Thaw

A March thaw at Ryerson Woods.
Snow melt at Ryerson Woods.

by Luke Buckardt

Although it seems that we may never escape this winter’s grasp, spring is near.  This transition into a warmer season is driven by a lengthening day and more direct sunlight.  Every year, spring brings about a plethora of changes to our local environment.  We think of ephemeral flowers and migrating songbirds, but what happens to the environment during the early stages of the transition?  The impending thaw is something we can look forward to, but it also brings many necessary changes to Ryerson Woods.

When the first thaw occurs, the ground is usually still frozen on the surface, which creates an impermeable surface.  The water needs somewhere to go, so it acts as it would during a heavy rain.  Water is affected by gravity, and it will go to the lowest point possible.  In many areas, including our own corner of Lake County, this is in a river or stream.

The Des Plaines River overflowed its banks last spring.
The Des Plaines River overflowed its banks last spring.

The Des Plaines River breaks out of its banks and causes flooding, which varies from year to year depending on many factors.  These include snow totals, the speed of the melt, and any additional precipitation that occurs during a thaw.  Flooding is considered a nuisance for many reasons.  It affects homeowners along the river and can close streets.  However, the annual spring flood plays an essential part in developing and sustaining a healthy ecosystem.  Each year, the flood alters the river landscape, rearranging downed trees and other debris.  This constant change keeps habitat available for many species.  This extra material can accumulate in the river, making necessary habitat for native fish and invertebrate species.  It can also pile up along the river, creating protection for other native fauna.   Debris carried by floods can alter the entire hydrology of a river or stream.

Snow melt and river flooding creates vernal pools at Ryerson Woods.
Snow melt and river flooding creates vernal pools at Ryerson Woods.

Floodwaters often creep into the riparian areas alongside the river, which adds many benefits to a habitat.  When the water is out of its banks, it often slows down due to increased vegetation and a less channeled path.  When the water slows, it deposits the suspended sediments.  These are often very nutrient-rich.  Once the water recedes, the sediment is left along the banks and regenerates the nutrient levels along the river.  This leads to an increase in productivity for both plants and animals that are found within a riparian zone.

Finally, flooding benefits the diversification of plants along a river.  The floods transport seeds down river.  This increases diversity within a plant community, but it also perpetuates the success of many species.  The river can carry seeds or pollen to new areas where they have not been previously.  This aids in the genetic diversification of a plant species, which ultimately strengthens that plants ability to survive.

Blue-spotted salamander.  © Scott Albert; www.ilherps.com
Blue-spotted salamander.
© Scott Albert; www.ilherps.com

Once the thaw begins, it also creates another important habitat for many species in Lake County.  When water cannot travel to a stream or river, it pools in low-lying areas.  These temporary vernal pools are an extremely important wetland for many plant and animal species.  Because they are often void of predators, these ponds attract many species of amphibian.  Frogs and salamanders live close to vernal ponds year round, but during the spring thaw, they flock to the area for mating purposes.  They attract mating partners in the water, mate, and lay eggs.  Because these areas are void of constant aquatic predation, they are perfect for perpetuating a species.  Chorus frogs, spring peepers, and wood frogs all use these vernal ponds for mating.   The blue-spotted salamander frequents vernal ponds of Lake County in order to mate and lay eggs.  These habitats are necessary for some of the county’s most endangered species, particularly the tiger salamander.  For just a few weeks out of the year, these pools become extremely busy areas in the forest.

wood frog by Luke Buckardt
Spring peepers, a tiny species of frog, are often referred to as the “harbinger of spring.” As soon as things thaw in the spring, they leave the trees to converge upon vernal pools where they sing to attract a mate and breed. Photo by Luke Buckardt.

The spring thaw is a wonderful thing for all the inhabitants of Lake County.  Although it can cause some temporary issues for people, the thaw is essential in the perpetuation of many species of plants and animals.  Now all we can do is wait and enjoy the thaw when it comes.  It is just the first step in a very exciting transitional time for the local environment.

This blog post was written by Luke Buckardt, who assists Brushwood Center with social media.  Luke graduated from Northland College in 2012 with a degree in biology.  He grew up in Riverwoods and has roamed Ryerson Woods since he was young, knowing the preserve intimately.

