The Rise and Fall of the Scale Trees


If I had a time machine, the first place I would visit would be the Carboniferous. Spanning from 358.9 to 298.9 million years ago, this was a strange time in Earth’s history. The continents were jumbled together into two great landmasses - Laurasia to the north and Gondwana to the south and the equatorial regions were dominated by humid, tropical swamps. To explore these swamps would be to explore one of the most alien landscapes this world has ever known.

The Carboniferous was the heyday for early land plants. Giant lycopods, ferns, and horsetails formed the backbone of terrestrial ecosystems. By far the most abundant plants during these times were a group of giant, tree-like lycopsids known as the scale trees. Scale trees collectively make up the extinct genus Lepidodendron and despite constantly being compared to modern day club mosses (Lycopodiopsida), experts believe they were more closely related to the quillworts (Isoetopsida).

Carboniferous coal swamp reconstruction dating back to the 1800’s

Carboniferous coal swamp reconstruction dating back to the 1800’s

It is hard to say for sure just how many species of scale tree there were. Early on, each fragmentary fossil was given its own unique taxonomic classification; a branch was considered to be one species while a root fragment was considered to be another and juvenile tree fossils were classified differently than adults. As more complete specimens were unearthed, a better picture of scale tree diversity started to emerge. Today I can find references to anywhere between 4 and 13 named species of scale tree and surely more await discovery. What we can say for sure is that scale tree biology was bizarre.

The name “scale tree” stems from the fossilized remains of their bark, which resembles reptile skin more than it does anything botanical. Fossilized trunk and stem casts are adorned with diamond shaped impressions arranged in rows of ascending spirals. These are not scales, of course, but rather they are leaf scars. In life, scale trees were adorned with long, needle-like leaves, each with a single vein for plumbing. Before the started branching, young trees would have resembled a bushy, green bottle brush.

Juvenile scale tree on the left & the adult on the right

Juvenile scale tree on the left & the adult on the right

As scale trees grew, it is likely that they shed their lower leaves, which left behind the characteristic diamond patterns that make their fossils so recognizable. How these plants achieved growth is rather fascinating. Scale tree cambium was unifacial, meaning it only produced cells towards its interior, not in both directions as we see in modern trees. As such, only secondary xylem was produced. Overall, scale trees would not have been very woody plants. Most of the interior of the trunk and stems was comprised of a spongy cortical meristem. Because of this, the structural integrity of the plant relied on the thick outer “bark.” Many paleobotanists believe that this anatomical quirk made scale trees vulnerable to high winds.

Scale trees were anchored into their peaty substrate by rather peculiar roots. Originally described as a separate species, the roots of these trees still retain their species name. Paleobotanists refer to them as “stigmaria” and they were unlike most roots we encounter today. Stigmaria were large, limb-like structures that branched dichotomously in the soil. Each main branch was covered in tiny spots that were also arranged in rows of ascending spirals. At each spot, a rootlet would have grown outward, likely partnering with mycorrhizal fungi in search of water and nutrients.

A preserved  Lepidodendron  stump

A preserved Lepidodendron stump

Eventually scale trees would reach a height in which branching began. Their tree-like canopy was also the result of dichotomous branching of each new stem. Amazingly, the scale tree canopy reached staggering heights. Some specimens have been found that were an estimated 100 ft (30 m) tall! It was once thought that scale trees reached these lofty heights in as little as 10 to 15 years, which is absolutely bonkers to think about. However, more recent estimates have cast doubt on these numbers. The authors of one paper suggest that there is no biological mechanism available that could explain such rapid growth rates, concluding that the life span of a typical scale tree was more likely measured in centuries rather than years.

Regardless of how long it took them to reach such heights, they nonetheless would have been impressive sites. Remarkably, enough of these trees have been preserved in situ that we can actually get a sense for how these swampy habitats would have been structured. Whenever preserved stumps have been found, paleobotanists remark on the density of their stems. Scale trees did not seem to suffer much from overcrowding.


The fact that they spent most of their life as a single, unbranched stem may have allowed for more success in such dense situations. In fact, those that have been lucky enough to explore these fossilized forests often comment on how similar their structure seems compared to modern day cypress swamps. It appears that warm, water-logged conditions present similar selection pressures today as they did 350+ million years ago.

