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]

Southern Beeches and Biogeography

If you spend any time learning about paleontology, you are bound to come across at least one reference to the southern beeches (genus Nothofagus). This remarkable and ecologically important group of trees can be found growing throughout the Southern Hemisphere at high latitudes in South America, Australia, New Zealand, New Guinea, and New Caledonia. Not only are they prominent players in the forests in which they grow, their fossil history has provided scientists with invaluable data on plate tectonics and biogeography.

Southern beeches may not be the tallest trees in any forest but that doesn’t mean they aren’t impressive. Numbering around 37 species, southern beeches have conquered a range of climate zones from temperate to tropical. Those living in lowland tropical forests tend to be evergreen, holding onto their leaves throughout the year whereas those living in temperate or montane habitats have evolved a deciduous habit. Some species of southern beech are also known for their longevity, with individuals estimated to be in excess of 500 years in age.

Nothofagus alpina

Anyone familiar with the true beeches (genus Fagus) will quickly recognize many similarities among these genera. From their toothy leaves to their triangular nuts, these trees are strikingly similar in appearance. Indeed, for much of their botanical history, southern beeches were included in the beech family (Fagaceae). However, recent molecular work has revealed that the southern beeches are genetically distinct enough to warrant their own family - Nothofagaceae.

The beech-like fruits of Nothofagus obliqua var. macrocarpa

As mentioned, the southern beeches, both extant and extinct, have been important players in our understanding of plate tectonics. Their modern day distribution throughout the Southern Hemisphere seems to hint at a more concentrated distribution at some point in the past. All of the continents and islands on which they are found today were once part of the supercontinent of Gondwana, which has led many to suggest that the southern beech family arose before Gondwana broke apart during the Jurassic, with ancestors of extant species riding the southern land masses to their modern day positions. Indeed, the paleo record seems to support this quite well.

Fall colors of Nothofagus cunninghamii.

The southern beeches have an impressive fossil record that dates back some 80 million years to the late Cretaceous. Their fossils have been found throughout many of the Southern Hemisphere continents including the now-frozen Antarctica. It would seem that the modern distribution of these trees is the result of plate tectonics rather than the movement of seeds across oceans. This is bolstered by lines of evidence such as seed dispersal. Southern beech nuts are fairly large and do not show any adaptations for long distance dispersal, leading many to suggest that they simply cannot ocean hop without serious help from other forms of life.

Nothofagus fusca

However, life is rarely so simple. Recent molecular work suggests that continental drift can’t explain the distribution of every southern beech species. By studying trees growing in New Zealand and comparing them to those growing in Australia and Tasmania, scientists have discovered that these lineages are far too young to have originated before the breakup of Gondwana. As such, the southern beeches of Austrialasia more likely got to their current distributions via long distance dispersal events. Exactly what allowed their seeds to cross the Tasman Sea is up for debate, but certainly not impossible given the expanse of time available for rare events to occur. Regardless of where anyone stands on this recent evidence, it nonetheless suggests that the biogeographic history of the southern beech family isn’t as clear cut as once thought.

Nothofagus fusca

Unfortunately, while southern beeches hold a prominent place in the minds of naturalists, the same cannot be said for the rest of the world. Little care has been given to their scientific and ecological importance and massive quantities of these trees are logged each and every year. Today it is estimated that 30% of all southern beech species are threatened with extinction. Luckily, large portions of the remaining populations for these trees are growing on protected lands. Also, because of their scientific importance, numerous southern beeches can be found growing in botanical collections and their seeds are well represented in seed banks. Still, southern beeches and the forests they comprise are worthy of respect and protection.

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

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

The Overcup Oak

Photo by Bruce Kirchoff licensed under CC BY 2.0

I sure do love me a good oak. Moving to the Midwest of North America has given me the opportunity to meet many new oak species. One oak that has captured my attention in recent years is the overcup oak (Quercus lyrata) whose both common and scientific names first attracted me to this wonderful tree.

Let’s start by looking at the scientific name of this species. The specific epithet “lyrata” was given to this tree because its leaves are said to resemble a lyre. Having no familiarity with popular instruments of Ancient Greece, I had to look this one up. Personally, I have a hard time seeing the resemblance in most leaves. Perhaps this is because the leaves on any given tree can be highly variable in both shape and size depending on both where they are positioned in the canopy and where the tree itself is rooted.

Photo by Bruce Kirchoff licensed under CC BY 2.0

The name “overcup” comes from the fact that the caps of each acorn nearly encompass the entire seed. It is neat to see a mature acorn of this species as they appear to be immature at all stages of development. The odd morphology of these acorns has everything to do with where these trees grow in nature and the way in which they manage seed dispersal.

Photo by Bruce Kirchoff licensed under CC BY 2.0

Overcup oak is one of the most flood tolerant oaks in all of North America. In fact, it most often grows in around wetlands and in floodplains throughout south-central portions of the continent. As such, this species has evolved to tolerate and take advantage of periodic flooding from one year to the next. Not only can mature trees handle weeks of having their roots and trunks completely submerged, the overcup oak also utilizes flooding as a means of seed dispersal.

The cap that covers each seed is very corky, which causes the acorns to float. This is good news for the seeds as young trees have a hard time making a living in the shade of their parents. Historically, floods would pick up and move overcup acorn crops and, with any luck, deposit the acorns in a new floodplain where disturbance has cleared enough spots in the canopy for the acorns to germinate and grow into vigorous young saplings.

USGS/Public Domain

Speaking of germination, overcup oaks are unique among the white oak tribe in that their seeds exhibit a prolonged dormancy. Normally, acorns of the various white oaks germinate in the fall, not long after they were shed from the trees above. However, living in areas prone to flooding would make germinating at that time of year a risky endeavor. As such, overcup oak acorns lay dormant for months until some environmental cue(s) signals enough time has passed.

Overcup oak is also extremely intolerant of fires. Even modest sized burns can severely damage or kill all but the largest individuals. Normally, the forests in which these trees grow are too wet to produce large fires but prolonged droughts and altered flood regimes can change those dynamics to such a degree that large swaths of overcup oak can be killed.

In fact, altered flooding regimes are one of the biggest threats facing overcup oaks in their native range. Because we have dammed, diverted, and channeled so many waterways in North America, the floods that once maintained overcup oak habitats have changed in a big way. Without regular flooding to disperse their seeds and reduce competition from the canopy above, overcup oaks are having a much harder time regenerating. Saplings gradually dwindle in the shade of their parents and, where rivers do continue to flood, these events are often much more severe than they were in the past. Saplings that aren’t tall enough to rise above the floodwaters eventually drown. Overcup oak may be tolerant of flooding but it is by no means its preferred way to live.

