Production physiology of three native ornamental shrubs intercropped in a young longleaf pine plantation

Abstract

The production of woody floral products -- the fresh or dried stems that are used for decorative purposes -- may be an attractive option for southeastern landowners looking to generate income from small landholdings. Since many shrubs native to the understory of the longleaf pine ecosystem have market potential, one possibility is the intercropping of select species in the between-row spacing of young longleaf pine plantations. The objective of this study was to evaluate how competition affects the physiology, and thus the productivity of American beautyberry (Callicarpa americana L.), wax myrtle (Morella cerifera (L.) Small) and inkberry (Ilex glabra (L.) A.Gray) when intercropped in a longleaf pine (Pinus palustris Mill.) plantation in the southeastern United States. The effect of competition was assessed via comparisons of mortality, biomass, light transmittance, gas exchange and soil moisture between intercropping and monoculture (treeless) treatments. Overall, shrubs in the intercropping treatment performed worse than those in the monoculture, with higher mortality, and reductions in biomass of 75.5 [percent], 50.6 [percent], and 68.7 [percent] for C. americana, M. cerifera and I. glabra, respectively. Root-shoot ratios for all species were significantly higher and soil moisture during dry periods was significantly lower in the intercropping treatment. Light transmittance below the pine canopy was high (57.7 [percent]) and I. glabra was the only species that exhibited reduced photosynthesis due to shading. These results suggest that the effect of shading is minimal and belowground competition is likely the most important determinant of productivity in this system.