Like all living things, scale trees eventually had to reproduce. From the tips of their dichotomosly branching stems emerged spore-bearing cones. The fact that they emerge from the growing tips of the branches suggests that each scale tree only got one shot at reproduction. Again, analyses of some fossilized scale tree forests suggests that these plants were monocarpic, meaning each plant died after a single reproductive event. In fact, fossilized remains of a scale tree forest in Illinois suggests that mass reproductive events may have been the standard for at least some species. Scale trees would all have established at around the same time, grown up together, and then reproduced and died en masse. Their death would have cleared the way for their developing offspring. What an experience that must have been for any insect flying around these ancient swamps.

The fossilized strobilus of a Lepidodendron

The fossilized strobilus of a Lepidodendron

Compared to modern day angiosperms, the habits of the various scale trees may seem a bit inefficient. Nonetheless, this was an extremely successful lineage of plants. Scale trees were the dominant players of the warm, humid, equatorial swamps. However, their dominance on the landscape may have actually been their downfall. In fact, scale trees may have helped bring about an ice age that marked the end of the Carboniferous.

You see, while plants were busy experimenting with building ever taller, more complex anatomies using compounds such as cellulose and lignin, the fungal communities of that time had not yet figured out how to digest them. As these trees grew into 100 ft monsters and died, more and more carbon was being tied up in plant tissues that simply weren’t decomposing. This lack of decomposition is why we humans have had so much Carboniferous coal available to us. It also meant that tons of CO2, a potent greenhouse gas, were being pulled out of the atmosphere millennia after millennia.

A fossilized root or “stigmaria”

A fossilized root or “stigmaria”

As atmospheric CO2 levels plummeted and continents continued to shift, the climate was growing more and more seasonal. This was bad news for the scale trees. All evidence suggests that they were not capable of keeping up with the changes that they themselves had a big part in bringing about. By the end of the Carboniferous, Earth had dipped into an ice age. Earth’s new climate regime appeared to be too much for the scale trees to handle and they were driven to extinction. The world they left behind was primed and ready for new players. The Permian would see a whole new set of plants take over the land and would set the stage for even more terrestrial life to explode onto the scene.

It is amazing to think that we owe much of our industrialized society to scale trees whose leaves captured CO2 and turned it into usable carbon so many millions of years ago. It seems oddly fitting that, thanks to us, scale trees are once again changing Earth’s climate. As we continue to pump Carboniferous CO2 into our atmosphere, one must stop to ask themselves which dominant organisms are most at risk from all of this recent climate change?

Photo Credits: [1] [2] [3] [4] [5] [6] [7]

Further Reading: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

Arctic Vegetation is Growing Taller & Why That Matters


The Arctic ecosystem is changing and it is doing so at an alarming rate. Indeed, the Arctic Circle is warming faster than most other ecosystems on this planet. All of this change has implications for the plant communities that call this region home. In a landmark study that incorporated thousands of data points from places like Alaska, Canada, Iceland, Scandinavia, and Russia, researchers have demonstrated that Arctic vegetation is, on average, getting taller.

Imagine what it is like to be a plant growing in the Arctic. Extreme winds, low temperatures, a short growing season, and plenty of snow are just some of the hardships that characterize life on the tundra. Such harsh conditions have shaped the plants of this region into what we know and love today. Arctic plants tend to hug the ground, hunkering down behind whatever nook or cranny offers the most respite from their surroundings. As such, plants of Arctic-type habitats tend to be pretty small in stature. As you can probably imagine, if these limits to plant growth become less severe, plants will respond accordingly.


That is part of what makes this new paper so alarming. The vegetation that comprise these Arctic communities is nearly twice as tall today as it was 30 years ago. However, the increase in height is not because the plants that currently grow there are getting taller but rather because new plants are moving northwards into these Arctic regions. New players in the system are usually cause for concern. Other studies have shown that it isn’t warming necessarily that hurts Arctic and alpine plants but rather competition. They simply cannot compete as well with more aggressive plant species from lower latitudes.

Taller plants moving into the Arctic may have even larger consequences than just changes in species interactions. It can also change ecosystem processes, however, this is much harder to predict. One possible consequence of taller plants invading the Arctic involves carbon storage. It is possible that as conditions continue to favor taller and more woody vegetation, there could actually be more carbon storage in this system. Woody tissues tend to sequester more carbon and shading from taller vegetation may slow decomposition rates of debris in and around the soil.

