Anoka Ecosystems:
Alder Swamp
Alder swamps are seasonally flooded communities on organic peat and muck of varying nutrient availability. They typically have more than 70% tall shrub cover, of which alder, most commonly speckled alder, is the dominant species.
This community has a similar species composition to the willow swamp but has a greater percentage of canopy cover by tall shrubs. Though alders are the most common, other tall shrubs found in these ecosystems include a mix of willows, bog birch, poison sumac or alder buckthorn. The shrub layer grows to be incredibly thick with small openings containing a diverse mixture of sedges. The ground layer is especially diverse and contains wetland forbs such as spotted touch-me-not, northern marsh fern, dwarf raspberry, and royal fern, as well as marsh plants such as nodding beggar-ticks, mad-dog skullcap, and cattails. Patches of trees may grow throughout the community consisting of tamaracks, black ashes and paper birches.
Alder Swamps have historically been common on the Anoka sandplain and the Grantsburg sublobe till plain in shallow wetlands. Though neighboring counties still have these ecosystems, alder swamps have nearly disappeared from Anoka County. These ecosystems were lost primarily due to the draining of wetlands and conversion to agricultural land in the early twentieth century. Today, the alder swamps that are remaining are commonly infested with the very aggressive invasive shrub alder buckthorn, which can outcompete many of the native species.
Sources:
"Minnesota Land Cover Classification System: User Manual." Version 5.3 Minnesota Department of Natural Resources, Central Region, 2004.
"Minnesota's Native Vegetation: A Key to Natural Communities" Version 1.5 Minnesota Department of Natural Resources, Natural Heritage Program, 1993.
Wovcha, D, Delaney, B, Nordquist, G. Minnesota's St. Croix River Valley and Anoka Sandplain: A Guide to Native Habitats Minneapolis: University of Minnesota, 1995.
