North America's Native Bamboos

James H. Miller & Ted Bodner, Southern Weed Science Society, Bugwood.org

I would like to introduce you to North America's native bamboos. There are three species, all hailing from the same genus - Arundinaria. Today they hardly get the attention they deserve but in the past, they were an incredibly important group of plants both ecologically and culturally. They now occupy a mere shadow of this former glory so in keeping with the goal of In Defense of Plants, I am here to defend these plants. 

There are three species in the genus Arundinaria -- A. appalachiana, A. gigantea, and A. tecta -- and all of these are native to the southeast. There has been a whole lot of taxonomic debate over these plants ever since Thomas Walter first described the first of them in 1788. Since then, there have been many revisions. Whether or not any Asian bamboos belong in this genus is a story for another time but recent genetic work confirms that these three species are valid. 

Each differs slightly in its ecology. Giant or river cane (A. gigantea) is a denizen of alluvial forests and swamps as is switch cane (A. tecta), although switch cane seems to be a bit more obligate in its need for swamp-like habitats. Hill cane (A. appalachiana) was only described in 2006 and prefers dry to moist forested slopes and forest edges. One interesting things about hill cane is that it drops its leaves in the fall, an unusual trait for a bamboo. 

A majority of their reproduction is asexual via spreading rhizomes. All three species of cane rarely flower. When they do, plants usually die after setting seed. As such, a majority of canes you may encounter in the wild are clones connected by a vast network of large rhizomes. These rhizomes can persist for decades or even centuries meaning persistent patches are quite old. These rhizomes can lay dormant for some time as well, waiting for some form of canopy clearing disturbance to provide the conditions they need to grow again. 

Photo by Tim Ross Public Domain

Despite how common these canes may seem in some areas, they are nowhere near what they once were. European settlers wrote of vast stretches of rivers and swamps completely covered in cane. They called these "canebrakes" and they persisted as such due to the importance of Arundinaria to Native Americans. Regular burning created perfect conditions for cane to thrive and thrive it did. 

Because it was once so prolific, its ecological impacts were quite immense. Many animals relied on canebrakes for food, shelter, and a place to breed. Unfortunately, cane was also highly sought after as food for cattle. Unsustainable grazing took its toll, as did fire suppression. What's more, the rich soils and relatively flat topography in which these canes tend to grow was also the preferred spot for farming. In fact, settlers used canebrakes as an indicator of good soils. Vast acres of cane were cleared and plowed under. Unfortunately for cane and the habitat it created, when it disappeared, so did much of its function.

Once cleared, cane is slow to return. Its tendency to not flower frequently means few seeds are ever produced. Even clonal reproduction can be tedious if the right conditions are not present. Cane has lost most of the ground in which it once grew. With it went vital components of the southeastern ecosystem. It has even been suggested that the loss of canebrakes played a major role in the extinction of Bachman's warbler (Vermivora bachmanii) though it is hard to say for sure. 

Though all three species of cane still persist today, they are not the ecosystem builders they once were. It will take a lot of changes here in North America both ecologically and culturally before these three bamboos can ever regain much of their former range. Still, they are interesting plants to encounter and well worth taking some time to enjoy. 

Photo Credits: [1] [2]

Further Reading: [1] [2] [3] [4] [5]

Invasion of the Earthworms

Photo by Rob Hille licensed under CC BY-SA 3.0

As an avid gardener, amateur fisherman, and a descendant of a long line of farmers, I have always held earthworms in high regard. These little ecosystem engineers are great for all of the above, right?

Not so fast! Things in life are never that simple! Let's start at the beginning. If you live in an area of North America where the glaciers once rested, there are no native terrestrial worms in your region. All of North America's native worm populations reside in the southeast and the Pacific northwest. All other worms species were wiped out by the glaciers. This means that, for millennia, northern North America's native ecosystems have evolved without the influence of any type of worms in the soil.

When Europeans settled the continent, they brought with them earthworms, specifically those known as night crawlers and red wigglers, in the ballasts of their ships. Since then, these worms have been spread all over the continent by a wide range of human activities like farming, composting, and fishing. Since their introduction, many forests have been invaded by these annelids and are now suffering heavily from earthworm activities.

