More than 85% of terrestrial plant species associate with arbuscular mycorrhizal fungi (AMF). Most plant individuals stimulate nutrient availability through their fungal partner. Highly mycorrhizal-dependent plant species derive more benefits from AMF in comparison with plant species with a relatively low mycorrhizal dependency. Until recently, the effects of AMF on the competition between mycorrhizal and non-mycorrhizal plants (with high phosphate foraging ability) remained largely unclear, particularly in an environment with low phosphate bioavailability.
Mycorrhizal effects on plant interactions are most likely due to alterations in the soil nutrient availability. AMF colonization could increase nutrient (particularly phosphate) availability for host plants and consequently increase plant biomass. The larger plants are then expected to be successful competitors.
In the present study, maize (Zea mays L.) and rape (Brassica napus L.) plants were cultivated in three different interaction status, namely monoculture, intercropping and nylon net split. All the plants were inoculated with Glomus intraradices, Glomus mosseae or remained uninoculated. The strength of competition is measured as the reduction in biomass caused by the presence of a competitor. The results showed that maize growth and mineral nutrition was suppressed, while the mycorrhizal dependency increased to some extent, in intercropping compared with monoculture system. In intercropping system inoculation with G. intraradices and G. mosseae significantly decreased phosphorus concentration and content of rape roots compared with non-inoculation treatments, while in contrast mycorrhizal association improved phosphorus nutrition of maize plants. The experimental results clearly showed the beneficial effects of mycorrhizal associations on AMF host plants in competition with non-host plants. All these revealed that AMF may play an important role in structuring plant community and influencing plant biodiversity in ecosystems.