Abstract:

Biological diversity of ecosystems are traditionally measured by several diversity indices such as species richness, Simpson index, Shannon index. But these indices are not appropriate tools to analyze the changes of community diversity when soil fauna are classified into broad taxonomic units although a great shift of habitat appears. To overcome this limitation, Liao (1990, 2009) reported a new diversity index, known as density-group index (DG index). Many researchers reported thatDGindex, as a measure of diversity, is widely applicable to estimate soil faunal diversity. However, after reviewing recent documented data on soil fauna community diversity by several researchers, we found a negative correlation between Pielou’s evenness index andDGindex (r = -0.534,P =0.000). A higher evenness may lead to a lower diversity value. Using these data for further correlation analysis, strong positive relationships betweenDGindex and taxon number (r = 0.648,P =0.000) and taxon density (r = 0.487,P =0.000) appeared. It indicates that decrease in taxon number could be compensated with increasing density of some taxa. Therefore, loss of some taxa in a faunal community may lead to a constant or higher diversity ranges. Due to this reason, we do not suggest thatDGindex could be used as a diversity measurement. Furthermore, to explore intrinsic implication ofDGindex as a community parameter, we propose that the mean ratio of actual density to potential density of each taxon as parameter estimation for percent of community achieving potential abundance (maximum). By all means, if we useDGindex as an indicator of actual habitat condition, it might be a measurement of potential of increase in community abundance in the habitat.

Key words: biodiversity, soil biology, soil indicator, potential density, soil community