Underplanting Shortleaf Pine Seedlings Beneath a Residual Hardwood Stand in the Ouachita Mountains: Results after Seven Growing Seasons
An unreplicated demonstration was established in the Ouachita Mountains in which shortleaf pine (Pinus echinata Mill.) trees were harvested and overstory hardwoods were retained. A new stand was established by underplanting shortleaf pine seedlings. After the third growing season, five 0.5-acre plots were established, and one of five overstory hardwood retention treatments 0, 10, 20, 30, or 40 square feet per acre of residual basal area (RBA) was randomly assigned to each. Pine seedlings were measured after the third, fifth, and seventh growing seasons. Over time, pine seedling density changed very little by treatment, but seedling basal area varied inversely with increasing overstory retention. After the lifth and scvcnth growing seasons, the basal area of the average tree in the RBA 0 treatment was greater than in any other treatment, and differences in height among treatments were also observed. Between the third and seventh growing seasons, average annual growth of pine in both height and basal area declined with increasing overstory hardwood basal area. The decline in height growth occurred uniformly from the RBA 0 through the RBA 40 treatments; but the decline in seedling basal area growth occurred between the RBA 0 and RBA 10 treatments. To date, seedlings have survived and growth has increased across all treatments. Future monitoring will determine if and when growth rates cease on any of the plots.