Red Mountain Park’s Forests Are Ever Changing

- Photo Credit: R. Scot Duncan
Along the ridge the forest is drier and shorter
- Photo Credit: R. Scot Duncan
At lower elevations the trees are taller
- Photo Credit: R. Scot Duncan
Chinese Privet and other plants thrive in low, wet areas
- Photo Credit: R. Scot Duncan
Remnant trees of the Longleaf Pine woodland
- Photo Credit: R. Scot Duncan

There is tree-mendous variation in the forests on Red Mountain. Some of this variation is the product of natural processes, while some is the result of the human influence. Either way, all of Red Mountain Park’s forests are second-growth forests, meaning they grew after the original forests were felled.

These new forests – which are still maturing – are growing back with ecological conditions quite different from those in place before the original forests were cut down. Much of the soil was washed away when the slopes were logged. The availability of groundwater for trees was altered by roads, mines, and deposits of mine tailings. Wildfire no longer sweeps across the ridgeline and down the dry southeastern slopes. And native trees must compete with swarms of Chinese Privet shrubs and sprawling masses of Kudzu. But despite all that, forests are reclaiming the mountain. These new post-industrial forests help the city by cleaning polluted air and reducing flash flooding.

Much of the variety in the types of forest in the park is due to the park’s many different environments. The structure of a forest (e.g., tree height) and the types of trees you’ll see depend on the kind of soil, amount of water, and even the type of rock under their roots. These differences can be striking throughout the park, especially in the areas least impacted by mining.

At the base of Red Mountain’s northwest-facing slopes, you’ll find moist forests growing atop the Chickamauga Limestone. These are South-Central Interior Mesophytic Forests (“mesophytic” refers to plants that grow on moderately moist soils). Because the sun is always in the southern sky in Alabama, these forests do not receive much direct sunlight, and their soils rarely dry out. The abundant moisture allows for a longer growing season for plants in this zone. Another distinct feature of these forests is their “sweet” or alkaline soils. Because limestone is mostly calcium carbonate, weathering releases an abundance of calcium into the soil. The trees on these northwest-facing slopes can tolerate high alkalinity and include Shagbark Hickory, Slippery Elm, and Shumard and Chinkapin Oak.

Near the ridge and on the tops of spur ridges of Red Mountain’s southeastern slopes, the soils are thinner due to erosion and drier due to sun exposure. For the same reasons such a soil would not grow a good garden, the trees growing here tend to be shorter. Today, these rocky soils support the Allegheny-Cumberland Dry Oak Forest and Woodland ecosystem. Trees that grow here – including Mockernut Hickory, Winged Elm, Black Gum, and Blackjack and Post Oak – can get by with less water than species found at lower elevations. Before mining, montane Longleaf Pine woodlands occupied the dry southeastern slopes of the mountain. Sturdy, tall Longleaf Pines stood where hickory and oak are today.

Trees that prefer moist soils creep up the southeastern slopes in the narrow valleys between the spur ridges. These types of trees are common along the base of the slope and in the large valleys of the region. The moisture available in these side-valleys allows these trees to survive higher on the mountain than is typically possible. You’ll see such species as Northern Red, Water, and Willow Oak, American Beech, Sweet Gum, Red Maple, Yellow-Poplar, Green Ash, and the occasional American Sycamore.

The park’s forests are changing. When mining ceased, the slopes became available for pioneer trees – fast-growing, sun-loving species whose seeds travel long distances. The first to fill the canopy included Black Cherry, Sugar Berry, Yellow-Poplar, and Water Oak. Today, the pioneers are reaching the end of their life span and are disappearing. Since their seedlings need full sun, there’s little room for them to replace themselves. Instead, trees that can get by in the shade beneath the pioneers are growing, including the numerous oaks and hickories. Many of these late-comers are already several decades old and are taking their places in the forest canopy. This type of change in ecosystems is known to biologists as succession. Through this process, the forests at Red Mountain Park will continue to change over the next century. Ultimately – perhaps in the 22nd century – the forest will reach a point where mature forest trees fill the canopy except where storms or other disturbances create opportunities for the pioneers to temporarily move back in.

-R. Scot Duncan