Site preparation effects on foliar N and P use, retranslocation, and transfer to litter in 15-years old Pinus taeda

Abstract

Intensive site preparation in loblolly pine ( Pinus taeda L.) plantations may remove nutrients and lower site productivity. We evaluated the effects of nutrient removal in site preparation on mid-rotation pine foliar production, and foliar N- and P-use, retranslocation, and transfer to litter for two years. We also investigated changes in foliar nutrients one year after fertilization. Site preparation treatments were: shear–pile–disk and chop–burn, used with or without vegetation control. Mid-rotation pines were fertilized with 200 kg ha −1 N and 50 kg ha −1 P, or with 200 kg ha −1 N and 50 kg ha −1 P and micronutrients. Foliar production was estimated from litter mass. N- and P-use was estimated from N and P concentrations in green foliage and foliar production. Retranslocation was the difference in N and P between green foliage and litter, in percent. N and P transfer to litter was estimated from litter N and P concentration and litter mass. Nutrient removal in site preparation at plantation establishment did not affect mid-rotation pine foliar production, foliar N- and P-use, retranslocation, or nutrient transfer to litter. The lack of site preparation effects may be related to the length of time after treatment; the stage of decomposition of organic matter that may be removed in site preparation may determine when nutrient supply will be affected. Competition with hardwoods decreased pine foliar production by 56%, and N- and P-use by 55% and 52%, but not percent retranslocation. On shear–pile–disk/herbicide, shear–pile–disk/no-herbicide, and chop–burn/herbicide plots (none or small hardwood component), average pine foliar production was 4365 kg ha −1 year −1, N- and P-use was 53.2 and 4.5 kg ha −1 year −1, N and P retranslocation was 63.7% and 69.8%, N and P transfer to litter was 18.9 and 1.3 kg ha −1 year −1. Based on a hypothetical N budget for the total stand, an N limitation may develop on those treatments that lost more nutrients in site preparation. Fertilization increased foliage production by 26%, and N- and P-use both by 49%, indicating some luxury consumption.