Disking Effects on Fifth-year Volume Production of Four Eastern Cottonwood Clones Established on an Afforestation Site, Sharkey County, Mississippi

In spring 1995, an eastern cottonwood (Populus delfoides) plantation was established on a former agricultural field in Sharkey County, MS to evaluate the effects of clonal variety and mechanical weed control on aboveground biomass production. Four cottonwood clones, ST-66, ST-72, ST-75 and S7C-1 were planted on a 12 foot x 12 foot spacing and subjected to 2 mechanical weed control treatments (disking in year 1 versus disking in year 1 and 2). Survival in the plantation ranged from 96 percent for ST-66 and S7C-1 to 87 percent for ST-72. But, survival was not influenced by mechanical weed control as it averaged 93 percent for each treatment level. After the fifth growing season, mean cottonwood height ranged from 48.3 feet for ST-66 to 39.8 feet for the other three clones. Similarly, diameter of ST-66 averaged 5.5 inches, while diameter of the other clones averaged 4.8 inches. Two years of mechanical weed control did not improve tree growth as heights averaged 41.8 feet and diameters averaged 4.9 inches regardless of disking treatment. Clonal effects on volume production were obvious after 5 growing seasons, ranging from 1038 feet3 acre-’ outside bark for ST-66 to 574 feet3 acre-’ outside bark for ST75. Volume inside bark ranged from 631 feet3 acre’ for ST-66 to 279 feet3 acre’ for ST-75 Multiple years of mechanical weed control did not improve eastern cottonwood volume production five growing seasons after plantation establishment. Results indicate that eastern cottonwood plantations may be established to rapidly develop a forest structure on a wide range of afforestation sites in the Lower Mississippi River Alluvial Valley. INTRODUCTION Extensive deforestation in the Lower Mississippi River Alluvial Valley, driven primarily by land use conversion to agricultural production, reduced bottomland hardwood forest acreage by more than 75 percent in the region (Stanturf and others 2000, Sternitzke 1976). Recently, interest in restoring bottomland hardwood forests on marginally economical agricultural land has been spurred by several governmental incentive programs (Stanturf and others 1998). Although most afforestation projects in the Lower Mississippi River Alluvial Valley focus on establishing heavy mast species such as bottomland oaks (Quercusspp.) (King and Keeland 1999) some landowners have management objectives that require establishment of fast growing, intensively managed and economically sustainable hardwood plantations (Stanturf and Portwood 1999). Eastern cottonwood (fopulus deltoides Bar-tram ex Marshall), a native, pioneer species that thrives on alluvial soils throughout the central and eastern United States, has several attributes which make it an appealing selection for afforestation in the Lower Mississippi River Alluvial Valley (Cooper 1990) . Re la t i ve to p lan ta t ion es tab l i shment and deve lopment , eas te rn co t tonwood can be p ropagated w i th vege ta tive cuttings, superior clones are available for a variety of site types, plantation cultural practices are well established, it exhibits extremely fast growth rates, and growth and yield models are available for the species (Cao and Durand 1991a, Krinard 1988, McKnight 1970). The suitability of this species to plantation culture has led to its es tab l i shment in f iber fa rms and b io fue l p lan ta t ions worldwide. As an example, more than 3.7 million acres of eas te rn co t tonwood have been p lan ted in Ch ina s ince i t s in t roduct ion in the 1970s (Cao and Conner 1999) . Although sustainable fiber production is often the driving force behind establishment of eastern cottonwood plantations, other environmental benefits can be derived through afforestation wi th th is spec ies . Gard iner and o thers ( In Press) demonstrated that the understory of eastern cottonwood plantations may be suitable for facilitating establishment of other native bo t tomland t ree spec ies on a f fo res ta t ion s i tes . The importance of eastern cottonwood forests as habitat for game and non-game wi ld l i fe spec ies has been es tablished for several decades (Twedt and Portwood 1997, Wesley and others 1981, Wigley and others 1980). Thorn ton and o thers (1998) demonst ra ted tha t sed iment loss in runo f f f rom co t tonwood p lan ta t ions was subs tan tially lower than runoff from fields under conventional ‘Forestry Technician and Research Forester, USDA Forest Service, Southern Research Station, Center for Bottomland Hardwoods Research, Stoneville, MS 38776, respectively; 2Project Leader, USDA Forest Service, Southern Research Station, Forestry Sciences Laboratory, Athens, GA 30602;30perations Manager Hardwood Resources, Temple-Inland Forest Products Corporation, Diboll, TX 75941, respectively. Citation for proceedings: Outcalt, Kenneth W., ed. 2002. Proceedings of the eleventh biennial southern silvicultural research conference Gen. Tech. Rep. SRS-48. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 622 p.