Anoka Ecosystems:
Oak Savanna
Historically, oak savannas were among the most common ecosystems within the region. Oak savannas are open, expansive ecosystems which feature less than 25% total tree coverage and an understory of grassy prairie vegetation. Commonly found vegetation in dry oak savannas include Bur oaks and northern pin oaks, which exist singly or in dense clumps, depending on soils and level of human disturbance. Oaks in the Anoka savannas are sometimes relatively small and stunted due to nutrient-poor sandy soils.
Associate shrubs which would be common in oak savannas include chokecherry, hazelnut, sand cherry, juneberry, and prairie willow. Grass and forb vegetation on oak savannas is similar to prairies in the area in that species diversity and composition depends on the soils and disturbance level of the site. Common prairie species in Anoka include lead plant, purple prairie clover, tough blazing-star, big bluestem, little bluestem, junegrass and many others.
Oak savanna was once a much more common habitat on the Anoka Sandplain. Today, however, there are few areas on the Anoka Sandplain with native savannas. This is due to several human-influenced changes. First, fire, which plays an important role in maintaining the ecosystem, has been largely suppressed. The openness of savannas have made this rare system an easy target for conversion to parkland, pasture, golf courses, and residential development. Also, areas that currently look like oak savannas, in actuality, are not true oak savannas because they no longer contain an understory of native prairie species. Remaining oak savannas in Anoka County exist in Bunker Hills Regional Park, Cedar Creek Natural History Area and Helen Allison Savanna Scientific and Natural Area.
Sources:
"Minnesota's Native Vegetation: A Key to Natural Communities"
Version 1.5 Minnesota Department of Natural Resources, Natural Heritage
Program, 1993.
Wovcha, D., B. Delaney, and G. Nordquist. Minnesota's St. Croix River Valley and Anoka Sandplain: A Guide to Native Habitats. Minneapolis: University of Minnesota Press. 1995.
