natural regeneration which has to do with AGRICULTURAL

NATURAL REGENERATION

Natural regeneration is defined as species reproduction obtained by natural seeding or from sprouts. The literature available concerning natural regeneration is limited, especially for restoration of riparian areas.

What is known is that naturally vegetated riparian areas are among the most productive and diverse plant communities (Klapproth 2001). This vegetation is adapted to wide fluctuations in water levels and regular disturbances. One of the most recent studies to be completed was in

Maryland by the Department of Natural Resources - Forest Service in April of 2001.

They found that a large percentage of their planted survey sites contained natural regeneration, and that regeneration reflected the native plant communities at those sites.

They found higher stocking levels and survival rates on sites with natural regeneration.

On the other hand, a study being conducted by Sweeney in Pennsylvania concluded that natural regeneration was not a viable option for restoring forest buffers there. This is because of high local incidence of herbivores and exotic, invasive species competitors, an insufficient quantity or poor diversity of local desirable seed source, and a need to quickly restore habitat and water quality of the stream.

In Maryland, sites that contained an abundance of natural regeneration also were sites that had very little maintenance and showed a greater diversity of species.

Regeneration was found more in clumps then equally dispersed across the whole buffer survey site. Of the trees and shrubs found as natural regeneration in a Maryland study by Pannill, the top ten species found were: sweetgum, boxelder, hawthorn, black cherry, green ash, ailanthus, red maple, black walnut, black locust, and loblolly pine.

In a Virginia study conducted by J. G. Okay, a considerable number of the sites with natural regeneration were populated with short-lived pioneer species. Common Riparian Corridor Pioneer Species according to Verry et al. in 2000 are: Acer rubrum, Betula nigra, Carya sp., Fraxinus pennsylvanica, Liriodendron tulipifera, Populus deltoids, Nyssa sylvatica, Platinus occidentalis, Quercus alba, Salix nigra, Quercus bicolor, Taxodiuhum distichum,

and Ulmus sp.

In C. J. Barden's publication, "Establishing Riparian Buffers", natural regeneration is the least expensive, least certain method. It requires a nearby seed source of mature trees. The resulting stand usually is dominated by fast-growing species, such as cottonwood, elm, silver maple, boxelder, and willow, all of which have wind-borne seeds. In many cases, pastureland can be naturally regenerated by fencing off the area for several years.

The stand resulting from fencing the riparian area usually will be dominated by bird-dispersed or largerseeded species that were not palatable to grazing livestock, typically honeylocust, Osage orange (hedge), hackberry, and eastern redcedar. Some sites have a good number of oak and ash seedlings already present that simply need protection from the trampling and grazing to grow well (Barden 2001). Suppression of competing pasture plants may be necessary for native plant establishment (Reichard 1984).

The Connecticut River Joint Commission of NH & VT suggests that natural regeneration can be accomplished by simply ignoring the riverbank and creating a no-mow zone. Over time plants can be added and non-native or unhealthy ones can be removed. This is the easiest and least costly way to establish a buffer, but you'll have to wait awhile and if your bank is poorly vegetated, it may erode in the meantime. Using natural regeneration to revegetate channelized streams (those with stabilization structures) can be unpredictable and depends on a number of little-understood variables (Goldner 1984). These variables include channel slope lining (concrete or rip rap), availability of upstream seed sources, soil temperature and moisture, stream flow regime and velocities, steepness of side slopes, fertility and compactness of fill material, and intensity of vegetation and sediment removal in the channel to maintain the constructed flow capacity.

Studies by Pannill et al., revealed the importance of natural regeneration in buffer creation and restoration. Natural regeneration has limitations such as invasive exotic species and very patchy seedling density, but it can offer inexpensive regeneration with native seed sources, desirable for wildlife and biodiversity.

Considerations for naturally regenerating a buffer or augmenting a planted buffer include: minimizing noxious or invasive\weeds, minimizing poor species diversity, and identifying sites where natural regeneration will not achieve the desired results.

Research by Binelli in 2000 concluded that natural areas in urban settings have much lower maintenance requirements when compared to traditional landscaping, but careful planning and monitoring are essential for success. In some urban landscapes, seed sources are sparse and deer browse has taken its toll on natural regeneration. This is similar to results in a Pennsylvania study by B. Sweeney (Sweeney, 2002).

In a study conducted in northwestern Pennsylvania on soil seed banks it was found that only a subset of the ground-layer species that occur in Allegheny Plateau riparian forests relies on the seed bank as a mechanism for population regeneration and maintenance. There was low overall similarity between species composition of the soil seed bank (13 species) and the existing vegetation (25 species) in the riparian forest (Hanlon, et.al. 1998).