Alopecurus alpinus  is one of the new tall plant species moving into the Arctic

Alopecurus alpinus is one of the new tall plant species moving into the Arctic

It is also possible that taller vegetation will alter snowpack, which is vital to the health and function of life in the Arctic. Taller plants with more leaf area could result in a reduced albedo in the surrounding area. Lowering the albedo means increased soil temperatures and reduced snowpack as a result. Alternatively, taller plants could also increase the amount of snowpack thanks to snow piling up among branches and leaves. This could very well lead (counterintuitively) to warmer soils and higher decomposition rates as snowpack acts like an insulating blanket, keeping the soil slightly above freezing throughout most of the winter.

It is difficult to make predictions on how a system is going to respond to massive changes in the average conditions. However, studies looking at how vegetation communities are responding to changes in their environment offer us one of the best windows we have into how ecosystems might change moving into the uncertain future we are creating for ourselves.

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

Further Reading: [1]

America's Trees are Moving West

Understanding how individual species are going to respond to climate change requires far more nuanced discussions than most popular media outlets are willing to cover. Regardless, countless scientists are working diligently on these issues each and every day so that we can attempt to make better conservation decisions. Sometimes they discover that things aren't panning out as expected. Take, for instance, the trees of eastern North America.

Climate change predictions have largely revolved around the idea that in response to warming temperatures, plant species will begin to track favorable climates by shifting their ranges northward. Of course, plants do not migrate as individuals but rather generationally as spores and seeds. As the conditions required for favorable germination and growth shift, the propagules that end up in those newly habitable areas are the ones that will perform the best.

Certainly data exists that demonstrates that this is the case for many plant species. However, a recent analysis of 86 tree species native to eastern North America suggests that predictions of northward migration aren't painting a full picture. Researchers at Purdue University found that a majority of the species they looked at have actually moved westward rather than northward.

Of the trees they looked at, 73% have increased their ranges to the west whereas only 62% have increased their ranges northward. These data span a relatively short period of time between 1980 and 2015, which is even more surprising considering the speed at which these species are moving. The team calculated that they have been expanding westward at a rate of 15.4 km per decade!

These westward shifts have largely occurred in broad-leaf deciduous trees, which got the team thinking about what could be causing this shift. They suspected that this westward movement likely has something to do with changes in precipitation. Midwestern North America has indeed experienced increased average rainfall but still not nearly as much as eastern tree species are used to getting in their historic ranges. Taken together, precipitation only explains a small fraction of the patterns they are observing.

Although a smoking gun still has not been found, the researchers are quick to point out that just because changes in climate can not explain 100% of the data, it nonetheless plays a significant role. It's just that in ecology, we must consider as many factors as possible. Decades of fire suppression ,changes in land use, pest outbreaks, and even conservation efforts must all be factored into the equation.

Our world is changing at an ever-increasing rate. We must do our best to try and understand how these myriad changes are going to influence the species around us. This is especially important for plants as they form the foundation of every major terrestrial ecosystem on this planet. As author John Eastman so eloquently put it "Since plants provide the ultimate power base for all the food and energy chains and webs that hold our natural world together, they also form the hubs of community structure and thus the centers of our focus."

Further Reading:  [1]

The Power of Leaves

When we think of the dominance of flowering plants on the landscape, we usually invoke the evolution of flowers and seed characteristics like endosperm and fruit. However, evolutionary adaptations in the structure of the angiosperm leaf may have been one of the most critical factors in the massive diversification that elevated them to their dominant position on the landscape today. 

Leaves are the primary organs used in water and gas exchange. They are the centers of photosynthesis, allowing plants to take energy from our closest star and turn it into food. To optimize this system, plants must balance water loss with transpiration in order to maximize their energy gain. This requires a complex plumbing system that can deliver water where it needs to be. It makes sense that plant physiology should maximize vein production, however, there are tradeoffs in doing so. Veins are not only costly to construct, they also displace valuable photosynthetic machinery. 

It appears that this is something that flowering plants do quite well. Because leaves fossilize with magnificent detail, researchers are able to look back in time through 400 million years of leaf evolution. What they found is quite incredible. There appears to be a consistent pattern in the vein densities between flowering and non-flowering plants. The densities found in angiosperm leaves both past and present are orders of magnitude higher than all non-flowering plants. These high densities are unique to flowering plants alone. 

This innovation in leaf physiology allowed flowering plants to maintain transpiration and carbon assimilation rates that are three and four times higher than those of non-flowering plants. This gives them a competitive edge across a multitude of different environments. The evolution of such dense vein structure also had major ramifications on the environment. 

