Forest trees rely on two general methods to reproduce - natural means and artificial means. Natural regeneration (as the name implies) is that established from seed, sprouts, or root suckers of trees on or formerly occupying the land. Conversely, artificial regeneration is that established from seed or seedlings brought on site by man expressly for purposes of tree re-establishment. Artificial regeneration involves direct seeding or planting.
Area size and pattern varies greatly for "new" forests. In both natural and artificial regeneration, boundary patterns designed by mankind can be significant. However, in natural replacement other natural factors can play major roles in stand size, boundary pattern, species composition, density and age class distribution. Factors such as sunlight, nutrients, moisture, soil characteristics, temperature, wind and associated animal and plant species can have an effect on tree reproduction.
Large areas of tree regeneration can be created by extreme natural catastrophes (such as fire and windstorm) while smaller areas are created by individual tree mortality and gradual change (succession). Natural phenomena can be simulated by various forms of timber cutting for stand improvement or harvest, followed by or in concurrence with natural or artificial regeneration. Numerous options are available for forest regeneration.
Each selection will show influence on the species composition, age class distribution, density, growth, and other attributes of the new stand, and benefits to be obtained.
Natural regeneration includes both seeding and vegetative reproduction. Most species of hardwoods combine both seed and vegetative regeneration for reproducing. Most pines reproduce principally from seeds. Hardwoods such as oak, maple, and yellow poplar commonly sprout from the stump after being cut or burned. These sprouts often form clumps. Beech, sweetgum, and black locust commonly sprout along the roots (suckering). Based on numerous factors, vegetative reproduction is fairly predictable. Follow-up management practices can be influenced significantly by the form of natural regeneration.
Successful Natural Seeding occurs when conditions are favorable:
- trees must be present which are old enough to produce seed,
- sufficient numbers of healthy, viable seed must be produced and survive to germinate,
- the seed must be carried to and distributed on a site favorable for germination, and
- conditions must remain favorable until the seed germinates and establishes itself. The results of natural seeding are often erratic and fail without proper planning, or without an "element of luck from Mother Nature."
Because natural regeneration often is less predictable and slow, artificial methods are commonly used to establish desired species on prepared sites before favorable site conditions deteriorate. Artificial regeneration is synonymous with the term reforestation. Two methods of reforestation are Direct Seeding and Planting. While the two methods provide more control than natural regeneration, it is critical that the site be adequately prepared and that the species match the site conditions.
Direct Seeding is (in the conventional sense) most often used with "lightweight" seeds (like loblolly and white pine) that in nature would be dispersed by wind. However, heavier seeds (like oaks-acorns and black walnuts) that in nature are often dispersed by gravity, birds, and animals, can be direct seeded in spots. Light seeds can be sown with specialized equipment (spot seeder, cyclone seeder, or by helicopter). Heavier seed like black walnuts can simply be placed by hand. While direct seeding can be relatively fast and low cost, creating a good seedbed and maintaining satisfactory conditions for seed germination and early tree growth are critical. Without proper attention to details, direct seeding is more uncertain than planting. Direct seeding is seldom used in Virginia.
Planting can be accomplished with a high degree of certainty and is a popular method of tree regeneration in Virginia. The method has been used extensively on harvested tracts and for converting idle fields and opening to trees, shrubs and wildlife plants.
Planting allows landowners flexibility to choose suitable species and to more effectively design areas for timber production, wildlife habitat, forest beauty and landscape, erosion control and water quality maintenance, Christmas tree production or some combination of these objectives. Seedlings are commonly planted by hand with various tools (shovel, planting bar, or hoe-dad) on small areas, wet or rolling sites, or tracts with stumps or rocks. On other sites such as large, relatively level areas, those free of large stumps and rocks, or abandoned agricultural fields, various models of mechanical planting machines are used. Machine planting may be faster than hand methods, and of higher quality on many sites. Some planting machines are equipped with special attachments (scalpers) to peel away competing sod.
Your county forester is trained to assist you with analysis, prescriptions, and options for forest tree regeneration.
Reforestation and conservation species are available from the Virginia Department of Forestry.