Despite these challenges, overcup oak is still a prominent member of seasonally flooded forests throughout its range. It is a magnificent species well worth spending the time to become familiar. It can also make an excellent specimen tree in all but the driest of south-central North American soils. Also, because it is an oak, this incredible species is also chock full of wildlife value, making it an important component of the ecology wherever it is native.

Photo Credits: Bruce Kirchoff [1] [2] (Licensed under CC-BY), U.S. Geological Survey, Chhe, USDA

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

Deer Skew Jack-in-the-Pulpit Sex Ratios

Photo by Michael Janke licensed under CC BY-ND 2.0.

Deer populations in North America are higher than they have been at any point in history. Their explosion in numbers not only leads to series health issues like starvation and chronic wasting disease, it has also had serious impacts on regional plant diversity. Wherever hungry herds of deer go, plants disappear from the landscape. However, the impacts of deer on plants aren’t limited to species they can eat. Research on Jack-in-the-Pulpit (Arisaema triphyllum) has shown that deer can have plenty of surprising indirect impacts on plants as well.

Though I wouldn’t put anything past a hungry deer, plants like Jack-in-the-Pulpit aren’t usually on the menu for these ungulates. Their leaves, stems, and flowers are chock full of raphide crystals that will burn the mouths and esophagus of most herbivores. Still, this doesn’t mean deer aren’t impacting these plants in other ways. Because deer are congregating in high abundance in our ever-shrinking natural spaces, they are having serious impacts on local growing conditions. Wherever deer herds are at high numbers, forests are experiencing soil compaction, soil erosion, and a disappearance of soil leaf litter (also due in part to invasive earthworms). Thanks to issues like these, plants like Jack-in-the-Pulpit are undergoing some serious changes.

Like many aroids, sex expression in the genus Arisaema is fluid and relies on energy stores. Smaller plants store less energy and tend to only produce male flowers when they bloom. Pollen, after all, is cheap compared to eggs and fruit. Only when a plant has stored enough energy over the years will it begin to produce female flowers in addition to males and only the largest, most robust plants will switch over entirely to female flowers. As you can imagine, the ability of a plant to acquire and store enough energy is dependent on the quality of the habitat in which it grows. This is where deer enter into the equation.

High densities of deer inevitably cause serious declines in habitat quality of plants like Jack-in-the-Pulpit. As leaf litter disappears and soil compaction grows more severe, individual plants have a much harder time storing enough energy each growing season. In places where deer impacts are heaviest, the sex ratios of Jack-in-the-Pulpit populations begin to skew heavily towards males because individual plants must grow much longer before they can store enough energy to produce female flowers. It doesn’t end there either. Not only does it take longer for a plant to begin producing female flowers, individual plants must also reach a much larger size in order to produce female flowers than in areas with fewer deer.

Photo by Charles de Mille-Isles licensed under CC BY-ND 2.0.

As mentioned, seed production takes a lot of energy and any plant that is able to produce viable fruits will have less energy stores going into the next season. This means that even if a plant is able to produce female flowers and successfully set seed, they will have burned through so much energy that they will likely revert right back to producing only male flowers the following year, further skewing the sex ratios of any given population towards males. Interestingly, this often results in more individuals being produced via clonal offshoots. The more clones there are in a population, the less diverse the gene pool of that population becomes.

Without actually eating the plants, deer are having serious impacts on Jack-in-the-Pulpit population dynamics. I am certain that this species isn’t alone either. At least Jack-in-the-Pulpit is somewhat flexible in its reproductive behaviors. Other plants aren’t so lucky. I realize deer are a hot button issue but there is no getting around the fact that our mismanagement of their natural predators, habitat, and numbers are having serious and detrimental impacts on wild spaces and all the species they support.

Photo Credits: [1] [2]

Further Reading: [1]

Good News For Mangrove Restoration

Mangrove forests are among the most productive ecosystems on Earth. Bridging the gap between land and sea, these forests function as important habitats for organisms of all shapes, sizes, and ecologies. From a purely structural standpoint, mangrove forests are vital for stabilizing coastlines, reducing erosion, and minimizing damage from storm surges. They are also extremely important habitats for carbon sequestration.

The key component of the carbon storing abilities of mangrove forests involves the formation of peat. Whereas we tend to think of bogs when we think about peat, mangroves form it as well. Peat is the result of the accumulation of partially decomposed vegetation and other organic matter. It’s the partially decomposed part of peat that makes it a major carbon store. Because it doesn’t decompose, all of the carbon locked up in the organic matter stays there instead of entering back into the atmosphere.

As they grow, the roots of mangrove forests accumulate debris and sediments, which builds and builds over time. As the organic layer grows, mangroves grow upward on their propped roots. Over decades and centuries, massive quantities of peat can develop under mangrove forests. This is also one of the ways by which coastal land develops. Needless to say, mangrove forests are extremely important ecosystems.

Photo by Phils 1stPix Licensed under CC BY-NC-SA 2.0

Sadly, because they occur along the coast, mangrove forests the world over have been degraded and destroyed at unsustainable rates. As these forests are razed, the land supporting them erodes, removing all of the accumulated sediments and peat. Not only does this destroy all of the ecological and economic benefits of mangrove forests, it also releases huge quantities of carbon.

In recent years, humans have finally begun to realize the environmental and economic costs of mangrove destruction and many regions are starting to implement mangrove restoration efforts. However, the success of any restoration can sometimes take years or even decades to fully assess. This is where chronosequences come in. By studying mangrove restoration projects at different stages of development, scientists can better understand mangrove restoration efforts over relatively short time periods instead of having to wait for individual projects to age to collect all of their data.

Recently, researchers in Florida decided to look at peat accumulation in various mangrove restoration projects. They looked at mangrove restorations of various ages, spanning 25 years of effort. They found that soil and peat accumulation in these forests is surprisingly rapid. In terms of soil accumulation, restored mangrove forests kept pace with and even outpaced natural mangrove forests within the first 5 years of restoration. Even more exciting, peat accumulation in these restored mangrove forests was very rapid, occurring within only a decade of the completion of a mangrove restoration attempt. When you consider the fact that each of the restoration projects they studied started in nothing but pure sand, these results are extremely encouraging.

The scientists point to mangrove roots as the main driver of soil and peat accumulation in these restored forests. As mangroves grow, their roots expand into the surrounding sand. As roots grow and die, they leave all of that organic matter in the soil. Also, the more roots there are, the more debris like wood, leaves, and sediments get trapped in and around the mangroves. This is why peat accumulation occurs so rapidly. What’s more, as sediment and peat builds up below the mangroves, their height increases. At current, the increase in height of these restored mangrove forests is outpacing the rate of sea level rise in coastal Florida. These are encouraging results when one considers just how fast these coastal habitats are changing as our climate continues to change.

