Recognizing and Overcoming Difficult Site Conditions for Afforestation of Bottomland Hardwoods
In the last decade, about 370,000 acres (150,000 ha) of economically marginal farmland in the Lower Mississippi Alluvial Valley (LMAV) have been restored to bottomland hardwood forests (Stanturf and others 1998, King and Keeland 1999, Schoenholtz and others 2001). Planting of this considerable acreage is due to several federal programs, such as the Wetlands Reserve Program (WRP), that assist landowners by financing afforestation (Figure 1).
Unfortunately, these operational plantings have not performed as well as smaller plantings or research plots (Stanturf and others 2001a). For example, a recent survey of WRP plantings in westcentral Mississippi revealed that more than 90 percent of the sites failed to meet the criteria of 100 woody stems per acre (247 stems per ha) three years after planting or direct seeding. While planting 1-0 bareroot seedlings of oak was more successful than direct-seeding acorns, only 23 percent of the land planted with seedlings met the criteria (C.J. Schweitzer unpublished data). Planting and direct seeding oak (Quercus spp.) on public land in the same area has been more successful. Meanwhile, Allen (1990) found 70 percent of the planted bottomland hardwood stands on the national wildlife refuges he evaluated had more than 200 trees per acre (494 stems per ha).
We believe that the recurring problems in operational plantings on private lands are due in part to the failure of planters to recognize adverse site conditions and their failure to use appropriate methods for overcoming site limitations. Our objectives in this paper are to synthesize research and experience into guidelines for recognizing adverse site conditions due to hydroperiod, soil, competing vegetation, and herbivory. We describe techniques for overcoming these conditions and suggest promising research areas.