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]

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]

On Crickets and Seed Dispersal

Photo by Vojtěch Zavadil licensed under CC BY-SA 4.0

The world of seed dispersal strategies is fascinating. Since the survival of any plant species requires that its seed find a suitable place to germinate, it is no wonder then that there are myriad ways in which plants disseminate their propagules. Probably my favorite strategies to ponder are those involving diplochory. Diplochory is a fancy way of saying that seed dispersal involves two or more dispersal agents. Probably the most obvious to us are those that utilize fruit. For example, any time a bird eats a fruit and poops out the seeds elsewhere, diplochory has happened.

Less familiar but equally as cool forms of diplochory involve insect vectors. We have discussed myrmecochory (ant dispersal) in the past as well as a unique form of dispersal in which seeds mimic animal dung and are dispersed by dung beetles. But what about other insects? Are there more forms of insect seed dispersal out there? Yes there are. In fact, a 2016 paper offers evidence of a completely overlooked form of insect seed dispersal in the rainforests of Brazil. The seed dispersers in this case are crickets.

Yes, you read that correctly - crickets. Crickets have been largely ignored as potential seed dispersers. Most are omnivores that eat everything from leaves to seeds and even other insects. One report from New Zealand showed that a large species of cricket known as the King weta can disperse viable seeds in its poop after consuming fruits. However, this is largely thought to be incidental. Despite this, few plant folk have ever considered looking at this melodic group of insects... until now. 

The team who published the paper noticed some interesting behavior between crickets and seeds of plants in the family Marantaceae. Plants in this group attach a fleshy structure to their seeds called an aril. The function of this aril is to attract potential seed dispersers. By offering up seeds from various members of the family, the research team were able to demonstrate that seed dispersal by crickets in this region is quite common. Even more astounding, they found that at least six different species of cricket were involved in removing seeds from the study area. What's more, these crickets only ate the aril, leaving the seed behind.

[SOURCE]

The question of whether this constitutes effective seed dispersal remains to be seen. Still, this research suggests some very interesting things regarding crickets as seed dispersal agents. Not only did the crickets in this study remove the same amount of seeds as ants, they also removed larger seeds and took them farther than any ant species. Since only the aril is consumed, such behavior can seriously benefit large-seeded plants. Also, whereas ant seed dispersal occurs largely during daylight hours, cricket dispersal occurs mostly at night, thus adding more resolution to the story of seed dispersal in these habitats. I am very interested to see if this sort of cricket/seed interaction happens elsewhere in the world.

Photo Credits: [1] [2]

Further Reading: [1]

Is it a pine? Is it an apple? It's neither!

Photo by Fractalux Public Domain

Pineapples - the fruit that is neither a pine nor an apple. In reality, pineapples are a type of bromeliad. The genus to which they belong, Ananas, is comprised of something like 7 different species, all of which are native to Central and South America. Considering we rarely encounter these plants outside of a grocery store, it is no wonder then that many are surprised to realize how pineapples grow.

Photo by H. Zell licensed under CC BY-SA 3.0

The fruit itself is not the entire plant. It is made up of many fruits that fuse together after flowering. The flowers themselves are quite lovely and originate from the center of the hexagonal units that make up the tough rind. The whole inflorescence arises from the center of a large rosette of leaves. Only when you see the entire plant does the bromeliad affinity become apparent. Like all other bromeliads, pineapples undergo vegetative reproduction as well. Small offshoots called "pups" arise from the base of the plant and the axils of the leaves. These can take root and grow into clones of the parent plant.

In the wild, pineapples require pollination to set seed. This is undesirable in cultivation because pollination means lots of seeds that consumers don't want to contend with. Because of this, pineapples are gassed with ethylene, the simplest of plant hormones. Ethylene causes the fruits to artificially ripen without being pollinated. In this way, no ovules mature into seeds.

Photo by hiroo yamagata licensed under CC BY-SA 2.0

The dirty little secret about pineapple farming is that it is done at great environmental cost. The dominant producer of pineapples is Costa Rica. Because of the humid, tropical climate, insects and fungi flourish. In order to ensure that production is maximized, pineapple farmers dump thousands of gallons of pesticides and herbicides onto their crops. These farms are largely void of all other lifeforms save for endless hectares of pineapples. This, however, is not a story unique to pineapple farming. The same could be said for all other forms of monoculture farming.

Photo Credits: Fractalux, H. Zell, and hiyori13 - Wikimedia Commons

Further Reading:

http://www.kew.org/science-conservation/plants-fungi/ananas-comosus-pineapple

http://www.theguardian.com/business/2010/oct/02/truth-about-pineapple-production

Insect Eating Bats Eat More Insects Than Birds in Tropical Forests

If the early bird gets the worm, it is only because we haven't been observing bats the right way, at least not in the rainforests of Central America. It has long been thought that insects such as katydids and caterpillars exhibit night feeding in order to escape day-active birds. This theory has influenced the way in which researchers investigate insect herbivory in tropical forests. However, recent studies have shown that bats, not birds, are doing the bulk of the insect eating in both natural and man-made habitats. 

In order to accurately investigate the role of insectivorous bats play in limiting herbivory in tropical forests, researchers decided to look at the common big-eared bat (Micronycteris microtis). They wanted to find out exactly how much insect predation could be attributed to these nocturnal hunters. As it turns out, 70% of the bats diet consists of plant eating insects, which is quite significant. Extrapolating upwards, it was apparent that we have been overlooking quite a bit.

Photo by Christian Ziegler via Santana SE, Geipel I, Dumont ER, Kalka MB, Kalko EKV (2011) All You Can Eat: High Performance Capacity and Plasticity in the Common Big-Eared Bat, Micronycteris microtis (Chiroptera: Phyllostomidae). PLoS ONE 6(12): e28584. doi:10.1371/journal.pone.0028584 licensed under CC BY 2.5

Using special exclosures, researchers set out to try to quantify herbivory rates when bats and birds were excluded. What they found was staggering. When birds were excluded from hunting on trees, insect presence went up 65%. When bats were excluded, insect presence skyrocketed by 153%! What this amounts to is roughly three times as much damage to trees when bats are removed - a significant cost to forests. 

To prove that it wasn't only natural forests that were benefitting from the presence of bats, the researchers then replicated their experiments in an organic cacao farm. Again, bats proved to be the top insect predators, eating three times as many insects than birds. This amounts to massive economic benefits to farmers. Bats have long been viewed as the enemies of both the farm as well as the farmers. Research like this is starting to change such perspectives. 

This certainly doesn't diminish the role of birds in such systems. Instead, it serves to elevate bats to a more prominent stature in the healthy functioning of forest ecosystems. Findings such as these are changing the way we look at these furry fliers and hopefully improving our relationship as well. 

Photo Credit: Christian Ziegler - Wikimedia Commons

Further Reading: [1] [2]