The authors of this research are quick to point out that the fast rates of peat accumulation and mangrove growth are likely to slow as these ecosystems mature. Eventually, many of these processes are likely to balance out. They estimate that it would take at least 55 years for mangrove restoration projects in Florida to match their natural counterparts in terms of ecosystem services. Nonetheless, many components of healthy mangrove ecologies, like herbaceous and juvenile vegetation layers, are already established in restorations long before that 55 year mark.

These results are very exciting. Though there is no substitute for protecting natural mangrove forests (or any wild space for that matter), we need to start putting the pieces of our planet back together. If these data are representative of mangrove restoration efforts across the world, there is hope yet that we can replace at least some of what has been lost. Still, until more of the human race starts to value protecting wild spaces and the species they support, we stand to loose so much more. Support your local land conservancy today!!

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

Further Reading: [1]

The Sinewy American Hornbeam

Photo by Richard Webb licensed by CC BY-SA 3.0

Winter is when I really start to notice trees. Admittedly, I am pretty poor when it comes to tree ID and taxonomy but there are a few species that really stand out. One of my all time favorite trees is Carpinus caroliniana.

Carpinus caroliniana goes by a handful of common names including ironwood, musclewood, and American hornbeam. All of these names have been applied to other trees so I'll stick with its scientific name. Finding C. caroliniana is rather easy. All you have to do is look for its unmistakable bark.

Photo by Rob Duval licensed by CC BY-SA 3.0

With smooth, sinewy striations and ridges, it is no wonder how this tree got the name "musclewood." The wood is extremely close-grained and is therefore very hard, earning it another nickname of "ironwood."They are generally small trees, rarely exceeding a few meters in height, though records have shown that some individuals can grow to upwards of 20 meters in rare circumstances. I hope that someday I will be able to meet one of these rare giants.

Carpinus caroliniana is also an indicator of fairly rich soils. Due to their high tolerance for shade, they are often a tree of the mixed hardwood understory. Their foliage resembles that of the family in which they belong, the birch family (Betulaceae).

Photo by Katja Schulz licensed by CC BY 2.0

The caterpillar of the io moth (Automeris io)

An adult io moth (Automeris io). Photo by Andy Reago & Chrissy McClarren licensed by CC BY 2.0

A multitude of insect species utilize C. caroliniana as a larval food source including the famed io moth. In the spring, male and female catkins are born on the same tree and, after fertilization, they are replaced by interesting looking nutlets covered by leaf-like involucres. The seeds are an important food source for a variety of birds, mammals, and insects alike.

The male flowers of Carpinus caroliniana. Photo by Philip Bouchard licensed by CC BY-NC-ND 2.0

Carpinus caroliniana is a tree I could never get bored with. Not only does it have immense ecological value, it is aesthetically pleasing too. Its small size and shade tolerance also makes it a great landscape tree in areas too cramped for something larger. Why this species isn't more popular in native landscaping is beyond me.

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

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

Maxipiñon: One of the Rarest Pines in the World

Photo by Ruff tuff cream puff licensed under public domain

The maxipiñon (Pinus maximartinezii) is one of the rarest pines on Earth. A native of southern Sierra Madre Occidental, Mexico, nearly all individuals of this species can be found scattered over an area that collectively spans only about 3 to 6 square miles (5 – 10 km²) in size. Needless to say, the maxipiñon teeters on the brink of extinction. As a result, a lot of effort has been put forward to better understand this species and to develop plans aimed at ensuring it is not lost forever.

The maxipiñon has only been known to science for a few decades. It was described back in 1964 after botanist Jerzy Rzedowski noted some exceptionally large pine seeds for sale at a local market. He named the species in honor of Maximino Martínez, who contributed greatly to our understanding of Mexican conifers. However, it was very obvious that the maxipiñon was well known among the residents of Zacatecas.

The reason for this are its seeds. The maxipiñon is said to produce the largest and most nutritious seeds of all the pines. As such, it is a staple of the regional diet. Conversations with local farmers suggest that it was much more common as recent as 60 years ago. Since then, its numbers have been greatly reduced. It soon became apparent that in order to save this species, we had to learn a lot more about what threatens its survival.

The most obvious place to start was recruitment. If any species is to survive, reproduction must outpace death. A survey of local markets revealed that a lot of maxipiñon seeds were being harvest from the wild. This would be fine if maxipiñon were widespread but this is not the case. Over-harvesting of seeds could spell disaster for a species with such small population sizes.

Indeed, surveys of wild maxipiñon revealed there to be only 2,000 to 2,500 mature individuals and almost no seedlings. However, mature trees do produce a considerable amount of cones. Therefore, the conclusion was made that seed harvesting may be the single largest threat to this tree. Subsequent research has suggested that seed harvests actually may not be the cause of its rarity. It turns out, maxipiñon population growth appears to be rather insensitive to the number of seeds produced each year. Instead, juvenile tree survival seems to form the biggest bottleneck to population growth.

Photo by Krzysztof Ziarnek, Kenraiz licensed under CC BY-SA 4.0

You see, this tree appears to be more limited by suitable germination sites than it does seed numbers. It doesn’t matter if thousands of seeds are produced if very few of them ever find a good spot to grow. Because of this, scientists feel that there are other more serious threats to the maxipiñon than seed harvesting. However, humans are still not off the hook. Other human activities proved to be far more damaging.

About 50 years ago, big changes were made to local farming practices. More and more land was being cleared for cattle grazing. Much of that clearing was done by purposefully setting fires. The bark of the maxipiñon is very thin, which makes it highly susceptible to fire. As fires burn through its habitat, many trees are killed. Those that survive must then contend with relentless overgrazing by cattle. If that wasn’t enough, the cleared land also becomes highly eroded, thus further reducing its suitability for maxipiñon regeneration. Taken together, these are the biggest threats to the ongoing survival of this pine. Its highly fragmented habitat no longer offers suitable sites for seedling growth and survival.

As with any species this rare, issues of genetic diversity also come into play. Though molecular analyses have shown that maxipiñon does not currently suffer from inbreeding, it has revealed some interesting data that give us hints into the deeper history of this species. Written in maxipiñon DNA is evidence of an extreme population bottleneck that occurred somewhere between 400 and 1000 years ago. It appears that this is not the first time this tree has undergone population decline.

There are a few ways in which these data can be interpreted. One is that the maxipiñon evolved relatively recently from a small number of unique and isolated individuals. Perhaps a hybridization event occurred between two closely related piñon species - the weeping piñon (Pinus pinceana) and Nelson piñon (Pinus nelsonii). Another possibility, which does not rule out hybridization, is that the maxipiñon may actually be the result of artificial selection by agriculturists of the region. Considering the value of its seeds today, it is not hard to imagine farmers selecting and breeding piñon for larger seeds. It goes without saying that these claims are largely unsubstantiated and would require much more evidence to say with any certainty, however, there is plenty of evidence that civilizations like the Mayans were conserving and propagation useful tree species much earlier than this.