As I said above, any areas that experienced glaciation have evolved without the influence of worms. Because of this, forests in these regions have built up a large, nutrient-rich, layer of decomposing organic material commonly referred to as "duff" or "humus." Native trees, shrubs, and forbs rely on this slowly decomposing organic material to grow. It is high in nutrients and holds onto moisture extremely well. When earthworms invade an area of a forest, they disrupt this rich, organic layer in very serious ways.

Worms break through the duff and and distribute it deeper into the soil where tree and forb species can no longer access it. Worms also pull down and speed up the decomposition of leaves and other plant materials that normally build up and slowly create this rich organic soil. Finally, earthworm castings or poop actually speed up runoff and soil erosion.

All of this leads to seriously negative impacts on native ecosystems. As leaves and other organic materials disappear into the soil at an alarming rate via earthworms, important habitat and food is lost for myriad forest floor organisms. In areas with high earthworm infestations, there is a significant lack of small invertebrates like copepods. The loss of these organisms has rippling effects throughout the ecosystem as well. It has been shown that, through these activities, earthworms are causing declines in salamander populations.

It gets worse too. As earthworms speed up the breakdown of the duff or humus, our native plant species are suffering. They have evolved to germinate and grow in these rich, organic soils. They rely on these soils for survival. As the nutrient rich layers get redistributed by earthworms, native plant and tree populations take a hit. Spring ephemerals have been hit the hardest by earthworm invasions for these reasons and more. There is very little recruitment and, in time, many species are lost. For small seeded species like orchids, earthworms can even consume seeds, which either destroys them outright or drags them down deeper into the soil where they cannot germinate. Earthworms have also been shown to upset the mycorrhizal fungi networks which most plant species cannot live without.

Top Left: Forest soil horizons without earthworms; Top Right: Forest soil mixed due to earthworms; Bottom Left: Forest understory diversity without earthworms; Bottom Right: Forest understory diversity with earthworms. Credits: [1]

So, what can we do about this? Well, for starters, avoid introducing new populations of earthworms to your neighborhood. If you are using earthworms as bait, do not dump them out onto land when you're done. If you must get rid of them, dump them into the water. Also, if you are using worm castings in your garden, it has been recommended that you freeze them for about a week to assure that no eggs or small worms survive the ride. If you are bringing new plants onto your property, make sure to check their root masses for any worm travelers. Remember, no worms are native if you live in a once glaciated region.

Sadly, there is not much we have come up with at this point for dealing with the current earthworm invasion. What few control methods have been developed are not practical on a large scale and can also be as upsetting to the native ecology as the earthworms. The best bet we have is to minimize the cases of new introductions. Earthworms are slow critters. They do not colonize new areas swiftly. In fact, studies have shown that it takes upwards of 100 years for earthworm populations to migrate 1/2 mile! Armed with new knowledge and a little attention to detail, we can at least slow their rampage.

Further Reading: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

An Orchid With Body Odor

Photo by Ryan LeBlanc licensed under CC BY-NC-SA 2.0

Aside from ourselves, mosquitoes may be humanity's largest threat. For many species of mosquito, females require blood to produce eggs. As such, they voraciously seek out animals and in doing so can spread deadly diseases. They do this by homing in on the chemicals such as CO2 and other compounds given off by animals. What is less commonly known about mosquitoes is that blood isn't their only food source. Males and females alike seek out nectar as source of carbohydrates.

Though mosquitoes visit flowers on a regular basis, they are pretty poor pollinators. However, some plants have managed to hone in on the mosquito as a pollinator. It should be no surprise that some orchids utilize this strategy. Despite knowledge of this relationship, it has been largely unknown exactly how these plants lure mosquitoes to their flowers. Recent work on one orchid, Platanthera obtusata, has revealed a very intriguing strategy to attract their mosquito pollinators.

This orchid produces human body odor. Though it is undetectable to the human nose, it seems to work for mosquitoes. Researchers at the University of Washington were able to isolate the scent compounds and found that they elicited electrical activity in the mosquitoes antennae. Though more work needs to be done to verify that these compounds do indeed attract mosquitoes in the wild, it nonetheless hints at one of the most unique ruses in the floral world.

Photo Credit: Kiley Riffell and Jacob W. Frank

Further Reading:

http://bit.ly/1JXP2jk

A Case of Sexual Fluidity in the Plant World

In humans, sex is determined at fertilization. The embryo receives either an X or a Y chromosome. Many other organisms have their sex determined in a manner similar to this as well. The case with plants is not so rigid. Many plants produce both male and female parts on the same flower, others have flowers that are either male or female, while some can change their sex throughout their lifetime. The latter is quite interesting and offers an insight into the differences in maleness and femaleness. 

