摘要 : After cultural treatments such as site preparation, release and fertilizing, changes in the supply of mineral nutrients relative to each other and shifts in the composition of vegetation may have a delayed effect on the nutrition,... 展开 After cultural treatments such as site preparation, release and fertilizing, changes in the supply of mineral nutrients relative to each other and shifts in the composition of vegetation may have a delayed effect on the nutrition, carbon partitioning and growth of forest trees. The study described here was conducted to evaluate the influence of early management options that control vegetation and fertility on the nutrition and productivity of a young loblolly pine (Pinus taeda) plantation on a phosphorus-deficient mixed conifer-hardwood site harvested 22 yr earlier in the Gulf Coastal Plain (Rapides, Louisiana). Site preparation was by mowing and glyphosate broadcast in September 1987, and 28-wk-old container grown loblolly pine seedlings were planted at 2.5X2.5 m spacing in November 1988. Two levels each of herbicide application (none after site preparation; or broadcast application of hexazinone and sulfomethron [sulfometuron] with spot application of glyphosate in April 1989 and 1990, and broadcast application of glyphosate and sulfometuron in April 1991), fertilizer (none; or N and P as diammonium phosphate in March 1988, and N as urea in March 1989) and litter addition (none; or monthly broadcast application of loblolly pine needle litter from December 1988 to April 1989) treatments were applied in a factorial arrangement to plots of 3 open-pollinated families of seedlings. Competing vegetation was evaluated after 3 growing seasons, pine nutrition and tannin synthesis were evaluated after4 growing seasons and pine productivity (volume increment) was quantified after 5 growing seasons. Fertilizing and herbicide application increased the growth and decreased the foliar tannin concentration of the trees. Herbicide application also increasedthe potassium concentration of the pine foliage. A negative correlation between foliar tannin and potassium concentrations was found on plots that were fertilized with nitrogen and phosphorus. On southern pine sites that are fertilized with phosphorus,the accelerated growth of planted pine and invading vegetation may create new nutrient limitations. Where phosphorus is limiting, however, nutrient utilization may not be great enough for new deficiencies to develop. Stand productivity and foliar nutrient concentrations were affected by genetics (family), and the foliar calcium and magnesium concentrations of different families responded differently to the establishment treatments. The establishment treatments also influenced the occurrence of herbaceous and woody competitors. It is hypothesized that corresponding treatment effects on exchangeable cation concentrations and pH of the soil were caused by changes in vegetation. 收起