Hike along the flanks of Red Mountain and you’ll see the trees and plants change along the trail. Here are the forests you can look for:
• At the base of Ruffner’s northwest-facing slopes are moist forests growing atop Chickamauga Limestone. These are South-Central Interior Mesophytic Forests; mesophytic means plants that grow on moderately moist soils. At Ruffner, because they get little direct sunlight and stay wet, they have a longer growing season than the other forests nearby. Also, as the limestone bedrock below them weathers, it releases calcium ions to give the soil a high pH level. Some plants love these calcium-rich, low-acid soils, including American basswood (Tilia americana), slippery elm (Ulmus rubra) and Shumard oak (Quercus shumardii). In the spring, these forests are rich in wildflowers called ephemerals – they sprout, bloom and disappear early in the season before the trees above grow their leaves, then they disappear until the next year.
• Near the southwestern end, the mountain is brought to its knees by the Red Gap Fault, the same gap through which Oporto-Madrid Road, Interstate 20 and the railroad cross the mountain. Along the margins of the gap, the slopes face the southwest, and although the soils are still calcium-rich, the plants get more direct sunlight. This is the Southern Ridge and Valley/Cumberland Dry Calcareous Forest. You’ll find trees that can take drier conditions: red cedar (Juniperus virginiana), chinkapin oak (Q. muehlenbergii) , Eastern redbud (Cercis canadensis) and dwarf hackberry (Celtis tenuifolia). And because it gets less water, the forest is shorter and growing more slowly.
• Near the mountain’s ridge, the forest is shorter still and the older trees are getting gnarled by the stress of living on the high slopes, where there is less groundwater and more drying winds. The trees here can take the xeric, or dry conditions; the forest is often called the Xeric Oak-Hickory Forest, although it’s also classed as the Allegheny-Cumberland Dry Oak Forest and Woodland. The rock below has less limestone, which means there are different trees, including chestnut, post and southern red oaks (Q. montana, Q. stellata, and Q. falcata) and sand and mockernut hickory (Carya pallida and C. tormentosa).
• The southeast slopes were once covered with pine forests that liked the drier, acidic or neutral soils there. But most of these Montane Longleaf Pine Woodlands in the Birmingham area were cut down long ago for timber or charcoal or to make room for houses. There are now just a few small spots at Ruffner Mountain Nature Center where the longleaf pine (Pinus palustris) is being restored. In its place are several species that can survive the dry, rocky soils but, unlike longleaf, cannot tolerate forest fires, including loblolly pine (P. taeda), sweetgum (Liquidambarstyraciflua), winged elm (Ulmus alata), northern red oak (Q. rubra), pignut hickory (C. glabra) and tulip-poplar (Liriodendron tulipifera).