to grow through photosynthesis. And in the process, they released unneeded oxygen, though not yet enough to change the earth’s atmosphere significantly. Oxygen was still a rare commodity. (Click on photos to enlarge; hover cursor for captions.)

According to Wikipedia’s Evolutionary History of Plants, the first land plants may have evolved about 850 million years ago at the edge of those ancient bodies of water. These early mat-forming plants had no vascular system or roots so it was impossible for them to find a reliable source of water and nutrients on land which was still solid rock. Soil, after all, was created later by decaying plants. So they were either restricted to moist settings as mosses are today, until they developed a waterproof outer layer (or “cuticle”) and other adaptations that allowed them to survive until water was available again.

Modern day mosses function a bit like the first land plants – needing a wet location to survive and reproduce.

According to Plantae, a website founded by the American Society of Plant Biologists, primitive forms of those mycorrhizal fungi may have helped out by attaching themselves to plants and bringing them the inorganic nutrients and water they needed to photosynthesize in their rocky new environment. So the relationship between plants of all kinds and these weblike fungi goes back hundreds of millions of years! Perhaps our very existence, then, is owed to mycorrhizal fungi! Hooray for those ancient mushrooms!

The highly toxic mushrooms on the left below are the reproductive fruiting bodies of Deadly Webcap (Cortinarius rubellus), one of the thousands of species of mycorrhizal  fungi worldwide, some toxic and some not.  On the right, is a photo of one of the fungi from the genus Cortinarius with structural filaments, or hyphae,  beginning to grow out from the roots of a beech or oak to seek out nutrients. [The Deadly Webcap  photo was shared by  iNaturalist photographer, Andrea Aiardi. The photo on the right of the mycorrhizal association between plants roots and fungal hyphae was taken through a microscope and kindly provided by Dr. David Burke of Holden Arboretum in Kirtland, Ohio and is posted with his permission.]

Ancient Plants Living and Dying Made Life Possible for Oxygen-dependent Creatures like Us!

Eventually, around 400 million years ago, some land plants began to develop leaves, roots, and a vascular system which transported water and nutrients. The rigid vascular tissue also allowed plants to grow sturdier and taller. Below is a fossil photo and an artist’s rendering of Cooksonia, an ancient vascular plant group that is now extinct and seen only in fossil remains.

During warm periods, newly developed roots allowed prehistoric plants to take in water and nutrients from the earth, while newly evolved leaves took in carbon dioxide from the air through their stomata, the little mouth-like holes in leaves.

The photosynthesis cycle on which essentially all of our food depends. [At09kg : originalWattcle : vector graphics [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)%5D)
Through photosynthesis, plants converted light energy to chemical energy stored in sugars. They used the sugars to grow larger and reproduce. Oxygen is the other byproduct of photosynthesis, so as leafy trees got larger, they began putting greater amounts of oxygen into the atmosphere and removing larger amounts of carbon. Eons of land-based plant material changed the earth’s atmosphere, making life possible for the oxygen-breathing creatures that evolved millions of years later – including us, of course!

Thank goodness for that algae and cyanobacteria combo a billion years ago! Because of photosynthesis and the new abundance of oxygen in the atmosphere, organisms like mammals and birds with fast metabolisms evolved. A rich diversity of oxygen-loving organisms occupied the earth for millions of years before humans and their predecessors came on the scene.

Trees Still Supporting Life on Earth – including Ours!

The trees we know, love and rely on today – oaks, maples, walnuts and such – first appeared on earth about 65 to 144 million years ago. They blanketed the earth long before modern humans arrived about 30-50,000 years ago. Their leaves, like the ancestral leaves of early plants and trees, are still supplied with chloroplasts stocked with chlorophyll and other light-absorbing pigments from those ancient cyanobacteria; in fact they turn the leaves green by absorbing reds and blues while reflecting the green part of the spectrum. So trees are still  busy storing carbon and sugars while releasing the very oxygen we need to survive.

Many of the trees we know in modern Michigan originally appeared 65-144 million years ago and colonized our  landscape after the last glaciers retreated.

I  learned from a National Geographic article that during  northern hemisphere winters, carbon dioxide builds up in the atmosphere. Once deciduous trees drop their leaves, they temporarily cease their photosynthesis. Check out the fascinating month-by-month NASA video down the page in this article to see the red areas of carbon dioxide in the northern hemisphere during the winter months, December through March. When springs arrives, leaves sprout and a huge number of trees in the northern hemisphere go back to absorbing carbon dioxide through photosynthesis. Watch the months June through September on the NASA video and see what I mean!

