Plant species diversity is often thought to reflect also the biodiversity of other species groups in ecosystems but this assumption is poorly justified. We report on the changes in abundance and diversity of almost all aboveground and belowground functional groups (bacteria, fungi, plants, soil and aboveground invertebrates at different trophic levels, vertebrates) during 100 years of primary succession in a saltmarsh ecosystem. We compare sites in a calibrated chronosequence, i.e. sites that are 20 years different in successional age but have each been followed for 25 years. In additiona, we measured various aspects of ecosystem structure and functioning
We find that, while species richness for plants and invertebrate herbivores (green web groups) both peaked at intermediate productivity and successional age, the diversity of macrodetritivores, microarthropod microbivores and secondary consumers (brown web groups) continuously increased towards the latest successional stages. Microbial diversity, in contrast, was highest in the earliest (bare soil) successional stages. Plant productivity and soil organic matter biomass was highest in the latest successional stages while herbivore abundance peaked at intermediate stages. Our study yields important generalizations on the changes in diversity, ecological strategies and functional roles within and between different organismal and trophic groups during ecosystem assembly. We conclude that aboveground invertebrates diversity is associated with high plant diversity, but the diversity of soil biota is highly uncoupled from this diversity. The diversity of many soil invertebrate groups increased with higher soil organic matter and vertical structure, but was surprisingly negatively associated with microbe diversity.