Tree Bark: Botanical Bodyguard

                                                  Why is the forest always so loud? 

                                                 Because there is so much bark(ing)!

                                                                              ***

A Tree in the Woods

Look at a tree and you will notice three things: there is a top, filled with greenery; there is a cacophonous network of branches; there is the main trunk. The top – the “crown” – is where photosynthesis happens and flowering (usually*) happens. The branches hold the crown up and in place, and “branch out” to increase the amount of sunlight the tree can capture. The trunk holds them both high above the ground, into the sky. The trunk also provides strength against wind and physical damage, such as other falling trees. In the end, the structure, or “architecture” of various species of trees will be different – trunks thin to fat, crowns patchy to dense, branches growing upright or at right angles to the tree, for example – but the general plan of a tree is just that. Grow up and compete with other trees for valuable sunlight by making branches that grow smaller branches that grow leaves and flowers, and hopefully, you will make enough energy to survive and reproduce. Nature at its finest.

Let us look at that trunk. Find a tree in the forest or in your mind, and look closely at the trunk and only the trunk. That trunk is made up of many parts that help keep the tree alive – a tree is a complex living organism. Leaves, roots, flowers, buds, bark, vascular tissue, … it is a biologically amazing thing to have evolved!

Back to the trunk itself. Within that trunk are the conduits for nutrients and water from the roots in the soil to move up and feed and hydrate the leaves; within that trunk are also the conduits for nutrients and gases and a whole assortment of goodies made in the leaves to move down through the plant and to the roots.

Other things move along the trunk, too. Chemicals – exudates – that are there to protect or feed the tree that we have found a secondary use for. Rubber comes from the trunks of trees. Maple syrup comes from the trunks of trees. To get these, we need to puncture the tree somehow to make the inner liquids or latex leak out – no different than you cutting your arm and your inner blood leaking out. We need, somehow, to access the inner part of the tree.

Why? Because the inner part of the tree is still alive. The outer part, the bark, is dead. Stone cold dead. Mostly. The term “bark” is what ecologists call a non-technical term, meaning that it is a general description of a general part of the tree that surrounds the trunk and is generally dead. Generally.

Every species will have bark with different characteristics, and it is hard to give a complete and reasonably concise definition. But here goes: it is three layers of the dead to dead-ish material that surrounds the living wood in the trunk. The layers are (again, “generally”!) cork, secondary phloem (flow-um) and bark.

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Above: Bark can share a common character, but present in different ways. Look for the size of gaps, the depth of ridges, the pattern – do the ridges go straight or wander around. There will be many things that stick out to you the more you look and the more you compare trees to each other.

Bark Layers

One of those words should sound familiar to you. Well, maybe two! Cork is used to plug up the tops of wine bottles and is good for wine preservation for the same reason that it is good for trees – it is an exceptionally good barrier that does not allow moisture or even gases to pass through. If you left a wine bottle open all night (I’m thinking of a nice Malbec or a Syrah…) you would potentially wake to something edging closer to cooking wine or vinegar than that which the grapes of Argentina had in mind when they were plucked, stomped, fermented and bottled. Cork (now being replaced by plastic “cork”; the real cork will break and chip off with a fingernail dig if you try) is a natural layer within the bark of trees that, when jammed into a bottle, stops the ageing process (or the fouling process). The cork used in wine bottles comes from an oak tree that makes peculiarly thick cork layers that are easily peeled off, causing little harm to the tree (“little harm” is a contentious phrase here, but it paints the right picture. Anything you do to a tree that requires it to spend energy fixing or rebuilding tissue or chemicals will impact the tree growth or health. It may not kill it, but it does take energy away from other necessary deeds, such as growth. So, harvesting sap to make maple syrup is sustainable – it will not kill the tree – but it does have a measurable impact on tree growth).

Cork layers in bark protect the tree. Then there is a secondary phloem layer, which transports some liquid goodies through the tree. This gets complicated but is a vital part of the tree’s system.

Then there is the bark we are all familiar with – the outermost layer.

If you get a chance to see a cut tree or even branch (branches have bark, too!), look closely at the “bark” and you will see some distinct layering. That layering is all part of the tree’s bark system!

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Above: Some bark is flaky and will almost shatter off the tree when touched (left; Bischofia javanica), some is like low-grade sandpaper (middle; Ficus species with “cauloflory” figs growing off the trunk), or patterned like a map of a distant planet (right; Fraxinus grifithii)

Why do Trees Have Bark?

The bark of a tree is its protection. The stuff inside is vital – keeping the tree standing upright (there is strong dead wood at the centre of most trees) and keeping the tree fed and hydrated and filled with necessary chemicals and nutrients (the living tissues inside) keeps the tree alive. The bark, as an outside layer, protects this. Bark is the tree’s bodyguard. One of them, at least.

Some of the main things that bark protects the tree from are fire, insects, fungi, physical damage, and water loss. All these and many more will severely hurt the tree, and an outer bark layer has evolved as a way to protect the tree’s vital organs.

Trees can also adapt as infections or infestations happen, and be noticeable in the bark appearance. Not quickly, but quick enough. Some severe damage is unavoidable – woodpecker holes, for example. They peck and pluck too hard and too fast for a tree to compete by mending its wounds. But trees have other ways to protect themselves in these cases. For example, trees can simply close off the living tissue around these wounds, so insects and fungi that can invade afterwards have nothing to keep them alive.

Have you ever seen a tree with a weird, sometimes grotesque bulge on its trunk? This is a tree response to an infection of some sort, where the tree grows new wood quicker than normal around and infected area and cuts it off. The result is a healthy tree, but with bulges.

Bark is there to protect the tree, in many ways, from the many assaults encountered daily. And bark is very species-specific, making it a very useful tool to identify or recognize trees.