Despite all we have learned about the maxipiñon over the last few decades, the fate of this tree is far from secure. Ex situ conservation efforts are well underway and you can now see maxipiñon specimens growing in arboreta and botanical gardens around the world. Seeds from these populations are being used for storage and to propagate more trees. Sadly, until something is done to protect the habitat on which it relies, there is no telling how long this species will last in the wild. This is why habitat conservation efforts are so important. Please support local land conservation efforts in your area because the maxipiñon is but one species facing the loss of its habitat.

Photo Credits: [1] [2] [3] [4]

Further Reading [1] [2] [3]

The Rise and Fall of the Scale Trees

Photo by Ghedoghedo licensed under CC BY-SA 3.0

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

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 they started branching, young trees would have resembled a bushy, green bottle brush.

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

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. Photo by Verisimilus T licensed under the GNU Free Documentation License.

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”. Photo by Verisimilus T licensed under CC BY-SA 3.0

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] [4] [5] [6] [7]

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

The Only True Cedars

Cedrus deodara. Photo by PabloEvans licensed under CC BY 2.0

The only true cedars on this planet can be found growing throughout mountainous regions of the western Himalayas and Mediterranean. All others are cedars by name only. The so-called “cedars” we encounter here in North America are not even in the same family as the true cedars. Instead, they belong to the Cypress family (Cupressaceae). The true cedars all belong to the genus Cedrus and are members of the family Pinaceae. They are remarkable trees with tons of ecological and cultural value.

J. White,1803-1824.

The true cedars are stunning trees to say the least. They regularly reach heights of 100 ft. (30 m.) or more and can live for thousands of years. Cedars exhibit a dimorphic branching structure, with long shoots forming branches and smaller shoots carrying most of the needle load. The needles themselves are borne in dense, spiral clusters, giving the branches a rather aesthetic appearance. Each needle produces layers of wax, which vary in thickness depending on how exposed the tree is growing. This waxy layer helps protect the tree from sunburn and desiccation.

Cedrus libani. Photo by Zeynel Cebeci licensed under CC BY-SA 4.0

Cedrus libani. Photo by Leonid Mamchenkov licensed under CC BY 2.0

One of the easiest ways to identify a cedar is by checking out its cones. All members of the genus Cedrus produce upright, barrel-shaped cones. Male cones are smaller and don’t stay on the tree for very long. Female cones, on the other hand, are quite large and stay on the tree until the seeds are ripe. Upon ripening, the entire female cone disintegrates, releasing the seeds held within. Each seed comes complete with blisters full of distasteful resin, which is thought to deter seed predators.

Male cones of Cedrus atlantica. Photo by Meneerke bloem licensed under CC BY-SA 3.0

Female Cedrus cones. Photo by Zeynel Cebeci licensed under CC BY-SA 4.0

In total, there are only four recognized species of cedar - the Atlas cedar (Cedrus atlantica), the Cyprus cedar (C. brevifolia), the deodar cedar (C. deodara), and the Lebanon cedar (C. libani). I have heard arguments that C. brevifolia is no more than a variant of C. libani but I have yet to come across any source that can say this for certain. Much more work is needed to assess the genetic structure of these species. Even their place within Pinaceae is up for debate. Historically it seems that Cedrus has been allied with the firs (genus Abies), however, work done in the early 2000’s suggests that Cedrus may actually be sister to all other Pinaceae. We need more data before anything can be said with certainty.

Regardless, two of these cedars - C. atlantica & C. libani - are threatened with extinction. Centuries of over-harvesting, over-grazing, and unsustainable fire regimes have taken their toll on wild populations. Much of what remains is not considered old growth. Gone is the heyday of giant cedar forests. Luckily, many populations are now located in protected areas and reforestation efforts are being put into place throughout their range. Still, the ever present threat of climate change is causing massive pest outbreaks in these forests. The future for these trees hangs in the balance.

Photo Credit: Wikimedia Commons

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

Maples, Epiphytes, and a Canopy Full of Goodies

The forests of the Pacific Northwest are known for the grandeur. This region is home to one of the greatest temperate rainforests in the world. A hiker is both dwarfed and enveloped by greenery as soon as they hit the trail. One aspect of these forests that is readily apparent are the carpets of epiphytes that drape limbs and branches all the way up into the canopy. Their arboreal lifestyle is made possible by a combination of mild winters and plenty of precipitation. 

We are frequently taught that the relationship between trees and their epiphytes are commensal - the epiphytes get a place to live and the trees are no worse for wear. However, there are a handful of trees native to the Pacific Northwest that are changing the way we think about the relationship between these organisms in temperate rainforests.

Though conifers dominate the Pacific Northwest landscape, plenty of broad leaved tree species abound. One of the most easily recognizable is the bigleaf maple (Acer macrophyllum). Both its common and scientific names hint at its most distinguishing feature, its large leaves. Another striking feature of this tree are its epiphyte communities. Indeed, along with the vine maple (A. circinatum), these two tree species carry the greatest epiphyte to shoot biomass ratio in the entire forest. Numerous species of moss, liverworts, lichens, and ferns have been found growing on the bark and branches of these two species.

Epiphyte loads are pretty intense. One study found that the average epiphyte crop of a bigleaf maple weighs around 78 lbs. (35.5 Kg). That is a lot of biomass living in the canopy! The trees seem just fine despite all of that extra weight. In fact, the relationship between bigleaf and vine maples and their epiphyte communities run far deeper than commensalism. Evidence accumulated over the last few decades has revealed that these maples are benefiting greatly from their epiphytic adornments.

Rainforests, both tropical and temperate, generally grow on poor soils. Lots of rain and plenty of biodiversity means that soils are quickly leached of valuable nutrients. Any boost a plant can get from its environment will have serious benefits for growth and survival. This is where the epiphytes come in. The richly textured mix of epiphytic plants greatly increase the surface area of any branch they live on. And all of that added surface area equates to more nooks and crannies for water and dust to get caught and accumulate.

Photo by SuperFantastic licensed under CC BY 2.0

When researchers investigated just how much of a nutrient load gets incorporated into these epiphyte communities, the results painted quite an impressive picture. On a single bigleaf maple, epiphyte leaf biomass was 4 times that of the host tree despite comprising less than 2% of the tree's above ground weight. All of that biomass equates to a massive canopy nutrient pool rich in nitrogen, phosphorus, potassium, calcium, magnesium, and sodium. Much of these nutrients arrive in the form of dust-sized soil particles blowing around on the breeze. What's more, epiphytes act like sponges, soaking up and holding onto precious water well into the dry summer months.

