Competitive Interference Between Selected Herbaceous and Woody Plants and Pinus taeda L. During Two Growing Seasons Following Planting

Abstract

Abstract Interference between loblolly pine (Pinus taeda) seedlings and selected herbaceous (panicum grass, Panicum dichotomiflorum; coffeeweed, Sesbania exaltata; broomsedge, Andropogon spp.) and woody (sweetgum, Liquidambar styraciflua) competitors was evaluated during the first two growing seasons following planting on a loamy sand Coastal Plain site. Pine seedling growth was reduced by all competitors. During the first growing season, competition for water was the dominant factor affecting pine growth. Panicum grass, which most rapidly depleted available water in the soil surface, was the strongest competitor. Reductions in N, Ca, and K foliar concentrations were associated with reduced surface soil water availability in grass and coffeeweed plots during this period. On plots with less competitive broomsedge and sweetgum, only K and Ca concentrations of pine foliage were reduced. Fertilization with NPK or P alone had no affect on pine growth and had only a minor affect on pine foliage nutrient concentrations. Although differences in growth occurred among families, all families responded to competitor and fertilizer treatments in a similar manner. Competitors had less influence on seedling water use and nutrition during the second growing season. Although absolute differences in seedling size among competitor treatments increased, much of this was due to differences in seedling size at the start of the growing season. FOR. SCI. 39:166-187.