 

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Above: Some bark is bumpy (left; these are lenticels, places where the bark allows gas exchange – yes, trunks (and branches) breathe, too!), some bark is remarkably smooth (middle; this is Lagerstroemia subcostata, sometimes referred to as ‘monkey-no-climb’ tree as it is too smooth and hard to climb), or kind of a mix of rough and cracked (right).

See the forest for the bark

Do you still have that tree in your mind? Look at its bark. What does it look like? Colour, texture, everything.

Bark is a good way to get to know various trees. I must warn though that many trees have similar types of bark; however, within a given species the bark type will be very consistent. So if you learn to recognize what Bischofia javanica (Autumn Maple) bark looks like, it will look like that on every individual of Bischofia javanica.

The best way to learn your barks is to get close and touch a tree. Does the bark peel off or is it tough? Smooth or rough? Brown or grey? You may find trees that have wildly patterned bark, with green and yellow and white kaleidoscopic patterns up and down the trunk. This is not the bark colouration itself; this is lichen growing on the tree. Lichen will often grow on trees with smooth bark.

In places where many trees have smooth bark, for example, many aseasonal tropical forests, you may have five species around you that all have the same pattern of bark and all look alike. However, if you find a lichen-free section, you will notice differences.

So go look and look hard. Try to find differences and patterns, and try to combine this with leaf patterns and soon some more trees will start to make more sense. And always remember that when you are checking out a tree’s bark, you are communicating with an aged and evolved natural bodyguard that has allowed trees to grow and survive amidst a chaotic world.

Sterile Features: Leaves

This post will be one of multiple to help people get acquainted with the forests and parks around them by helping people look closer and notice the small, but important, parts. Enjoy!

***

Know Why You Know it, Don’t Just Memorize It

A handful of years ago (a large, overflowing handful!) in the middle of a tropical plant taxonomy course in southern China, our instructor asked us a simple question: “how do you know this is Litsea?”

It doesn’t matter what the species actually was – it indeed was a Litsea, but that is not the point here – it was the question that mattered. We were taking this taxonomy course in a lovely botanic garden. We had already spent a couple of weeks walking the garden in the mornings and working on preserving and practicing specimen identification in the afternoon. It was a full-on course, thick with heat and content, and we were on a roll.

So back to the question: “how do you know…?” Our instructor meant how do you know you know it is a certain species? What are the characteristics that make you know this is a certain species?

A voice from the back of the group yelled out something – in jest, but important nonetheless – that led to perhaps the most important botanical lesson I have ever learned.

“Because the sign says so!” the voice said, pointing to a small green and black metal sign at the base of the tree. In botanic gardens almost every tree (or at least one in a group of similar trees) has a plaque with species name and, often, interesting things to notice or points of ecological or cultural importance.

And this is what the student was referring to. Look at the sign! It made us all laugh, even the instructor who added something about waking up early and pulling every sign in the garden up before the next day’s lesson so we could never cheat again. This was in jest, too, but he had a point.

Laughs died down, we went back to the real work. But before our instructor explained details of this species, he told us that the key to understanding plants is to know why you know them, not to just memorize them. A single species can live in various places, and look kind of different in each; a young tree can look different than an adult; a tree recovering from damage can sprout new growth that is different than a healthy tree. The secret, he told us, was to know and know why we know the tree and its characteristics. All those different versions of the same tree will have a different look that will make someone who simply memorized a tree confused; but they will all maintain a group of core characteristics that will be present across the species, genus, and often family of plants.

Moraceae (the fig family) will all have alternate leaves. Apocynaceae (dogbane and milkweed family) will all bleed toxic white goo. Myrtaceae (wax apples!) will all have special “looping” secondary veins and have opposite leaves. It takes a while to know them all, and I certainly do not. But I learned on that day to focus on the key characteristics to know why a plant is in the Apocynaceae family, not just the look of a tree.

Better stated: why is this species not Moraceae? What are the characteristics I see? What are the characteristics I don’t see?

“A good botanist knows what to look for, not just what they are looking at”. This is what I scrawled in my field book as we walked off to the next group of plants. And I have never forgotten it.

Knowing Plants

So how do we get to know why we know a plant?

We look! That’s the first step. And here I want to share a few ideas of what to look for. Don’t worry about species names, technical descriptions, or even proper characteristics. Look for things that stand out to you. In time, you will start to see the details that will make you know you know.

We can think of two main groups of characteristics – reproductive and sterile. Reproductive characteristics are flowers and fruit. Sterile characteristics are everything else. Leaves, twig shape, bark, for example.

Seeing flowers, you can immediately remember big, obvious things like colour, general shape, smell, or size. Seeing fruit, you can similarly see colour, shape, texture (well, feel texture). These are fairly excellent ways to get to know many plants. But they are here for such a short time that they are not necessarily the best things to rely on.

That job is for sterile characteristics. Learning to look at the non-reproductive parts of plants and becoming familiar with these always-present features will help you see the forest as more than a bunch of leaves and trunks, and instead as a group of individual species.

Let us look at leaves. Closely.

 

What to Look For

Here is a little dive into what you should do when you find a tree and are curious. You need to touch, rip, look, rub, smell, and anything you can think of to make a list of a few characteristics. Then look for repeats. Maybe two different trees that share some characteristics…

Over time patterns will emerge. You will become more familiar. You will start to see that plants have characteristics that help explain who they are. And with this, we begin!

                                                                               ***

Look at it. Leaf shape is actually quite variable (“plastic”, we say) within even a single tree. Lower leaves on a tree may be vastly different than upper leaves. Newer different than old. Two trees of the same species beside each other may have different shaped leaves. But the differences will be consistent. Make sense? Look enough and you will see that often any variation is repeated and these trees will become the species with the weird leaves. You recognized a tree by its uniqueness! Most commonly, though, the leaves will be fairly stable and will be a good guide.

pacifica leaf collage 4

Above: Check the front and back of leaves. Both have important clues and traits. Notice the different vein patterns, colours, patterns of the edges, and shape.

