Weed Seed Bank in an Agroforestry System With Eucalyptus in Subtropical Brazil

ABSTRACT : Trees can modify the weed seed bank composition and distribution in the cropped area of an agroforestry system. This study aimed at analyzing the eucalyptus (Eucalyptus dunnii) effect on spatial distribution, functional traits abundance and weed seed bank botanic composition in an agroforestry system under no-tillage in Subtropical Brazil. The experiment was conducted in a randomized block design with five replications, and five positions between 4.5-year-old eucalyptus double rows [(4x3) x 20 m] as treatments. Soil sampling was performed at 0-20 cm and the method to quantify and identify seeds was the seedling emergence in trays, inside a greenhouse. Weed phytosociological indices (relative density, frequency and importance), functional traits abundance (life cycle, shade tolerance, reproduction, spread and seed form) and seed densities (m-2) of families and species were evaluated; 17 weed families and 49 species were found. The indices that contributed to the relative importance of families and species differed among the positions between rows. Eucalyptus grown as an intercrop changed the composition and size of the weed seed bank, in a different way for functional traits, families and species depeding on the distance from trees.