Composição florística e estrutura das plantas espontâneas das pastagens de Urochloa no norte do Amapá.

Abstract

In pastures, trees and shrubs, remaining from original forest or the rain ofseeds, arepartofspontaneous plants; in this backgroundthey are consideredcompetitors thatweaken a forageor may be responsible for a balanced dynamic, decreasing the density ofcompeting plants. The aimofthis study was to describe the structure and floristic composition ofspontaneous pasture plantsand to verify the influence offorage species and the presence ofwoody plants existing above theherbaceous stratum, besides investigating the presence or not of infestation along the BR-156highway, in the municipality ofOiapoque, Amapá state, Brazil. Thirty-one pastures were sampledonsmallholder family farms; these were categorized according to: (1) the foragespeciesUrochloabrizantha cv. Marandu and U. humidicola); (2) and the presence ofwoody plants (clean or dirtypastures) above the herbaceous stratum. In each area, the floristic survey was performedin a 1 x 50m (50 m2) transect, where all individuals with 0.10 ≤ height < 2.0 m were inventoried. A total of90species were recorded, predominantly herbaceous. The floristic composition ofspontaneous plants isvery similar to those found in other pastures ofthe Amazonia, however several pastures showedinfestation by some species, such as Stigmaphyllon convolvulifolium, Stigmaphyllon sinuatum,Borreria verticillata, Hyptis atrorubens, Desmodium barbatum, or Stachytarpheta cayennensis. Thestructure andfloristic composition ofspontaneous plants is not influencedeither by forage or by thepresence ofwoody plants existingabove the herbaceous stratum.