The massive change in transpiration rates among the angiosperm lineage is likely to have completely changed the way water moved through the environment. These effects would be most extreme in tropical regions. Today, transpiration from tropical forests account for 30-50% of precipitation. A lot of this has to do with patterns in the intertropical convergence zone, which ensures that such humid conditions can be maintained. However, in areas outside of this zone such as in the Amazon, a high abundance of flowering plants with their increased rates of transpiration enhances the amount of rainfall and thus forms a sort of positive feedback.

Because precipitation is the single greatest factor in maintaining plant diversity in these regions, increases in rainfall due to angiosperm transpiration effectively helps to maintain such diversity. As angiosperms rose to dominance, this effect would have propagated throughout the ecosystems of the world. Plants really are the ultimate ecosystem engineers. 

Photo Credit: Bourassamr (Wikimedia Commons)

Further Reading: [1]

Spring Has Sprung Earlier

Phenology is defined as "the study of cyclic and seasonal natural phenomenon, especially in relation to climate, plant, and animal life." Whether its deciding when to plant certain crops or when to start taking your allergy medication, our lives are intricately tied to such cycles. The study of phenology has other applications as well. By and large, it is one of the best methods we have in understanding the effects of climate change on ecosystems around the globe. 

For plants, phenology can be applied to a variety of things. We use it every time we take note of the first signs of leaf out, the first flowers to open, or the emergence of insect herbivores.  In the temperate zones of the world, phenology plays a considerable role in helping us track the emergence of spring and the onset of fall. As we collect more and more data on how global climates are changing, phenology is confirming what many climate change models have predicted - spring is starting earlier and fall is lasting longer.

Researchers at the USA National Phenology Network have created a series of maps that illustrate the early onset of spring by using decades worth of data on leaf out. Leaf out is controlled by a variety of factors such as the length of chilling temperatures in winter, the rate of heat accumulation in the spring, and photoperiod. Still, for woody species, the timing of leaf out is strongly tied to changes in local climate. And, although it varies from year to year and from species to species, the overall trend has been one in which plants are emerging much earlier than they have in the past.

For the southern United States, the difference is quite startling. Spring leaf out is happening as much as 20 days earlier than it has in past decades. Stark differences between current and past leaf out dates are called "anomalies" and the 2017 anomaly in the southern United States is one of the most extreme on record.

How this is going to alter ecosystems is hard to predict. The extended growing seasons are likely to increase productivity for many plant species, however, this will also change competitive interactions among species in the long term. Early leaf out also comes with increased risk of frost damage. Cold snaps are still quite possible, especially in February and March, and these can cause serious damage to leaves and branches. Such damage can result in a reduction of productivity for these species.

Changes in leaf out dates are not only going to affect individual species or even just the plants themselves. Changes in natural cycles such as leaf out and flowering can have ramifications across entire landscapes. Mismatches in leaf emergence and insect herbivores, or flowers and pollinators have the potential to alter entire food webs. It is hard to make predictions on exactly how ecosystems are going to respond but what we can say is that things are already changing and they are doing so more rapidly than they have in a very long time. 

For these reasons and so many more, the study of phenology in natural systems is crucial for understanding how the natural world is changing. Although we have impressive amounts of data to draw from, we still have a lot to learn. The great news is that anyone can partake in phenological data collection. Phenology offers many great citizen science opportunities. Anyone and everyone can get involved. You can join the National Phenology Network in their effort to track phenological changes in your neighborhood. Check out this link to learn more: USA National Phenology Network

Further Reading: [1] [2]  


Important Lessons From Ascension Island

Located in the middle of the South Atlantic, Ascension Island is probably not on the top of anyone's travel list. This bleak volcanic island doesn't have much to offer the casual tourist but what it lacks in amenities it makes up for in a rich and bizarre history. Situated about 2,200 km east of Brazil and 3,200 km west of Angola, this remote island is home to one of the most remarkable ecological experiments that is rarely talked about. The roots of this experiment stem back to a peculiar time in history and the results have so much to teach the human species about botany, climate, extinction, speciation, and much more. What follows is not a complete story; far from it actually. However, my hope is that you can take away some lessons from this and, at the very least, use it as a jumping off point for future discussions. 

Ascension Island is, as land masses go, quite young. It arose from the ocean floor a mere 1 million years ago and is the result of intense volcanic activity. Estimates suggest that volcanism was still shaping this island as little as 1000 years ago. Its volcanic birth, young age, isolated conditions, and nearly non-existent soils meant that for most of its existence, Ascension Island was a depauperate place. It was essentially a desert island. Early sailors saw it as little more than a stopover point to gather turtles and birds to eat as they sailed on to other regions. It wasn't until 1815 that any permanent settlements were erected on Ascension. 

