Olivia (00:11):

Welcome back to another episode of Naturally Speaking. My name is Olivia Bernier and today I'm going to be talking about sugar maples.

Olivia (00:19):

I'll discuss how sugar maples change throughout the season and the role they play in forest communities. Stay tuned! Sugar maples, the tree responsible for that liquid gold called maple syrup. These trees are important culturally and economically for their role in syrup production and their use in the timber industry. However, the importance of sugar maples goes way beyond their economic value. Not only are they important from a social standpoint, but they play an important role ecologically as well. Unfortunately, studies are revealing that sugar maples are in decline throughout the Northeast, including in the North Country. There are many factors contributing to sugar maple decline, including insects feeding on their leaves, disease, and drought. Climate change is also contributing to the issue. To help you understand why sugar maples are so important and why they're declining numbers are so concerning, I'm going to take you through how a sugar maple tree experiences the four seasons and the role they serve to the ecological community during each season.

Olivia (01:30):

But first, let's take a minute to identify a sugar maple. Sugar maple believes have five major points called lobes. Almost like a human hand. Between these lobes are smooth valleys called sinuses. The buds on a sugar maple are very pointy and dark brown in color. The bark on a sugar maple can look different depending on the age of the tree. On older trees it is brown and shaggy, but on younger trees it tends to be smoother. To learn more about ID'ing sugar maples, the Nature Up North website has a handy webpage, which you'll find linked below the podcast.

Olivia (02:09):

Now onto the seasons. In the spring sugar maples go through a period of growth and development. This is a time when buds begin to open up into leaves. A process known as leaf out. Generally leaf out is cued to begin by exposure to warm temperatures and sunlight after the previous winter. Even if all of the trees in a geographic area are exposed to the same environmental cues, there can be variation in the timing of leaf emergence between species. Sugar maples tend to leaf out on the earlier side. However, climate change is causing warm spring temperatures to arrive earlier and earlier in the calendar year, meaning leaf out is slowly shifting to be earlier for all species. As I'm sure many of you are familiar with, sugar maples are often tapped in the spring in the process of making maple syrup.

Olivia (03:05):

Does that boiling sap sound sound familiar? Traditional tapping techniques with the bucket hanging from a tap, do not cause much damage to the tree. The amount of sap that leaves the tree via the tap is not enough to hinder the growth rate and the scar tissue that builds around the tap hole does not greatly impact the overall health of the tree. However, some new tapping technologies have the potential to cause more damage. There are now vacuum pumps that use pressure to suck the sap out of the tree through a tubing system. This process can substantially increase syrup production because approximately two times the volume of sap can be collected from a tree that is vacuumed in comparison to traditional non pressurized, or only slightly pressurized form of sap collection. These newer methods don't impact the tap whole wounds. However because sap is where the tree stores a lot of its carbohydrates.

Olivia (04:04):

Harvesting excessive amounts of sap can slow the growth rate of the tree and be unsustainable for the tree's health in the long run. But don't worry, current research shows that you won't take enough sap to kill the tree and probably won't cause any significant harm either. By following standard tapping practices, you can enjoy your maple syrup guilt free. In the spring, sugar maples not only experience a lot of changes themselves, but they also play an important role in the forest ecosystem. For instance, they're an important food source for many animals. Red squirrels, a common species in the North Country, rely on sugar maple buds as a food source in the spring. Studies have shown that sugar maple buds can be essential for the survival of squirrel populations. In the summer as temperatures rise, sugar maples continue to grow and develop. During this time of growth, sugar, maple have resource requirements that allow them to thrive.

Olivia (05:08):

Nutritionally sugar maples require a range of nutrients, such as calcium and magnesium. When soils are deficient in magnesium or magnesium uptake through the roots is inhibited in some way, it can negatively impact chlorophyll production in the leaves, which in turn reduces photosynthesis capability and the ability to acquire and transport carbohydrates, which are necessary for growth. In addition to nutrients, sugar maples also require sufficient sunlight during this time to properly photosynthesize. Stephen Horsely, a member of US Forest Service said sugar maple is sensitive to both drought and excessive soil moisture. As you're probably familiar with North Country, summers can contain both droughts and periods of heavy rain. This provides an obstacle for the species to overcome in the summers and limits the areas where sugar maples are able to successfully grow. Another obstacle faced by sugar maples in the summertime is when animals, including some mammals and lots of insects, feed on the tree.

