Measurement of weed species diversity in crop/weed competition studies

Abstract

Summary Data on dry matter accumulation by weeds in the presence or absence of two densities of vining peas was used to compare six diversity indices as measures of changes in the structure and behaviour of the weed flora. Analysis of variance was carried out for each index and the residuals were examined for skewness, kurtosis and heteroscedasticity. Indices based on species number (richness) and species evenness were found to be effective and reliable over the wide range of data examined and permitted new information to be derived. They showed that while increasing competition from the pea crops suppressed weed growth and reduced the number of species recorded at successive sampling dates, there was no selection pressure and species evenness was not reduced.