Other Considerations

Additional silvicultural considerations are important in the management of naturally regenerated stands by even-aged or uneven-aged methods. 

Seedbed preparation is critical. Southern pine seeds germinate best on exposed mineral soil. In southern pine types that produce prolific seed crops, such as the loblolly-shortleaf pine type in the west gulf region, the scarification associated with logging provides enough exposure of mineral soil to promote establishment of regeneration. For other species, such as longleaf pine, supplemental mineral soil scarification is often recommended. Prescribed burning can also be used to prepare seedbeds. 

The relative competitive abilities of pines and hardwoods after a harvest dictate that foresters must pay attention to relative growth rates and intervene if necessary. After a seed cut or cutting-cycle harvest, the intent is to allow pine seed to germinate on exposed mineral soil, become established, and be free to develop. However, hardwoods cut during harvest or subsequent site preparation will sprout and quickly outgrow seed-origin pines. Similarly, under certain circumstances grasses and other herbaceous plants may become sufficiently dense to impede pine seedling development, and control of grasses may also be necessary. Therefore site preparation or release treatments are often an integral part of effective silvicultural prescriptions for natural regeneration. 

For example, competing hardwoods, as well as nonnatives such as privet (Ligustrum vulgare L.) and honeysuckle (Lonicera japonica Thunb.), commonly inhibit the development of pine regeneration (Shelton and Cain 2000). Given the slow rates of height growth of pine seedlings and the competition provided by hardwood sprouts and invasive nonnative plant species, herbicides are critically important in managing stands of naturally regenerated pines, and may be more important to the establishment and development of naturally regenerated pine seedlings than to the survival and development of planted pine seedlings. The use of herbicides has in fact been an element of every successful long-term demonstration of uneven-aged silviculture in southern pines, including the successful practical experience of which the author is aware. Periodic control of hardwoods by applying herbicides at roughly 10-year intervals was an element of uneven-aged silvicultural prescriptions at CEF (Baker 1986). Farrar and others (1984) noted that deficits in the smaller diameter classes in uneven-aged stands were due in part to the failure of recruitment from regeneration to pulpwood-size classes, which was attributable to hardwood competition and the presence of privet. Farrar and others (1989) reported that control of hardwoods by cutting, girdling, or herbicide treatments occurred in the past on the uneven-aged Mississippi State Farm Forestry Forties, and was recommended in the future for all hardwood stems > 1.0 cm (0.4 inch) in diameter. Prescribed fire and herbicides were used in much the same way in stands regenerated using the shelterwood method on the Escambia Experimental Forest (Croker and Boyer 1975). Their use has been recommended in industrial seed tree silvicultural guidelines for south Arkansas and north Louisiana (Zeide and Sharer 2000). Prescribed fire, which does not kill larger hardwoods, probably cannot completely eliminate the need for herbicides in naturally regenerated stands, especially in uneven-aged stands.  

Finally control of regeneration density is fundamental to the successful application of natural regeneration in managed stands. Regeneration development in loblolly pine is improved by early precommercial thinnings to control stem density (Cain 1995). Nevertheless regeneration density will always be less uniformly distributed in naturally regenerated stands than in successfully established planted stands. Industry foresters in the west gulf region observed a long-term average rate of understocking of 7 percent of the stand area in managing naturally regenerated stands (see footnote 2). Invariably, one of the challenges in managing naturally regenerated stands is the likelihood of damage to regeneration when conducting removal cuts or subsequent cutting-cycle harvests. In situations where regeneration is far in excess of desired density, such logging-related precommercial thinning may actually be desirable. However, the situation is more critical when regeneration density is marginal prior to the removal cut or to subsequent cutting-cycle harvests. Careful supervision of logging operations is needed in such situations.