The main goal of this study was to describe the floristic composition and the community structure of the vegetation under avocado and pecan trees growing at Fazenda Experimental Lageado, FCA -UNESP, Botucatu -SP, Brazil. The studied areas differ in relation to light exposure conditioned by canopy architecture and pecan leaf deciduousness. A rectangular frame measuring 25 x 55 m was divided in 55 quadrats of 5 x 5 m. Forty quadrats were located under avocado trees and 15 under pecan trees. Frequency and percentage weed cover were estimated in both conditions at March, May and August 1993. Quadrats of 1 x 1 m were randomly assigned to a new area within each plot, each month. A Cluster Analysis was performed with six experimental groups (3 sampling dates x environmental conditions). Fifty four species, 38 genera and 19 families were recorded in total. Asteraceae and Poaceae had greater number of species. Species richness was greater at pecan tree community. In both areas, the richness was greater at the wet season. Total percentage of weed cover showed small variation only under the avocado trees during the study period. Most populations showed an aggregate distribution pattern. Floristic similarity was greater among the two areas at each sampling period. Commelina nudiflora and some other weed species had high cover values during all the study period. Therefore, a continuous weed control is indicated to the studied orchard.
Weeds; ecology; orchard; avocado; pecan