Nature of the belowground ecosystem and its development during pedogenesis

While much is known regarding the development of plant communities during primary succession and concomitant pedogenesis, considerably less is known regarding the development of soil microbial and soil fauna communities. In view of the importance of soil biota to soil processes, the nature of the belowground ecosystem and its development during pedogenesis is reviewed and discussed using recent chronosequence studies. During primary succession plant communities characteristically turnover several times. By contrast, community development for soil biota is characterized by progressive addition with many pioneer species remaining throughout soil development. In general, the size and diversity of soil biotic communities increases rapidly during the first 20-50. years and then more or less stabilizes after hundreds of years, while plant biomass and soil organic matter content do not reach a peak for many hundreds or even thousands of years. The development of the soil faunal community is less rapid than that of the microbial community because dispersal is slower and in addition some faunal species require a certain depth of organic topsoil and/or litter layer before high populations develop. With increasing successional time the food web (based on organic detritus) becomes increasingly complex. Based on the reviewed data, a conceptual model of changes in plant, soil microbial, and soil faunal communities that occur during succession is presented. The significance of such changes to restoration of unweathered mine tailings is also discussed