In looking for an inescapable place to imprison Napoleon Bonaparte, the Royal Navy claimed Ascension in the name of King George III. Because Napoleon had a penchant for being an escape artist, the British decided to build a garrison on the island in order to make sure Napoleon would not be rescued. In doing so, the limitations of the island quickly became apparent. There were scant soils in which to grow vegetables and fresh water was nearly nonexistent. 

The native flora of Ascension was minimal. It is estimated that, until the island was settled, only about 25 to 30 plant species grew on the island. Of those 10 (2 grasses, 2 shrubs, and 6 ferns) were considered endemic. If the garrison was to persist, something had to be done. Thus, the Green Mountain garden was established. British marines planted this garden at an elevation of roughly 2000 feet. Here the thin soils supported a handful of different fruits and vegetables. In 1836, Ascension was visited by a man named Charles Darwin. Darwin took note of the farm that had developed and, although he admired the work that was done in making Ascension "livable" he also noted that the island was "destitute of trees."

One of Ascension Island's endemic ferns -  Pteris adscensionis

One of Ascension Island's endemic ferns - Pteris adscensionis

Others shared Darwin's sentiment. The prevailing view of this time period was that any land owned by the British empire must be transformed to support people. Thus, the wheels of 'progress' turned ever forward. Not long after Darwin's visit, a botanist by the name of Joseph Hooker paid a visit to Ascension. Hooker, who was a fan of Darwin's work, shared his sentiments on the paucity of vegetation on the island. Hooker was able to convince the British navy that vegetating the island would capture rain and improve the soil. With the support of Kew Gardens, this is exactly what happened. Thus began the terraforming of Green Mountain.

For about a decade, Kew shipped something to the tune of 330 different species of plants to be planted on Ascension Island. The plants were specifically chosen to withstand the harsh conditions of life on this volcanic desert in the middle of the South Atlantic. It is estimated that 5,000 trees were planted on the island between 1860 and 1870. Most of these species came from places like Argentina and South Africa. Soon, more plants and seeds from botanical gardens in London and Cape Town were added to the mix. The most incredible terraforming experiment in the world was underway on this tiny volcanic rock. 

By the late 1870's it was clear the the experiment was working. Trees like Norfolk pines (Araucaria heterophylla), Eucalyptus spp. and figs (Ficus spp.), as well as different species of banana and bamboo had established themselves along the slopes of Green Mountain. Where there was once little more than a few species of grass, there was now the start of a lush cloud forest. The vegetation community wasn't the only thing that started to change on Ascension. Along with it changed the climate. 

Estimates of rainfall prior to these terraforming efforts are sparse at best. What we have to go on are anecdotes and notes written down by early sailors and visitors. These reports, however, paint a picture of astounding change. Before terraforming began, it was said that few if any clouds ever passed overhead and rain rarely fell. Those living on the island during the decade or so of planting attested to the fact that as vegetation began to establish, the climate of the island began to change. One of the greatest changes was the rain. Settlers on the island noticed that rain storms were becoming more frequent. Also, as one captain noted "seldom more than a day passes over now without a shower or mist on the mountain." The development of forests on Ascension were causing a shift in the island's water cycle. 

Plants are essentially living straws. Water taken up by the roots travels through their tissues eventually evaporating from their leaves. The increase in plant life on the island was putting more moisture into the air. The humid microclimate of the forest understory cooled the surrounding landscape. Water that would once have evaporated was now lingering. Pools were beginning to form as developed soils retained additional moisture.

Now, if you are anything like me, at this point you must be thinking to yourself "but what about the native flora?!" You have every right to be concerned. I don't want to paint the picture that everything was fine and dandy on Ascension Island. It wasn't. Even before the terraforming experiment began, humans and other trespassers left their mark on the local biota. With humans inevitably comes animals like goats, donkeys, pigs, and rats. These voracious mammals went to work on the local vegetation. The early ecology that was starting to develop on Ascension was rocked by these animals. Things were only made worse when the planting began.

Of the 10 endemic plants native to Ascension Island, 3 went extinct, having been pushed out by all of the now invasive plant species brought to the island. Another endemic, the Ascension Island parsley fern (Anogramma ascensionis) was thought to be extinct until four plants were discovered in 2010. The native flora of Ascension island was, for the most part, marginalized by the introduction of so many invasive species. This fact was not lost of Joseph Hooker. He eventually came to regret his ignorance to the impacts terraforming would have on the native vegetation stating “The consequences to the native vegetation of the peak will, I fear, be fatal, and especially to the rich carpet of ferns that clothed the top of the mountain when I visited it." Still, some plants have adapted to life among their new neighbors. Many of the ferns that once grew terrestrially, can now be found growing epiphytically among the introduced trees on Green Mountain. 