Flip it over. Look at the veins. There will be one main (large) vein running up the middle. Or are there three, all starting from the bottom and spreading apart? Or do the three veins curl around and unite again near the top of the leaf? Look at the smaller veins running off of this main vein. Do they go straight and end at the edges? Do they curl at the edges and loop back (they never actually end; they never touch the leaf edge)? Are they rough or smooth?

While you have it flipped over, what colour is it? Is it the same green as the top of the leaf? Is it a paler green? Is it white? Does it have dots? Is it almost stripy?

pacific leaf collage 5

Above: Leaves can have unique shapes (top left; these seven leaves are actually one leaf of Shefflera octophylla!), patterns (bottom left; “pellucid dots”), or attach themselves in strange and unique ways to the branch or stem.

Look at the edges. Is the edge of the leaf smooth? Is it like teeth? Is it bubbly (smoothed out teeth)? Is it in lobes?

Rub it. Touch the surface of the leaf between your thumb and index finger. Is it smooth and rubbery like a tire? Tense and tough like leather? Rigid and dry like cardboard? Smooth and papery like, well, paper? Rough and hairy? Look at it on an angle. Is it hairy on the top and bottom, or just the top?

pacifica - leaf collage 1

Above: Leaf vein patterns can be giveaways. The larger, central vein is the “primary” vein. The lateral smaller ones are “secondary” veins, and the mini ones weaving around are “tertiary” veins. Sometimes the tertiary are not noticeable. Sometimes the secondary veins make neat patterns, like in Lauraceae (Camphor tree, bottom right), and Melastomataceae (top right). Sometimes the veins branch out and end in the spikes (Ilex, bottom right)

Fold it. Is it thick and tough? Is it flappy and soft? Is it thin? Does it snap in half like a piece of fresh cabbage, or fold like a piece of paper?

Rip it. Does it bleed? What colour is it? White? Red? Yellow? Is it a lot? Is it a little? If you have time, let it sit and dry. What colour does it become? (Beware: many species of plants have somewhat toxic “exudate”, the proper name covering all types of stuff that leaks out of injured plant material. Try to not get any on your skin!)

Crush it. Does it have a smell? Is that smell like cut grass or like lemons?

Feel the stem. This is the “petiole”, the part that connects the leaf blade itself to the branch of the plant. Is it short and thick? Is it long and narrow? Is it long and narrow, but has weird swollen parts neat the blade? Same swollen parts near the blade and the branch? Is it patterned? Is it twisted? Does it look like it is clasping or hugging the branch where it attaches?

pacifica - leaf collage 2

Above: Leaves on a single tree can vary in shape (left) and size (right). However, despite shape and size being very plastic in some species, venation and texture and petiole length and pattern and leaf arrangement….many things will be consistent. So, learn to look past the shape and size to see the true sterile characteristics that define plants!

How does it attach?  Take a branch and look at the pattern of how the leaves attach to the branch. There are many technical terms for may nuanced differences, but key ones are simple: are two leaves growing from the same part of the branch, on opposite sides (“opposite leaves”)? Are leaves growing from the branch at different points along the branch, alternating left-right-left-right (“alternate leaves”)? Or something else?

Put the leaf up to the sky. Look at a backlit leaf. Some leaves will have little dots (these are often the places where the smelly, volatile chemicals are kept that make the leaf smell when you rip it open!). Some will have unique patterns that cannot be detected normally.

paficica leaf collage 3

Above: Leaves attach to plants in various ways, but the most common and easy to compare are those that attach as opposite leaves (right) and alternate leaves (left). Also note the length of the leaf stem (petiole), the shape, and the shape of the leaf where the petiole and leaf blade meet. All are clues and things to notice!

Go Outside and Explore!

Look and see the difference in all the greenery around you. You may not know each tree by name, but that is not the point. The point is to see the difference and to know what to look for. You will see patterns. Similarities. Differences. Unique things will start to stick out. Geographical patterns will stick out (hey, isn’t this the same thing that we saw in Taipingshan?)

Learning to look for differences and similarities is the key. Plants have traits, like these above and many more, that are conserved throughout a species. That is why a plant ecologist or naturalist or horticulturalists or anyone who just plain likes plants can look at a plant and detect their way to an estimate of at least what family it is. If a species (or family, a higher ranking grouping of plants: Kingdom, Phylum, Class, Order, Family, Genus, Species) has smooth, leathery leaves that are opposite and smell like garlic, then the same species 40 km away will have the same traits. (I made that garlic plant up, by the way.)

So go out and notice, look, observe, and take some time to interact with the non-flower world in the forests. You may be surprised how fast you get to know some species, even if you don’t (yet) know their name!

Leaves have impressive stories to tell. Go look for them!

Sequential Flowering: Nature’s Clock

Why a Flower?

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Flowers are perhaps the most memorable part of a hike in the forest or a stroll down a treed street. Yellows and blues and oranges and whites, the air filled with their fragrance.

And there are many stories to be told about flowers; I hope to get through many in this space. However, one thing that might be noticeable right now is that many species are blooming.

Let’s take a quick dive into how (and why) flowers ‘bloom’. The flower is a plant’s reproductive structure. It is from the flower that fruit develops. Inside the fruit are seeds, which when dispersed – wind, animal, water, or gravity – they land and grow to make a new plant.

A flowering period starts from various triggers – night length, rain, temperature. When the time is right a plant starts to make flowers, packed tightly first into a flower bud as everything matures. These buds expand and, when ready, open. This is the bloom.

