The unique alder thicket
September 23, 2001

In the fall many first graders visit Woodland Dunes and take part in our Cottonwood Trail Program, where they learn about birds, trees, deer, brush piles any many other autumn delights.

At one station we introduce children to the art of "groking"---experiencing nature using their senses other than sight. The focus of this exercise is a special shrub, the Speckled Alder.

The children learn that although they may be the same species, the individual shrubs in a thicket are all unique, just as we are.

We hope, too, that they gain some appreciation for this interesting species.

Speckled Alders are an important component of the northern forest and are one of the nine species found in the U.S.

They are shrubs (relatively small woody plants with multiple stems) of wet areas having slow moving water, both in streams and through the soil.

Their stems have a speckled appearance, being dotted with lenticels; small pores which allow air to enter the plant.

These lenticels help alders to grow in soils saturated with water. Alders are able o take nitrogen from the atmosphere and chemically "fix' or capture it.

This is done with the aid of bacteria present in nodules in the plant's roots---a mutually beneficial arrangement. As the alders' abundant leaves are shed in the fall, the nitrogen and other nutrients enrich the soil.

This aids them in their role as colorizers---they are often pioneers establishing cover quickly on recently glaciated or deforested areas. Their growth sets the stage for other plants to make their homes, and the community they create is referred to as an alder thicket, a common habitat along lakes and streams in the north.

The southern counterpart is shrub-carr, dominated by dogwoods and willows.

Because we lie within the tension zone, which bisects Wisconsin, both shrub communities are present at Woodland dunes, sometimes adjacent to each other.

Speckled alders are interesting, too, in their reproduction. The plants are monoecius, meaning they bear separate male and female flowers on the same plant.

The clusters of flowers are in catkins, which remain on the plant much of the year. The male catkin is cylindrical and drooping, and the female is round and upright, resembling a miniature pine cone.

The seeds are small and have woody or papery wings. Alders also send out new shoots from underground stems, and aerial branches coming in contact with soil can root themselves thus expanding the colony.

Anyone fond of stream fishing for trout in the north is familiar with alder thickets, and can appreciate the value of their dense cover for wildlife (despite the difficulties they pose for the fisherman!).

This may be the greatest value to wildlife, as they are only moderately consumed as food. Grouse feed on the buds, finches on the seeds, and beaver, hares, deer and moose browse the branches.

An excellent place to view a northern alder thicket is on the Cattail Trail at Woodland Dunes.

The boardwalk winds through a thicket, north of our headquarters, where one can see the alders up close, along with many plants that grow with them. The trail is short and easy, and makes a lovely stroll on these beautiful autumn days.