SHE ANALYSIS, A TOOL TO STUDY THE WEED DIVERSITY

Abstract

Weeds are constant components of agroecosystems, but are poorly understood and rarely studied with ecological methods. The aim of this research was to study the spatial and temporal variability in a diversity of weeds associated with sugarcane (Saccharum officinarum L.), and the relative contribution of species to the diversity richness and evenness. This study was conducted in Tlalquiltenango, Morelos, Mexico. Ten first-year sugarcane plantations with different management systems were selected during the growing season 2003- 2004. Within 10 x 10 m permanent quadrants, two plots of 1 m² were sampled monthly, and the species richness and density measured. These data were analyzed with the Shannon diversity index, with the Buzas and Gibson evenness index, and integrated by the SHE analysis. The graphical representation of the SHE analysis showed high richness (ln(S)) and diversity (H) in February, June to August, October and January. Generally, the influence of evenness (E) decreased as species richness (S) increased, and viceversa. As expected, the diversity of the weed communities is influenced by management, but it also behaves in a similar way as some types of natural vegetation.