The next step is pollination. The flower needs to get pollen transferred from another flower’s pollen-making structure (stamen) to its egg-making structure (pistil). Somehow, the part of the flower that holds the flower version of an egg needs to somehow get a flower version of sperm.

Making Love in the Plant Kingdom

Flowers do this in many ways. Some use animals and have a variety of colours and fragrances to attract them. Some use wind, and, well, just wait for a gust to blow the pollen off and hope it lands on a receptive flower. The key here is that a single species needs pollen from flowers of another individual from the same species. So when the flowers are doing their pollinator-attracting work, they are trying to attract pollinators to the species, not just the single flower. This is called “outcrossing” and is necessary for genetic variation in a population.

Many species do pollinate themselves. This is called “selfing” and is a good way to maintain a population when things are tough. Low pollinator populations or small populations of the plant species means that pollen does not move very well. So, plants that have faced these tougher conditions have sometimes found ways to pollinate themselves. Genetic diversity is lower, but the population increases or sustains. This is a simplified version of a vast area of study, and one into which I hope to dig deeper in later posts.

So, flowers mature, open, and attract pollinators. The pollinators feed on nectar (some species of flowers don’t provide any reward for pollinators, but rather trick them…) and swap pollen between individuals. Much pollen is wasted, but some pollen gets stuck on the pistil and makes its way to the ovule, where the ‘eggs’ are and fertilizes.

Then the plant builds protection around the developing seeds. This protection also is key to the seeds dispersing. Some are fleshy and sweet, attracting animals to eat and, eventually poop out and disperse the seed. Others are dry, often popping open when the seeds are mature.

Back to the Flowers

Flowers are not all the same. Some are large, some are small; some are blue, some are orange; some have petals, some do not; some make nectar, some do not; some have volatiles (fragrances), some do not; some grow on branches, some grow on trunks.

Compare two flowers you find next time you are out and note all the differences. One important difference is the pattern in which they grow.

There are many styles, but you may see that some flowers grow on long stems. There are many names for these types of structures, such as ‘raceme’ and ‘panicle’, but we can simplify this by just thinking of long structures with lots of flowers growing on them.

These are interesting to watch. These types of flowers – together called an inflorescence – do something kind of interesting. Instead of opening all at once, the flowers will open in sequence.

Find one next time you are out – they are everywhere – and look closely. The flowers near the bottom of the long structure (closer to the plant itself) are older; those further away are younger. The older flower will open first, the younger flowers ill open later. It is a sequential flowering pattern within a single flowering structure.

When you look at these inflorescences, you will notice that almost none of them are all blooming at once – every flower in the group is waiting its turn. Now go find a bunch of these inflorescences from the same species (same plant or even different plants) and you will notice that every one of them is basically at the same pace. Because a single species will flower based on the same trigger – climate, season – each individual will be flowering at roughly the same pace. There are reasons that this can differ of course. But it is a neat way to look at a group of flowers and figure out how far into its flowering stage it is!

Look again at the images in this post. All of them are doing this. The lower, older flowers are blooming while the upper, younger flowers are waiting to mature and bloom. This is not just an age thing, this is vital to make sure that there are enough flowers available for a longer pollination period. If all flowers bloomed at once, and the timing was slightly off with pollinators, then there may be no fruit, and therefore no seeds. But by doing this, the plant increases the length of time that it is making reproduction possible.

So, go outside and find some flowers. If you find some that are arranged in a group take a closer look and see if there are some open, and some closed.  Investigate a bit and you will be able to find a pattern and maybe even have a useful ‘forest clock’ to help you better understand the timing of the flowering season.

Delayed Greening: A Plant’s Genius Idea

Red Leaves?

Have you ever been walking in a park or hiking on a trail and come across a plant with vibrant, captivatingly bright red leaves?  Did you notice that these red leaves are just on the tops or tips of branches and that the rest of the plant is green (the way leaves ‘should’ be)?

This is called ‘delayed greening’, quite literally a delay in the plant making its leaves green.

There are a few reasons to do this, but the main reason is because of herbivores – plant-eating animals. Herbivores like to eat leaves, and this causes a problem for plants. More properly, herbivores have evolved to be attracted to green leaves. Delayed greening – in essence camouflaging their leaves – is a way plants have evolved to limit this loss.

 

Why Are Leaves Green?

The green in a typical leaf is because of chlorophyll, a green pigment that is responsible for the majority of the photosynthesis a leaf does. Remember that photosynthesis is the process of, roughly, taking sunlight and carbon dioxide in and turning it into sugar, which the plant then uses as energy. This along with nutrients delivered from the roots keeps the plant (let’s go with a nice tree for this example) alive. The green leaves are basically biological solar panels.

So, in short, leaves are green because the photosynthetic chemical that allows for sunlight to become energy is green.

Importantly, making leaves takes a lot of energy, and the green chlorophyll is an expensive part of this process. People use the term ‘expensive’, meaning that it takes a lot of energy to build these photosynthetic structures. Similar to real solar panels, the money (energy) needed to build the footings and support structures (branches and stems, veins), and to buy the solar panels themselves (leaves) is quite a lot. So a tree will do what it can to protect them. If a herbivore eats a batch of fresh green leaves, all the energy that went into the leaves is lost (energy is never truly ‘lost’; it is transferred to the herbivore – let’s say a beautiful caterpillar – and is no longer available or useful to the tree).

Defending the Energy Sector

Some plants, such as mangos (Anacardiaceae family, along with cashews, pistachios, sumac, and the horrible poison ivy) or figs (Moraceae family, along with breadfruit and mulberries) produce chemical defences for their leaves. Find one next time you are hiking or in a field, and pluck off a leaf; you will see a white, gooey liquid dripping out. This is a chemical defence that stops herbivores – deer, caterpillars, insects – from eating their important leaves (some chemicals are toxic, some literally clog mouths and suffocate critters, some are just rather bad tasting; like different venoms on snakes have different modes of operation, different plant chemical defences have different ways to stop things from eating leaves).