Carbon dioxide increases above the northern hemisphere in winter when trees are bare and little photosynthesis can occur .

Sadly, trees can’t remove enough carbon dioxide from earth’s atmosphere these days due to human use of fossil fuels, which is releasing huge amounts of stored, compressed carbon from the remains of ancient living organisms, including trees.

Trees as “Kin” We Count on for Survival

The Hickory Lane at Cranberry Lake

In Shakespeare’s Troilus and Cressida, Ulysses tells Achilles, “One touch of Nature makes the whole world kin.” Though Shakespeare meant something quite different, the line occurred to me as I came to a deeper understanding of our intimate, essential connection to trees and other plants as well as our fellow humans. We share the double helix of DNA, after all, with all living organisms – plants as well as animals.

And though it’s the small number of genes that are unique to humans that make us what we are, genome experts say we share a large portion of our DNA with plants. So in a way, trees and plants truly are our “kin!”

What we don’t share is the ability of plants to turn sunlight into sugars, fiber, fruits, nuts, vegetables, grains, etc. Every single thing that we eat to stay alive comes originally from plants (although algae and some other organisms also photosynthesize). Even the meat in our diet comes from animals who survive by eating plants or by eating other animals that eat plants. We depend on plants to feed us and we depend on them for the very oxygen we breathe. Up until the 20th century, trees and other plants could also effectively use or store all the carbon dioxide we and our activities exhaled into the earth’s atmosphere. They still contribute to that process.

Respecting Our Elders…

Foot of a Giant Sequoia (Sequoiadendron giganteum)  in Yosemite National Park, California, a Redwood that can live thousands of years, one of the oldest organisms on the earth

We can’t survive without plants. Yet they survived for millions of years without us. So that encourages me to think that caring for nature isn’t just a matter of loving and enjoying nature or being a good-hearted steward of our “natural resources.” It’s really a matter of enlightened self-interest for our species. Caring for and respecting our “kin” in the natural world that support us and nurture us is simply a matter of our survival,  as well as a joyful activity.

TREES AND US: More in Common Than You Might Think!

The Schuette Oak may be 500 years old. It was named to the Champion Trees National Register in 1973.

The Schuette Oak has been living at the corner of Letts Road and Rush Road for probably 500 years. In 1973, it was recognized in the Champion Trees National Register.   I spent many of my childhood summers sitting in a huge, very old tree – in my case, a sugar maple –   in the field next to my parent’s house on Lake George Road. Held in its woody embrace,  I read books, ate snacks, sang and watched tall field grasses dance in the wind.

Blog post and photos by Cam Mannino

So when I came across The Hidden Life of Trees by Peter Wohlleben, I grabbed it and have enjoyed what this German forester had to teach me.   So here’s a baker’s dozen of interesting facts about these giants of the plant world.  Here’s hoping that you’re as surprised and delighted by some of them as I was.

MOST TREES ARE UNIQUE INDIVIDUALS.  

Like us humans, trees mostly reproduce sexually through sperm and egg – carried in the pollen and and ovary of plants (one exception is vegetative reproduction through suckering in trees like aspens and black locust,  a kind of cloning to make offspring that have the same genes as the parent). Each of those trees,  like each of us, have a unique set of chromosomes. The pollen of oaks, for instance,  is carried on the wind, bringing sperm to fertilize the eggs of other oaks.

The catkins on this Black Oak (Quercus velutina) are releasing their pollen. (Ah-choo!)

One advantage of reproducing sexually with pollen from another plant is greater genetic diversity of offspring. Differences in genetic makeup may help some individual trees better resist the challenges of plant life – disease, insects, drought or a warming climate. That creates a greater likelihood the at least some individuals of a species will survive even if the rest of the forest doesn’t.  A hopeful thought.

TREES BREATHE.   

Trees, like all plants, have pores, not visible to the naked eye, on the underside of their leaves called “stomata.” Trees breathe in carbon dioxide (CO2) and breathe out (“transpire”) oxygen gas and water vapor through these pores.  In pine trees, stomata are on the underside of their needles and sunken below the surface of the needle, helping reduce water loss when the air is very dry in the winter. Thanks goodness trees and plants do this! We need that oxygen and of course, we return the favor by taking in oxygen and transpiring CO2.

Tiny holes on the bottom of leaves, not seen by the naked eye,  are the “mouths” of the trees, called “stomata.”  All plants have them.
Stomata on the cuticle of a leaf. By Tyanna – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=45217985

TREES FEED THEIR YOUNG AND OTHER NEEDY TREES  

As explained in a February “Photo of the the Week,” mychorrhizal fungi wrap around tree roots creating a “wood-wide web” of amazing density beneath the forest floor. According to Wohlleben, “One teaspoon of forest soil contains many miles of … ‘hyphae’ ” – the microscopically thin filaments of fungi in the web. This fungal network provides a way for trees to feed sugars to their young, which we call saplings. Occasionally large trees feed other needy trees in the forest, those in too much shade, for example – thereby creating a healthier tree community.

