Alder Thicketsor

Alder Thicketsor

Alder Thickets

We are surrounded by forests of alders — and thicksets. In fact, alders comprise as much as 30% of all hardwood tree species in temperate zones of the Northern Hemisphere and East Asia.This Ecological Landscape is a good place to maintain the alder thicket community because of its abundance and large amount of land under public ownership. Examples occur on federal, state, and county forests in this Ecological Landscape, such as Dailey's Marsh, Hunting River Alders, and Wildcat Springs (Langlade County); Sidney Creek Swamp (Marinette County); and Ruby Swamp (Chippewa County). Altered hydrology is an issue in some parts of this Ecological Landscape, especially from road construction and residential development. Invasives are not a large problem at present, but should be monitored.


Alder thicket is defined as having few trees and at least 50% cover of shrubs (>5 feet in height), of which alder contributes at least half of the relative shrub cover. Similar communities include shrub-carr, which also has at least 50% cover of shrubs, but has a greater diversity of shrubs, often at least 4 or 5 species that are co-dominant. While alder is often present in a shrub-carr (especially in northern Wisconsin), it comprises less than half of the relative shrub cover. Alder thickets often intergrade with northern sedge meadows; either community can constitute the dominant matrix community across hundreds of acres, with pockets of the non-matrix community embedded within. Alder thickets also border and intergrade with hardwood swamps (or aspen stands on wet ground), but can be differentiated by having, on average, <25% cover of trees.

Speckled alder (Alnus incana ssp. rugosa), also known as tag alder, gray alder, or hazel alder, is a member of the birch family, but it usually falls somewhere between a shrub and a tree (growing 10 to 25 feet tall). It is an often multi-stemmed deciduous plant that can form impressive and seemingly impenetrable thickets. It can grow via seed germination, root suckering (where new shoots grow up from the root system/rhizome), or layering (where a low branch that touches the ground forms new roots and detaches to form a new shrub) (Minnesota Wildflowers 2019). Because of these growing habits, an alder thicket usually consists of many individual plants that are actually clones of each other, much like aspen forests. As alder shrubs get older, new stems start to grow horizontally outward, creating the thicket formation. Younger stems are often brown, red, or gray with white lenticels (pores), while older stems are smooth and gray with white lenticels. (Source: ruffedgrousesociety.org)



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