Sugar Maple
| Scientific Name | Acer saccharum |
| Survival Strategy | Freeze-tolerance |
| Conservation status | Least Concern |
Spring
When daytime temperatures of the wood reach around 40 degrees, the tree releases the enzyme amylase to convert starches into sugars. Amylase is the same enzyme that you have in your saliva to help digest starches.
Warm daytime temperatures cause the gasses (CO2) inside the tree’s plumbing system to expand, creating pressure inside the trunk. This pressure pushes sap up from the roots (and into the sap buckets). The freezing temperatures at night cause these same gasses to contract, creating a vacuum that sucks more water up from the roots. If you can picture how a turkey baster works, you get the main idea.
Summer
Photosynthesis takes place in the leaves to produce sugar (glucose). The sugar is converted to starch and is stored in ray cells within the tree.
Autumn
The four pigments that give sugar maple leaves their color are Chlorophyll (green), Xanthophyll (yellow), Carotene (orange), and Anthocyanin (red). Triggered by cooler and shorter days, the leaves stop their chlorophyll production, and the green pigment fades. The red, orange and yellow pigments now take center stage.
Winter
Sugar maple trees remain dormant until daytime temperatures rise above freezing.
Physiology
Surviving Winter: Supercooling
Sugar maples take advantage of water’s ability to supercool. When cooled slowly, with no dust particles to serve as nuclei for ice crystals, pure water will remain a liquid at temperatures low as about -40 degrees Fahrenheit (Which is also -40 Celsius; math is so cool!).
Surviving Winter: Antifreeze
Because dissolved sugar freezes at a much lower temperature than pure water, the sugars in maple sap are antifreeze which prevents the plant’s cells from exploding.
Surviving Winter: Dehydration
Sugar maples can move almost all water from inside their cells to the spaces between the cells where ice crystals are less harmful.
The Dangers of Spring
Although the sugar maple can survive the harsh cold of winter, a late spring freeze can damage the newly rehydrated cells that have lost their cold-hardiness in anticipation of warmer weather
Nutrients
Trees Store Carbon
Sugar maples, like all green plants, use photosynthesis to make sugar (glucose). The chloroplasts use the energy from sunlight in the leaves to convert carbon dioxide and water into glucose and oxygen. Most of a tree’s mass comes from carbon taken out of the atmosphere through thousands of tiny openings in the leaves called stomata, and this carbon is stored until the tree decomposes or burns.
Nitrogen, Phosphorus, Calcium and Potassium
Sugar maples rely on their roots to bring water and nutrients to the rest of the tree. Water moves up through the xylem to replace water lost through transpiration. Nitrogen is vital for the growth of leaves and twigs, and it also increases the sweetness of the sap. Phosphorus plays a role in photosynthesis, energy transfer (ATP), and genetics (DNA). Calcium promotes strong trunks and branches. Potassium is essential for maintaining a proper water balance in cells.
Lifespan and Mortality
Sugar maple can survive for 300 to 400 years.
Sugar maples are a food source for white-tailed deer, red and gray squirrel, cottontail rabbit, porcupine, mice, and various birds.
Insect pests of sugar maple include the forest tent caterpillar and the gypsy moth. Fungal diseases such as Eutypella canker can severely damage the trunks of maples.
Climate Vulnerability
Deep snow prevents root damage caused by increased frost depth. Tree roots damaged by freezing soil cannot take up water and nutrients as well as healthy roots. A recent study suggested maple trees would grow about 40 percent slower with a reduced snowpack. The range of sugar maple in North America is projected to move north in response to global climate change.
Never stop learning
First Nations: The Ojibwe people have made maple sugar for centuries.
Invasive species: A study suggests earthworms are eating up humus that covers the forest floor. This loss of the nutrient-rich humus is causing sugar maples to die back. No earthworms are native to the Upper Midwest.
Aerodynamics: The winged fruit of the maple is called a samara, but every child knows them as helicopters.
Biomimicry: Improvements in the design of wind turbine cones were made by mimicking the angle of maple samara blades (coning angle) as they fall from the trees.
References
| Sugar Maples Beat the Cold | The Outside Story https://northernwoodlands.org/outside_story/article/sugar-maples-beat-the-cold |
| Reinmann, AB, Susser, JR, Demaria, EMC, Templer, PH. Declines in northern forest tree growth following snowpack decline and soil freezing. Glob Change Biol. 2019; 25: 420– 430. https://doi.org/10.1111/gcb.1442 |
| Sugar Maples and Climate Change — Paleontological Research Institution https://www.priweb.org/science-education-programs-and-resources/sugar-maples-and-climate-change |
| Redix, Erik. “Maple Sugaring and the Ojibwe.” MNopedia, Minnesota Historical Society. http://www.mnopedia.org/thing/maple-sugaring-and-ojibwe (accessed November 1, 2021). |
| Redix, Erik. “Maple Sugaring and the Ojibwe.” MNopedia, Minnesota Historical Society. http://www.mnopedia.org/thing/maple-sugaring-and-ojibwe (accessed November 1, 2021). |
| Wild, A.D., and Yanai, R.D. 2015. “Soil nutrients affects sweetness of sugar maple sap.” Forest Ecology and Management. 341: 30-36. DOI: 10.1016/j.foreco.2014.12.022 |
| Sugaring | Climate Wisconsin https://wisconsin.pbslearningmedia.org/resource/ecb10.sci.ess.watcyc.sugaring/climate-wisconsin-sugaring/ |
| Why Do Leaves Change Color? https://scijinks.gov/leaves-color/ |
| Houston, David R.; Allen, Douglas C.; Lachance, Denis. 1990. Sugarbush management: a guide to maintaining tree health. Gen. Tech. Rep. NE-129. Broomall, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 55p. https://doi.org/10.2737/NE-GTR-129 |
| Retrofit for Wind Turbines Inspired by the Kingfisher and Maple Seeds https://asknature.org/innovation/energy-saving-retrofit-for-wind-turbines-inspired-by-the-kingfisher-and-maple-seeds/ |