RESUMO
Arbuscular mycorrhiza (AM) and ectomycorrhiza (EcM) are the most abundant and widespread types of mycorrhizal symbiosis, but there is little and sometimes conflicting information regarding the interaction between AM fungi (AMF) and EcM fungi (EcMF) in soils. Their competition for resources can be particularly relevant in successional ecosystems, which usually present a transition from AM-forming herbaceous vegetation to EcM-forming woody species. The aims of this study were to describe the interaction between mycorrhizal fungal communities associated with AM and EcM hosts naturally coexisting during primary succession on spoil banks and to evaluate how this interaction affects growth and mycorrhizal colonization of seedlings of both species. We conducted a greenhouse microcosm experiment with Betula pendula and Hieracium caespitosum as EcM and AM hosts, respectively. They were cultivated in three-compartment rhizoboxes. Two lateral compartments contained different combinations of both host plants as sources of fungal mycelia colonizing the middle compartment, where fungal biomass, diversity, and community composition as well as the growth of each host plant species' seedlings were analyzed. The study's main finding was an asymmetric outcome of the interaction between the two plant species: while H. caespitosum and associated AMF reduced the abundance of EcMF in soil, modified the composition of EcMF communities, and also tended to decrease growth and mycorrhizal colonization of B. pendula seedlings, the EcM host did not have such effects on AM plants and associated AMF. In the context of primary succession, these findings suggest that ruderal AM hosts could hinder the development of EcM tree seedlings, thus slowing the transition from AM-dominated to EcM-dominated vegetation in early successional stages.
RESUMO
The great majority of plants gain access to soil nutrients and enhance their performance under stressful conditions through symbiosis with arbuscular mycorrhizal fungi (AMF). The benefits that AMF confer vary among species and taxonomic groups. However, a comparative analysis of the different benefits among AMF has not yet been performed. We conducted a global meta-analysis of recent studies testing the benefits of individual AMF species and main taxonomic groups in terms of plant performance (growth and nutrition). Separately, we examined AMF benefits to plants facing biotic (pathogens, parasites, and herbivores) and abiotic (drought, salinity, and heavy metals) stress. AMF had stronger positive effects on phosphorus nutrition than on plant growth and nitrogen nutrition and the effects on the growth of plants facing biotic and abiotic stresses were similarly positive. While the AMF taxonomic groups showed positive effects on plant performance either with or without stress, Diversisporales were the most beneficial to plants without stress and Gigasporales to plants facing biotic stress. Our results provide a comprehensive analysis of the benefits of different AMF species and taxonomic groups on plant performance and useful insights for their management and use as bio-inoculants for agriculture and restoration.