Interference Interactions in Simulated Pine-Hardwood Seedling Stands

Abstract

Abstract A multiresource factor approach, using biomass allocation patterns and resource-use efficiencies, was employed to investigate interference mechanisms in mixed species tree seedling stands. Seedling mixtures of loblolly pine (Pinus taeda L.) with one of two hardwood tree species, black locust (Robinia pseudoacacia L.) or red maple (Acer rubrum L.), were grown together at close spacing under well-watered and water-stressed conditions in a greenhouse. Pure stands of each species were included as controls. Greatest biomass growth increment was observed in pure hardwood stands, while pure pine stands had the lowest increments. Interference in mixed stands was highly one-sided, with hardwoods suppressing pine growth. Mechanisms or attributes accounting for interference outcomes included higher relative growth rates, increased below-ground allocation of photosynthate, effective display of foliage, and higher resource-use efficiencies of hardwood species. Interference strategies differed for hardwood species. Black locust could be classified as an uptake specialist with a high relative growth rate and a low root:shoot ratio. Red maple was a resource-use specialist, exhibiting high internal resource-use efficiencies for light, soil moisture, and nitrogen. FOR. SCI. 39(2):383-395.