Fraser Fir: A New Look at an Old Friend

Photo by James St. John licensed under CC BY 2.0

Growing up, Fraser fir (Abies fraseri) was a fairly common sight in our house. Each winter this species would usually win out over other options as the preferred tree for our living room during the holiday season. Indeed, its pleasing shape, lovely color, and soft needles have made it one of the most popular Christmas trees around the world. Amazingly, despite its popularity as a decoration, Fraser fir is so rare in the wild that it is considered an endangered species.

Fraser fir is native to only a handful of areas in the southern Appalachian Mountains. Together with red spruce (Picea rubens), this conifer makes up one of the rarest ecosystems on the continent - the southern Appalachian spruce-fir forest. Such forests only exist at elevations above 4,000 ft (1,200 m) from southwestern Virginia to western North Carolina and eastern Tennessee. The reason for this limited distribution is rooted in both modern day climate and North America’s glacial past.

USGS/Public Domain

Whereas anyone hiking through Appalachian spruce-fir forests could readily draw similarities to boreal forests found farther north, the Appalachian spruce-fir forests are nonetheless unique, hosting many species found nowhere else in the world. Indeed, these forests are holdovers from the Pleistocene when the southeast was much cooler than it is today. As glaciers retreated and the climate warmed, Appalachian spruce-fir forests “retreated” up the mountains, following their preferred climate zones until they hit the peaks of mountains and couldn’t go any further.

Indeed, Fraser fir is in large part limited in its distribution by temperature. This conifer does not perform well at high temperatures and is readily out-competed by other species under warmer conditions. Another factor that has maintained Appalachian spruce-fir forests at elevation is fog. The southern Appalachian Mountains host eastern North America’s only temperate rainforest and fog commonly blankets high elevation areas throughout the year. Research has shown that in addition to keeping these areas cool, fog also serves as an important source of water for Fraser fir and its neighbors. As fog condenses on its needles, these trees are able to absorb that water, keeping them hydrated even when rain is absent.

A view of an Appalachian spruce-fir forest from the Blue Ridge Parkway.

Due to its restricted habitat, Fraser fir has never been extremely common. However, things got even worse as Europeans colonized North America. Over the past two centuries, unsustainable logging and grazing practices have decimated southern Appalachian spruce-fir forests, fragmenting them into even smaller patches with no connectivity in between. In areas where thin, rocky soils were not completely washed away, Fraser fir seedlings did return, however, this was not always the case. In areas where soils were were lost, southern Appalachian spruce–fir forests were incapable of regenerating.

If the story ended there, Fraser fir and its habitat would still be in trouble but sadly, things only got worse with the introduction of the invasive balsam woolly adelgid (Adelges piceae) from Europe around 1900. Like the hemlock woolly adlegid, this invasive, sap-feeding insect has decimated Fraser fir populations throughout southern Appalachia. Having shared no evolutionary history with the adelgid, Fraser fir is essentially defenseless and estimates suggest that upwards of 90% of infect trees have been killed by the invasion. Although plenty of Fraser fir seedlings have sprung up in the wake of this destruction, experts fear that as soon as those trees grow large enough to start forming fissures in their bark, the balsam woolly adelgid will once again experience a massive population boom and repeat the process of destruction again.

Dead Fraser fir as seen from Clingman’s Dome. Photo by Brian Stansberry licensed under CC BY 3.0

The loss of Fraser fir from this imperiled ecosystem has had a ripple effect. Fraser fir is much sturdier than its red spruce neighbors and thus provides an important windbreak, protecting other trees from the powerful gusts that sweep over the mountain tops on a regular basis. With a decline in the Fraser fir canopy, red spruce and other trees are more susceptible to blowdowns. Also, the dense, evergreen canopy of these Appalachian spruce-fir forests produces a unique microclimate that fosters the growth of myriad mosses, liverworts, ferns, and herbs that in turn support species like the endangered endemic spruce-fir moss spider (Microhexura montivaga). As Fraser fir is lost from these areas, the species that it once supported decline as well, placing the whole ecosystem at risk of collapse.

The moss-dominated understory of an Appalachian spruce-fir forest supports species found nowhere else in the world. Photo by Miguel.v licensed under CC BY 3.0

Luckily, the plight of this tree and the habitat it supports has not gone unnoticed by conservationists. Numerous groups and agencies are working on conserving and restoring Fraser fir and southern Appalachian spruce-fir forests to at least a portion of their former glory. This is not an easy task by any means. Aside from lack of funding and human power, southern Appalachian spruce-fir forest conservation and restoration is hindered by the ever present threat of a changing climate. Fears that the life-giving fog that supports this ecosystem may be changing make it difficult to prioritize areas suitable for reforestation. Also, the continued threat from invasive species like the balsam woolly adelgid can hamper even the best restoration and conservation efforts. Still, this doesn’t mean we must give up hope. With continued collaboration and effort, we can still ensure that this unique ecosystem has a chance to persist.

