Big Trees and Small Parasites

Johnson Woods is a state nature preserve in northeast Ohio that features over 200 acres of old growth forest. On a recent visit we walked among its giant trees on a 1-mile boardwalk, marveling at the huge oaks, hickories, maples and other trees. Many of Johnson Woods' trees are over 400 years old and some reach 120 feet in height.

Here is a Black Gum (Nyssa sylvatica) that added a bit of spicy October color to the green canopy.

Gradually the dominant oaks and hickories are giving way to maples and beech. The American Beech (Fagus grandifolia) is a magnificent tree and I've never seen so many huge ones. It is one of my favorites partly because it is so easy to identify, thanks to its smooth bark:

Most beech trees next to a trail have been decorated in various ways:

Since trees grow in height from the top, Aaron and Marie have only become wider in the past 11 years (they are not alone), and will remain at eye level for the life of the tree.

Beech leaves are simple, slightly toothed, and alternate along the twig. The characteristic sharply pointed buds make winter identification very easy.

Fall color can be quite striking:

I really like the way young beeches retain their leaves into the winter, giving a delicate accent to a view through a forest:

The beech’s seeds are contained in these prickly husks. Each husk has seeds which fit neatly together until the husk dries, opens, and releases the edible seeds or beechnuts. 

Apparently beechnuts have little to do with Beech-Nut gum or baby food. The company was named for the beech trees that grew near the town in New York where it was founded, but the "nut" part comes from the nutty-flavored hams that were its first product.

One of the coolest things about beech trees are the Beechdrops (Epifagus virginiana) that often grow beneath them. These small plants produce no chlorophyll, gaining all their nutrition from the roots of American Beech, thus qualifying as parasites. Without the trees they could not survive.

The Johnson Woods beeches supported the greatest Beechdrop density and largest individual plants that I have ever seen. 

Parasitic plants have modified roots that penetrate the host's vascular tissue, but how does the seed of a parasitic plant know that it is near its host, and how do the developing roots find the host plant? Apparently the host plant exudes chemical signals that are recognized by the seed and that stimulate germination. The developing plant's roots then follow a chemical concentration gradient toward the host. Pretty amazing. 

I have a feeling that I'll be repeating that phrase often in this blog. It is fascinating to consider that despite the fact that plants are immobile, they are able to successfully reproduce, protect themselves, get nutrition, and grow. There is a whole lot going on in the plant world, and we probably don't have a clue about much of it.

Something else to ponder: what are the chances that T.S. still loves L.M.?

Fall Leaves

Lately a couple of people have remarked to me that the fall color this year is disappointing and speculated that this might be because of the summer drought and high temperatures. Personally, I think the color this year has been just fine, and in some cases, spectacular. I suppose it just depends on where you are, and fortunately we have been exploring in places where the color has been lovely.

I have a major job ahead raking lots of those lovely leaves, some perhaps for the second time thanks to the high winds we had over the weekend. Just as I was contemplating that chore yesterday I happened to see a beautifully written and illustrated essay by Rob Dunn in the October 2012 issue of National Geographic entitled "The Glory of Leaves".

The article delves into the evolution of leaves from the beginning, when a cyanobacterium entered a living cell and began to capture energy from the sun, giving rise to the amazing and varied world of plants. It muses about how natural selection has produced such a variety of leaf shapes and sizes, all contributing to intense competition for sunlight. 

In most cases we can't begin to imagine the selective advantage one leaf type might have over another in a temperate deciduous forest, whether they are rough, smooth, toothed, lobed, simple, compound, or a host of other descriptive attributes.

And why would leaves with different shapes occur on the same tree, as in sassafras and mulberry? What selective advantage might this characteristic, called polymorphism, offer to the plant?

The relationship between the shape and texture of leaves and their function is a fascinating topic for discussion but few definitive answers are available. The constantly changing mix of climate, competition for water and nutrients, and the need for defense mechanisms ensures that natural selection will continue and the plants upon which it acts will continue to slowly change in response.

So much is going on all the time in the plant world, most of it quite subtle by our standards, and that will give me lots to think about as I rake all these fallen leaves!

Glorious Goldenrod

Goldenrod is one of our most striking fall wildflowers but it often gets a bad rap as the cause of hay fever and other allergies. The true fall allergy culprits are the ragweeds,  which have quite inconspicuous flowers.

