Associations of root-inhabiting fungi with herbaceous plant species of temperate forests in relation to soil chemical properties

The overwhelming majority of research on fungal interactions with plants in the forest ecosystems of the temperate climate zone focuses on ectomycorrhizal associations and no studies so far have compared the occurrence of root-inhabiting fungi in herbaceous plant species. We thus studied arbuscular mycorrhizal fungi (AMF) and fungal root endophyte colonization rates as well as AMF species richness and composition under 19 herbaceous plant species in temperate forests (southeast Poland) in relation to soil chemical properties. Seventeen species formed arbuscular mycorrhiza (AM), while 2 were non-mycorrhizal. The intensity of AMF colonization varied between species. Relative mycorrhizal root length (M_AMF%) ranged from 0% to 100%. AMF spore abundance ranged from 0 to 11.4 in 1 g of soils. Sixteen AMF species were recorded, both widespread (e.g. Funneliformis constrictum, Claroideoglomus claroideum) and rare (Acaulospora cavernata, Entrophospora infrequens). The composition of AMF species related to the plants differed. Fungal root endophytes were recorded only in some plants; dark septate endophytes (DSE) in 13 species, while Olpidium spp. in 6 species. Moreover, DSE mycelia and Olpidium spp. sporangia were observed with low abundance, and their occurrence differed between particular plant species. Among soil chemical properties, only the concentration of available phosphorus was significantly negatively correlated with the M_AMF% parameter. In conclusion, several groups of root-inhabiting fungi were related to herbaceous plants; however, they occurred with varied frequency. AMF spore abundance and species richness differed as well; however, they persisted at a low level compared to other ecosystems. Nonetheless, we detected significant negative correlation between available P contents in soils and the intensity of mycorrhizal colonization, which suggests the importance of AM for the plants in sites with low P concentration.