Now its reasonable to think that nutrients and water tied up in epiphyte biomass would be unavailable to trees. Indeed, for many species, epiphytes may slow the rate at which nutrients fall to and enter into the soil. However, trees like bigleaf and vine maples appear to be tapping into these nutrient and water-rich epiphyte mats.

A subcanopy of vine maple (Acer circinatum) draped in epiphytes.

Both bigleaf and vine maples (as well as a handful of other tree species) are capable of producing canopy roots. Wherever the epiphyte load is thick enough, bundles of cells just under the bark awaken and begin growing roots. This is a common phenomenon in the tropics, however, the canopy roots of these temperate trees differ in that they are indistinguishable in form and function from subterranean roots.

Canopy roots significantly increase the amount of foraging an individual tree can do for precious water and nutrients. Additionally, it has been found that canopy roots of the bigleaf maple even go as far as to partner with mycorrhizal fungi, thus unlocking even more potential for nutrient and water gain. In the absence of soil nutrient and water pools, a small handful of trees in the Pacific Northwest have unlocked a massive pool of nutrients located above us in the canopy. Amazingly, it has been estimated that mature bigleaf and vine maples with well developed epiphyte communities may actually gain a substantial fraction of their water and nutrient needs via their canopy roots.

Photo Credits: [2]

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

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]

Life On a Floodplain

Floodplains can be pretty rough places for plant life. Despite readily a available water supply, the unpredictable, disturbance-prone nature of these habitats means that static lifeforms such as plants need to be quite adaptable to survive and persist. Join In Defense of Plants for a brief look at this sort of ecosystem.

Producer, Editor, Camera: Grant Czadzeck (http://www.grantczadzeck.com)

Music by
Artist: Somali Yacht Club
Track: Up In The Sky
http://somaliyachtclub.bandcamp.com

Saving Bornean Peatlands is a Must For Conservation

Photo by Dukeabruzzi licensed under CC BY-SA 4.0

The leading cause of extinction on this planet is loss of habitat. As an ecologist, it pains me to see how frequently this gets ignored. Plants, animals, fungi - literally every organism on this planet needs a place to live. Without habitat, we are forced to pack our flora and fauna into tiny collections in zoos and botanical gardens, completely disembodied from the environment that shaped them into what we know and love today. That’s not to say that zoos and botanical gardens don’t play critically important roles in conservation, however, if we are going to stave off total ecological meltdown, we must also be setting aside swaths of wild lands.

There is no way around it. We cannot have our cake and eat it too. Land conservation must be a priority both at the local and the global scale. Wild spaces support life. They buffer life from storms and minimize the impacts of deadly diseases. Healthy habitats filter the water we drink and, for many people around the globe, provide much of the food we eat. Every one of us can think back to our childhood and remember a favorite stretch of stream, meadow, or forest that has since been gobbled up by a housing development. For me it was a forested stream where I learned to love the natural world. I would spend hours playing in the creek, climbing trees, and capturing bugs to show my parents. Since that time, someone leveled the forest, built a house, and planted a lawn. With that patch of forest went all of the insects, birds, and wildflowers it once supported.

Scenarios like this play out all too often and sadly on a much larger scale than a backyard. Globally, forests have taken the brunt of human development. It is hard to get a sense of the scope of deforestation on a global scale, but the undisputed leaders in deforestation are Brazil and Indonesia. Though the Amazon gets a lot of press, few may truly grasp the gravity of the situation playing out in Southeast Asia.

Deforestation is a clear and present threat throughout tropical Asia. This region is growing both in its economy and population by about 6% every year and this growth has come at great cost to the environment. Indonesia (alongside Brazil) accounts for 55% of the world’s deforestation rates. This is a gut-wrenching statistic because Indonesia alone is home to the most extensive area of intact rainforest in all of Asia. So far, nearly a quarter of Indonesia’s forests have been cleared. It was estimated that by 2010, 2.3 million hectares of peatland forests had been felled and this number shows little signs of slowing. Experts believe that if these rates continue, this area could lose the remainder of its forests by 2056.

Consider the fact that Southeast Asia contains 6 of the world’s 25 biodiversity hotspots and you can begin to imagine the devastating blow that the levelling of these forests can have. Much of this deforestation is done in the name of agriculture, and of that, palm oil and rubber take the cake. Southeast Asia is responsible for producing 86% of the world’s palm oil and 87% of the world’s natural rubber. What’s more, the companies responsible for these plantations are ranked among some of the least sustainable in the world.

Borneo is home to a bewildering array of life. Researchers working there are constantly finding and describing new species, many of which are found nowhere else in the world. Of the roughly 15,000 plant species known from Borneo, botanists estimate that nearly 5,000 (~34%) of them are endemic. This includes some of the more charismatic plant species such as the beloved carnivorous pitcher plants in the genus Nepenthes. Of these, 50 species have been found growing in Borneo, many of which are only known from single mountain tops.

It has been said that nowhere else in the world has the diversity of orchid species found in Borneo. To date, roughly 3,000 species have been described but many, many more await discovery. For example, since 2007, 51 new species of orchid have been found. Borneo is also home to the largest flower in the world, Rafflesia arnoldii. It, along with its relatives, are parasites, living their entire lives inside of tropical vines. These amazing plants only ever emerge when it is time to flower and flower they do! Their superficial resemblance to a rotting carcass goes much deeper than looks alone. These flowers emit a fetid odor that is proportional to their size, earning them the name “carrion flowers.”

Rafflesia arnoldii in all of its glory. Photo by SofianRafflesia licensed under CC BY-SA 4.0

Photo by Orchi licensed under CC BY-SA 3.0

If deforestation wasn’t enough of a threat to these botanical treasures, poachers are having considerable impacts on Bornean botany. The illegal wildlife trade throughout southeast Asia gets a lot of media attention and rightfully so. At the same time, however, the illegal trade of ornamental and medicinal plants has gone largely unnoticed. Much of this is fueled by demands in China and Vietnam for plants considered medicinally valuable. At this point in time, we simply don’t know the extent to which poaching is harming plant populations. One survey found 347 different orchid species were being traded illegally across borders, many of which were considered threatened or endangered. Ever-shrinking forested areas only exacerbate the issue of plant poaching. It is the law of diminishing returns time and time again.