The green dragon (Arisaema dracontium) is an arum related to jack-in-the-pulpit. It is wide spread throughout the east but declining in much of its northern range. This species produces a single inflorescence that can be purely male, both male and female, or, in some rare cases, entirely female. The mechanism for this has been a subject of interest for many botanists as it does not seem to be dictated solely by genetics. It has been discovered that any given plant may switch up its flowering strategy from year to year.

What researchers have found is that male flowers are most often produced in younger plants as well as plants that are stressed. In years where environmental conditions are not as conducive to survival or if the plants have not had enough time to build up energy reserves, it is not uncommon to find only male plants. This is advantageous since male flowers and pollen are a lot less costly to produce than ovaries. Also, the plant does not have to allocate resources into developing seeds. In good years and also in older, larger plants, inflorescence are produced that are both male and female. If the plants are less stressed and large enough, more energy can be allocated to seed production. In some rare cases, very large plants have been known to produce only female flowers. This seems to be a strategy that is adopted only under the best of conditions. 

It should be noted that whereas there seems to be a threshold for environmental conditions as well as plant size in determining what kinds of flowers will be produced, each green dragon population seems to vary. In essence there is some genetic determination for how the plant will respond in any given year but this is where teasing the gene environment out of the actual environment gets tricky. Studying these plants is giving us more insight into the advantages and disadvantages of each sex as well as helping to inform how sensitive species like the green dragon will respond in a changing climate. 

Further Reading:

http://plants.usda.gov/core/profile?symbol=ardr3

http://www.jstor.org/stable/2656980

http://www.jstor.org/stable/2445597?seq=1

Rattlesnake Master

I first heard of rattlesnake master (Eryngium yuccifolium) in William K. Stevens' book “Miracle Under the Oaks: The Revival of Nature in America.” Ever since then I have been enamored by this species. Who could blame me? Such a common name deserves a deeper inquiry. It would take a few years before I would be able to see an actual tall grass prairie and lay eyes on this wonderful, albeit strange member of the carrot family. 

Rattlesnake master gets its common name from the erroneous belief that the roots of this plant could be used to cure rattlesnake bites. I don't know about you but I certainly will not be chancing it. Its specific epithet "yuccifolium" comes from the resemblance its leaves have to that of Yucca. Unlike most carrots, which have dissected, lacy foliage, the leaves of rattlesnake master are strap-like and pointed with teeth running up the margins.

The clustered flowers exhibit protandry meaning the anthers mature and senesce before the pistils become receptive. This reduces the chances of self-fertilization, which increases the amount of genetic variation in a population. Being a member of the carrot family, rattlesnake master develops a very deep taproot making it a difficult species to transplant. Despite this fact, it grows readily from seed making it an excellent addition to a native prairie planting. What's more, the caterpillars of the Eryngium root borer moth (Papaipema eryngii) live solely off the roots of rattlesnake master. Without this plant, the moths could not survive. 

Photo Credit: [1]

Further Reading: [1] [2] [3] [4] [5]

American Heart's Tongue Fern

When looking for ferns, it is easy to have a specific kind of search imagine in your head. Your mind's eye is tuned into the long, lacy look of dissected fronds but there are ferns out there that will challenge you to break that mold. I have had the wonderful privilege of meeting some of these fern species this year, but there is one species in particular that has really stuck out.

Meet the American hart's tongue fern, Asplenium scolopendrium var. americanum. The hart's tongue, as you can see, is absolutely striking. Its long, slender, uncut fronds form a disheveled rosette and the sori running along the underside make each frond look like a big, green centipede. Asplenium scolopendrium itself is a wide ranging species of fern, growing on limestone outcroppings throughout Europe but populations in North America are rather sparse and disjunct. In fact, the U.S. Fish and Wildlife Service has listed it as a threatened species. There are some morphological distinctions between the European and North American populations but the major difference is in their number of chromosomes. European hart's tongues are diploid whereas North America's are tetraploid. Because of these differences, botanists consider them distinct varieties.

Why the American variety is so rare is not fully understood, but human activities have not helped matters. Mining, logging, and development have wiped out many historic populations of these ferns. Their habitat specificity mixed with their already low numbers make for little to no range expansion for most populations. They seem to grow in close association with dolomitic limestone, which is high in magnesium. 

