Accelerating Forest Restoration Through Diverse Seedling Replanting
Mixed planting of multiple species is a more effective way of restoring logged or degraded forests than single-species reforestation․ A mixed planting of pine‚ red maple‚ Virginia pine‚ silver maple‚ pin oak‚ and red oak takes only 5 to 8 years‚ rather than 12 to 15 years‚ to reach canopy cover․ Mixed planted forests are also more resistant to the pests and diseases that kill single species reforestations․ And it's exactly how forestry departments across the Southeast (including in Tennessee) are doing restoration for thousands of acres today․
Whether trees are removed or left standing‚ these activities compact the soil‚ expose it to direct sunlight‚ and eliminate the fungi and leaf litter that normally sustain forest flora and fauna․ Mere planting of a tree is not sufficient for the land to recover to a self-sustaining forest․ It requires planting these species according to their conditions and staggering them from those that provide rapid soil stabilization to those that can create a longer-lasting canopy․
The Problem with Single-Species Reforestation
For decades the cheap and easy approach would be to plant a single fast-growing species over the entire cleared area‚ and loblolly pine is a good example of this across the southern US․ The problem comes when a pest like southern pine beetle goes through with no control․ Planting diversity can slow these pests by breaking the continuity․ If a beetle outbreak kills all the pines in mixed pines-oak-maple stands‚ the oaks and maples allow the forest canopy and the soil to remain while new pines grow beneath the old trees․
Pine and Virginia Pine: The First Responders
Pines go in first because they can tolerate poor compacted and sun-baked soils better than almost anything else you'd plant․ Since the Virginia pine (Pinus virginiana) is native to ridges and disturbed areas of the eastern United States‚ it makes a better choice for the rocky and acidic soils of Middle and East Tennessee․
Under good growing conditions‚ seedlings planted one or two years old should grow 4 to 6 ft (1․2 to 1․8 m) in three years․ For a working stand‚ space trees 8 to 10 ft (2․4 to 3 m) apart‚ or for faster canopy closure and to shade out intrusive groundcover‚ space trees 6 ft (1․8 m) apart․ Virginia pine grows in USDA hardiness zones 5 to 8‚ including all of Tennessee․ After establishment‚ generally by the second year‚ Virginia pine requires little supplemental water․
Red Maple: The Adaptable Middle Layer
Red maple (Acer rubrum) is also one of the most tolerant trees you can plant in a restoration‚ tolerating wet bottomland‚ well-drained uplands and anything in between‚ while growing relatively quickly (3-5 feet/year after roots are established)․ These trees also establish their canopy structure earlier than oaks‚ which take longer to establish․
Where red maple is used in mixed planting‚ it should be used between the pioneering pine trees to provide a broader leaf canopy‚ which can shade out competing brush and retain the moisture levels of the soil․ The red paddings of fall leaves are also important to reforesting the area‚ because in a wide resonance of visible payoff‚ people and landowners are often persuaded to restore forest with the deep red leaf․
Silver Maple: Built for Wet Ground
Silver maple (Acer saccharinum) is better adapted to wet spots and younger floodplains than most other restoration species․ If you have a creek bottom‚ floodplain‚ or an area where logging compacted the soil and made it poorly-drained‚ silver maple may be a suitable addition to your restoration project․ It has a rapid rooting system‚ and can grow 4-6 feet a year for the first few years‚ which can help restore soil structure eroded by floods and heavy machinery․
A drawback of this strength is its brittleness; silver maple will snap off in high winds more readily than oak or pine․ However‚ in a restoration project‚ ground cover and erosion control take precedence over susceptibility to wind damage․
Pin Oak: The Soil Stabilizer
Pin oak (Quercus palustris) tolerates a wider range of soil moisture conditions than most oaks‚ making it useful for sites with variable hydrology‚ such as logging-damaged lands․ Its fibrous root system‚ rather than a distinct taproot‚ penetrates the topsoil․ These roots knit together‚ preventing erosion‚ as they spread well on slopes․
It grows slower than either the pines or the maples (2 or 3 feet a year)‚ but pin oak's real benefits come 10 or 15 years later when its acorns are an important source of food for deer‚ turkey and songbirds․ Few fast-growing pioneer species such as the pines can do that․
Red Oak: Building Long-Term Canopy Diversity
Red oak (Quercus rubra) grows more slowly and will not dominate the canopy for another 20-30 years‚ but in time will provide the restored forest with a long-term canopy and hardwood value․ Its acorns are the most important wildlife food through late fall․ Dappled shade and small clearings under the canopy of mature red oaks‚ provides excellent conditions for the natural colonization of understory plants․
As red oak grows slowly‚ it should be planted early‚ with the pines‚ rather than later when the canopy is closed and it must struggle for light to catch up․
Putting It Together: A Realistic Planting Timeline
A mixed restoration in Tennessee might follow this approximate sequencing of factors․
In Year 1‚ you prepare the site and plant the pine‚ Virginia pine and red oak that would be the backbone․ They had initially been disturbed and would need the least babying․
Years 2-3: Plant red maple and silver maple in appropriate areas; silver where hydrology is more permanent and lower in elevation‚ and red maple everywhere else‚ and in areas of uncertain drainage pin oak․
Years 4-8: The forest canopy begins to close․ Pines and maples dominate as the tallest members of the early canopy․ Oaks do continue to grow roots‚ though none are visible as massive interlocking branches․
Year 15+: Now the oaks are beginning to dominate the canopy‚ the pines are mature and beginning to self thin‚ and the restored area is beginning to look much more like a real mixed hardwood forest․
A Note on Sourcing Seedlings
Seedling quality is as important as the species․ Bare-root seedlings that have been grown under the same conditions as the eventual site‚ rather than being transplants produced in a different climate zone‚ tend to establish and survive more readily․ TN Nursery raises Virginia pine‚ red maple‚ silver maple‚ pin oak and red oak seedlings for the soils and climate of the State of Tennessee and the Southeastern United States․ This avoids the transplant shock which causes a meaningful proportion of seedlings to die in mass plantings․
The Bottom Line
An effective replanting scheme does much more than add diversity to a restored forest; it makes the difference between a self-sustaining healthy forest and a scrubby stand that is vulnerable to the next pest or drought․ Starting with pine and Virginia pine on bare or rough soil‚ red maple and silver maple fill in according to moisture․ Pin and red oak will provide a durable‚ wildlife-friendly canopy and doing that in the right mix and sequence will mean that the logged tract can look and function like a real forest again in a couple of decades‚ not the half-century of letting nature take its course․