Cold Combatants of Lake County

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Ryerson Woods in winter.

by Luke Buckardt

This winter has been brutally cold.  With an average temperature of 19.4 degrees F, it is the fourth coldest on the record books here in the Chicago area.  Schools have been cancelled and people have been warned to stay inside on days with negative wind chills.  But what happens to the rest of the wintery world when temperatures dip to such lows?  The plants and animals in Ryerson also have to cope with these temperatures, but have no relief.  Both the plants and animals use incredible adaptations in order to make it through the long winter.

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Bur oak by Cemx86 from Wikimedia Commons.

Many of the trees in Ryerson are deciduous, which literally translates to  “tending to fall off.”  Tree species, such as the Bur oak and the Sugar maple, go through a yearly change in order to prepare for winter.  When light conditions shorten in the fall, trees begin to go through abscission, or loss their leaves.  This assists the tree in two major areas.  Primarily, it conserves water.  Leaves are where the tree transpires, or gathers CO2 for the transformation into oxygen.  However, water is lost through the stoma, or pores in the underside of the leaf, during this process.  In order to conserve water during the winter, deciduous trees drop these leaves.  They also drop their leaves in order to conserve energy.  It is not efficient for many temperate tree species to continue maintaining leaves throughout the winter, as the leaves do not receive ample sunlight.  The tree would be using excess energy to keep their leaves throughout the winter, so it sheds them when light conditions begin to deteriorate.

Coniferous trees handle the winter through a different method that does not involve dropping their specialized leaves, called needles.  Needles differ from deciduous leaves in two major areas.  First, they continually transpire throughout the year.  Needles have a waxy cuticle, or outer covering, that limits the amount of water that is lost during the process.  Their stoma are sunken deeper into the plant tissue, which also helps retain water.  Conifers are also shaped differently in order to prevent damage from snow and ice.  Pines, firs and cedars have a conic shape, with a thin top and wider base.  This shape does not allow for snow to build up, which can potentially break branches, endangering the tree.

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White-tailed deer at Ryerson Woods.

Animals must also endure the cold winters in the Chicago land area, and have many specialized physiologic adaptations.  One of the most prevalent animals in Lake County is the ubiquitous White-tailed deer.  They have a few adaptations that allow for them to maintain internal temperatures when the thermometer dips below zero.  First, they, like other mammals, abide by Bergmann’s rule.  It states that as a mammalian species ranges farther north, they are larger in colder climates.  By increasing size, they are better “designed” for colder temperatures.  They have a greater mass to surface ratio and therefore have an easier time retaining heat.  Deer also have unique fur that helps them stay warm.  Their fur has multiple layers, which help trap heat against their skin.  White-tailed deer have guard hairs that are exposed to the elements.  The outer hairs are hollow in order to trap air, which is used to insulate the animal.  When it is extremely cold, deer bed down in deep snow.  Snow is about 90 percent air, and acts as a wonderful insulator.

Another amazing animal is the Wood frog.  Being only 2 inches long can be tricky when temperatures get below freezing, but they enlist an incredible method, which helps them endure such temperatures, they freeze. Wood frogs hibernate in the top layers of soil.  During the fall, the wood frog begins to store urea within its tissue.  While in hibernation, they convert glycogen into glucose.  Both of these help break up internal ice formation within the blood and other fluids.  They can withstand up to 65% of their tissue freezing and still survive through hibernation.

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Southern Flying Squirrel by MimiMiaPhotography from Wikimedia Commons.

Animals also enlist behavioral adaptations to combat the chilling temperatures.  Birds, when it gets particularly cold, maintain their body temperature by manipulating their feathers.  Birds at feeders are often seen “puffed up” during the winter months.  They are actually expanding their feathers and trapping air for increased insulation.  Birds also enact thermogenesis to warm themselves.  Although it is not as apparent as with humans, birds shiver to maintain an appropriate body temperature for survival.  Certain animals will change their social behavior to perpetuate survival as well.  The Southern flying squirrel, a local Lake County resident, is primarily a loner.  Throughout most of the year, they live by themselves.  However, when temperatures become dangerously low, they huddle together in a collective den.  The added bodies maintain a more constant temperature throughout the whole den, allowing for more individuals to survive.

While we are buried under our comforters in our toasty houses, the world around us continues to endure and in many cases thrive during these frigid days.  Make sure to look outside to enjoy the nature around us, and to find many more adaptations that keep the plants and animals of Lake County going on these chilly days.

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Winter sunset at Ryerson Woods.