ESTABLISHMENT TREATMENTS AFFECT THE RELATIONSHIPS AMONG NUTRITION, PRODUCTIVITY AND COMPETING VEGETATION OF LOBLOLLY-PINE SAPLINGS ON A GULF COASTAL-PLAIN SITE

After cultural treatments such as site preparation, release and fertil ization, changes in the supply of mineral nutrients relative to each o ther and shifts in the composition of vegetation may have a delayed ef fect on the nutrition, carbon partitioning and growth of forest trees. This study was conducted to evaluate the influence of early managemen t options that control vegetation and fertility on the nutrition and p roductivity of a young loblolly pine (Pinus taeda L.) plantation on a phosphorus-deficient site in the Gulf Coastal plain. Two levels each o f herbicide application, fertilization and litter addition were applie d in a factorial arrangement to three open-pollinated families of newl y planted loblolly pine seedlings. Competing vegetation was evaluated after three growing seasons, loblolly pine nutrition and tannin synthe sis were evaluated after four growing seasons and loblolly pine produc tivity was quantified after five growing seasons. Fertilization and he rbicide application increased the growth and decreased the foliar tann in concentration of loblolly pine. Herbicide application also increase d the potassium concentration of loblolly pine foliage. A negative cor relation between foliar tannin and potassium concentrations was found on plots that were fertilized with nitrogen and phosphorus. On souther n pine sites that are fertilized with phosphorus, the accelerated grow th of planted pine and invading vegetation may create new nutrient lim itations. Where phosphorus is limiting, however, nutrient utilization may not be great enough for new deficiencies to develop. Loblolly pine stand productivity and foliar nutrient concentrations were affected b y genetic family and the foliar calcium and magnesium concentrations o f loblolly pine families responded differently to the establishment tr eatments. We also found that the establishment treatments influenced t he occurrence of herbaceous and woody competitors. We hypothesize that corresponding treatment effects on exchangeable cation concentrations and pH of the soil were caused by changes in vegetation. (C) 1998 Els evier Science B.V.