But it has its costs. All defences do. We fund our military to defend our country, we purchase home security cameras to protect our homes; money that could go to social programs, housing, food security, green tech goes, instead, to protection. Plants, less able to hook up electronics and fly planes, play with the evolutionary tool bag they have at hand.

Delayed greening is just another tactic that has evolved. And it is a good one.

What is Delayed Greening?

So what is it?

New leaves are softer (less developed) and often of great interest to herbivores. Think about eating a thick raw cabbage or an iceberg lettuce head. Not entirely perfect as analogies go, but I think you get the point. Old leaves are tough, dry, often thick; young leaves are supple, moist, chewy.

To protect their young, fresh, delectable leaves, some plants do something special – they delay releasing/producing the green pigment chlorophyll. This means that the leaf tissue does not have the colour green in it, and instead looks red. This red is from anthocyanins. This pigment is responsible for making some of our common foods somewhere in the red-purple-black range. Black rice has a lot while white rice does not; blue corn has a lot while regular yellow corn does not; red cabbage has a lot while white cabbage does not; taro, blueberries, acai, eggplant … it is a molecule that is common in our common foods.

So when the tree delays producing the green chlorophyll, the leaves are left looking red. (Some ‘delayed greening’ species have white leaves or pale green leaves, but red is the most obvious.)

Red leaves are less interesting to herbivores, so there is less nibbling.

As the leaves age and get tougher, then the tree will start pumping in chlorophyll, turning them green. If you can find a tree or bush or vine or anything that has red leaves, try to check in on it over a few weeks or months, you will see the red leaves slowly transition to green.

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Nature Doesn’t Need Perfect, Just Better

Delayed greening is not perfect, but perfection is not what evolution gives us. Instead, evolution gives us something that is better or good enough. And delayed greening is a perfect example of this.

By delaying the greening, plants loose photosynthetic capacity – no chlorophyll, no energy production. So leaves that are red are not really helping the tree out that much. Yet.

But making green leaves, rich with expensive chlorophyll and leaf material, and losing them to herbivores is worse. Delaying the greening of new leaves is a good investment because the total overall energy savings for the tree can be substantial – more energy is lost by having to continuously grow news leaves than a slight delay in the leaves producing energy. It is an investment.

Red Spring, Red Fall

Delayed greening is more dominant in tropical and sub-tropical areas, and in more seasonal areas like Taiwan it is more dominant in the springtime when rains return and temperatures warm (plants go through growth spurts). In temperate areas, where the summer season is shorter and plants do not have time to wait, the evolutionary pressure is not on maximizing overall energy balance long term but rather getting the most energy possible immediately – so leaves are mostly born green.

But in these temperate regions (and high elevation forests in tropical and subtropical areas, such as in Taiwan’s mountains) the opposite happens. In the fall leaves turn colours and eventually fall. This is caused by the tree drawing out chlorophyll first, leaving behind the red and yellow and orange chemicals. This is a neat story itself, perhaps for later.

Conclusion

Delayed greening is a very important evolutionary feature of many tropical plants. By delaying the leaves becoming green they are limiting herbivory, but also photosynthesis. But overall, the net benefit is clear – delayed greening keeps more leaves on the trees and is good for the plant.

More practically for us, delayed greening can be one of the most gorgeous things in the forest. If you find a tree or shrub or vine on a trailside that is sporting vibrant red leaves, think of it as a plant investing in its future. And looking beautiful while doing it!

 

 

 

 

 

Land Crabs of Taiwan: Banana Bay

“What is a crab?” “Where do they live?”

These are questions I ask people whenever I am introducing them to one of Taiwan’s most inspiring conservation projects. More about that later, I promise. I also ask my ecology class a similar version of these questions (I ask them in Mandarin, not English). Usually, the answers that come back are various incarnations of “crawling thing”, “delicious”, and “ocean.” I agree, mostly. They are crawling (even in the ocean they crawl more than anything else; they are not swimmers), they are in fact a tasty meal for humans and many oceanic creatures, and they do live in the ocean.

But not all of them. Live in the ocean, that is.

Land crabs are (you may have already guessed) “land” crabs; they live on the land. Still with me? And there are many ‘kinds’ of land crabs, which researchers give fancy names and dissecting classifications; here, I will just introduce the rough breakdown. Hopefully, this will help you better understand the crabs you may see on the beach, in the forest or climbing on the coastal rocks getting splashed by waves.

ABOVE: Photos (Credit: Trevor Padgett) of a few examples of land crabs found in Banana Bay and the surrounding region of the Hengchun Peninsula, southern Taiwan. Two images of Banana Bay are included; note the uplifted fringing reef. This provides excellent protection for the eggs once released, limiting the number of predators that can access this nutritious food. Species shown: Cardisoma carniflex (creamy yellow, standing on rock), Discoplex hirtipes (x2; blue and yellow crab, large), Labuanium scandens (on grass), Scandarma lintou (standing on blade of Pandanus tree), Ocypode sinensis (on sand), Ocypode species (not identified yet; on sand)), Metasesarma aubryi (on my hand with yellow ‘eyebrows’).

 

Types of Land Crabs

Land crabs are types of crabs that have evolved to live out of the water. They are diverse. Let’s very briefly look at a few common lifestyles so that their world can make a little more sense.

Arboreal: Some crabs, such as Labuanium scandens and Scandarma lintou, live almost their entire lives in trees. Some tree species of particular importance to arboreal land crabs in the coastal forests of Banana Bay are Pandanus species and Barringtonia asiatica. The crabs may live in the nooks of the leaves or branches, on old holes made by birds or rotten branches that were broken by typhoons. When the rains come, they will use the small puddles that form in the crotches of branches or leaves (that is the proper term for it!). The eggs will hatch, and flee to other parts of the tree or other trees. These spend relatively little to no time on the actual ground.

