Nutrients allocation along the stem in 17-year-old Pinus taeda L.

Abstract

This study was conducted in a 17-year-old Pinus taeda L. stand, in Cambará do Sul (RS state), in a soil classified as Humic Cambisol. It had as objective to study nutrients allocation pattern along the stem and its implications for sampling and the nutrient stock estimates. Eighteen (18) trees were sampled, distributed in 6 diametric classes, collecting bark and wood samples in the following relative heights (percentage from total height): h_0.1 (10%), h_0.3 (30%), h_0.5 (50%), h_0.7 (70%) e h_0.9 (90%). The nutrient allocation pattern along the stem was studied based on the comparison of averages and regression equations, correlating nutrient content and the sampling height. Different nutrient content estimators were tested: arithmetic average content (TM), level weighted average diameter of the section (TMPD), biomass-weighted average content of the section (TMPB), being TMPB considered as the standard treatment. Excepted for Mn and in wood, all nutrients showed higher content in the upper part of the stem (h_0.9), sometimes 2.7 times higher in wood and 5 times higher in bark, compared to stem base (h_0.1). Calcium (Ca) in the wood showed a reverse behavior, in other words, showed highest contents in the base of the stem (h_0.1); while Mn did not statistically differ among the sampling points. Among the tested nutrient content estimators, TM showed highest values, excepted for Ca in wood, that leads to nutrients stock overestimation. For the study conditions, considering TMPB as the best nutrient concentration estimator, the confidence interval for height sampling points was estimated in 35 - 53% for wood and 38 - 46% for bark.

Keywords:
Nutrient cycling; Forest nutrition; Biomass sampling