Variação temporal de nutrientes na serapilheira de um fragmento de floresta estacional semidecidual montana em Lavras, MG

Abstract

The study assessed total amount and concentration of macro and micronutrients of litterfall produced monthy in a fragment of tropical montane semideciduous forest in Lavras, Minas Gerais State, Brazil. From October 1991 to October 1992, litter was collected at 15-day intervals, from 0.5m x 0.5m wooden frames systematically distributed within a forest fragment. A monthly bulk sample was extracted from the collected litter according to fractions of leaves, propagules + flowers, and woody material. The samples were first naturally dried in shade followed by drying in a stove with forced air circulation at 65°C for 50 hours. After grinding, these samples underwent routine analyses at the Leaf Analysis Laboratory of the Federal University of Lavras. The amounts (kg/ha) of macronutrients present in the litter and probably returned to soil are concentration ranked as N>K>Ca>Mg>P for litter total. Micronutrients were present in the following concentration rank: Fe>Mn>B>Zn>Cu for the litter total and all studied fractions. N, K and Mg were the macronutrients with strongest seasonality, their highest amounts ocurring during rainiest months for all studied fractions. The amounts of N and P seem to be less variable. The behavior of content curves was very similar among categories for all macronutrients. The levels of B, Cu and Zn varied similarly within each fraction. Highest peaks were observed for B at end of dry season. Higher levels were detected for Fe and Mn, and these varied widely during the period studied. During the dry season there was a coincident inversion in the levels of Fe and Mn for all studied categories.