Plant functional identity has predictable effects on nematode communities across successional stages

Soil fauna communities are known to change during succession as the soil ages and vegetation develops. Moreover, plant functional identity (PFI) influences belowground assemblages within successional stages. Given changes in soil carbon (C) and nutrient content, this influence of PFI is likely to differ across successional stages; however, the relative contribution of PFI across successional stages remains unknown. We sampled nematode communities associated with nitrogen (N) fixing and non-fixing tree species across a well-described chronosequence (Cooloola, QLD, Australia) to assess the relative importance of PFI and successional stage on nematode community composition. Nematode densities were influenced by successional stage, peaking at the late progressive stage, associated with similar patterns in C and N contents. Successional stage and PFI accounted for more than half of the observed variation in nematode assemblage composition. K-strategists increased in abundance in the later successional stages while the two PFIs supported distinct communities by favouring certain genera. This supports our hypothesis that nematode assemblages change during succession, but that PFI plays a key role in structuring nematode communities within successional stages. Contrary to our expectations, there was no interaction between the two factors, indicating that PFI has largely consistent influences on soil nematode assemblage composition across successional stages. Still, a significant interactive effect of PFI and soil age on the basal and enrichment indexes indicate that nematode contributions to ecosystem functions associated with PFIs differ somewhat as succession proceed.