5.10. SR 12-20-2004 - Laserfiche WebLink

Home Browse Search

the deciduous forest-woodland zone and locally in the prairie zone near the ecotone between the prairie zone and the deciduous forest-woodland zone Oak woodland is floristically and structurally intermediate between oak savanna and oak forest, with a patchy tree canopy and an understory dominated by shrubs and tree saplings. The principal species in the tree canopy are bur oak, northern pin oak, white oak, and northern red oak. Aspens may form up to 70% of the tree canopy cover. The brush layer ranges in density from sparse (with 10-30% cover), to an impenetrable thicket. It is often especially dense in openings between clumps or groves of trees. Most of the floristic diversity in the community exists in the brush layer, which most commonly is composed of blackberries and raspberries (Rubus spp.), gooseberries (Ribes spp.), dogwoods (Comus spp.), cherries (Prunus spp.), hazelnuts (Corylus spp.), prickly ashes (Zanthoxylum americanum), and sprouts of oak (Quercus spp.) and quaking aspen. Prairie vegetation, if present, occurs only in small openings in the tree or shrub canopy. Except in these scattered prairie openings, the herbaceous layer is sparse and floristically poor. It is usually composed of woodland species capable of surviving in the dense shade beneath the brush layer. Oak woodland-brushland is a fire-maintained community. It is most common on rich sites where trees and shrubs grow well but where recurrent fires prevent the formation of true forest. Historically, Oak Woodland-Brushland was probably one of the most extensive community types in Minnesota, comprising much of the vegetation described as oak barrens, brushland, and thickets by the early surveyors. The fires that maintained oak woodland-brushland usually started on nearby prairies. Following the conversion of these prairies to agricultural land, oak woodland-brushland burned less frequently and rapidly succeeded to oak forest. Oak woodland-brushland is defined broadly enough here to include also communities in which the predominant cover is oak brush or oak-aspen brush (that originated following fire or limited human disturbance) instead of a well-developed tree canopy. There are four geographic sections of oak woodland-brush land in Minnesota. These sections may be modified in the future as more information becomes available. In southeastern and central Minnesota, oak woodland-brush land is present on southwest-facing slopes on the blufflands and on outwash terraces of the Mississippi River and its tributaries. It generally occurs on more gentle slopes than bluff prairie or on lower slopes below bluff prairies. Bur oaks (Quercus macrocarpa) are common canopy dominants and northern red oaks are common associates. Northern pin oaks, City of Elk River, MN - Natural Resouce Inventory BOllestroo Natural Resources, September 2004 24