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9/25/22:
As the end of one season is just the beginning of another, the experimental portion of our waterlogging project is coming to a close as we harvest what's left of our trees and prepare for lab work. Of course, the onset of fall has much wider implications than dates on a calendar, deadlines, Halloween, and all the other markers of time we have collected throughout the ages. The original conductor of Earth's cyclical rhythms herself, Mother Nature, is up to a lot of interesting stuff both inside and beyond the arboretum's walls. The changes occurring on but a single tree and its surrounding habitat — the ripening of fruit, leaves slowly draining of their greenness, the absence of the pollinators' buzz, could all be studied for an eternity with renewed appreciation and questions continuously emerging like the roots unknowingly growing beneath our feet. Right about now you may be thinking, "Can we pull it back a little with the philosophical pondering on the nature of the seasons?" ... To that I say: I had to match the energy of the intro picture! Marvin and I were looking quite contemplative, after all. Keep reading to find out what had us thinking so hard. There's also updates on the waterlogging project and some fall foraging finds that you won't want to miss. You have my word that the content will be less esoteric and more tree science (maybe).
A final farewell to the magnolias
The magnolia trees are gone, but not forgotten. Many of their lignified limbs (stems and coarse roots) and more ephemeral appendages (fine roots) remain with us, stored in -80 degree temperatures, awaiting the stress and nonstructural carbohydrate (NSC) tests I've mentioned in previous posts. For this last harvesting session, we had to separate the fine roots we collected into five age classes. You've been with us throughout this project and you've seen the different colors used in each tracing session. As a refresher, the colors were used in the following order: green, yellow, red, blue. The last age class, the youngest, most recently produced roots, was not traced. We separated these by looking at the traced plastic window and placing any non-traced roots into that group. Below you can see Marvin preparing to harvest some roots and the cups we were using to separate the age classes (one cup is missing in the picture).
Lexikon Blogion
Moving forward on this blogging odyssey (which I most definitely plan on traversing until my last days, feverishly typing away on my MacBook 57, rocking slowly in my solar powered Tesla chair that scoots me around from place to place and comes equipped with a heated seat), I thought it would be helpful to provide definitions for words that might be uncommon to some.
Lexikon blogion: derived from the Latin phrase "lexikon biblion" meaning 'book of words' ... this modern derivative was made-up by novice blogger, me, in hopes of being witty, BUT MORE IMPORTANTLY, to give a name to a 'blog of words'
Lignified: a process in which branches, stems, roots, and other plant parts become woody and stiff due to deposition of lignin in cell walls. Lignin is an organic material made by plants for structure. Its waterproofing abilities make it an important player in water transport.
Ephemeral: short-lived, temporary. In the context of describing fine-roots, ephemeral means that their lifespans are relatively short compared to coarse roots. Fine-roots exhibit a wide range of lifespans, This paper co-authored by Dr. McCormack showed a median of 95 - 336 days depending on tree species.
Can you remember back to a little over a month ago when we conducted our first destructive harvest after taking the trees out of the pools? If not, then I am deeply saddened by my poor communication skills and I vow to never let you, or science, down again! Just kidding, I had to scroll down the page to remind myself when the last destructive harvest was, so you're not alone. Turns out it was the week of August 5th for the magnolias and August 12th for the maples. Check out those posts for a full run-down of what we're looking at with the NSC analysis (fyi: I'm working on a better set-up for the blog update page so that navigating between posts and searching for specific topics is easier). For a refresher, during the destructive harvests we are collecting both stems (trunks) and coarse roots from the trees to analyze the sugar and starch content.
Here you can see two images comparing control (grown in normal conditions) and treated magnolias (waterlogged). The first image depicts the star magnolia species (Magnolia stellata) and the second shows the saucer magnolia (Magnolia soulangeana). The difference between the controls and treatments is obvious, with the treated trees showing a lot of root die-back. However, what we want to focus on is the comparison between the treated star and saucer. The star magnolia, expected to be more tolerant to waterlogging, has produced more fine roots than the saucer since being rescued from the pools. If a facial-hair reference could help put this in perspective for you, the star magnolia root systems looked more like the unkept beard of our friend from last week's post, John Muir, and the saucers looked more like the five o' clock shadow of a business man or whoever else has a five o' clock shadow.