The reason that ragweeds cause such a problem is that each plant depends on the wind to distribute its pollen. This is a random process which requires that the plant use its energy to produce A LOT of pollen in order to ensure that a few of the microscopic grains fall on a receptive plant of the same species. Goldenrod, on the other hand, is pollinated by insects, which is a much more targeted strategy, requires far less pollen, and releases little or no pollen to the air. It does, however, require the plant to use its energy to produce flowers that can attract insects via color, shape, aroma, and nectar.  Neither strategy is necessarily better than the other; they are just different means to the same end.

This fall I’ve put a bit of effort into learning to identify some of Ohio’s 22 species of goldenrods, and I have a long way to go. The most common species is the Canada Goldenrod (Solidago canadensis), which turns meadows bright yellow in the fall.

It has a large, triangular plume of flowers at the top of the flower stalk, and its nectar attracts and feeds myriad insects:

Stiff Goldenrod (S. rigida) is a prairie plant that can be found in restored prairies at Battelle Darby Metro Park and many other locations in central Ohio. Its thick leaves that seem to clasp the stem make it easy to identify.

 Gray Goldenrod (S. nemoralis) is usually smaller than Canada Goldenrod and occurs in prairies and disturbed areas such as freeway rights of way. Its inflorescence is at the top of the stem but it is narrow and bends a bit at the tip.

Zigzag Goldenrod (S. flexicaulis) is different in that its blooms occur all along the stem at the leaf axils. The stem has kind of a zigzag character, but I think someone could have come up with a better name. The leaves are much broader than many other goldenrods and they are sharply toothed.

 My personal favorite at the moment is the Blue-stemmed Goldenrod (S. caesia). In contrast to the others, it occurs in shady wooded areas. It has very narrow leaves and a much more delicate appearance.

Bog Goldenrod (S. uliginosa), as its name implies, grows in wetlands and marshes. It has a narrow plume of flowers:

Just for fun, here is a curious plant (with a visiting grasshopper) whose common name, Sneezeweed, sounds like it should produce an allergic reaction. Its showy flower, though, would indicate that it is insect pollinated, not wind pollinated. A bit of research shows that its name comes not from pollen-induced sneezing but from the fact that the leaves were at one time used as snuff!

Mysterious Missing Megafauna

Behind my house grows a gigantic wild Honeylocust tree that is at least 60 feet tall.

This has to be one of the most annoying trees around, with its tiny leaflets that get tracked into the house,

its unattractive, leathery pods that drop in great quantities into my garden in the fall,

and the giant thorns that line the trunk and branches and are strong enough to pierce a shoe.

In spite of these and a few other undesirable characteristics I can’t help but respect this giant and wonder why on earth it has all those thorns.

After all, it takes a lot of energy to produce huge thorns like these, and an expenditure of energy that doesn’t produce food or facilitate reproduction had better be worth it to the plant. The obvious answer to this structure-function question is that the thorns are protection from animals that might want to eat the bark and twigs of the tree. But digging a little deeper reveals an interesting story and a possible additional explanation.

The only large browsing herbivore in this part of the world is the White-tailed Deer. Its relatively small mouth, which could easily reach between the thorns, leads one to believe that the Honeylocust’s huge thorns are overkill, and not a sensible expenditure of the plant’s energy. Turn the clock back more than 13,000 years ago to the late Pleistocene, however, and things look mighty different. Huge mammals roamed the prairies, forests and savannas, becoming extinct around the same time as humans colonized North America and the last ice sheets retreated.

These animals included woolly mammoths, mastodons, horses, camels, sloths and many others, including large cats and other carnivores that fed on the herbivores. Recently I visited the geology museum at Orton Hall on the Ohio State University campus to check out the giant ground sloth skeleton there:

That is one big plant eater! Here is a rendering from the museum that shows the animal having no trouble reaching way up into trees to find leaves and fruit:

So it certainly makes sense that the thorns of the Honeylocust protected the tree from these huge mammals. The fact that the Honeylocust’s thorns only extend about 20 feet up the trunk is probably no coincidence, since that was about the extent of these animals’ reach.

Lately, though, I’ve been thinking that maybe the large, tough thorns might also function to attract giant mammals rather than simply to repel them. How? Picture a louse-y, flea-ridden woolly mammoth sidling up to a big Honeylocust, gently rubbing its huge flank against the thorns. Ahhh..relief!

