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]

The Curious Case of the Yellowwood Tree

Photo by Plant Image Library licensed under CC BY-SA 2.0

The immense beauty and grace of the yellowwood (Cladrastis kentukea) is inversely proportional to its abundance. This unique legume is endemic to the eastern United States and enjoys a strangely patchy distribution. Its ability to perform well when planted far outside of its natural range only deepens the mystery of the yellowwood.

The natural range of the yellowwood leaves a lot of room for speculation. It hits its highest abundances in the Appalachian and Ozark highlands where it tends to grow on shaded slopes in calcareous soils. Scattered populations can be found as far west as Oklahoma and as far north as southern Indiana but nowhere is this tree considered a common component of the flora.

Though the nature of its oddball distribution pattern iscurious to say the least, it is likely that its current status is the result of repeated glaciation events and a dash of stochasticity. The presence of multiple Cladrastis species in China and Japan and only one here in North America is a pattern shared by multiple taxa that once grew throughout each continent. A combination of geography, topography, and repeated glaciation events has since fragmented the ranges of many genera and perhaps Cladrastis is yet another example.

The fact that yellowwood seems to perform great as a specimen tree well outside of its natural range says to me that this species was probably once far more wide spread in North America than it is today. It may have been pushed south by the ebb and flow of the Laurentide Ice Sheet and, due to the stochastic nuances of seed dispersal, never had a chance to recolonize the ground it had lost. Again, this is all open to speculation as this point.

Despite being a member of the pea family, yellowwood is not a nitrogen fixer. It does not produce nodules on its roots that house rhizobium. As such, this species may be more restricted by soil type than other legumes. Perhaps its inability to fix nitrogen is part of the reason it tends to favor richer soils. It may also have played a part in its failure to recolonize land scraped clean by the glaciers.

Yellowwood's rarity in nature only makes finding this tree all the more special. It truly is a sight to behold. It isn't a large tree by any standards but what it lacks in height it makes up for in looks. Its multi-branched trunk exhibits smooth, gray bark reminiscent of beech trees. Each limb is decked out in large, compound leaves that turn bright yellow in autumn.

Photo by Elektryczne jabłko licensed under CC BY-SA 4.0

When mature, which can take upwards of ten years, yellowwood produces copious amounts of pendulous inflorescences. Each inflorescence sports bright white flowers with a dash of yellow on the petals. In some instances, even pink flowers are produced! It doesn't appear that any formal pollination work has been done on this tree but surely bees and butterflies alike visit the blooms. The name yellowwood comes from the yellow coloration of its heartwood, which has been used to make furniture and gunstocks in the past.

Whether growing in the forest or in your landscape, yellowwood is one of the more stunning trees you will find in eastern North America. Its peculiar natural history only lends to its allure.

Photo Credits: [1] [2] [3]

Further Reading: [1] [2]

Germinating a Seed After 32,000 Years

[SOURCE]

What you are looking at are plants that were grown from seeds buried in permafrost for nearly 32,000 years. The seeds were discovered on the banks of the Kolyma River in Siberia. The river is constantly eroding into the permafrost and uncovering frozen Pleistocene relics. Upon their discovery, researchers took the seeds and did the unthinkable - they grew them into adult plants. To date, this is the oldest resurrected plant material. 

The key to their extreme longevity lies in the permafrost. They were found inside the frozen burrow of an Arctic ground squirrel. The state of the burrow suggests that everything froze quite rapidly. As such, the seeds remained in a state of suspended animation for 32,000 years. This is not the first time viable plant materials have been recovered from Pleistocene permafrost. Spores, mosses, as well as seeds of other flowering plants have been rejuvenated to some degree in the past but none of these were grown to maturity. 

Using micropropagation techniques coupled with tissue cultures, researchers were able to grow and flower the 32,000 year old seeds. What they discovered was that these seeds belonged to a plant that can still be found in the Arctic today. It is a small species in the family Caryophyllaceae called Silene stenophylla. However, there were some interesting differences. 

As it turns out, the seeds taken from the burrow proved to be a phenotype quite distinct from extant S. stenophylla populations. For instance, their flowers were thinner and less dissected than extant populations. Also, whereas the flowers of extant populations are all bisexual, individuals grown from the ancient seeds first produced only female flowers followed by fewer bisexual flowers towards the end of their blooming period.Though there are many possible reasons for this, it certainly hints at the different environmental parameters faced by this species through time. What's more, such findings allow us a unique window into the world of seed dormancy. Researchers are now looking at such cases to better inform how we can preserve seeds for longer periods of time. 

Photo Credit: Svetlana Yashinaa, Stanislav Gubin, Stanislav Maksimovich, Alexandra Yashina, Edith Gakhova, and David Gilichinsky

Further Reading: [1]