Independent role of belowground organisms and plant cultivar diversity in legume-grass communities

Abstract

Plant diversity and different groups of belowground organisms have been shown to influence the characteristics of plant communities and their associated aboveground organisms; however, little is known about the interactions and combined effects of these biotic factors. Furthermore, while plant species richness has received a lot of attention, intraspecific diversity has only recently come into the focus of community ecology. The objective of this study was to determine whether the addition of beneficial soil organisms (arbuscular mycorrhizal fungi (AMF) and anecic earthworms (Lumbricus terrestris L.) and different levels of plant cultivar diversity interactively influence productivity, weed establishment, leaf damage by herbivores and pathogens, and the diversity of aboveground herbivores in legume-grass communities. Our results indicated that the addition of AMF increased aboveground plant productivity and tended to decrease the diversity of aboveground herbivores. Earthworms attenuated the effect of AMF addition on AMF root colonization, but had no effect on plant productivity or herbivore diversity. Weed biomass was significantly lower in plant communities with high cultivar diversity compared to low cultivar diversity. We did not find interactive effects of the two soil organism groups and plant cultivar diversity. Our results demonstrate the independent roles and additive positive effects of AMF and plant cultivar diversity on functions such as productivity and resistance against weeds in the field. We suggest that AMF and plant cultivar diversity manipulations may be applied more frequently in agriculture management programs that aim for sustainable yield enhancement and biocontrol of herbivores and weeds.