They also seem to rely on a specific mix of bryophyte communities, low light levels, moisture, and snow pack in order to persist. Spores that land on significant bryophyte patches seem to germinate better. Young ferns seem to perform better in mixed light levels, especially near canopy gaps. It has also been shown that snow pack is directly correlated to the vigor of each population. In years with below average snow pack, the plants seem to have trouble retaining enough moisture to survive.

This is such an incredible species of fern. To lose it would mean a serious loss for our planet. There is a good effort being put forth to protect, study, grow, and form a deeper understanding with the American hart's tongue fern. The more we learn about this species, the better we can understand what it is going to take to ensure that it persists far into the future.

Photo Credit: James Johnson (http://imgur.com/a/J1Ez5)

Further Reading:
http://www.fws.gov/northeast/nyfo/es/amhtfrecovplan.pdf

http://www.bioone.org/doi/abs/10.3159/TORREY-D-11-00054.1…

http://www.fs.fed.us/

http://www.centerforplantconservation.org/

When One Becomes Two

One of the most stunning spring flowering plants in the eastern forests has to be blue cohosh (Caulophyllum spp.). Around this time of year they begin poking up through the leaf litter, their deep purple stems gradually giving way to shades of blue and green as the leaves and flowers expand into the springtime sun. They seem almost otherworldly and finding them among the speckled leaves of trout lily is a sight I will never tire of.

For as long as it has been known, North America's Caulophyllum has been considered a single species, Caulophyllum thalictroides. The specific epithet hints at how similar this species can look to the meadow rues (Thalictrum spp.). However, a keen observer could tell you that there are apparent differences between some blue cohosh populations, especially in the northeast. Some cohosh flower much earlier than others. Also, there are differences in flower color as well. Some plants sport flowers decked in deep maroon whereas others are pale green. These differences have led some authors to list the purple flowering variety as a subspecies, Caulophyllum thalictroides giganteum.

Caulophyllum thalictroides

Photo by Tom Potterfield licensed under CC BY-NC-SA 2.0

More recently, however, it has become apparent that these two varieties may actually be separate species. Though their ranges overlap, what is now being called Caulophyllum giganteum is distributed much farther north than C. thalictroides. The key differences between these two has to do with flowering time. If these two species become reproductively active at different times, then they are in fact reproductively isolated from one another. Though they can hybridize, the resulting seeds experience reduced viability and do not perform as well as either parent.

Photo Credit: Tom Potterfield (http://bit.ly/1E0JcQ5)

Further Reading: [1] [2]
 

The Badass Spring Ephemerals

Spring ephemerals and the word "badass" are probably not frequent associates but I am here to argue that they should be.

Spring ephemeral season is here for some and just around the corner for the rest of us. It's my favorite wildflower season and I often go missing in the woods for those first few weeks of spring. It is easy to look at their diminutive size and their ephemeral nature as signs of delicacy but these plants are anything but. In fact, when one examines the intricacies of their lifestyle, they can see that spring ephemerals make most other plants look like total softies.

Spring ephemerals, the designation of which gets blurred depending on who you ask, have to complete most of their life cycle in the early spring before the trees and understory shrubs leaf out and completely take over most of the available light. This is an incredibly tough time to be a plant. Soil temperatures are low, which makes nutrient and water uptake a difficult task, all but the most robust pollinators are still sound asleep, and there is the ever present danger of a hard frost or freak snow storm. These factors have led to some incredible adaptations in all of the species that emerge around this time. Whereas each species has its own methods, there are some generalities that are common throughout.

For the most part, spring ephemerals have two distinct growth phases; epigeous (above ground) and hypogeous (below ground). The hypogeous phase of growth takes place throughout fall and winter. Yes, winter. This is the phase in which the plants put out more roots and develop next season’s buds. This goes on at the expense of nutrients that were stored the previous spring. Once spring arrives and soils begin to warm, the plants enter the epigeous phase of growth where leaves and flowers are produced and reproduction occurs. This is an incredibly short period of time and spring ephemerals are well suited for the task.

