Evaluation of four form classes of northern red oak (Quercus rubra) multi-cropped with shortleaf pine (Pinus echinata).

Evidence for the importance of seedling morphology and the benefits of multi-cropping in tree plantations continues to increase worldwide. The effects of seedling form on the performance of multi-cropped and monoculture plantings of northern red oak and shortleaf pine seedlings were quantified to test the hypotheses that: (1) multi-cropping northern red oak and shortleaf pine seedlings would lead to increased survival and growth of these species, and (2) that the productivity and overall success of mixed oak-pine plantations can be influenced by seedling morphology. Four different form classes of 1–0, bareroot northern red oak seedlings (Short:Thin, Short:Thick, Tall:Thin, and Tall:Thick) were planted with 1–0, bareroot shortleaf pine seedlings at a 2.44 m spacing, with 0.31 m between each planted oak and pine. Adjacent monocultures of shortleaf pine and all form classes of northern red oak were also planted for comparison. Measurements of seedling performance over six years revealed no significant differences in shortleaf pine and northern red oak survival and growth among multi-cropped and monoculture treatments. In contrast, mean height and mean basal diameter in Tall:Thick northern red oak seedlings were significantly greater than in the remaining three northern red oak form classes, regardless of multi-cropping treatment. Survival did not differ among form classes (p > 0.05). These results suggest that seedling morphology was more important than the effects of multi-cropping early on in the development of these plantations, and that further testing of the effects of form class across different multi-cropped species is warranted. [ABSTRACT FROM AUTHOR]