Black oak grows on all aspects and slope positions. It grows best in coves and on middle and lower slopes with northerly and easterly aspects. It is found at elevations up to in the southern Appalachians. The most important factors determining site quality for black oak are the thickness and texture of the A horizon, texture of the B horizon, aspect, and slope position. Other factors may be important in localized areas. For example, in northwestern West Virginia increasing precipitation to resulted in increased site quality; more than had no further effect. In southern Indiana, decreasing site quality was associated with increasing slope steepness. Near the limits of black oak's range, topographic factors may restrict its distribution. At the western limits black oak is often found only on north and east aspects where moisture conditions are most favorable. In southern Minnesota and Wisconsin it is usually found only on ridge tops and the lower two-thirds of south- and west-facing slopes. Black oak is often a predominant species in the canopy of an oak–heath forest. Black Oak is the forest cover type that designates pure stands of the species or those in which it makes up more than 50 percent of the stand basal area. Black oak is a major associate in white oak–black oak–northern red oak. Other tree associates of black oak include pignut hickory ("Carya glabra"), mockernut hickory ("C. tomentosa"), bitternut hickory ("C. cordiformis"), and shagbark hickory ("C. ovata"); American elm ("Ulmus americana") and slippery elm ("U. rubra"); white ash ("Fraxinus americana"); black walnut ("Juglans nigra") and butternut ("J. cinerea"); scarlet oak ("Quercus coccinea"), southern red oak ("Q. falcata"), and chinkapin oak ("Q. muehlenbergii"); red maple ("Acer rubrum") and sugar maple ("A. saccharum"); black cherry ("Prunus serotina"); and blackgum ("Nyssa sylvatica"). Common small tree associates of black oak include flowering dogwood ("Cornus florida"), sourwood ("Oxydendrum arboreum"), sassafras ("Sassafras albidum"), eastern hophornbeam ("Ostrya virginiana"), redbud ("Cercis canadensis"), pawpaw ("Asimina triloba"), downy serviceberry ("Amelanchier arborea"), and American bladdernut ("Staphylea trifolia").