Preliminary Evidence that Intraspecific Competition Increases Size of Restoration-Planted Pitch and Shortleaf Pines in a Mixed-Hardwood Clearcut in the Southern Appalachians

Abstract

Abstract Oak-pine (Quercus L. - Pinus L.) forest communities on low ridges in the southern Appalachian Mountains are losing diversity as mature pitch (P. rigida Mill.) and shortleaf (P. echinata Mill.) pines die and do not regenerate under a hardwood canopy. Restoration of biodiversity by planting pine seedlings is well known, but little is known regarding whether the configuration of planted seedlings affects growth and subsequent size (diameter at breast height, dbh) as trees age. The purpose of this study was to test the hypothesis that pines growing in groups of two or more trees respond with increased growth (expressed by dbh) to intraspecific competition with other pines compared to single trees subjected only to interspecific competition with surrounding hardwoods. For 13-year-old pitch and shortleaf pines, trees were larger in dbh when occurring in groups than trees occurring singly. Regression indicated that intraspecific competition accounted for 16% of the dbh variation of pitch pine and 29% for shortleaf pine. This study originated from chance observations in a small study of pine restoration. If a designed study confirms these results, resource managers could restore biodiversity with reduced site disturbance and establishment costs by planting pine seedlings in small groups rather than rows.