Ancient Plants of the North Woods

They are small plants that look like pine seedlings. No, perhaps they look like little cedars. But then again, maybe they are a weird kind of moss, or perhaps a fern.

These are just some of the reactions people have to these plants which are commonly found in the pine and spruce-fir forests of the North Woods. They go by the common names of Ground Pine, Running Pine, Ground Cedar, Prince’s Pine, or Princess Pine but they are neither pine nor cedar. In plant identification field guides you can find them under the section “Fern Allies”, but they are not really closely related to ferns. The most common name for them is Club Moss, but they are not mosses, either. Just what are these plants?

Common names are parochial and colloquial, and often imply false relationships based on superficial appearance. On the other hand, Latin, being a dead language remembered only by biologists and aging altar boys and monks, remains the same everywhere and at all times. That is why biologists continue to name species in Latin. The Latin name for an important genus within the club moss family is Lycopodium, which comes from two Greek root words, lycos, wolf, and podes, foot. The name describes the appearance of the shoot and branch tips of the plants, which supposedly resemble a wolf’s paw. They never resembled a wolf’s paw to me or anyone else I know, but we are now stuck with Lycopodium regardless of the origin of the name.

Lycopodia are characterized by trailing underground horizontal stems, from which emerge roots penetrating down into the soil and many upright shoots emerging aboveground. Each upright shoot is, at most, about 10 – 12 centimeters (4 – 5 inches) tall. There may be hundreds of these shoots aboveground in a given pine stand, but they are likely all connected belowground by the same network of long horizontal stems. All the Lycopodia “plants” you see in a pine forest may actually be one large plant. The leaves are small, scaly affairs arranged along branches that radiate outward a few centimeters from the main stem of each vertical shoot. The scaly appearance of the tiny leaves makes the Lycopodia resemble cedars, but the long thin branches covered with them look superficially like pine needles. The tips of the upright shoots often end in cone-like structures called strobili, suggesting another (false) affinity with pines.

Spores eventually arise from the strobili and are dispersed by wind currents along the forest floor or by small mammals brushing up against the stobili. The spores then undergo meiosis and produce either male or female structures called sporophylls. These produce and eject male sperm or female egg cells. When the sperm cell finds an egg, it fertilizes it with its genes and produces a zygote with full complement of chromosomes. If the zygotes find suitable habitat, some of them will generate into new adult plants. Lycopodia seem to like acid, infertile soil such as provided in pine forests, which appears to be their preferred habitat. Beyond this brief description of the plants’ life cycle and general habitat preference, we know much less about the ecology of Lycopodia than we do about plants we can harvest for commercial profit, such as timber producing species of trees.

The club mosses are among the world’s oldest terrestrial plants, dating back at least to the Devonian Period 345 – 405 million years ago. This is many hundreds of millions of years before the ancestors of today’s spruce and pine evolved, and even longer before any flowering plants appeared. The ancestral club mosses, then some of the largest plants on earth, dominated the world’s vegetation during the Carboniferous Period immediately following the Devonian. This was the period in earth’s history when the great deposits of organic matter from vast swampy forests accumulated in thick peat deposits. Over millions of years, these peat deposits were slowly buried and transformed into today’s fossil fuels. The carbon compounds in the gas you burn in your car or the natural gas you cook with or the coal that the power companies burn to generate electricity very likely were formed from the ancestors of today’s Lycopodia. You probably arrived at work today or cooked your supper tonight courtesy of some ancient club moss.

Distinguishing different species in the genus Lycopodium is extremely difficult, even for professional taxonomists. First, the different features that distinguish the species are tiny hairs on the leaves, scales on the strobili, and other minutiae that require a microscope. Second, different species hybridize, resulting in many intermediate forms. Third, much of the variation in Lycopodium characteristics, which would normally be used to distinguish different species, seems to be caused by differences in the environment from place to place, and so these characteristics are not intrinsic and stable properties that could reliably be used to identify each species.

Another reason why it is difficult to determine the number of species lies in the differing philosophies of plant taxonomists, botanists who classify plants. Taxonomists can themselves be classified into “lumpers” and “splitters.” Lumpers tend to lump different varieties together into an aggregate species, relegating the diversity of forms to sub-species levels. Splitters, on the other hand, tend to split different forms out into full-fledged species. How a group of species is classified depends on whether the botanist describing all the varieties is a lumper or a splitter.

Nathaniel Lord Britton and Addison Brown were two famous botanists in the early years of the twentieth century, and their three volume Illustrated Flora of the Northern United States and Canada lists 15 species of Lycopodium in North America. The National List of Scientific Plant Names published by the U.S. Dept. of Agriculture lists 23 more species names which are synonymous with those of Britton and Brown but named differently by other botanists. Of Britton and Brown’s 15 species, Gerald Ownbey and Thomas Morley locate eight of them in Minnesota in their Atlas of Vascular Plants of Minnesota. However, Ownbey and Morley recognize three other species not recognized by Britton and Brown that can be found in northern Minnesota. On the other hand, Rolla Tryon in his Ferns and Fern Allies of Minnesota lists only nine species of Lycopodium.

These taxonomists run the full range between splitters to lumpers. To end this rampant confusion, botanists from around the country are now cooperating in a definitive encyclopedia of plants called The Flora of North America, of which 20 volumes are planned. Here, the lumpers appear to have control, because they have aggregated all the Lycopodia which are found in North America into six species, five of which can be found in northern Minnesota.

This may seem like academic hair-splitting simply to guarantee job security for botanists, but it is not. The earth is losing species at a higher rate than since the great Permian Extinction because of the population explosion and global gluttony of Homo sapiens. Lycopodia face a particularly unusual conservation problem because the piney appearance of their upright shoots makes them attractive for Christmas wreaths and their habit of growing from one long trailing underground stem makes them easy to harvest. Once harvested, this long stem can be sliced up into many strands to be wound around the wreaths to display the upright shoots looking like miniature Christmas trees. Although there are no laws protecting these plants from being harvested for wreaths, this use should be discouraged as the growth rate of Lycopodium is very slow, so slow that it is entirely possible that many individual plants have lived for more than 100 years. The Princess Pine on your Christmas wreath may be old growth Lycopodium! Because of this slow growth, harvesting can easily outstrip the plant’s ability to recover. A local population can, and often is, driven to extinction in a few years of intense harvesting for Christmas decorations. Although we know little about the taxonomy of Lycopodium, we know next to nothing about how each species recovers from harvesting.

Determining what is a species, how it is distinguished from others, and how it responds to changes in its environment is of prime importance if we are to properly manage our environment (and ourselves) to preserve the richness of life on earth. There are numerous other plant genera with the same taxonomic confusion as Lycopodium. Unfortunately, time may be running out for many genera and species. We know a lot about plants of commercial importance, such as many commercial tree species or horticultural species. We know precious little about the plants of the understory of the forest such as Lycopodium – even to the extent of not knowing how many species there are – simply because no one cares to pay for the training it takes to learn how to classify them and then for the collectors and curators to preserve their specimens in museums. In the meantime, many may go extinct before we even know anything about them – indeed, we may not even be aware of how many are going extinct if we are not sure of how many species there really are. However many species there are in the genus Lycopodium, none of them appears to be endangered – yet. But who can say for sure if we are so uncertain of the taxonomy of these species, to say nothing of our almost complete ignorance of their ecology?

It is ironic that while we benefit from the fossil fuels ancestral club mosses provide, we know so little about their descendants that enrich our walks in the pine forests of the North Woods.

 

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