In awe of the Pawpaw
If you are a stranger to the pawpaw (Asimina triloba), please allow me to introduce you to the northernmost extending species within the genus Asimina, who also happens to hold the title for producing the largest fruit of any species native to North America. The pawpaw is within the Annonaceae family which contains mostly tropical to sub-tropical shrubs, trees, and vines. Also known as the custard apple family, many species within this group are important to local and commercial economies. Some of these include the custard apple, sweetsop, soursop, and cherimoya. Check them out here if you are interested in learning about their uses and native habitats.
Back on the taxonomic trail, Asimina is the only genus within the Annonaceae family that is native to North America. When researching for this topic I found different accounts of just how many species of Asimina have naturally made their way to the New World (ranging from 8-11, with one source claiming 13). I'm going with eight because the resource that I relied most heavily on, The Pawpaw, a forgotten North American Fruit Tree, was published in association with Harvard's Arnold Arboretum, and I'm just going to assume Harvard people know what they're talking about (don't listen to me, readers, check your sources). Anyway, out of the eight Asimina species, A. triloba extends the furthest north and produces the most palatable fruit. Below you can see some of the potato shaped green dudes we harvested this week, as well as the large, tropical looking leaves of the pawpaw.
According to the paper mentioned previously, the earliest written record of the pawpaw came from a Portuguese officer in 1541 when Spaniard Hernando de Soto's expedition of the Southeastern US came across native tribes in the Mississippi Valley cultivating the tree. The name pawpaw was derived from the Spanish word papaya, and the word papaya was derived from the Taino word papaia. The scientific name Asimina has origins from a different tribe, the Algonquian (Hormaza, 2014). What followed was a lot of back-and-forth and naming and re-naming throughout the centuries. If you are interested in learning more about the history of the pawpaw, or if you just want the scoop on all the botanist drama surrounding the naming process, check out Hormaza's paper linked above.
Right about now you may be wondering where you can find this magnificent tree and it's manana tasting fruit. Turns out, more places than ever, or less, depending on who you're asking. Pawpaw has historically been found in lowland, well-drained habitats. It can tolerate shade and typically grows as an understory species reaching heights between 12-30 feet. It also naturally propagates by cloning itself and sprouting new shoots that are all connected underground by an extensive root system. According to the National Park Service, pawpaw populations have been migrating upland to higher and drier habitats. What's the reason behind this move? Did the pawpaws have some nosy neighbors or are they just looking for lower property taxes? To my surprise, neither of those explanations are the cause.
Lucky for A. triloba, or perhaps by evolutionary design, their foliage isn't palatable to deer. Unlucky for most of the other dominant tree species in the Eastern US (think oak species, red maple, black gum, and spicebush), deer can't get enough of their saplings' leaves. This is allowing pawpaw to thrive in forests that are heavily impacted by deer browse and their numbers are expected to increase in regions experiencing this particular disturbance. On the other hand, habitat destruction via forest clearing and fire suppression have decreased populations.
Pawpaw are self-incompatible species, so they need pollen from a genetically distinct plant to fertilize their flowers and produce a tasty potato-looking fruit. As I mentioned earlier, they are a clonal species. You could find yourself standing in the middle of a group of pawpaws, and all of the trees surrounding you could genetically be the same individual. This is a pretty cool way to "surround yourself with like-minded individuals," as some people may recommend. Unfortunately, it also makes pollination a difficult feat. To add to the pawpaw's troubles, they are only pollinated by beetles and flies. Don't get me wrong, we have mad love for our beetles and flies in the Root Lab, but they are just simply less efficient at pollination when compared to our Hymenoptera homies. All this is to say, coming across a pawpaw bearing fruit in the forest can be a rare find. Stay on the look-out during the months of September and October and enjoy the fruits of your foraging!
Lexikon Blogion
Taino: indigenous peoples of the Caribbean, first New World population encountered by Columbus during 1492 expedition. They lived in agricultural societies based on systems of maternal inheritance.