This mature oak is probably feeding the four little saplings around it through the “wood-wide web” of mychorrhizal fungi at its roots.

WHEN ATTACKED BY INSECTS, SOME TREES WARN THEIR FELLOW TREES.

Using  chemicals released through the “wood-wide web,” trees notify other trees when under attack. This allows their tree neighbors to increase the chemicals in their leaves to repel the invading insects. An oak, for example can increase the tannin levels in its leaves.   Scientist have found that the tannin is either toxic to insects or perhaps just makes the leaves taste bad. Some trees can also release a scent that attracts the specific predator that preys on that particular insect.  Clever, eh?

This maze of tunnels is the result of an attack of bark beetles (subfamily Scolytinae), which tend to attack weak trees, but luckily, mostly dead ones.

SOME TREES SYNCHRONIZE THEIR NUT PRODUCTION…SOMEHOW.  

Oaks and Beeches, for instance, somehow coordinate the years in which they will produce a huge number of fruits (acorns for oaks and beech nuts for beeches). These are called “mast years.”  In normal years oaks will only produce a few acorns, limiting the populations of deer, blue jays, squirrels, mice and other animals who love the fatty oil in acorns. Animals will eat most of the acorns in the off years, limiting establishment of new saplings. In mast years, however, the volume of acorns is so high that these animals can’t  eat them all. So inevitably more survive to grow into saplings. It’s a nifty way to insure that at least some of your offspring survive in a world where, on average, each tree only has one “child” that reaches adulthood! Scientists don’t seem to know exactly how trees synchronize for mast years, although weather and seed production in previous years probably play a role.

Acorns in the White Oak family – Burr Oak (Quercus macrocarpa), I believe.

TREES DON’T MOVE (OF COURSE) –  BUT FORESTS DO.

As glaciers advanced and retreated during ice ages, forests had to adapt. Trees like Maples (genus Acer) sent their seeds flying on little wings, called “samaras,” or what children call “helicopters.” If the climate warmed, the samaras that flew north were more likely to thrive and start new forests,  while the ones that flew south did better as the glaciers advanced. In this way, over thousands of years, whole forests migrated.  Jays and their relatives, fond of nutritious acorns, are credited with helping oaks in southern Europe rapidly re-populate after the ice age. Today, the roads, houses, and lawns of human development have fragmented forests, limiting their movement and potentially hurting their ability to respond and move in response to changing climate.

The samaras, flying seeds, of a Box Elder (Acer negundo), a member of the Maple family.

TREES “HIBERNATE” LIKE MANY ANIMALS

We all know bears, raccoons, woodchucks etc., fatten themselves up before winter hibernation. Trees do something similar. Leaves use photosynthesis to capture the light energy from the sun and convert it to chemical energy stored in sugars. Throughout the summer trees store these sugars in their branches, trunk, and roots. As days get shorter and colder, trees begin to move nutrients out of their leaves in preparation for winter,  breaking down the chlorophyll (which makes them green) into its components so it can be sent back out in the spring to the new leaves. Once these green pigments are gone, the leaves turn the color of the remaining yellow and red pigments. As a final step before dropping their leaves, trees produce a layer of cells that seal off the connection between the  leaves and twigs – and the leaves ride the next breeze to the ground. Trees are finally ready for winter. The next spring the stored nutrients and sugars will power the burst of new leaves and branches!

This non-native Norway Maple (Acer platanoides) is extracting the green chlorophyll from its leaves and storing it in the roots for next spring’s leaves.

SOME ADULT TREES KEEP A CHECK ON THE YOUNG.   

Older oaks and beeches create a lot of shade that inhibits the rapid growth of younger trees. You’d think that would be a problem for the little trees, but at least for oaks and beeches, it isn’t. The older tree is still feeding the younger through the underground web,  so the sapling can survive without as much sunlight and its wood. According to Wohlleben, this slower, denser growth makes saplings more resistant to fungi and insects. The adult’s canopy may also protect the saplings from heavy spring frosts. When a gap develops in the canopy, the sapling is ready to grow. Biological child care, you might say.

Large trees shade saplings. That way they grow more slowly but have denser wood to resist disease and insects.

SOME YOUNG TREES TAKE ADVANTAGE OF “SLEEPING” ADULTS.  

