Spatial Patterns of Ectomycorrhizal Assemblages in a Monospecific Forest in Relation to Host Tree Genotype

Abstract

Ectomycorrhizas (EcM) are important for soil exploration and thereby may shape belowground interactions of roots. We investigated the composition and spatial structures of EcM assemblages in relation to host genotype in an old-growth, monospecific beech (Fagus sylvatica) forest. We hypothesized that neighboring roots of different beech individuals are colonized by similar EcM assemblages if host genotype had no influence on the fungal colonization and that the similarity would decrease with increasing distance of the sampling points. The alternative was that the EcM species showed preferences for distinct beech genotypes resulting in intraspecific variation of EcM-host assemblages. EcM species identities, abundance and exploration type as well as the genotypes of the colonized roots were determined in each sampling unit of a 1 L soil core (r = 0.04 m, depth 0.2 m). The Morisita-Horn similarity indices (MHSI) based on EcM species abundance and multiple community comparisons were calculated. No pronounced variation of MHSI with increasing distances of the sampling points within a plot was found, but variations between plots. Very high similarities and no between plot variation were found for MHSI based on EcM exploration types suggesting homogenous soil foraging in this ecosystem. The EcM community on different root genotypes in the same soil core exhibited high similarity, whereas the EcM communities on the root of the same tree genotype in different soil cores were significantly dissimilar. This finding suggests that spatial structuring of EcM assemblages occurs within the root system of an individual. This may constitute a novel, yet unknown mechanism ensuring colonization by a diverse EcM community of the roots of a given host individual.

Host Phylogenetic Relatedness and Soil Nutrients Shape Ectomycorrhizal Community Composition in Native and Exotic Pine Plantations

“…Within each site, the highest spatial autocorrelation occurred at small scales (<5 m). This result lends support to dispersal limitation in our sites [79], and is in general agreement with the degree of spatial patterning found in temperate forests [21,30,66,80]. As a result, these ECM communities likely comprise individuals that are closely related or have similar environmental requirements.…”

“…Such low-diversity limitations may reflect both neutral (dispersal) and niche processes (abiotic factors; e.g., [14][15][16][17]). Studies show that longer distances (>10 km) may limit the stochastic dispersal of fungal propagules from one location (native forest) to another (plantation) whereas deterministic traits such as dispersal via spores [14,18] versus mycorrhizal root tips and hyphal networks may operate at finer scales [19][20][21][22]. In addition, biotic (e.g., host nutrient demands, seed dispersal) and abiotic factors (e.g., soil chemistry) may facilitate ECM fungal species with physiological and ecological adaptations depending on the environmental context [23].Recent evidence has demonstrated that phylogenetic distance between exotic and native hosts might explain their (dis)similarities in ECM community composition and richness [24,25].…”

Early Stage Root-Associated Fungi Show a High Temporal Turnover, but Are Independent of Beech Progeny

“…These related results might indicate that different ecotypes deploy their influence on the mycobiome only at a later tree development stage or indeed not at all in the case of beech. In fact, previous investigations on mature beeches showed no impact of their genotypes on fungal composition [55]. However, abiotic parameters are probably involved in shaping the fungal communities at early stages.…”

Profiling functions of ectomycorrhizal diversity and root structuring in seedlings of Norway spruce (Picea abies) with fast‐ and slow‐growing phenotypes

“…Root architecture might indeed be the ‘unknown host mechanism’ suggested by Lang et al . (), resulting in spatial ECM species segregation and ensuring high diversity on an individual tree. In our experimental set‐up, variable root structuring was not likely to affect the colonization as the growing medium in the pots was homogenous and abundantly inoculated with ECM fungal mycelia in order to give equal opportunities for the fungi to colonize the roots.…”

“…Furthermore, the observed differences between the fine roots of fast-and slow-growing seedlings might later affect their ability to assemble ECM diversity in spatially heterogeneous forest soil (Peay et al, 2011). Root architecture might indeed be the 'unknown host mechanism' suggested by Lang et al (2013), resulting in spatial ECM species segregation and ensuring high diversity on an individual tree. In our experimental set-up, variable root structuring was not likely to affect the colonization as the growing medium in the pots was homogenous and Results are based on multivariate analysis of variance with the growth performance group, ECM richness and their interaction as fixed factors.…”