Some characteristics of Simpson index and the ShannonWiener index and their dilution effect

Based on the hypothesized community conditions, this study compared the characteristics of Simpson index and the ShannonWiener index, which were used to analyze the species diversity of community, to improve the understanding, application and interpretation of these two diversity indexes. At the hypothesized community conditions and scenario, this study proved that Simpson index was more sensitive to the evenness change than ShannonWiener index, and ShannonWiener index was more sensitive to the richness change than Simpson index. This study also showed that the relative important value of 0.72 could be considered as a criterion for enrichment species approximately. The dilution effect was found for ShannonWiener index and Simpson index, in which a community biodiversity index decreased when the relative abundance of a new immigrated species exceeded the threshold value, which was 0.67 for Simpson index and 0.77 for ShannonWiener index.