Freshwater: Other crabs, like Geothelphusa albogilva or Sesarmops intermedium, live on the land itself but reproduce in freshwater. These will migrate to streams and lay their eggs. Some eggs may make it to the ocean and some may not; however, the crabs themselves rarely ever go to the ocean themselves.

Coastal: Some species of land crab never leave the beach area. All year, after dark, you can find crabs scurrying around the beach and jumping in and out of the surf. The most common species you may find in the Kenting area is Ocypode species – very obvious by their alien-like tower eyes. Go to the beach and take a look, you will find one (but run, they are fast!).

Marine: Marine land crabs – crabs that live on land but must go back to saltwater – are the last general group. These are species like Discoplex hirtipes, Discoplex rotunda, Cardisoma carniflex, Metasesarma aubryi, etc.  These types of land crab live far off in the forest, and must make the trek to the ocean to lay their eggs.

Hermit crabs: These are, technically, not land crabs. In fact, they are not even crabs. Hmm… There are more than 5000 species of Decapod that are classified as “true crabs”. A solid carapace that is sealed and complete is a defining feature of a crab – a true crab – so to be in this group, basically, you need to have a shell. Hermit crabs do not (hence the name “hermit”; they get their protection by confiscating and living within another creature’s shell). So while hermit crabs act like and look like and seem like crabs, in the genetic and scientific taxonomy of crabs they are just, well, pretend crabs that steal shells from other animals (this includes the massive and in Taiwan nearly extirpated coconut crab, which is a hermit crab that does not have a shell on its back of any sort, fused to their body or borrowed. Nature is not clean-cut and definitive).

Banana Bay, Kenting: Land Crab Central

Banana Bay in southern Taiwan has – it is argued – the highest diversity of land crabs in the world. It certainly does not have the highest density – images of Christmas Island’s land crab migration does not ever play out in Taiwan – but measured by the total number of species, Taiwan comes in first. As a group, land crabs combine to be an ecologically important component of forest, river, and ocean ecosystems. The eggs feed fish, the crabs are vital to nutrient cycling in forests, and are important herbivores. Forests need land crabs; they have evolved together.

Becoming Land Crabs

Let us take a few steps – crawls – back in time and start closer to the beginning of crabs. Crabs are “decapods”, ten-feet, and evolved in the ocean. (this is rarely portrayed properly anywhere; next time you see a drawing or cartoon of a sign with crabs on it, count the legs and I bet you there are only eight! For example, check out the photo above of the key chain put out in support of a land crab conservation project.) The genetic voyage that led them to being able to survive on land were complex and myriad, physiological and morphological. Two things were sticklers and tough to overcome: how do they say hydrated on land, and how do they reproduce?

Staying hydrated was a magician’s evolutionary trick. In the ocean it is easy to stay wet – you just stay in the ocean. But they didn’t; land crabs over generations wandered out of the sea and found a niche on land that they occupied with professional zeal. Crabs breathe through a gill-like structure, and this must be moist in order to allow oxygen to make it into their body. A legacy of being marine creatures that took a gamble on land. Remember: evolution can’t see the future. They have, therefore, evolved ways to survive as best they can to make them survive as a population in a new land. In this case, literally a new ‘land’!

Land crabs also lose water through evaporation and will, if unchecked, simply dry out on land. Again, legacy problems from having evolved to live in the ocean for a long time and having to deal with land for a comparatively short time.

Land crabs have adapted to this by changing their life to being primarily nocturnal – they only come out at night. During the day, particularly the days – winter and summer – with a gnawing, pulsating sun in southern Taiwan, the land gets hot. The winters in the south are actually fairly free of rain, and it is not uncommon for there to be a three or four-month interval between rainfalls. The summers are hot, and even though there is more than 2000 mm of rain a year – a suitably “rainforest” climate measured this way – most of this comes in short typhoon-brought downpours. In short, much of the year here, where the largest diversity of land crabs exists, is dry and hot. So land crabs have taken to the nights. Cool and humid, particularly in the arid winters, they are safer. They spend their days in underground burrows, and come out at night to feed on leaves and other plant matter, sometimes a few critters and even another land crab, and return to their burrows for the sunrise. They will, however, emerge any time of the day if there is heavy rain. They track the water in the air and live their lives to its pattern.

This means that if you want to see land crabs it is best to go hiking during a rainstorm or in the night. My work on one project is in a place rich with one type of and crab, the freshwater land crab Geothelphusa albogilva, and when I am in the forest during heavy rains of the spring or leaving late at night in the summer the forest floor and become almost impassable because of their numbers, crawling and eating and showering in the rains. And beautiful.

What about reproduction? Land crabs, as mentioned earlier, evolved in the ocean. To live on land, they would have to figure out a way to reproduce on land. This was easy: they didn’t. Not exactly, anyway.

This gets a bit complicated and links back to the types of land crabs, but in general land, crabs need to go back to the ocean to lay their eggs. Males and females will live and survive in their burrows all year, mate in the summer, and then the females will start their migration to the ocean. They will step into the ocean during the three days following the full moons of July, August, September, and October (in Banana Bay, Kenting for Discoplex and a host of other species; dates of this change based on species and location). This can, for some, be more than three kilometres; for some, it is less than one. Regardless, this is a true migration – a land crab spawning migration.