Typical growth cycle of many spring ephemerals [Source}

For starters, photosynthetic activity for these species is at its best around 20 °C. Photosynthetic proteins activate very early on so that by the time the leaf is fully expanded, the plant is a powerhouse of carbohydrate production. Photosynthesizing in cool temperatures comes at a cost. Water stress in at this time of year is high. Low soil temperatures make uptake of water difficult and it is strange to note that many species of spring ephemeral have very little root surface area in the form of root hairs. These species, however, have extensive mycorrhizal associations which help assuage this issue.

Nutrient availability is also very limited by low soil temperatures. Chemical reactions that would unlock such nutrients are not efficient at low temperatures. Again, spring ephemerals get around this via their increased mycorrhizal associations. It should be noted that some species such as those belonging to the genus Dicentra, do not have these associations. In this situation, these species do in fact develop extensive root hairs as a coping mechanism. Despite specific adaptations for nutrient uptake, you will rarely find spring ephemerals not growing in deep, nutrient-rich soils.

Again, we must keep in mind that all of this is happening so that the plant can quickly complete what it needs to do in the few weeks before the canopy closes and things heat up. It has been observed that high temperatures are associated with slowed growth in most of these species. As temperatures increase, the plants begin to die back. Another adaptation to this ephemeral lifestyle is an increased ability to recycle nutrients in the leaves. As spring temperatures rise, the plants begin to pull in nutrients and store them in their perennial organs. They also show specific compartmentalization of energy stores. In many species, seed production is fueled solely by energy reserves in the stem. Some underground storage structures then receive nutrients to fuel autumn and winter growth while others receive nutrients to fuel leaf and stem growth in the early spring.

Despite all of these amazing adaptations, life is still no cake walk and growth is painstakingly slow. Many species, like trout lilies (Erythronium spp.), can take upwards of 8 years to flower! 8 years!! Think about that next time you are thinking of harvesting or picking some. Even worse in some areas are white tailed deer. East of the Mississippi their populations have grown to a point in which their foraging threatens the long term survival of many different plant species. Especially hard hit are spring ephemerals as they are the first plants to emerge after a long winter of near starvation. 

I hope this post wakes people up to how truly badass these species really are. As our climate warms, we can only speculate how things are going to change for many of them. Some research suggests that things may get easier whereas others suggest that conditions are going to get harsher. It's anyone's guess at this point. As populations are wiped out due to development or invasive species, we are losing much needed genetic diversity and corridors for gene transfer. This is yet another reason why land conservation efforts are so vital to resilient ecosystems. Support your local land conservancy today!

Spring is here and things are getting underway. Get out there and enjoy the heck out of the spring ephemerals! In a few short weeks they will be back underground, awaiting the next cold, damp spring.

Further Reading: [1] [2]

A North American Cycad and its Butterfly

Photo by andy_king50 licensed under CC BY-SA 3.0

Most of us here in North America probably know cycads mainly from those encountered in botanical gardens or as the occasional houseplant. However, if you want to see a cycad growing in the wild, you don't have to leave North America to do so. One must only travel to parts of Georgia and Florida where the coontie can be found growing in well drained sandy soils. 

Known scientifically as Zamia integrifolia, the coontie is a cycad on a small scale. Plants are either male or female and both are needed for viable seed production. Here in the United States, the coontie is considered near threatened. Decades of habitat destruction and poaching have caused serious declines in wild populations. This has come at a great cost to at least one other organism as well.

Photo by James St. John licensed under CC BY 2.0

Thought to be extinct for over 20 years, a butterfly known as the atala (Eumaeus atala) require this lovely little cycad to complete their lifecycle. The coontie produces a toxin known as "cycasin" and, just as monarchs become rather distasteful to predators by feeding on milkweeds during their larval stage, so too do the larvae of the atala. The brightly contrasting colors of both the caterpillars and the adults let potential predators know that messing with them isn't going to be a pleasant experience. The reason for its decline in the wild is due to the loss of the coontie. 

Rediscovered only recently, populations of this lovely butterfly are starting to rebound. Caterpillars of the atala are voracious eaters and a small group of them can quickly strip a coontie of its foliage. For this reason, large populations of coontie are needed to support a viable breeding population of the atala. The coontie is becoming a popular choice for landscaping, especially in suburban areas of southeastern Florida, which is good news for the atala. As more and more people plant coonties on their property, more and more caterpillars are finding food to eat. This just goes to show you the benefits of planting natives!

An atala caterpillar and chrysalis. Photo by Monica R. licensed under CC BY 2.0

Further Reading: [1] [2] [3]