A new index for assessing the value of importance of species - VIS

Abstract

Phytosociological analysis in native forests is performed considering the horizontal and vertical structure of the studied population, whose most expressive parameters are the density, dominance, frequency, value of coverage and value of importance of species. Many phytosociological studies include a value of importance of species calculated by adding density, dominance and frequency, in their relative forms, however, this estimator is a mathematical impropriety because the result is a sum of indexes and does not express the true meaning of species' value. This is because the estimator is still influenced predominantly by the density of occurrence of species and cannot capture the relevant hierarchical participation of emerging species that occur with low density in the biocoenosis. In this work, we propose a new index to characterize the value of importance of species based on the hierarchy and spatial absolute probability of the species in the biocoenosis, illustrated with data from a forest fragment of semideciduous tropical forest located in Cassia, MG, Brazil. The new index appropriately expressed the importance of species in the evaluated fragment.

Comparative responses of dominant and subordinate periphytic diatom species to environmental gradients in Donghu Lake, China

“…The relative abundance is a description of percentage of each different species encountered within a community, customarily ranked from largest to smallest (McGill et al, ; Su, ). The frequency is understood as the percentage of occurrence of a species in a set of samples during an integrated survey, which can be considered as the probability of finding a certain species in the study area (Netto et al, ). The “outlier” F. recapitellata at site C possessed the highest abundance (65%) in May but is absent in all other months, suggesting that it could not be categorized as the dominant species.…”