If a Tree Falls in the Forest

Parasites and diseases are what population ecologists call density-dependent causes of mortality; factors that only affect an individuals’ survival when populations are at high densities. Other density-dependent factors affecting plant survival include: competition for resources, such as water, light and soil minerals, and intense herbivory (usually by insects). In general, density-dependent causes of mortality are biotic, that is, caused by other organisms. Density-independent factors of mortality are usually abiotic (not alive) or environmental: forest fires, drought and volcanic eruptions that bury vegetation in lava are a few examples.

There are plenty of plant parasites and diseases that evolved right here in North America. However, most native plants have evolved methods to resist these organisms to some degree so it is not always fatal to the plant, unless it is in a weakened state. During droughts for example, trees are much more likely to die of a disease. Since the colonization of North America occurred, species of diseases that were not native to this continent have been accidentally introduced, typically with dire consequences. In my next blog, I will be discussing how three species of native Canadian trees (American Chestnut, American Elm, and Green Ash) are being negatively impacted by introduced diseases, and how we can change our behaviour to protect our forests, both wild and urban.

One of the most significant contributions that America’s Indigenous peoples have made is with respect to agriculture. Many of our most beloved foods (e.g. chocolate, potatoes, corn) are native to the Americas, being initially cultivated or domesticated by Indigenous farmers. 

Indigenous agriculture has a long history with the most recent archaeological evidence suggesting it has been practiced in the Americas for at least 10,000 years, almost the same time length of time as in the Fertile Crescent of the Middle East. There were five agricultural centers of origin (i.e. places where multiple species were cultivated or domesticated) in the Americas: three in South America and one each in Central and North America. 

Crop plants cultivated or domesticated in the Americas by Indigenous peoples. 

Cereals & pseudo-cereals: Amaranth, chia, goosefoot, knotweed, little barley, maize (corn), maygrass, quinoa, sunflower and wild rice. 

Legumes & nuts: American chestnut, black walnut, Brazil nut, cashew, common beans (green, black, pinto, navy, etc.), hickory, lima beans, peanut, pecan, scarlet runner beans and tepary bean 

Roots & tubers: Arrachacha, arrowroot, camas root, cassava, hopniss, jicama, leren, mashua, oca, potatoes,  sunroot, sweet potato and yacón 

 Fruits: Acai, avocado, blueberry, chayote, cherimoya, cranberry, feijoa, guava, huckleberry, papaya, passionfruit, peppers, persimmon, pineapple, prickly pear, raspberry, squash,  strawberry, tomato and tomatillo 

Spices, beverages & flavours: Achiote, chicle, chocolate, coca, maple, tobacco,  vanilla and yerba mate 

 The Andes was where the earliest American crops (e.g. potatoes (Solanum spp.) were domesticated, about 10,000 years ago. Corn (Zea mays) and squash (Cucurbita spp.) domestication began in Central America 8,700 years ago and beans (Phaseolus spp.) shortly after. In the eastern U.S., agriculture was being practiced 3,800 years ago. 

Crops that were part of the “Eastern Agricultural Complex” in the southeastern U.S. included a variety of nutritious seed plants such as sunflower (Helianthus annuus), goosefoot (Chenopodium berlandieri), bottle gourd (Lagenaria siceraria), marshelder (Iva annua), little barley (Hordeum pusillum) and squash (Cucurbita pepo). Other domesticates that followed include ragweed (Ambrosia trifida), pigweed (Amaranthus spp.), and knotweed (Polygonum spp.).  After ~200 BCE  (before common era) corn, beans and squash from Mexico were brought to this region, and cold-tolerant varieties (e.g. Northern Flint) bred. The productivity of corn was so high that the traditional seed crops fell out of favour and were gradually abandoned. Sunflowers and squash are the only crop plants left from the original Eastern Agricultural Complex that are still grown today. The other species have largely reverted to their wild state. Some of these species are considered “weeds” in croplands today even though they are still edible. 

Most people are surprised to find out that Indigenous people were practicing agriculture in the Dakotas and Manitoba in the early 1400’s. In 1986, Manitoba Museum Curator Dr. Leigh Syms unearthed evidence that corn, beans, squash and sunflowers were being grown as far north as Lockport during that time (Learn more).  These three plants were traditionally grown close together, with the beans climbing up the corn stalks and the squash helping suppress weeds (Wilson 1987). Raising plants in this manner improved the fertility of the soil as beans harbour special bacteria that turn gaseous nitrogen into a form available to all plants (ammonium or nitrate). Together, these three plants were the foundation of a healthy, vegetarian Indigenous diet. Sunflowers, often called the fourth sister, were typically grown along the edges of Indigenous fields, and provided an additional source of fat and protein (Wilson 1987).  Climatic changes which resulted in a shorter growing season, and population losses due to diseases introduced after European contact in 1492, may have resulted in the abandonment of the cropland in Manitoba. 

