Document: JOS-3-29-13

Limiting factors to regeneration of large-seeded hardwoods in the Upper Coastal Plain of South Carolina.

RILEY, J.M.* and R.H.JONES

Virginia Polytechnic Institute and State University ¹

Abstract:
Quercus alba (white oak) and Cornus florida (dogwood) seedlings were planted in recently clearcut pine plantations and in pine plantation understories to determine: 1) Which of these contrasting environments is best for seedling survival and growth and 2) if differences in seedling performance are related to resources (water, nutrients and light) or herbivory. Our hypotheses were that clearcuts would offer more resources for plant growth thereby resulting in: 1) Greater survival and productivity and 2) less herbivory. The soil proximate to each seedling was sampled to estimate carbon content, concentration of available nutrients, and water availability. Total sunlight received in the growing season was estimated by determining percent open sky and gap light index above each seedling. At the end of the growing season, the seedlings were assessed for survival, height and basal diameter growth, leaf area production, and percent herbivory. Soil carbon, soil water, and seedling performance data are reported here. Clearcuts had greater mean soil water availability (P < 0.05), but less soil carbon (P < 0.02). Overall, one-year survival was significantly lower (P < 0.001) in the clearcuts than in the understory, but the difference was minor (mean of 59.2 versus 64.7%). The presence of overstory trees had no significant effect on dogwood height or basal diameter growth and only a marginal influence on dogwood leaf area production (clearcut--276.6 cm²; understory--207.9 cm²; P = 0.06, adjusted for basal diameter as covariate). In contrast, overstory trees had stronger influences on white oak height growth (clearcut--14.0 cm; understory--11.96 cm; P < 0.01), basal diameter growth (clearcut--0.77 cm; understory--0.25 cm; P = 0.06) and leaf area production (clearcuts--942.4 cm²; understory--379.5 cm²; P < 0.001). Percent leaf herbivory was significantly greater in clearcuts for both dogwood (P < 0.001) and white oak (P < 0.001). These first-year results of a multi-year study show that white oak is more sensitive to the range of conditions imposed in our study. As hypothesized, white oak performed better where light and water were more abundant. However, contrary to our second hypothesis, herbivory was greater for seedlings in clearcuts.

Keywords: Quercus alba, Cornus florida, Resource limitations, Herbivory, Upper Coastal Plain

This abstract is being presented at: 10:30 AM in session:
Poster Session #1: Light Relations.