And how does this benefit the tree? Regardless of whether the thorns attract and/or repel the large mammals, the mammoth, or mastodon, or giant ground sloth has no trouble chewing up the plant’s leathery pods. According to Wikipedia, the unripe pods are “strongly crisp, sweet and succulent” (hence the name Honeylocust,and no, I’ve never tried to eat one). Any seeds that pass intact through the animal’s intestinal tract are deposited away from the parent tree, ready to produce another thorny scratching post and food source. Pleistocene seed dispersal at its best!

In future posts I’ll discuss some of the other Ohio trees that depended on the Pleistocene megafauna for seed dispersal such as the Osage Orange, Persimmon, Pawpaw and Kentucky Coffee Tree. In the meantime, imagine how different life would be if these huge animals still roamed our plains, forests, and backyards!

For more information about this topic, check these articles:

Floral Legacies of the Megafauna

The Trees That Miss the Mammoths

Rethinking Eastern Grasslands: A Deep Time Perspective

Diving into the blogging world

I always said that I would never do a blog, but here I am. I dabbled with Blogger two years ago, when I was doing a 6-week substitute teaching gig in 9^th grade Physical Science. One of the assignments was to create a blog, so I figured that I had better noodle around a bit with Blogger so that I could be of some help to the students. 

The title, Around the Bend, reflected both my mental state resulting from trying, with very little knowledge, to help students for whom the blogging assignment was extremely difficult, and my lifelong love of exploring the out-of-doors and discovering the interesting plants and critters that might be lurking just around the next curve in the trail. That blog pretty much languished in draft form for two years, but for several reasons I am resurrecting it and as it turns out I still like the title and am still passionate about the subject matter.

So why start this blog now? Well, the house renovations are just about done, the kids are raised, and I’m ready for a new project! I’ve always enjoyed writing, but didn’t want to take on another deadline-intensive newsletter editor position. On our weekend forays into Ohio’s parks and nature preserves we have rekindled our interest in botany; I figure that blogging about what we find will help me remember what I’m learning. (I’m finding it much harder to retain all this new information than when I was younger!) Lastly, it is just fun to share nature information and I miss doing that since I’m not working as a naturalist right now.

So this blog will explain and illustrate plants, insects, birds and other critters that we encounter in our travels. I’ll focus on what I find most interesting, in the hope that readers will learn a bit, be inspired to get outside, and find many reasons to support conservation and wise stewardship of our natural resources in Ohio and beyond.

Saturday's outing took us to Blendon Woods Metro Park. It has become a favorite destination because it is only about a half hour from home, has a variety of habitats, and often has friendly birders and plant enthusiasts wandering the trails. The fall color there was excellent, from bright red sassafras and poison ivy to the rich yellows of goldenrod, walnuts and spicebush.

 The purple of the New England Asters and the yellow of the Canada Goldenrod was particularly striking:

Here is another gorgeous fall wildflower in full bloom, the Bottle Gentian:

Our most exciting find of the day was an enormous caterpillar, slowly making its way across a paved trail:

This creature was longer than an iPhone is wide and as thick as a non-pinky finger. At first we thought it was a Hickory Horned Devil, the cat of the Royal Walnut Moth, but it didn’t look quite right. A quick check in my caterpillar book revealed its identity as an Imperial Moth which was really exciting because I had never even heard of an Imperial Moth! (I’d still really love to see a Hickory Horned Devil sometime—what a great name.)  Bruce Simpson, the Blendon Woods naturalist, said that these caterpillars were a staple feature of Japanese horror films in the 1960s—who knew. 

These caterpillars overwinter in the soil and emerge as adults in the spring. The white spots surround the openings through which the animal breathes, and the hairs probably make it less palatable to hungry birds. The head end of the caterpillar is on the right in the photo above, and just behind the head you can almost see 3 pairs of true legs—the six jointed legs which are characteristic of all insects. The other four pairs of “legs” are actually called prolegs. They are muscular protrusions that enable the animal to cling to skinny twigs and branches.

Here's an upside down view--up close and personal! Jointed legs are on the left and prolegs are in the middle, with two more muscular structures on the end.

So there you have it--my first blog post. Now it's time to get off the computer and go outside!