After Europeans arrived in the Americas, crops from Eurasia (e.g. wheat, barley, oats) were brought here while American crop plants were transported to Africa, Asia and Europe; this process was known as the Columbian Exchange. Sometimes the new American foods were embraced readily (e.g. beans) but others were not, particularly those in the nightshade family (e.g. tomatoes, potatoes and peppers). In Europe, nightshade plants are mainly poisonous rather than edible, so people were suspicious of them. In France, people initially rejected the potato (they thought it caused leprosy) but King Louis the 16th was convinced by the agronomist Antoine Parmentier that it was a good food plant to grow. Apparently, Parmentier had potatoes planted in the Kings’ gardens and then set guards around them to prevent thefts (although the guards were told to accept bribes). This reverse psychology apparently worked and after some people got their hands on the potato, its cultivation spread. Many American crops are now an integral part of European, African and Asian food culture. However, introduction of these new foods did cause some problems. 

The knowledge of how to prepare American foods did not always accompany the food, possibly because Europeans of that time period were generally disdainful of Indigenous knowledge, customs and food culture. Unfortunately, this attitude ended up causing a lot of unnecessary deaths. 

People in warmer parts of Europe and Africa readily adopted corn because it was so much more productive than other crops. But after doing so, a strange new disease began affecting poor people who were relying mainly on corn for food. This disease is pellagra, a condition that causes dermatitis, diarrhea, dementia and eventually, after four or five years, death. Physicians were confused about this new diet-related disease because they noticed that even though Mexicans ate a lot of corn, they rarely got pellagra. The answer to this puzzle was in Indigenous food culture. Corn was often softened by soaking it in an alkaline solution. This softened corn, known as hominy, is then eaten as is, or dried and ground to make masa, the flour used to make tortillas and tamales, among other things. This process, known as nixtimilization, increases the bioavailability of niacin (vitamin B3) and tryptophan in corn. Pellagra is caused by a deficiency in niacin and tryptophan in the diet. In Europe, Asia, Africa and, even among poor, non-Indigenous people in the southern U.S. , people were just drying the corn, grinding it up and cooking it in dishes like cornbread or polenta. Eaten in this manner, with no other foods containing niacin in the diet, pellagra is the result. Another aspect of Indigenous food culture that was not taken to heart was the custom of eating corn with niacin-containing beans, resulting in a balanced diet. 

Racism, and the intellectual and cultural arrogance that accompanies it, has caused tremendous human suffering. Colonization and the discouragement of traditional Indigenous agricultural practices and cooking, resulted in the near loss of ancient varieties of crop plants such as quinoa, as well as the memory of how these foods should be grown and prepared. It is heartening to see Indigenous peoples embracing their gastronomic legacy by planting Three Sisters gardens, writing cookbooks featuring pre-colonial foods (e.g. The Sioux Chef’s Indigenous Kitchen, Cooking with the Wolfman, and tawâw) and opening innovative restaurants (e.g. Ishkode Indigenous Pop-up ). Part of reconciliation is simply accepting that Indigenous culture is valuable. Another part is supporting the efforts of Indigenous peoples in keeping their culture alive. Food has a way of bringing people together so maybe the path forward is to sit down and share a meal together. 

Reference 

Wilson, G. 1987. Buffalo Bird Woman’s Garden: Agriculture of the Hidatsa Indians. Minnesota Historical Society Press, MN. 

Plants with fruits that ripen late in the year often rely on flocks of migratory birds for dispersal. Birds are particularly good seed dispersers because they lack teeth, typically swallowing fruits whole. In bird stomachs, the fleshy part of the fruit is digested but the tough seeds usually excreted intact. In fact, the seeds of many plants need to pass through the guts of animals before they will even germinate. However, some fruits are toxic to mammals (like rodents) but not birds.  This is because mammals tend to chew the seeds as well as the fleshy parts, killing the baby plant. For that reason, berries that birds can eat are not always safe for people!  Therefore, make sure you have correctly identified and researched the toxicity of any fruit before you eat it.

Just like all creatures, plants want to reproduce themselves. But they typically don’t want their offspring hanging around for too long, eating all the food in the fridge and drinking all the beer. But plant babies living on the land can’t move on their own, so how is an exasperated plant parent going to get their children to leave the nest?

Instead of producing swimming babies like algae do, the very first land plants produced special structures called spores. These spores, which grow into tiny plants, are small enough to be carried away easily by the wind, just like dust. For about 80 million years or so, the only plants on land were species that produced spores: club mosses, horsetails, ferns and mosses.

