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Barrens Oak Savanna Fact Sheet <br />Fig. 9.3 A barrens oak savanna on dry dune sand at Helen Allison Savanna Scientific and Natural Area in Anoka County. Fire man- <br />agement at this site limits woody growth and maintains a ground layer dominated by little bluestem, porcupine grass, and white sage <br />below a canopy of scattered bur oak trees. <br />Status: 2 <br />Structure <br />A relatively open community of scattered <br />(10 to 70% canopy cover), short (15 to 35 <br />feet), open -grown bur oak trees above a <br />herbaceous ground layer; northern pin oak <br />sometimes present; trees scattered or in <br />groves with tree seedlings and shrubs. The <br />ground layer is mostly composed of prairie <br />grasses and forbs, but their cover is patchy, <br />with bare ground in between; bowl -shaped, <br />wind -scoured sand blowouts are common <br />on eroded dune slopes; sparsely vegetated <br />areas may have small patches of lichens or <br />mosses. <br />Other characteristics <br />A few green ash trees are sometimes pre- <br />sent on dry dune crests where ground fires <br />are too light to kill them; small-scale nat- <br />ural disturbances such as gopher mounds, <br />thatch ant nests, and deer trails. <br />Soils and substrate <br />Occurs on fine -textured sand originally <br />derived from glacial outwash, then <br />deposited by wind in dune fields; also on <br />medium to coarse-textured sand. Soil devel- <br />opment is poor or absent; sands are well <br />drained to excessively well drained. <br />Historic distribution <br />Almost exclusively on dune formations on <br />the Anoka sandplain; small inclusions of <br />barrens savanna occurred in dry sand - <br />gravel savanna or dry prairie in local areas <br />of wind -deposited sand and on unstable, <br />gravelly slopes on the Mississippi River <br />terraces. <br />Present distribution <br />Small fragments occur on dune formations, <br />but most are surrounded by pine plan- <br />tations, abandoned fields, and housing <br />developments. <br />Existing acreage: 2,360 <br />Number of known locations: 41 <br />Common plant species <br />— Canopy <br />Bur oak (Quercus macrocarpa) <br />Northern pin oak (Q. ellipsoidalis) <br />— Shrub layer <br />Chokecherry (Prunus virginiana) <br />— Ground layer <br />WOODY SPECIES <br />Leadplant (Amorpha canescens) <br />Poison ivy (Rhus radicans) <br />Prairie rose (Rosa arkansana) <br />FORDS <br />Western ragweed (Ambrosia coronopifolia) <br />From: Wovcha, Daniel S., Minnesota's St. Croix River Valley and Anoka Sandplain, A Guide to Native Habitats, <br />1995, University of Minnesota Press. <br />ai <br />0 <br />0 <br />a <br />