Please visit the Central Appalachian Spruce Restoration Initiative (CASRI) website to learn more!

Photo Credits: [1] [2] [4] [5]

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

Screw Pines, Volcanism, and Diamonds

Photo by Jakob Fahr/iNaturalist (CC BY-NC)

The association between geology and botany has always fascinated me. The closer you look, the more you can't separate the two. Rocks and minerals influence soil characteristics, which in turn influences which plant species will grow and where, which in turn influences soil properties. Take for instance the case of kimberlite.

Kimberlite is a volcanic rock whose origin is quite intense. Kimberlite is found in the form of large vertical columns, often referred to as pipes. They are the result of some seriously explosive volcanism. Intense heat and pressure builds deep within the mantle until it explodes upward, forming a column of this igneous rock. 

Over long spans of time, these pipes begin to weather and erode. This results in soil that is rich in minerals like magnesium, potassium, and phosphorous. As anyone who gardens can tell you, these are the ingredients of many fertilizers. In Africa where these sorts of pipes are well known, there is a species of plant that seems to take advantage of these conditions. 

It has been coined Pandanus candelabrum and it belongs to a group of plants called the screw pines. They aren't true pines but are instead a type of angiosperm. Now, the taxonomy of the genus Pandanus is a bit shaky. Systematics within the family as a whole has largely been based on fragmentary materials such as fruits and flowers. What's more, for much of its taxonomic history, each new collection was largely regarded as a new species. You might be asking why this is important. The answer has something to do with the kimberlite P. candelabrum grows upon. 

There is something other than explosive volcanic activity that makes kimberlite famous. It is mostly known for containing diamonds. In a 2015 paper, geologist Stephen E. Haggerty made this connection between P. candelabrum and kimberlite. As far as anyone can tell, the plant is a specialist on this soil type. As such, prospectors are now using the presence of this plant as a sort of litmus test for finding diamond deposits. This is why I think taxonomy becomes important. 

If P. candelabrum turns out not to be a unique species but rather a variation then perhaps this discovery doesn't mean much for the genus as a whole. However, if it turns out that P. candelabrum is a truly unique species then this new-found association with diamond-rich rocks may spell disaster. Mining for diamonds is a destructive process and if every population of P. candelabrum signals the potential for diamonds, then the future of this species lies in the balance of how much our species loves clear, shiny chunks of carbon. A bit unsettling if you ask me. 


Further Reading:
http://econgeol.geoscienceworld.org/content/110/4/851.full

The Curly-Whirly Plants of South Africa

Gethyllis villosa. Photo by Capetown Botanist: www.capetownbotanist.com

In a region of South Africa traditionally referred to as Namaqualand there exists a guild of plants that exhibit a strange pattern in their growth habits. These plants hail from at least eight different monocot families as well as the family Oxalidaceae. They are all geophytes, meaning they live out the driest months of the year as dormant, bulb-like structure underground. However, this is not the only feature that unites them.

A walk through this region during the growing season would reveal that members of this guild all produce leaves that at least one author has described as "curly-whirly." To the casual observer it would seem that they had left the natural expanse of the desert flora and entered into the garden of someone with very particular tastes.

What these plants have managed to do is to converge on a morphological strategy that allows them to take full advantage of their unique geographical location. The region along the coastal belt of Namibia is famous for being a "fog desert." Despite receiving very little rain, humid air blowing in from the southwestern Atlantic runs into colder air blowing down from the north and condenses, carrying fog inland. This produces copious amounts of dew.

Normally dew would be unavailable to most plants. It simply doesn't penetrate the soil enough to be useful for roots. This is where those curly-whirly leaves come in. Researchers have discovered that this leaf anatomy is specifically adapted for capturing and concentrating fog and dew. This has the effect of significantly improving their water budget in this otherwise arid region. What's more, the advantages are additive.

The most obvious advantage has to do with surface area. Curled leaves increase the amount of edge a leaf has. This provides ample area for capturing fog and dew. Also, by curling up, the leaves are able to reduce the overall size of the leaf exposed to the air, which reduces the amount of transpiration stress these plants encounter in their hot desert environment. Another advantage is direct absorption. Although no specific organs exist for absorbing water, the leaves of most of these species are nonetheless capable of absorbing considerable amounts.