Photo by Orchi licensed under CC BY-SA 3.0

But to lump all Bornean forests under the general label of “rainforest” is a bit misleading. Borneo has multitude of forest types and one of the most globally important of these are the peatland forests. Peatlands are vital areas of carbon storage for this planet because they are the result of a lack of decay. Whereas leaves and twigs quickly breakdown in most rainforest situations, plant debris never quite makes it that far in a peatland. Plant materials that fall into a peatland stick around and build up over hundreds and thousands of years. As such, an extremely thick layer of peat is formed. In some areas, this layer can be as much as 20 meters deep! All the carbon tied up in the undecayed plant matter is carbon that isn’t finding its way back into our atmosphere.

Sadly, tropical peatlands like those found in Borneo are facing a multitude of threats. In Indonesia alone, draining, burning, and farming (especially for palm oil) have led to the destruction of 1 million hectares (20%) of peatland habitat in only a single decade. The fires themselves are especially worrisome. For instance, it was estimated that fires set between 1997-1998 and 2002-2003 in order to clear the land for palm oil plantations released 200 million to 1 billion tonnes of carbon into our atmosphere. Considering that 60% of the world’s tropical peatlands are found in the Indo-Malayan region, these numbers are troubling.

The peatlands of Borneo are totally unlike peatlands elsewhere in the world. Instead of mosses, gramminoids, and shrubs, these tropical peatlands are covered in forests. Massive dipterocarp trees dominate the landscape, growing on a spongey mat of peat. What’s more, no water flows into these habitats. They are fed entirely by rain. The spongey nature of the peat mat holds onto water well into the dry season, providing clean, filtered water where it otherwise wouldn’t be available.

Photo by JeremiahsCPs licensed under CC BY-SA 3.0

This lack of decay coupled with their extremely acidic nature and near complete saturation makes peat lands difficult places for survival. Still, life has found a way, and Borneo’s peatlands are home to a staggering diversity of plant life. They are so diverse, in fact, that when I asked Dr. Craig Costion, a plant conservation officer for the Rainforest Trust, for something approaching a plant list for an area of peatland known as Rungan River region, he replied:

“Certainly not nor would there ever be one in the conceivable future given the sheer size of the property and the level of diversity in Borneo. There can be as many as a 100 species per acre of trees in Borneo... Certainly a high percentage of the species would only be able to be assigned to a genus then sit in an herbarium for decades until someone describes them.”

And that is quite remarkable when you think about it. When you consider that the Rungan River property is approximately 385,000 acres, the number of plant species to consider quickly becomes overwhelming. To put that in perspective, there are only about 500 tree species native to the whole of Europe! And that’s just considering the trees. Borneo’s peatlands are home to myriad plant species from liverworts, mosses, and ferns, to countless flowering plants like orchids and others. We simply do not know what kind of diversity places like Borneo hold. One could easily spend a week in a place like the Rungan River and walk away with dozens of plant species completely new to science. Losing a tract of forest in such a biodiverse region is a huge blow to global biodiversity.

Nepenthes ampullaria relies on decaying plant material within its pitcher for its nutrient needs. Photo by en:User:NepGrower licensed under Public Domain

Also, consider that all this plant diversity is supporting even more animal diversity. For instance, the high diversity of fruit trees in this region support a population of over 2,000 Bornean orangutans. That is nearly 4% of the entire global population of these great apes. They aren’t alone either, the forested peatlands of Borneo are home to species such as the critically endangered Bornean white-bearded gibbon, the proboscis monkey, the rare flat-headed cat, and the oddly named otter civet. All these animals and more rely on the habitat provided by these forests. Without forests, these animals are no more.

The flat-headed cat, an endemic of Borneo. Photo by Jim Sanderson licensed under CC BY-SA 3.0

At this point, many of you may be feeling quite depressed. I know how easy it is to feel like there is nothing you can do to help. Well, what if I told you that there is something you can do right now to save a 385,000 acre chunk of peatland rainforest? That’s right, by heading over to the Rainforest Trust’s website (https://www.rainforesttrust.org/project/saving-stronghold-critically-endangered-bornean-orangutan/) you can donate to their campaign to buy up and protect the Rungan River forest tract.

Click on the logo to learn more!

By donating to the Rainforest Trust, you are doing your part in protecting biodiversity in one of the most biodiverse regions in the world. What’s more, you can rest assured that your money is being used effectively. The Rainforest Trust consistently ranks as one of the top environmental protection charities in the world. Over their nearly three decades of operation, the Rainforest Trust has protected more than 15.7 million acres of land in over 20 countries. Like I said in the beginning, habitat loss is the leading cause of extinction on this planet. Without habitat, we have nothing. Plants are that habitat and by supporting organizations such as the Rainforest Trust, you are doing your part to fight the biggest threats our planet faces. 

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

Photo Credits: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

How Trees Fight Disease

Plants do not have immune systems like animals. Instead, they have evolved an entirely different way of dealing with infections. In trees, this process is known as the "compartmentalization of decay in trees" or "CODIT." CODIT is a fascinating process and many of us will recognize its physical manifestations.

In order to understand CODIT, one must know a little something about how trees grow. Trees have an amazing ability to generate new cells. However, they do not have the ability to repair damage. Instead, trees respond to disease and injury  by walling it off from their living tissues. This involves three distinct processes. The first of these has to do with minimizing the spread of damage. Trees accomplish this by strengthening the walls between cells. Essentially this begins the process of isolating whatever may be harming the living tissues.

This is done via chemical means. In the living sapwood, it is the result of changes in chemical environment within each cell. In heartwood, enzymatic changes work on the structure of the already deceased cells. Though the process is still poorly understood, these chemical changes are surprisingly similar to the process of tanning leather. Compounds like tannic and gallic acids are created, which protect tissues from further decay. They also result in a discoloration of the surrounding wood. 

The second step in the CODIT process involves the construction of new walls around the damaged area. This is where the real compartmentalization process begins. The cambium layer changes the types of cells it produces around the area so that it blocks that compartment off from the surrounding vascular tissues. These new cells also exhibit highly altered metabolisms so that they begin to produce even more compounds that help resist and hopefully stave off the spread of whatever microbes may be causing the injury. Many of the defects we see in wood products are the result of these changes.

The third response the tree undergoes is to keep growing. New tissues grow around the infected compartment and, if the tree is healthy enough, will outpace further infection. You see, whether its bacteria, fungi, or a virus, microbes need living tissues to survive. By walling off the affected area and pumping it full of compounds that kill living tissues, the tree essentially cuts off the food supply to the disease-causing organism. Only if the tree is weakened will the infection outpace its ability to cope.

Of course, CODIT is not 100% effective. Many a tree falls victim to disease. If a tree is not killed outright, it can face years or even decades of repeated infection. This is why we see wounds on trees like perennial cankers. Even if the tree is able to successfully fight these repeat infections over a series of years, the buildup of scar tissues can effectively girdle the tree if they are severe enough.