Females will forgo eating and march, tirelessly, to the ocean. They know where to go, they know how to time their trek so that they make it to the ocean on or just after the full moon. On the final leg of her journey, just as she is approaching the ocean, she will wait until night, usually around 6pm, and make the final push. Arriving at the ocean around the same time most of us will be eating dinner, she will slip into the water and wet herself, then crawl up on a rock or nestle into the beach sand and wait a while. Remember that need to say hydrated – both her body and gills? Well, this dunk in the ocean is what I assume the equivalent of a glass of water after a marathon to us would be. Wet, happy, and tired, she will rest. They will rest; she and hundreds like her are all here on this one night trying to lay their eggs. Some species carry hundreds; others, such as the most common Discoplex hirtipes carry hundreds of thousands.

Then when it is time, the throng of egg-laden female land crabs will slip back into the ocean and spawn. The event is fast, and quite enjoyable to watch. She will stand still, fully submerged in water, and start to dance, jiggling her body while her claws scrape her eggs off her body. Then she will leave the water for another year.

Her eggs will float away, and start to hatch almost immediately. If you listen closely you can hear the snapping of thousands of egg cases popping open. The ocean knows that the crabs are coming, though. Just as crabs have evolved over the years to live on land, so too have the creatures of the ocean evolved and adapted to their lifestyle. Curious and hungry fish flock to the bay and eat up protein-rich crab eggs. The mother will never know what happens to her kids, and she will never know who made it past the fish feeding frenzy. But some do. Many do.

The eggs will hatch and grow, passing through morphological phases until they finally look like little crabs. They will emerge from the ocean and race to the forest. They survived the ocean, and are now on to chapter two of their lives – to grow old and, if they are female, someday return to these shores to lay their own eggs.

Life Continues

Land crabs have evolved to live on land, and over thousands of generations have etched their way deeper into the fabric of terrestrial ecosystems. But they need to keep their feet – so to speak – in the ocean. A little. To breathe they need to keep wet – damp, at least – and to do so they have become nocturnal. To reproduce they have taken on the task of making an amazing journey each year to get back to their ancestral home.

Watching a crab spawn, I always wonder if it knows, deep down in its DNA, that is where it came from. I know it doesn’t, that it can’t. But I imaging it would love to know the story.

Get Outside (at night)

If you have a chance, go to the forest at night. Take a flashlight and wear long-sleeved shirts and pants and take care, but get out. And go to the beach at night.  You will find land crabs. If it has been rainy recently, there will probably be more. There is a whole world of life in the forest that is rarely seen, yet both important and extremely interesting. Go check it out!

Ocean Botany: Drift Seeds

Take a walk on any beach and you will find a bounty of curiosities. Driftwood, polished rocks, algae, land crabs, sand… And unfortunately a high diversity of garbage: fishing bobbers, shoes, plastic bottles, and endless flecks of nameless plastic pieces.

But let’s look closer. If you ever find yourself on a beach, in Taiwan that can be a popular place like Taipei’ Fulong, Kenting’s Nan-Wan, or any of the smaller and less known beaches in between, you will be surprised to know that the sand beneath your feet is also hiding botanical treasures – drift seeds.

Take a handful of sand and let the grains fall through your fingers, pluck out the blue plastic shard and flick away the piece of seaweed, and you may find nestled in the fold of your hand a lovely, voyaging seed.

To understand why we must consider the evolutionary track of plants. Very briefly, very generally.

Plants basically reproduce by seeds or spores. Ferns and mosses don’t make seeds, they make spores (look under a fern ‘leaf’, and look at those tall, bulbous emergent growths on a moss; those reddish clusters and mini-balloons hold the spores).  Spores evolved in a time when the world was wetter and these plants that use them still today rely on water to move them around – dispersal by water. If you are hiking you may notice that some areas are fern rich and some are fern poor; this will directly relate to the moisture of the soil – wetter places, which may be based on soil type (high clay soils and high organic matter hold more moisture) or climate (more rain) have more ferns and mosses. Generally; there always caveats!

Plants that make true seeds are from the gymnosperms (cone-bearing) or the angiosperms (flower-bearing), together known as the spermatophytes. Redwoods, palms, roses, bamboos, olives, apples, figs, spruces, mangoes, oleander, cedars, Ixora, maples, ironwoods, tea, camphor, hinoki, oaks…almost any plant you can think of, from the tall trees to the shrubs and ‘flowers’ of our ornamental gardens, make true seeds as a way to reproduce. Next time you are out in the forest and find a fruit or a cone, rip it open and fish around and you will find seeds. Many people are woefully unaware of the connection between flower and fruit and seed, or that massive trees make flowers. It is a simple yet telling misstep of our collective educational schemas and a key indicator for ore eco-literacy. More on that in a later post.

Back to the seeds. So a bunch of plants on our planet make fruit. Some have flowers, some don’t. And these fruit have seeds; getting these seeds moved away from the mother plant – dispersed – is the sole purpose of plant reproduction. Exactly how it is done is a fantastic tale and too rich and long for a simple blog post. But we can restrict dispersal methods to a few important groups.

Animal dispersal is where animals are attracted to a fruit and become a seed disperser. To be effective, the seeds must be either small enough to be passed through a digestive tract or large enough to be tossed to the side once the animal is done eating (and not crunched and killed in the process). Consider a bear eating a blueberry (all those tiny seeds inside) or a squirrel eating an acorn. The bear swallows the blueberries almost whole and defecates out the seeds in a pile of fertilizer. The squirrel actively eats the oak fruit – the acorn – itself, killing the seed. (Acorns use this to their advantage in a curious way, by often masting and forcing squirrels to hoard their seeds. Some get eaten and some get forgotten, and these forgotten ones have a chance to germinate and test their luck in the forest.) Consider us humans eating a dragon fruit or a mango. Dragonfruit seeds go through us, mango seeds get tossed to the side; both get dispersed by animals.

Burrs are another type of animal dispersal, only these get dispersed on an animal rather than through an animal.

