Disentangling the relative importance of spatio-temporal parameters and host specificity in shaping arbuscular mycorrhizal fungus communities in a temperate forest.

Many woody and herbaceous plants in temperate forests cannot establish and survive in the absence of mycorrhizal associations. Most temperate forests are dominated by ectomycorrhizal woody plant species, which implies that the carrying capacity of the habitat for arbuscular mycorrhizal fungi (AMF) is relatively low and AMF could in some cases experience a limitation of propagules. Here we address how the AMF community composition varied in a small temperate forest site in Germany in relation to time, space, two plant host species, and also with regard to the degree to which plots were covered with AMF-associating woody species. The AMF communities in our study were non-random. We observed that space had a greater impact on fungal community composition than either time, mycorrhizal state of the close-by woody species, or the identity of the host plant. The identity of the host plant was the only parameter that modified AMF richness in the roots. The set of parameters which we addressed has rarely been studied together, and the resulting ranking could ease prioritizing some of them to be included in future surveys. AMF are crucial for the establishment of understory plants in temperate forests, making it desirable to further explore how they vary in time and space.

Grünfeld L ，Mola M ，Wulf M ，Hempel S ，Veresoglou SD ... -  《-》

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 (MAMF%) 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 MAMF% 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.

Rożek K ，Rola K ，Błaszkowski J ，Zubek S ... -  《-》

Host age and surrounding vegetation affect the community and colonization rates of arbuscular mycorrhizal fungi in a temperate grassland.

Arbuscular mycorrhizal fungi (AMF) are important symbionts for the majority of terrestrial vascular plants, yet the drivers of the compositional variation in AMF communities need to be better understood. What effects does the ontogenetic stage of host plants have and do these effects differ between plant functional groups? Are the AMF communities modified by the properties of surrounding vegetation, such as the proportion of different functional groups or nonmycorrhizal plants ? We addressed these questions in a temperate grassland and studied AMF communities using next-generation sequencing and light microscopy, evaluating their composition, taxonomic, phylogenetic and functional diversity, functional traits and root colonization levels. We found important differences between AMF communities and their diversity between seedlings and adults which are larger than the differences among host species or between functional groups. The proportion of nonmycorrhizal plants in the surrounding affected AMF community composition and increased its richness. Our results highlight the need for further investigating the existence of a common mycelial networks. The decision to use seedlings for experimental work can affect the results more than the chosen host species.

Šmilauer P ，Košnar J ，Kotilínek M ，Pecháčková S ，Šmilauerová M ... -  《-》

Mycorrhizal type of woody plants influences understory species richness in British broadleaved woodlands.

Mature temperate woodlands are commonly dominated by ectomycorrhizal trees, whereas understory plants predominantly form arbuscular mycorrhizal associations. Due to differences in plant-fungus compatibility between canopy and ground layer vegetation the 'mycorrhizal mediation hypothesis' predicts that herbaceous plant establishment may be limited by a lack of suitable mycorrhizal fungal inoculum. We examined plant species data for 103 woodlands across Great Britain recorded in 1971 and in 2000 to test whether herbaceous plant species richness was related to the proportion of arbuscular mycorrhizal woody plants. We compared the effect of mycorrhizal type with other important drivers of woodland plant species richness. We found a positive effect of the relative abundance of arbuscular mycorrhizal woody plants on herbaceous plant species richness. The size of the observed effect was smaller than that of pH. Moreover, the effect persisted over time, despite many woodlands undergoing marked successional change and increased understorey shading. This work supports the mycorrhizal mediation hypothesis in British woodlands and suggests that increased abundance of arbuscular mycorrhizal woody plants is associated with greater understory plant species richness.

Guy P ，Sibly R ，Smart SM ，Tibbett M ，Pickles BJ ... -  《-》

Local abiotic conditions are more important than landscape context for structuring arbuscular mycorrhizal fungal communities in the roots of a forest herb.

Boeraeve M ，Honnay O ，Jacquemyn H 《-》