CODIT is a well appreciated phenomenon. It has set the foundation for better tree management, especially as it relates to pruning. It is even helping us develop better controls against deadly invasive pathogens. Still, many of the underlying processes involved in this response are poorly understood. This is an area begging for deeper understanding.

Photo Credits: kaydubsthehikingscientist & Alex Shigo

Further Reading: [1]

The First Trees Ripped Themselves Apart To Grow

Illustration by Falconaumanni licensed under CC BY-SA 3.0

A new set of fossil discoveries show that the evolutionary arms race that are forests started with plants that literally had to rip themselves apart in their battle for the canopy. The first forests on this planet arose some 385 million years ago and were unlike anything we know today. They consisted of a clade of trees known scientifically as Cladoxylopsids, which have no living representatives in these modern times. How these trees lived and grew has remained a mystery since their fossilized trunks were first discovered but a new set of fossils from China reveals that these trees were unique in more ways than one.

Laying eyes on a full grown Cladoxylopsid would be a strange experience to say the least. Their oddly swollen base would gradually taper up a trunk that stretched some 10 to 12 meters (~30 - 40 feet) into a canopy of its relatives. They had no leaves either. Instead, their photosynthetic organs consisted of branch-like growths that were covered in twig-like projections. Whereas most fossils revealed great detail about their outward appearance, we have largely been in the dark on what their internal anatomy was like. Excitingly, a set of exquisitely preserved fossils from Xinjiang, China has changed that. What they reveal about these early trees is quite remarkable.

[SOURCE]

As it turns out, the trunks of these early trees were hollow. Unlike the trees we know today, whose xylem expands in concentric rings and forms a solid trunk, the trunk of Cladoxylopsid was made up of strands of xylem connected by a network of softer tissues. Each of these strands was like a mini tree in and of itself. Each strand formed its own concentric rings that gradually increased the size of the trunk. However, this gradual expansion did not appear to be a gentle process.

As these strands increased in size, the trunk would grow larger and larger. In doing so, the tissues connecting the strands were pulled tighter and tighter. Eventually they would tear under the strain. They would gradually repair themselves over time but the effect on the trunk was quite remarkable. In effect, the base of the tree would literally collapse in on itself in a controlled manner. You could say that older Cladoxylopsids developed a bit of a muffin top at their base. 

A cross section of a Cladoxylopsid trunk showing the hollow center, individual xylem strands, and the network of connective tissues. [SOURCE]

Although this seems very detrimental, the overall structure of the tree would have been sturdy. The authors liken this to the design of the Eiffel tower. Indeed, a hollow cylinder is actually stronger than a solid one of the same dimensions. When looked at in the context of all other trees, this form of growth is truly unique. No other trees are constructed in such a manner.

The authors speculate that this form of growth may be why these trees eventually went extinct. It would have taken a lot of energy to grow in that manner. It is possible that, as more efficient forms of growth were evolving, the Cladoxylopsids may not have been able to compete. It is anyone's guess at this point but this certainly offers a window back into the early days of tree growth. It also shows that there has always been more than one way to grow a tree.

LEARN MORE ABOUT THESE TREES AND THE FORESTS THEY MADE IN EPISODE 253 OF THE IN DEFENSE OF PLANTS PODCAST.

Photo Credits: [1] [2]

Further Reading: [1]

Arums, Orchids and Vines, Oh My!

This week we head into the forests of Illinois to see what late spring botany we can find. This is one of the coolest times of the year to look for plants in temperate North America. 

Producer, Writer, Creator, Host:
Matt Candeias (http://www.indefenseofplants.com)

Producer, Editor, Camera:
Grant Czadzeck (http://www.grantczadzeck.com)

Twitter: @indfnsofplnts

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Track: Molasses
Album: Lazy Legs EP
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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]

On Fungi and Forest Diversity

One simply can't talk about plants without eventually talking about fungi. The fact of the matter is the vast majority of plant species rely on fungal interactions for survival. This mutualistic relationship is referred to as mycorrhizal. Fungi in the soil colonize the root system of plants and assist in the acquisition of nutrients such as nitrogen and phosphorus. In return, most photosynthetic plants pay their mycorrhizal symbionts with carbohydrates. 

There are two major categories of mycorrhizal fungi - ectomycorrhizae (EMF) and arbuscular mycorrhizae (AMF). Though there are a variety of different species of fungi that fall into either of these groups, their strategies are pretty much the same. EMF make up roughly 10% of all the known mycorrhizal symbionts. The prefix "ecto" hints at the fact that these fungi form on the outside of root cells. They form a sort of sheath that encases the outside of the root as well as a "hartig net" around the outside of individual cells within the root cortex. AMF, on the other hand, literally penetrate the root cells and form two different kinds of structures once inside. One of these structures looks like the crown of a tree, hence the term "arbuscular." What's more, they are considered the oldest mycorrhizal group to have evolved. 

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The type of mycorrhizal fungi a plant partners with has greater implications that simple nutrient uptake. Evidence is now showing that the dominant fungi of a region can actually influence the overall health and diversity forest ecosystems. The mechanism behind this has a lot to do with the two different categories discussed above. 

Researchers have discovered that trees partnering with AMF experience negative feedbacks in biomass whereas those that partner with EMF experience positive feedbacks in biomass. When grown in soils that previously harbored similar tree species, trees that partnered with AMF grew poorly whereas trees that partnered with EMF grew much better. Additionally, by repeating the experiments with seedlings, researchers found that seedling survival was reduced for AMF trees whereas seedling survival increased in EMF trees. 

What is going on here? If mycorrhizae are symbionts, why would there be any detrimental effects? The answer to this may have something to do with soil pathogens. Thinking back to the major differences between EMF and AMF, you will remember that it comes down to the way in which they form their root associations. EMF form a protective sheath around the roots whereas AMF penetrate the cells.  As it turns out, this has major implications for pathogen resistance. Because they form a sheath around the entire root, EMF perform much better at keeping pathogens away from sensitive root tissues. The same can't be said for AMF. Researchers found that AMF trees experienced significantly more root damage when grown in soils that previously contained AMF trees. 

The differences in the type of feedback experienced by EMF and AMF trees can have serious consequences for tree diversity. Because EMF trees are healthier and experience increased seedling establishment in soils containing other EMF species, it stands to reason that this would lead to a dominance of EMF species, thus reducing the variety of species capable of establishing in that area. Conversely, areas dominated by AMF trees may actually be more diverse due to the reduction in fitness that would arise if AMF trees started to dominate. Though they are detrimental, the negative feedbacks experienced by AMF trees may lead to healthier and more diverse forests in the grand scheme of things. 