Olivia (06:17):

This is known as herbivory. A study published in 2010 conducted by Sean Thomas, Agnieszka Sztaba, and Sandy Smith, who worked for the University of Toronto, found that on average sugar maples lost 11.5% of their tissues on a yearly basis due to herbivory. Much of this herbivory was a result of insects feeding on the leaves found in the lower canopy. Insects that formed galls on the tree were also responsible for tissue damage. For individual trees faced with excessive herbivory, the loss of leaves can be damaging because it decreases the amount the tree is able to photosynthesize. However, it is important to recognize the role sugar maples play in their landscape. Many insects rely on sugar maples as the location to form a gall and successfully reproduce. Nutrients are very important for growth in the summer, but as temperatures begin to drop and fall arrives, nutrition becomes an important factor in determining how colorful the fall foliage will be.

Olivia (07:24):

You are probably familiar with the gorgeous hues that color the landscape during North Country autumns. Sugar maples typically contribute a bright orange hue. A study conducted by a collaboration of scientists who work for the US Forest Service and the University of Vermont looked at factors influencing foliage color expression. They found that "nitrogen concentration was the factor best associated with the timing and intensity of red coloration in our study." Fall foliage is a large tourist attraction and draws business to small communities, thus serving as an economy booster. However, the process of leaves changing color and dropping to the ground is not only an aesthetic event, valued by humans, but also important to the ecosystem. The process of leaves turning color and dropping from the tree is called senescence. Environmental cues, including temperature, nutrient deficiency and water availability are responsible for initiating senescence. The process of senescene involves the release of hormones, that cues cell division at the base of the leaf. After the leaf falls off, the wound is healed to avoid infection and water loss.

Olivia (08:45):

The leaf litter that accumulates on the forest floor during this time provides many species with habitat. For instance, a study conducted by Vanessa Fox, Charlotte Buehler, Chad Byers, and Summer Drake at DePaul University found that maple leaves tended to decompose slowly in, in comparison with the leaves of some other species of hardwood. The study found that the amount of leaf litter on the ground affected the numbers of ground nesting songbirds that nested in the area. Earthworms also consume leaf litter, and in the process assist with the decomposition of the leaves. As leaf litter, decomposes the nutrients found in the leaves are released back to the soil. This makes them available to be taken up by tree roots in the future. Thus continuing the nutrient cycle. After leaf senescence is complete, trees are ready to take on the harsh winter months of the North Country. The freezing temperatures and ample snow accumulation lead to sugar maples entering a period of dormancy where growth is suspended.

Olivia (09:51):

The decrease in temperature and the shortening days both play a role in leading the trees to enter dormancy. In the peak of winter, the trees may be totally unable to grow, a phase known as endodormancy. The buds on the tree are in a state where even a warm day during the winter won't trigger growth. This ensures that the buds remain closed for the entirety of the winter, thus keeping the and reproductive mechanisms inside the buds, safe from the cold conditions. The buds will only, open a process known as bud break, when they experience a lengthy period of warm conditions in the spring. This state of non-growth during the cold months is essential in trees' ability to survive winter. It means the tree does not require as much water during this time, which aligns with the scarcity of water in the winter months. Most precipitation falls as snow and moisture in the ground is usually frozen and unavailable to the tree. Because water is scarce in winter,

Olivia (10:52):

trees have developed mechanisms to prevent water loss from the tissues of the tree. This is a primary reason that hardwoods, including sugar maples, lose their leaves in the fall. Leaves have high surface area, which means water easily evaporates from them. Going through senescence, where leaves are dropped and the breaking point is sealed off prevents water from evaporating throughout the winter as the tree enters dormancy. To take a look at the bigger ecological picture during the winter months, sugar maples play a key role in the lives of whitetail deer. A study conducted by the University of Maine found that litter fall was an important food source for whitetail deer, as it offered both nutritional value and it tended to be palatable. Depending on snow depth, litter fall might be more or less accessible than other forms of food. If the snow pack fully covers litter fall, whitetail deer will browse on the buds and twigs of sugar maples and other trees.

Olivia (11:55):

Wow. Sugar maples really go through a lot during one year. And so many species and ecological processes depend on their presence. Next time you're enjoying maple syrup on your stack of pancakes or harvesting a sugar maple for firewood or lumber, remember how important these trees are. Do you want to help sugar Maples? You're in luck! Nature Up North has a citizen science project called Monitor My Maple, and you can participate. Monitor My Maple asks volunteers like you to select a sugar maple tree to follow through the seasons and record the dates of when the buds break, the leaves come out in the spring, when the fall colors emerge, and when leaves drop from the tree in the fall. This information is critical in understanding how the timing of these landmark events in a sugar maple seasonal cycle are changing in response to a changing climate. So thank you all for tuning in to another episode of Naturally Speaking, check out our other podcasts and engage with Nature Up North to learn more about the local environment by visiting our website, natureupnorth.org and following us on social media @natureupnorth on Instagram, Facebook and Twitter. Get up and get outdoors with Nature Up North!