Dipcadi crispum By roncorylus

Finally, each curled leaf acts like a mini gutter, channeling water to the base of the plant. Many of these plants have surprisingly shallow root zones. The lack of a deep taproot may seem odd until one considers the fact that dew dripping down from the leaves above doesn't penetrate too deeply into the soil. These roots are sometimes referred to as "dew roots."

I don't know about you but this may be one of the coolest plant guilds I have ever heard about. This is such a wonderfully clear example of just how strong of a selective pressure the combination of geography and climate can be. What's more, this is not the only region in the world where drought-tolerant plants have converged on this curly strategy. Similar guilds exist in other arid regions of Africa, as well as in Turkey, Australia, and Asia.

Albuca spiralis. Photo by Wolf G. licensed under CC BY-NC-ND 2.0

Photo Credits: Cape Town Botanist (http://bit.ly/1PzPkP7), www.ispotnature.org, roncorylus (http://bit.ly/1PzPoi6), and Wolf G. (http://bit.ly/1n4Mo6b)

Further Reading: [1]

Bird's Foot Violet

As a life long denizen of deciduous forests, prairies and savannas present an entirely new set of stimuli. A recent excursion into an expansive oak savanna found me overwhelmed by the beauty of such places. Being mid October, the color pallet of the landscape ranged from myriad shades of reds, browns, yellows, and oranges. I was walking through a particularly sandy patch of soil when something caught my eye. A little flash of lavender shone through the amber grasses. To my astonishment I had found a plant that has managed to elude me for many years. 

What I had found was a bird's-foot violet (Viola pedata). Its deeply divided leaves, which faintly resemble a bird's foot, are unmistakable. What was even more fantastic was that this particular plant was in full bloom. I looked around and found only a small handful of other plants. This one was the only one in bloom. Though not unheard of for this time of year, I couldn't help but revel in the serendipity of the moment. 

Like all members of the genus Viola, bird's-foot violet is a photoperiodic plant. By this I mean that all aspects of its growth are sensitive to the relative amount of sunlight in any given day. Violets are generally spring time plants, however, the shortening days and cooler temperatures of fall aren't that different from spring. As such, this lovely little plant was perhaps a bit confused by the cool October weather. I didn't see any pollinators out and about but that doesn't mean that a hardy bumblebee wouldn't be lucky to stumble into its blooms. 

Back in my home state of New York, this particular species of violet is truly a rare find. The kind of habitats which it frequents have been largely destroyed. It is a xeric species that doesn't appreciate water hanging around for very long. Finding it growing in mostly sand was not surprising to say the least. Like most other violets, its seeds come complete with their own fleshy protuberance called an elaiosome. The purpose of these fatty attachments are to attract foraging ants in the genus Aphenogaster. The ants find the elaiosomes to their liking and take them back to their nest. Once the elaiosome is eaten, the seed is discarded into a refuse chamber inside the nest. There it finds a favorable microsite for germination full of nutrient-rich ant compost.

Further Reading:
http://www.jstor.org/stable/3668940?seq=1#page_scan_tab_contents

http://www.illinoiswildflowers.info/prairie/plantx/bird_violet.htm

"The Mountains Are Calling and I Must Go..." - John Muir

I find myself thinking the same thing as I drive to work every morning - "Screw you, North Carolina! How dare you be so beautiful?" I say this with love of course. I mean it too. My daily commute takes me through the Cowee Mountains, which represent only the tiniest fraction of the giant fold in the continent that we collectively refer to as the "Appalachian Mountains." Driving between these forested peaks, it feels as if time stands still. They are a stark and constant reminder of just how small and insignificant our time on this planet really is. 

What so few realize is that these mountains are some of the oldest on Earth. They are the collective result of some serious geology. Between 325 million and 260 million years ago, Africa slammed into North America (though it wasn't the continent we know today) causing massive upheaval of the crust. This was also the birth of the super-continent Pangea. The resulting upheaval produced a mountain chain similar in size to the present day Himalayas (think Mt. Everest). They have been steadily eroding ever since. 

Today, the highest peaks reach somewhere in the 6,000 feet (1,800 m) range. Despite this reduction in size, the Appalachian Mountains have nonetheless been a major driver in the ecology of eastern North America. They have served as refugia for species escaping glaciation, they act as corridors for migration, and they even produce their own climate. They may not be the snow capped mountains of the American West but they have a uniqueness all their own. There aren't many places in this world in which one can explore broadleaf deciduous forests at elevation. If I could end up here I think I would die a happy man. For now, I am spending every free moment absorbing the beauty and splendor of this place. It is going to be hard to leave...