Autumn is doubtlessly called “Fall” because it is when trees drop their leaves, and those leaves turn from green to shades of red, yellow or brown prior to their fall. This colorful display of foliage begins in late September and continues throughout October – by November, the show is usually over.
Many of those colors have actually been present in leaves during the entire growing season but masked by chlorophyll, the light-absorbing green pigment that is essential for photosynthesis. When days shorten in the fall, photosynthesis slows and eventually ceases causing deciduous trees to stop making chlorophyll, allowing other pigments in leaves to become visible. Carotenoids are the pigments responsible for yellows, oranges and browns; anthocyanins create reds and purples; and mixes of the two pigments result in bronzes and deeper shades of orange.
Location, weather, and type of tree determine when this color change takes place. Cooler locations are where the transition begins, causing trees at higher elevations to change color first. However, timing can change from year to year, influenced by temperature and rainfall. Drought causes less brilliant colors and trees in dry years drop their leaves earlier. At any one location, fall colors typically follow a sequence determined by tree species. Ashes are known for their early color change. Aspens, cottonwoods and maples often follow, and oaks change color later. Evergreens, of course, don’t change color or drop their needles, causing the dark greens of the Black Hills’ pines to contrast vividly with deciduous trees in October.
LeafQuest provides handy online guides for fall foliage viewing across North America, including three popular routes in South Dakota. Sugar maples are known for their fall colors and a good location for enjoying their fall foliage is Sica Hollow State Park in northeastern South Dakota. Cottonwoods are large trees that have brilliant yellow leaves in the fall and often line waterways. The cottonwoods along Cascade Springs at the Conservancy’s Whitney Preserve in the southern Black Hills can be impressive in October. Conservancy preserves that protect grasslands in the Prairie Coteau region of eastern South Dakota are also colorful in October: asters may still be in flower and the grasses that were green during summer turn russet in the fall. Consider visiting the Conservancy’s Sioux Prairie, Aurora Prairie, or Makoce Washte prairie at this time of year.
Fall foliage isn’t the only impressive natural event in South Dakota during October. Waterfowl migrate through the state in large numbers and there are many good locations for seeing these birds. Ducks and geese are excellent subjects for beginning birders since they often are easily seen on open water (unlike small songbirds that can be hidden behind leaves) and most have distinctive field marks and behaviors that can be quickly recognized with practice. Grab a field guide and binoculars and look for waterfowl at wetlands such as Sand Lake National Wildlife Refuge. The Wildlife Drive Auto Route closes for the season at dusk on October 14th, but the Migration Observation Area remains open and is a good spot for watching the thousands of snow geese that visit the refuge in the fall. Sandhill cranes are another impressive bird that migrates through the state in the fall; listen for their bugling calls then look for their flocks often flying past high overhead.September 28, 2012
Bill Allen is a freelance writer who resides in St. Louis Park, Minnesota.