The first frosts of autumn trigger a wave of changes in the natural world. Usually arriving in late September, the first frost of the season serves as a final reminder of the coming cold weather. Since our native plants are already ideally adapted for our climate, they are not taken by surprise by a frost. For weeks, they have been gradually slowing down their metabolism, going through a process of senescence, with the loss of bright green leaf color, the weakening of the connection between leaf and stem on woody plants, and the absence of any new shoot and stem growth. The frost just completes what these native plants started naturally.
For native grasses, the post-frost period often leads to a period of particularly lovely fall color. For deciduous trees and shrubs, the frost ultimately leads to the dropping of leaves from the plant. The period of time after the first hard frost is a good time for separating native plants from exotic plants. Many plants which do not really belong in western Minnesota do not go through a period of senescence before the frost; the frost catches them with green and growing leaves and stems. During the period after a hard frost, these exotic plants stand out with an abundance of green dead leaves still attached to the plant. Look at a tree grove in late October; the exotic and highly undesirable European buckthorn will be easily distinguished from all other shrubs because it will still have green leaves attached.
Like native plants, our native wildlife is generally in tune with the seasons. Bird migrations are triggered by a combination of factors, varying with species, but often including day length, temperature, and weather fronts. Many of the earliest migrants, certain shorebirds, swallows, hawks, and teal for example, have already left by the time of the first frost. For many other species, the period around the first frost involves a frenzy of feeding followed by the intense October migration period. The last of the migrants, the late ducks and geese, aren't troubled by a little frost. They generally stay until the true cold of winter freezes the last lakes and winter snows cover their feeding areas, finally driving them south.
Throughout September, many reptiles and amphibians have been anticipating the frost and the winter to follow. Frogs and salamanders are on the move every day, moving from site to site. Some are moving from water to upland sites where they will hibernate for the winter. Others move from small shallow marshes to deeper water where they will remain in a barely active torpor through the winter, deep in the water. American toads burrow into the soil to spend the winter just below the frost line. In the spring, during mid-April tree planting time, it is not uncommon to unearth an exceedingly sluggish toad still resting in the soil, just a few inches from the surface with the warming temperatures.
Reptiles such as turtles, lizards, and snakes are especially active and visible in September too. They spend warm sunny days basking, trying to stay warm during the diminishing days. Many snakes hibernate in communal sites with dozens, even hundreds of other snakes. These communal wintering sites are called hibernacula, and the snakes are moving towards them or towards other, solitary hibernation sites. Turtles, like many frogs, usually head to the bottom of deeper marshes to spend the winter in slow motion.
For a few species, fall is not a time to hunker down. Instead, it is a time to glow, to flower, to reproduce. Many species of gentian, a deeply blue and deeply beautiful prairie plant, don't begin to bloom until the time of the first frost when other flowers are scarce. The gentian flowers thus become wildly attractive to the remaining pollinators. Closed gentian has an even more elaborate scheme; closed gentian flowers have petals which remain in a perpetual closed-bud stage. Large bodied bumble bees are able to force their way into the closed gentian flower, reaping a rich reward for the bee and increasing the chance that the pollen from one closed gentian flower will only be brought to another closed gentian flower.
The time of the first frost is a glorious time for people to enjoy the wonders of nature. Moderate temperatures, few troublesome insects, a particularly glowing quality to the light, and the wonderful sights, smells, and sounds of autumn combine to make for a particularly rich outdoor experience. We too need to be prompted by the first frost to get outside, enjoy nature, and prepare for the coming winter.
Featured WPA: Welker Waterfowl Production Area, Swift County
Welker WPA is a fine, 244-acre unit in extreme northern Swift County, straight north of Benson. There is a large, 121-acre shallow marsh which dominates the unit, with bays and lobes going in various directions. There are several smaller marshes on the WPA too. Most of the upland areas are native prairie and Welker is a likely area to search for gentians or other late blooming prairie flowers. The large, cattail dominated marsh makes for superb pheasant cover in late fall and winter, making Welker WPA a good late season pheasant hunting spot.
For a map of Welker WPA or any other WPA in the Morris district, go to http://midwest.fws.gov/ Morris.