About 390 million years ago in the mid-Devonian, a new group of plants evolved that were capable of growing very quickly. They are known as the seed plants, and they have dominated life on land for many millions of years. But what exactly is a seed anyway and how is it different from a spore? A spore consists of only one cell; it’s basically a naked baby. For that reason, spore-producing plants aren’t very good parents; they just boot out their kids with nothing to eat and no clothes on. A seed on the other hand consists of three things: a baby, a bottle to feed the baby and clothes to protect the baby.

What if a plant lives somewhere that isn’t very windy though? What do they do? Stay tuned for part 2 of “The Perils of Plant Parenthood” to find out.

During a reconnaissance trip in July, I found a nice specimen that was eroding out of the dunes and in all likelihood would soon die. After taking some pictures and making a few notes, we channelled our inner badgers and began digging it up. In the end we obtained an impressive 160 cm piece of root along with the flowering stems. Although there were more fine roots lower down, the part we dug up is longer than we can even fit in the case so we left them behind. Since the site was a bit of a mess afterwards, we filled in the hole and patted the dune back to its previous contours. I was happy that a heavy rain that evening obliterated all evidence that we were ever there. The plant is now being pickled by the Diorama and Collections Technician in our secret proprietary solution (even I don’t know what’s in it!) to keep it fresh-looking and bendy!  Eventually it will be painted and mounted in its permenent home next fall.

So what is happening with the old crested wheatgrass plant? Don’t worry, it will still be on display but reinterpreted for its role in soil stabilization during the Great Depression.

Water-saturated bogs and burning hot, cactus-covered sand dunes are not the kinds of habitats that you would normally expect to find near each other. But on a recent trip to Canadian Forces Base Shilo, I was surprised to find just that!

In July, I was able to visit this restricted area to collect plants as part of a research project. We went to a part of the base that I have never been to before: Sewell Lake. I was expecting the kind of vegetation that you typically find along a prairie wetland: cattails, sedges and bulrushes. What I discovered was an area that looked more like a bog in the middle of the boreal forest. Thick mats of moss floated on top of water and threatened to swallow you up if you weren’t careful. Aquatic plants like water calla (Calla palustris), buckbean (Menyanthes trifoliata) and marsh cinquefoil (Comarum palustre) lined the shore. Even pitcherplants (Sarracenia purpurea) have been found in the deepest areas of the bog. Turtles swam in the water and all sorts of amazing insects were everywhere. It was truly unusual and a biologists’ delight.

So, on the one side there were plants that were adapted to dealing with an excess of water and on the other plants that dealt with an almost complete lack of it. So how do plants deal with these conditions? They possess completely different internal structures. In wet habitats, the biggest danger to plants is a lack of oxygen. You’re probably puzzled. Don’t plants need carbon dioxide? Well yes they need carbon dioxide for photosynthesis, which occurs mainly in the leaves, but they also need oxygen to break down the sugars they create to obtain energy for growth. This isn’t a problem for leaves and roots living in soil with lots of air pockets but it is a problem in water-saturated soils. To get oxygen to the roots, many aquatic plants have special tissue called aerenchyma–tissue with big air tubes in it–which functions a bit like a snorkel. The plant moves oxygen from the holes in their leaves, called stomata, all the way through these tubes to the roots. Problem solved! Regular dryland plants don’t have aerenchyma, which is why over-watering your houseplants can kill them; they basically suffocate.

In contrast, for plants in dry habitats like sand dunes, obtaining and retaining water is the problem. To obtain water they either grow roots deep enough to reach the water table, or absorb water quickly when it does rain by growing extra root hairs. To prevent water loss, they may possess thick “skin” that prevents evaporation; cacti are a good example of this. As well, they can prevent evaporation of their water by keeping their air holes (stomata) closed during the heat of the day, opening them to obtain gases at times when it isn’t so hot.

The structural uniqueness of plants is not always appreciated, recognized or understood by non-botanists. But really the difference between plants in bogs and sand dunes is like the difference between a fish and a camel!

Surprising to many people is the fact that a wide diversity of flies are pollinators. In fact they are second in importance to bees (take that butterflies!). Flies tend to like open (not tubular) flowers that are white or yellow. Flower flies (Syrphidae) often look similar to bees with yellow or orange and black stripes while bee flies (Bombyliidae) look like tiny pussy willow catkins with wings. Soldier (Stratiomyiidae) and blow flies (Calliphoridae) are often bright green in colour and not very hairy, while parasitic (Tachinidae) and Muscid (Muscidae) flies look very similar to house flies with black or grey bodies and long, coarse hairs.

The key ways to tell these insects apart though are:

• Two wings only;
• No waist;
• Large eyes near the front of the head;
• Short, club-like antennae;
• Unbranched hairs, if any;
• No pollen-carrying structures;
• Straight short or long tongues.

Great web pages with image of pollinators can be found at BugGuide, here, and Xerces Society, here.

Happy pollinator watching!