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• • common in the southeast. Northwards, quaking aspens become more frequent in the community. The stature and spacing of trees is somewhat variable, reflecting differences in soils, topography, and climate, factors that strongly affect local droughtiness and fire frequency. Small, gnarly, open -grown trees are most common, although in moister spots, or in heavier soils, larger trees are sometimes more common. Tree spacing ranges from sparsely and evenly distributed to strongly clumped in moderately dense patches. Shrub cover is variable as well. The species composition of the shrub layer depends somewhat upon soil characteristics. Oak grubs and chokecherries are common on all soil types. On sandier soils, prairie willows (Salix humilis), New Jersey tea (Ceanothus americanus), American hazelnuts (Corylus americana), sand cherries (Prunus pumila), and juneberries (Amelanchier spp.) are usually present. Wolfberries (Symphoricarpos occidentalis) are commoner on heavier soils. Dry Oak Savanna occurs on the same kinds of landforms as Dry Prairie, except for bedrock bluffs. Correspondingly, substrates range from excessively - drained to well - drained, sand to loam soils. The presence of savanna rather than prairie indicates a lower fire frequency or intensity (or both) than in prairie. Dry Oak Savanna requires less frequent fire than Mesic Savanna for maintenance. However, in the complete absence of fire woodland will eventually replace Dry Oak Savanna. Grazing and browsing animals may also have had a role in the maintenance of Dry Oak Savanna. Because Dry Oak Savanna occurs on sites that are not as suitable for cultivation as Mesic Savanna sites, and because succession in the absence of fire is not as rapid, more examples remain of Dry Oak Savanna than of Mesic Oak Savanna. A comprehensive plant species list for Foxborough's Oak Savanna restoration areas is provided in Appendix B of this report. Mesic Prairie Mesic Prairies are upland grassland dominated by prairie species, with <10% tree cover and <50% shrub cover ( <30% in far northwestern Minnesota), and NOT growing on steep slopes or on sand- or gravel - dominated soil. Mesic Prairie is a type of Upland Prairie, which occurs primarily in the prairie zone, with scattered occurrences in the deciduous forest - woodland zone. Mesic Prairies are dominated by grasses. The tall grasses, big bluestem (Andropogon gerardii) and Indiangrass (Sorghastrum nutans), are the major dominants on moist sites. Prairie dropseed (Sporobolus heterolepis) is common on both dry and moist sites. Forbs typically are abundant (but subdominant to the grasses) and may have high local diversity. Forb species composition varies with site moisture, although some forb species occur on almost all sites, moist or dry. Several low shrub or sub -shrub species are common on Upland Prairie; the most characteristic is leadplant (Amorpha canescens). Taller brush and trees are absent or scattered, however brush or woodland areas may be interspersed with prairie, usually in association with topographic and aquatic features that provide protection from fire. The most important cause of variation in species composition in prairie communities is variation in soil moisture. The local soil moisture regime is determined by slope, aspect, proximity to the water table, and soil texture. On a regional scale, variation in species composition is primarily caused by climatic variation (i.e., the westward decline in precipitation and northward decline in temperature in Minnesota). Foxborough Conservation Development Restoration and Management Plan 19