The Ascension Island parsley fern ( Anogramma ascensionis )

The Ascension Island parsley fern (Anogramma ascensionis)

Today Ascension Island exists as a quandary for conservation ecologists. On the one hand the effort to protect and conserve the native flora and fauna of the island is of top priority. On the other hand, the existence of possibly the greatest terraforming effort in the world begs for ecological research and understanding. A balance must be sought if both goals are to be met. Much effort is being put forth to control invasive vegetation that is getting out of hand. For instance, the relatively recent introduction of a type of mesquite called the Mexican thorn (Prosopis juliflora) threatens the breeding habitat of the green sea turtle. Efforts to remove this aggressive species are now underway. Although it is far too late to reverse what has been done to Ascension Island, it nonetheless offers us something else that may be more important in the long run: perspective.

If anything, Ascension Island stands as a perfect example of the role plants play in regulating climate. The introduction of these 330+ plant species to Ascension Island and the subsequent development of a forest was enough to completely change the weather of that region. Where there was once a volcanic desert there is a now a cloud forest. With that forest came clouds and rain. If adding plants to an island can change the climate this much, imagine what the loss of plants from habitats around the world is doing. 

Each year an estimated 18 million acres of forest are lost from this planet. As human populations continue to rise, that number is only going to get bigger. It is woefully ignorant to assume that habitat destruction isn't having an influence on global climate. It is. Plants are habitat and when they go, so does pretty much everything else we hold near and dear (not to mention require for survival). If the story of Ascension does anything, I hope it serves as a reminder of the important role plants play in the function of the ecosystems of our planet. 

The endemic Ascension spurge ( Euphorbia origanoides )

The endemic Ascension spurge (Euphorbia origanoides)

Photo Credits: [1] [2] [3] [4] [5] [6] [7] [8]

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


High Elevation Record Breakers Are Evidence of Climate Change

A new record has been set for vascular plants. Three mustards, two composits, and a grass have been found growing at an elevation of 20,177 feet (6,150 m) above sea level!

Mountains are a brutal place to live. Freezing temperatures, fierce winds, limited soil, and punishing UV radiation are serious hurdles for any form of life. Whereas algae and mosses can often eke out an existence at such altitudes, more derived forms of life have largely been excluded from such habitats. That is, until now. The area in which these plants were discovered measured about the size of a football field and is situated atop an Indian mountain known as Mount Shukule II.

Although stressed, these plants were nonetheless established among the scree of this menacing peak. Most were quite young, having only been there for a few seasons but growth rings on the roots of at least one plant indicated that it had been growing there for nearly 20 years!

All of them have taken the cushion-like growth habit of most high elevation plant species in order to reduce exposure and conserve water. The leaves of each species also contained high levels of sugary anti-freeze, a must in this bitter cold habitat.

The research team, who could only muster a few hours of work each day, believed that the seeds of these plants were blown up there by wind. Because soils in alpine zones are often non-existent, the team wanted to take a closer look at what kind of microbial community, if any, was associated with their roots.

Whereas no mycorrhizal species were identified, the team did find a complex community of bacteria living among the roots that are characteristic of species living in arid, desert-like regions. It is likely that these bacteria came in with the seeds. Aside from wind, sun, and a lack of soil, one of the other great challenges for these plants is a short growing season. In order to persist at this elevation, the plants require a minimum of 40 days of frost-free soil each year.

Because climate change is happening much faster in mountainous regions, it is likely that such favorable growing conditions are a relatively recent phenomenon. The area in question has only recently become deglaciated. As average yearly temperatures continue to increase, the habitable zone for plants such as these is also moving up the mountain. The question is, what happens when it reaches the top? Once at the peak, plants have nowhere to go. One of the greatest issues alpine plants face is that they will gradually be squeezed off of these habitat islands.

Although expanding habitable zones in these mountains may sound like a good thing, it is likely a short term benefit for most species. Whereas temperature bands in the Tibetan mountains are moving upwards at a rate of 20 feet (6 m) per year, most alpine plants can only track favorable climates at a rate of about 2 inches (0.06 m) per year. In other words, they simply can't keep up. As such, this record breaking discovery is somewhat bitter sweet.

Photo Credit: [1]

Further Reading: [1]