Infographic by [1]

Further Reading: [1]

The Longleaf Pine: A Champion of the Coastal Plain

As far as habitat types are concerned, the longleaf pine savannas of southeastern North America are some of the most stunning. What's more, they are also a major part of one of the world's great biodiversity hotspots. Sadly, they are disappearing fast. Agriculture and other forms of development are gobbling up the southeast coastal plain at a bewildering rate. For far too long we have ignored, or at the very least, misunderstood these habitats. Today I would like to give a brief introduction to the longleaf pine and the habitat it creates.

The longleaf pine (Pinus palustris) is an impressive species. Capable of reaching heights of 100 feet or more, it towers over a landscape that boggles the mind. It is a landscape born of fire, of which the long leaf pine is supremely adapted to dealing with. These pines start out life quite differently than other pines. Seedlings do not immediately reach for the canopy. Instead, young long leaf pines spend their first few years looking more like a grass than a tree. Lasting anywhere between 5 to 12 years, the grass stage of development gives the young tree a chance to save up energy before it makes any attempt at vertical growth. 

The reason for this is fire. If young long leaf pines were to start their canopy race immediately, they would very likely be burned to death before they grew big enough to escape the harmful effects of fire. Instead, the sensitive growing tip is safely tucked away in the dense needle clusters. If a fire burns through the area only the tips of the needles will be scorched, leaving the rest of the tree safe and sound. During this stage, the tree is busy putting down an impressive root system. The taproot alone can reach depths of 6 to 9 feet!

Once a hardy root system has been formed and enough energy has been acquired, young longleaf pines go through a serious growth spurt. Starting in later winter or early spring, the grass-like tuft will put up a white growth tip called a candle. This tip shoots upwards quite rapidly, growing a few feet in only a couple of months. This is sometimes referred to as the bottlebrush phase because no horizontal branches are formed during this time. The goal at this point is to get the sensitive growing tip as far away from the ground as possible so as to avoid damaging fires. It is fun to encounter long leaf pines at this stage because like any young adult, they look a bit awkward.

Photo Credit: Woodlot - Wikimedia Commons

Once the tree reaches about 6 to 10 feet in height, it will finally begin to produce horizontal branches. This doesn't stop its canopy bid, however, as it still will put on upwards of 3 feet of vertical growth each year! Every year its bark grows thicker and thicker, thus each year it becomes more and more resistant to fire. Far from being a force to cope with, fire unwittingly gives longleaf pines a helping hand by clearing the habitat of potential competitors that are less adapted to dealing with burns. After about 30 years of growth, longleaf pines reach maturity and will start to produce fertile cones.

Before European settlement, longleaf pine savanna covered roughly 90,000,000 acres of southeastern North America. Clearing and development have reduced that to a mere 5% of its former glory. For far too long its coastal plain habitat was thought to be a flat, monotonous region created by early human burning in the last few thousand years. We now know how untrue those assumptions are. Sure, the region is flat but it is anything but monotonous. Additionally, the coastal plain is one of the most lightning prone regions in North America. Fires would have been a regular occurrence long before any humans ever got there. 

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Red indicates forest loss between 2011 and 2014. http://glad.umd.edu/gladmaps

Evidence suggests that this coastal plain habitat has remained relatively stable for the last 62,000 years. As such, it is full of unique species. Surveys of the southeastern coastal plain have revealed multiple centers of plant endemism, rivaled in North America only by the southern Appalachian Mountains. In fact, taken together, the coastal plain forests are widely considered one of the world's biodiversity hotspots! Of the 62,000 vascular plants found in these forests, 1,816 species (29.3%) are endemic. Its not just plants either. Roughly 1,400 species of fish, amphibians, reptiles, birds, and mammals rely on the coast plain forests for survival.

Luckily, we are starting to wake up to the fact that we are losing one of the world's great biodiversity hotspots. Efforts are being put forth in order to conserve and restore at least some of what has been lost. Still, the forests of southeastern North America are disappearing at an alarming rate. Despite comprising only 2% of the world's forest cover, the southern forests are being harvested to supply 12% of the world's wood products. This is simply not sustainable. If nothing is done to slow this progress, the world stands to lose yet another biodiversity hotspot. 

If this sounds as bad to you as it does to me then you probably want to do something. Please check out what organizations such as The Longleaf Alliance, Partnership For Southern Forestland Conservation, The Nature Conservancy, and The National Wildlife Federation are doing to protect this amazing region. Simply click the name of the organization to find out more.

Further Reading: [1] [2] [3] [4] 

Shade Gives This Begonia the Iridescent Blues

Believe it or not, the blue iridescence of Begonia pavonina is an evolutionary adaptation to extracting the most amount of energy out of the dim light that makes it through the thick rainforest canopy above. Even more bizarre, it works thanks to an interesting property of quantum mechanics. 

Native to Malaysia, B. pavonina lives out its life in deep shade. Most of the sunlight that hits this region is absorbed by the thick canopy of trees above. As such, eking out an existence is a challenge for these understory herbs. That is where this fantastic blue iridescence comes in. To understand it better, researchers had to take a closer look at its cause. 

Inside any photosynthetic leaves resides the chloroplasts. Chloroplasts are filled with tiny stacks of membranous compartments called "thylakoids." This is where the light reactions of photosynthesis take place. Now, in most plants, these thylakoids are haphazardly distributed throughout the chloroplast. This is not the case for B. pavonina. For this species, the thylakoids are arranged in a very precise way.

It is this precision that gives the leaves their iridescent color. Their placement causes blue wavelengths of light to be reflected. This isn't a big loss for the plant as most of the blue light is absorbed by the canopy above anyway. What it does instead is quite fascinating. The stacked thylakoids act like a dense crystal. When light enters the chloroplasts of B. pavonina it is physically slowed down.

This effect is known to quantum physicists as "slow light." Whereas light traveling through a vacuum maintains a constant speed, light passing through different types of matter can actually be slowed down. By slowing light as it passes through the chloroplasts, the thylakoids are able to take advantage of what little light the leaves are able to intercept. For B. pavonina, this equates to a 10% increase in photosynthetic rates. Coupled with an increase in the absorbance of red-green light, one can understand why this is such an advantage. 

Another interesting aspect of its physiology is the fact that B. pavonina produces both "normal" and iridescent chloroplasts. It is thought that this is a form of backup for the plant. In instances where enough light actually does make it through to the forest floor, B. pavonina can use its normal chloroplasts instead. It should be noted that this is not the only case of blue iridescent leaves in the plant kingdom. Many other species including spike mosses, ferns, and even orchids exhibit this trait. Even leaves that don't appear iridescent to our eyes may be utilizing nanostructures such as those seen in B. pavonina to increase their photosynthetic efficiency in low light conditions. It is very likely that many different kinds of plants are physically manipulating light to their benefit.

Photo Credit: Michael Perry

Further Reading:

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