Algonquian: a family of North American languages spoken by one of the most wide-spread and populous groups of indigenous peoples. Territories included the Great Lakes and Great Plains regions. Algonquian tribes relied on hunting and fishing for food, but also cultivated corn, beans, and squash (a planting method also known as the "three sisters"). Wild rice (manoomin) was cultivated by the Ojibwe tribe around the Great Lakes region and Canada.
Manana: word invented by Root Lab members to describe the distinct "banana with a hint of mango" taste of pawpaw fruit
The pawpaw is also the host plant of two caterpillar species, zebra swallowtail (Eurytides marcellus) and pawpaw sphinx (Dolba hyloeus). They transform into quite the beautiful butterfly and moth. Image source #1 | Image source #2
Chestnuts roasting .. in a modern-day stove
The chestnut genus, Castanea, is in the Fagaceae family along with all beech and oak species. There are nine species of chestnuts, though some sources report numbers as high as 13, that may just be because of their prevalence towards hybridization. The most economically and/or historically important species are the American chestnut (C. dentata), European or sweet chestnut (C. sativa), Chinese chestnut (C. mollissima), and Japanese chestnut (C. crenata). The American and European chestnuts are fast growing and can reach huge proportions of 100 feet with 5 - 10 foot diameters. There are remains of ancient chestnut forests in Europe, with the oldest existing chestnut dated over 1000 years old in Eastern Sicily. The Chinese and Japanese species are smaller, maxing out at around 30 - 40 feet.
You can't look into the history of the chestnut without also peering into humanity's past and present. I was surprised to learn how these multipurpose trees have influenced societies, not only as a huge source of food and nutrients for people and livestock, but also through their impacts on mythologies, religions, politics, and science. Over 4,000 years ago, ancient Greek empires took advantage of the carbohydrate rich nut by making it a staple in their diet and celebrating holidays during the seasonal harvest. The durability of the tree's rot resistant wood also served as a great building material. Next thing you know, trees were being planted for both culinary and timber uses. Back before Zeus was even a thought in some imaginative Greek author's mind, ancient Japanese settlements were subsisting mainly on kuri, the Japanese translation for chestnut. Jomon period (10,500 BC - 300 BC) archeological sites were found to contain 9,000 year old charred chestnut remains.
Meet the Chinese chestnut (C. mollissima), a common species planted for its resistance to chestnut blight and its large and tasty nuts. The spikey looking things you see, burrs, have evolved to protect the chestnut's seeds. All Castanea species are monoecious, meaning they have both the female and male reproductive organs on one tree. However, they do not tend to self-pollinate because their female flowers are fertile before their male flowers release pollen. For this reason, they need another compatible chestnut tree in the near vicinity for pollination to occur and for nuts to be produced. Chestnuts are primarily wind pollinated but recent studies have shown that their flower's morphology is indicative of beetle pollination as well.
How can such an important genus of trees, so intertwined with human civilization from the very start, be so undervalued in our history books? I remember learning about the importance of corn and tobacco, but I don't recall reading about the vast populations of people and ecosystems across Asia, Europe, and North America, sustained by the chestnut tree. During the late 16th century famine in Northern Italy, chestnuts saved many starving families. Later when European settlers came to the Americas, chestnuts served as a main food crop for families and livestock. It wasn't until 1904 that a deadly fungus would sweep through the eastern US and wipe the native chestnut from our collective memory.
It was that very same summer that chief forester of what is now the Bronx Zoo, Herman Merkel, noticed the dying leaves on one of the park's American chestnuts. Upon closer inspection, the infected branches had rings of dry bark populated with little orange dots. Herman, aware enough to know that this chestnut wasn't just making a fashion statement, contacted disease specialists right away to sus out the situation. The USDA wasn't too helpful, suggesting that it was the workings of the common cytospora fungus. Herman was adamant in getting a clear diagnosis, as he foresaw the widespread devastation that the loss of a keystone species such as the American Chestnut would have on our nation. He contacted the on-sight mycologist at the neighboring New York Botanic Garden, William Murrill, who cultured the unknown species and reported on his findings. In a 1906 publication, Murrill would write the ominous line, "this fungus may be classed with the most destructive parasites."
