Great Lakes Pine-Oak Barrens

These pine-oak barrens occur in the northern and western Great Lakes region. They occur on sandplains/outwash habitats, with droughty, infertile sand or loamy sands and frequent fires (every 5-30 years). Pinus banksiana, Pinus resinosa, Quercus ellipsoidalis, and Pinus strobus are common overstory dominants. Prairie species are common throughout much of the range of the type. Common shrub and ground cover species include Andropogon gerardii, Carex pensylvanica, Corylus americana, Schizachyrium scoparium, and Vaccinium angustifolium. Oak grubs may be common under frequent burning. Catastrophic burns may create open bracken grasslands.

These barrens occur on sandy outwash plains, glacial lakeplains, and broad riverine terraces. Soils are generally infertile, coarse-textured, and acidic sands and loamy sands. The landscape is flat to gently rolling.

Fire and droughty soil conditions maintain the characteristic open tree/shrub canopy and prairie-like understory of this system. The dry, relatively infertile soil limits the rate of tree growth, while periodic fires remove most tree regeneration and, less commonly, canopy trees. Fires are also necessary for regeneration of Pinus banksiana. Sites with finer-textured and more fertile soils need greater fire frequency, while sites with coarser-textured, less fertile soils need less frequent fires to maintain this system. The historical fire-return interval is 5-20 years (Landfire 2007a). Fire-return intervals of 20-30 years result in abundant woody cover. Occasional frost during the growing season, sustained drought, and catastrophic winds can kill canopy trees (Quercus spp. would be more affected by frost) (Kost et al. 2007).

The main threats to this system are fire suppression, high grazing and browsing rates, conversion to pine plantations, landscape fragmentation, and logging. In the absence of fire, Quercus spp. and other hardwoods and deciduous shrubs spread, creating a short, dense woody canopy. This shades out the shade-intolerant herbaceous species and pines and makes future fires less likely, though possibly more severe if they occur. Sustained high grazing and browsing pressure can eliminate native herbaceous species and will favor woody shrubs and other species not preferred by livestock or deer as well as provide more opportunities for invasive species. Landscape fragmentation due to agricultural and rural development disrupts the ecological processes under which this system developed, particularly fire, and can make managing stands through prescribed fire more difficult due to fragmented ownership and perceived threat to private property (WNHI 2012). Fragmentation also creates greater edge-to-interior ratio and increases the opportunities for introduction of exotic species. Logging is currently uncommon but previously occurred on pine-oak barrens and removed all the large overstory Pinus resinosa and Pinus strobus (Vogl 1964). Recreational use (off-road vehicles, in particular) can affect limited areas but also can serve as a source for introduction of invasive species that can tolerate the dry conditions, among them Centaurea biebersteinii (= Centaurea maculosa), Elaeagnus umbellata, Leucanthemum vulgare (= Chrysanthemum leucanthemum), Lonicera spp., Rhamnus cathartica, and Rosa multiflora. Due to the relatively infertile soils, this system recovers fairly slowly from disturbance, so effects can accumulate over time.

Occurs in the northern and western Great Lakes region.