Once  larger trees shed their autumn leaves and “sleep” for the winter, the youngsters seize the moment! Many keep their leaves later into the fall so they can make more sugars from the autumn sunlight available under the bare adult trees. Young trees also “wake” on average about two weeks earlier than older trees.  That gives them a little extra spring sunlight for growth. The youngsters can get caught, though, by an early freeze, preventing them from shedding their leaves. That’s not a huge problem for little trees in the winter, which are more flexible in winter wind and snow.  Smaller trees may also keep their leaves to discourage deer and other herbivores from nibbling their twigs and bark – who wants a mouthful of lifeless leaves?

This old White Oak (Quercus alba) lost its leaves in the fall but the sapling nearby kept its leaves to take advantage of late fall light.

TREES  NEED THEIR “SLEEP.”

 Wohlleben reports that tree lovers experimented with taking tiny oaks inside in pots on windowsills during the winter. The result was that the seedlings, taking advantage of the heat and light, continued to grow all winter. But without a rest from all that growing, most of them died during their first year. Trees may need rest at night too, when the air cools and their metabolism slows.  Sleep deprivation – evidently it’s a problem for both humans and trees!

Trees may benefit from a bit of a rest at night and during the winter  just as we do.

CONIFERS “BUNDLE UP” TO COPE WITH WINTER  

Needles are actually the leaves of conifers. Their leaves survive short summers and harsh winters by being tightly rolled  into needles and by “bundling up” with a waxy coating on their bark and needles that acts like anti-freeze and helps retains moisture. Green needles allow conifers to start photosynthesizing as soon as the weather warms.  Like us human Michiganders, they soak up as much sunshine as possible when spring arrives.

In a bog near Lost Lake Nature Park is a remnant stand of Black Spruce (Picea mariana). These trees typically grow in colder environments and would have populated large areas of Michigan as the glaciers retreated. The cool bog microclimate provides a southern refuge for black spruce. Their sparse, pointed tops and flexible branches, which layer downward when snow-laden, shed snow nicely too, an important survival strategy in snowy climes.

A remnant stand of Black Spruce near Lost Lake Park, trees that thrived in the cool climate as the glaciers receded.

AGE AFFECTS TREES IN WAYS SIMILAR TO AGE IN HUMANS.

Bark is essentially the skin of a tree. It holds in and releases moisture, protects a tree’s “insides” and is a barrier against pathogens that seek their way into the circulatory system. According to Wohlleben, “In young trees of all species, the outer bark is smooth as a baby’s bottom. As trees age, wrinkles gradually appear (beginning from below) –  and they steadily deepen as the years progress.” Their girth, of course, increases, too. The crowns of trees thin out with age, just like the locks of aging humans. So we’re not the only ones who get stouter, balder and more wrinkled with age!

The young White Pine (Pinus strobus)  has smooth skin, or bark, like all saplings, whereas the adult pine behind has “wrinkled” bark.

TREES CONTINUE TO AFFECT THE LIVES OF OTHERS LONG AFTER DEATH  

Wohlleben says that “In total, a fifth of all animal and plant species  – that’s about six thousand of the species we know about – depend on dead wood.” Insect and fungus specialists process a fallen log over many years, and woodpeckers, salamanders, and other critters find food and refuge in the rotting wood. Nutrients stored in bark and wood for perhaps hundreds of years are slowly returned to the forest floor. In some cases, young trees even sprout in the fallen bodies of their elders, creating “nurse-logs.”  Trees, like humans, leave a legacy for future generations.

Insects and fungi will gradually process this fallen tree, returning nutrients that will feed the whole forest, including new saplings. A tree legacy.

Trees as Living Beings

Black Walnut (Juglans nigra) on a foggy autumn morning at Bear Creek.

Without faces, it’s easy to see trees as “things” instead of living, breathing beings.  They can become just a backdrop to our lives. But trees communicate with each other, feed their young, breathe – do so many of things that we do.  Wohlleben’s book helped me see trees in a new and more complex light, even though I’ve always loved trees. I hope this brief taste of what the book has to offer does the same for you.

Footnote: The main source for this blog was The Hidden Life of Trees:  What They Feel, How They Communicate by Peter Wohlleben, Copyright 2015 by Ludwig Verlag, Munich, part of Random House GmbH publishing group.  English translation copyright 2016 by Jane Billinghurst .  Other sources include Wikipedia, www.Michiganflora.net, Trees in My Forest by Bernd Heinrich (Cliff Street Books, 1997) and Dr. Ben VanderWeide, Natural Areas Stewardship Manager for Oakland Townships Park and Recreation.