That fungus turned out to be Cryphonectria parasitica, otherwise known as chestnut blight. It kills its host by infecting an open wound, quickly girdling the tree by strangling the inner bark, called the cambium, with its mycelial tendrils. This disrupts the flow of water and nutrients throughout the tree. I hate to break it to you, but the story doesn't get better from here. To put it lightly, what followed was mass destruction and the death of over 4 billion trees, permanently impacting environments and economies throughout the US and Canada. Right about now I'm starting to enjoy the challenge of ending this story on a positive note. Do you think I can do it in one paragraph? Let's find out.
To break up the doom and gloom of this dreary chestnut tale, I thought I'd offer up some quick roasting tips. Set your oven to around 425, place your chestnuts flat side down, and cut an "x" deep enough to penetrate the outer shell (otherwise the pressure will cause mini-chestnut explosions in your kitchen). All it takes is about 20 minutes before you have deliciously soft and sweet nuts ready to be peeled and enjoyed.
Staying hot on the trail of the mysterious fungus responsible for such widespread havoc, in 1913, USDA officials tracked C. parasitica to its native home in China. There, the unassuming fungus was found on many Chinese chestnut trees, but these populations seemed to be living somewhat peacefully with the canker causing agent. Maybe an apt comparison here would be someone living with the foot ailment known as "athlete's foot." Sure, no one wants to have the itchy and smelly symptoms that accompany this common foot dweller, but it's not going to go around killing 4 billion feet and forever altering the North American landscape. How and why are the Asian species of chestnut able to cohabitate with C. parasitica while much larger and durable species like the American and European chestnuts seemed to have absolutely no defenses? Millions of years of evolution, folks! Just like we've seen with the spread of human diseases, invasive species, and other unnatural introductions resulting from globalization, environments and species often lack the natural defenses and checks/balances that would, under normal conditions, evolve slowly over time. The bright sides of this tragic moment in US history are the awareness it spurred for plant importation laws and regulations, the furthering of our knowledge in plant pathology, and the hopeful (and exciting) new avenues of research exploring ways to bring back the American chestnut and/or hybridize it with other resistant species. How did I do? Are you feeling inspired?
In last weeks post I suggested Eric Rutkow's American Canopy for readers who were interested in learning more about the history of trees in the US. I will mention it here again for any of those who want to learn more about the loss of trees in the US. He does an extensive dive on the impacts of the chestnut blight epidemic, as well as other microbial wars waged against our trees like Dutch elm disease. Check out this podcast to learn more about American chestnut conservation efforts and hybridizing breeding programs. Last but not least, this website offers an informative overview on the other issues, management techniques, and genetic engineering technologies being used to fight C. parasitica. Perhaps I will do a separate post on these topics because there's a lot to cover here!
Prime puffball season
Our last guest of the evening is the easy-to-spot giant puffball (Calvatia gigantea). Puffball mushrooms are in the division Basidiomycota. Remember back to our intro on the world of fungi where I discussed (with myself) the two main divisions of the higher order fungi: Basidiomycota and Ascomycota? If you don't, no worries, all you need to know is that basidiomycetes store their spores in a club-shaped organ and ascomycetes store their spores in a sac-shaped organ. Basically they're just a bunch of fungi with different purses.
Apologies for the aggressive meme, but I thought the giant puffball would want a grand introduction. I've never seen this movie, but I can just tell that Al Pacino wasn't playin' here.
Puffballs include multiple genera but the ones mentioned most frequently are Calvatia, Calbovista, and Lycoperdon. They are reported to be saprotrophic, but recent articles have claimed they might be mycorrhizal because of their habit of reappearing in the same locations year after year. I haven't found any research supporting that claim, so we'll revisit that when someone uncovers the puffball's secrets. They are frequently found in grassy meadows and on the edges of forests. Most puffballs are edible, but you better forage fast! If there is any hint of yellow or light brown upon opening the giant marshmallow-esque 'shroom, that means spore production has begun (what that means for YOU is an upset stomach). Forage wisely and keep an eye out for them from August to October!
Lexikon Blogion
Saprotrophic: feeding off decaying organic matter. Fungi that meet their nutritional needs this way are called saprobes, whereas decay-loving plants and bacteria are called saprophytes.
Mycorrhizal: fungi associated with plant roots. Mycorrhiza is the symbiosis between fungi (myco) and roots (rhiza).
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