Dispersal by wind is another all too familiar method. It will not be too foreign to anyone to think of those whispy white-tailed seeds floating through the summer air or dandelions exploding with a gust of wind. Maples and ash trees also use this, though they are clearly much heavier. But they still use wind, aided by their morphology helping them ‘helicopter’ through the air, to not just fall directly to the ground but rather fall further away from their mother.

While we are on the topic of gravity, that is another way seeds get dispersed. Often it is in collaboration with animals, maybe pigs or monkeys or ants or rodents, but this seed-filled fruit will fall to the ground almost directly at the base of the mother tree.

Others explode. Explosive dehiscence is the term, and these plants that have evolved this dispersal method have fruit that dry out as they ripen, eventually snapping open and thrusting their seeds into the forest. These can be impressive; I remember collecting some Bauhinia fruit from the side of the road one year and hoping to plant the seeds in my garden. I collected them and put them on my counter, and eventually got busy with life and simply forgot about them. Until one night, close to 3 a.m., when I was awoken to the sounds of what seemed like gunshots and the sound of nearly a hundred seeds splattering around my bedroom. The fruit had dried enough, and were doing their due diligence to try to reproduce; nobody told them I was sleeping, I guess.

And there is water dispersal. This one is what brings us back to our title and topic: drift seeds. Many plants have evolved to disperse their seeds by means of water. Remember that the ecological goal of plants spending energy and resources to make flowers and fruit is to reproduce, and to do that seeds need to be moved – dispersed – away from the mother plant (survival increases with distance from mothers in the forest). Rives, typhoon and monsoon duluges all can transport seeds. So too can the ocean.

Plants that have evolved to live near the ocean are “coastal plants”; beyond some special dispersal tricks, they also have had to evolve to a general lack of freshwater, extreme wind, and increased salt content from ocean spray. But we are on the topic of their fruit, so let’s restrict our thoughts to that.

Some coastal plants have coopted the ocean to transport their fruit (and therefore seed or seeds) to places very far. Fruit drop off the trees, and a few storms or perhaps a windy day or two later they may make it to the ocean and drift for weeks or months until they hit the shore of another land.

DSC09463

Above: Taidong, Taiwan. People enter the beach to watch a sea turtle release organized by National Taiwan Ocean University. The east coast beaches are fed with driftwood and seeds from places afar; particularly after typhoons.

Below: Wang’An Island, Penghu Archipelago, Taiwan. The creamy gold beaches of Wang’An are where sea turtles by the hundreds – mostly green turtles – used to come to lay their eggs. For various reasons, predominantly by-catch by non-Taiwanese fishing fleets, the sea turtles in this region have been decimated. However, these beaches are still dotted with a wide diversity of drift seeds for the attentive visitor.

Wangan_beach3

If you walk along any of Taiwan’s beaches you may find some seeds tucked in amongst the sand and plastic. Some, of course, could be from the plants just a few meters away on the shore. But some may be from places across the planet, washing up on Taiwan’s shores after a lifetime at sea. Next time you are on the beach take a moment to look and see what botanical wonders are waiting at your feet.

This is more than just a curiosity; this long-distance dispersal increases genetic diversity and helps plant spread their ranges and access islands. If saltwater and months at sea killed their seeds, hundreds of species would probably never have made it to Taiwan and similarly many would not have spread to places from Taiwan.

So go to the beach and botanize! Find a seed sunk into its sandy home and wonder out loud where it came from, what stories it has, and what it will grow into. Wait a decade and come back – you may find a brand new tree!

(Best places to look are at or above the high-water line; wander around up and down for a while and you will figure out where most of the seeds are. A great activity for families and schools, too!)

 

 

 

 

 

 

Welcome to PACIFICA

The Pacific Ocean was my first taste of true freedom and inspiration.

Pacifica is the natural extension of what the Pacific did to me, and what I have become since it entangled me in it and Taiwan.

Though I grew up in glorious forests and mountains, nothing prepared me for the emotion of the glistening expanse of the blue Pacific ocean that met me when I first stepped out of a then lonely now busy east coast train station in Taiwan.

I breached the station doors and stood in the sun. I sweat. I looked. Green trees white buildings; loud cars ocean smells; the sun… I wanted to be in it all. So I shouldered my bag and walked into the thick humid air, towards the ocean.

As a road forked and buildings obscured the way, I stopped to fumble my way through a request for directions from a small-statured man selling what I later discovered were Betel nuts.

I used the words I had practiced – hai, haaaai, haiiiiii… I gestured a person swimming with my arms. I gestured fish with my hands.

He gestured to his stomach to ask if I was hungry.

No, I was not. Thirsty, but not hungry. I bought a drink – again by pointing – as a way to break the incompatible moment of our language impasse. My incompatibility, not his.

The man then disappeared and brought out his elementary-aged grandson, pointing at him, suggesting I speak to the boy, not the man.

“Ocean. I want to go to the ocean” I said. The boy turned and said something. I at the time did not know what he said, just like I didn’t know those green wrapped candies were not exactly candies, but it worked.

Together they pointed out a disjointed set of routes I should follow. Then the man pointed at the sun and handed me a second drink. Free. At least I assumed that is what his waving hand and scowled face meant. I thanked him and the boy. I followed their directions.

Minutes, maybe an hour, I don’t remember, I made it to the sandy shores, bespeckled with rocks scoured and polished by ages of sand and water.

From there I saw more than I ever did. And it became the moment that I decided to never leave.

That train station and that Betel nut stand and a strangers kindness and the rock-speckled sandy shore and the blue expanse also started Pacifica, though it took years for me to realize it. Now deeply embedded in ecological research, education, and writing worlds of Taiwan, I plan to use this platform to share the stories of Taiwan as spoken through its natural world (reader be warned – it’s mostly about plants!).