Biomassa e macronutrientes de uma floresta estacional decidual em Itaara-RS, Brasil

The present study was conducted in a fragment of a seasonal deciduous forest in Itaara-RS, Brazil. The objective of this work was to quantify the nutrient in above ground biomass of forestry species. For the above ground biomass evaluation, 20 trees were cut down according to five different diameter classes (3,2-13,5 cm; 13,6-23,9 cm; 24,0-33,6 cm; 33,7-44,6 cm; 44,7-55,0 cm). The above ground biomass was separated in the compartment trunk wood, trunk bark, branches and leaves. The contents of N, P, K, Ca, Mg and S in the biomass samples were determined. The stock of nutrients in the biomass for each component was obtained based on the estimated dry biomass, multiplied by the nutrient content. The total production of above ground biomass was estimated at 210.0 Mg ha-1. The branches, trunk wood, trunk bark and leaves corresponded to 48.8, 43.3, 5.4 and 2.4% of the above ground biomass. The largest contents of N, P, K, Mg and S were verified in leaves; while greatest Ca content was found in trunk bark. The trunk wood was the component that showed the lowest concentration of nutrients in its biomass. In general, Ca, N and K are the nutrients with the largest stock in the above ground biomass. The largest stocks of nutrients are present in branches, which is mainly due to the great biomass, followed by trunk wood.