Distribution Of Mycorrhizal Fungi Research Articles

Fine Root Size and Morphology of Associated Hyphae Reflect the Phosphorus Nutrition Strategies of European Beech Forests

Roots are among the major controls of nutrient and C cycles and together with mycorrhizal fungi they are assumed to play a key role especially in P nutrition of forest ecosystems. Current publications emphasized that size distribution of fine roots reflects the crucial impact of roots on biogeochemical cycles. However, we know hardly anything about the spatial distribution of fine root size classes and their specific surface as well as distribution of mycorrhizal fungi among different size classes in undisturbed soils. We used a novel method based on epifluorescence microscopy to analyze fine roots in undisturbed soil samples. We expected that based on these analyses proposed differences between P-rich and P-poor soils get clearer than based on routine methods for fine root analysis. This was examined at two European beech forests in Germany at silicate rock that differ in P supply by the parent material. We analyzed the fine root frequency, size distribution and surface based on resin impregnated cross sections taken from undisturbed soil samples. Fine roots were classified according to their size and morphology of associated ectomycorrhiza with epifluorescence microscopy. More than 82% of the absorbing surface was associated with roots having a diameter smaller than 100µm. The fine root surface area present per square meter of soil was 388m² at the P-poor site and 220m² at the P-rich site. In addition, percentage of mycorrhization of fine root surface was 47% at P-poor site and only 38% at P-rich site. The biggest root length density and the highest absorbing fine root surface with mycorrhization and abundance of extramatrical mycelia was observed in forest floor at the P-poor site and in subsoil at P-rich site. Our results confirm that beech trees adapt their root traits according to P availability showing higher absorbing surface at the P-poor site compared to the P-rich site. In contrast, at the soil-profile scale, rooting density and mycorrhization increased with P availability thereby showing an efficient way of root and mycorrhizal fungi placement. Overall, distinct differences in fine root traits, between the P-rich and P-poor site were most evident for fine roots smaller than 100μm.

Topographic and Host Effects on Arbuscular Mycorrhizal and Ectomycorrhizal Fungal Communities in a Forested Watershed

In a forested watershed, identity of tree species and topographical position could be important driving factors shaping mycorrhizal fungal communities. Here we aimed to disentangle the contributions of these two factors to mycorrhizal fungal community structure. We collected tree roots colonized by either arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi in a small, temperate, forested watershed of the Susquehanna-Shale Hills Critical Zone Observatory. Relative abundances of fungal OTUs were assessed using high-throughput DNA sequencing. The structures of fungal communities, both AM and EM, were compared between different host species at the same slope position, and within the same host species at different slope positions that vary in soil moisture, nutrient content and belowground biomass. We found that structures of AM fungal communities were significantly affected by host species but not by slope position. Although the structures of EM fungal communities were not significantly affected by either host identity or slope position, there were three core EM fungal OTUs (occurrence ≥ 50%) for which their relative abundances were significantly affected by slope position and three for which their relative abundances were significantly affected by host species. In our system, the effects of host identity and slope position were only moderately strong and varied between mycorrhizal types. Our findings provide guidance to those attempting to link the fine-scale distribution of mycorrhizal fungi and mycorrhizal-mediated ecosystem functions to both host species and topographic position.

吉林省杨树群落中菌根真菌资源分布

吉林省杨树群落中菌根真菌资源分布

Nonrandom seedling establishment corresponds with distance-dependent decline in mycorrhizal abundance in two terrestrial orchids.

In plant species that critically rely on mycorrhizal symbionts for germination and seedling establishment, distance-dependent decline of mycorrhizal fungi in the soil can be hypothesized to lead to significant spatial clustering as a result of nonrandom spatial patterns of seedling establishment. To test this hypothesis, we investigated the abundance and distribution of mycorrhizal fungi in the soil and how they relate to spatial patterns of adults and seedling recruitment in two related orchid species. We combined assessments of spatial variation in fungal abundance using quantitative PCR (qPCR) with spatial point pattern analyses based on long-term demographic data and cluster point process models. qPCR analyses showed that fungal abundance declined rapidly with distance from the adult host plants. Spatial point pattern analyses showed that successful recruitment in both species was clustered significantly around adult plants and that the decline in the neighborhood density of recruits around adults coincided with the decline of fungal abundance around adult plants. Overall, these results indicate that the distribution and abundance of fungal associates in the soil may have a strong impact on the aboveground distribution of its partner.

Translocation of mycorrhizal fungi by earthworms during early succession

The distribution of propagules of vesicular-arbuscular mycorrhizal (VAM) fungi by earthworms was investigated in a number of natural plant communities, differing in successional age. Propagule numbers were quantified using direct spore counts and the Most Probable Number (MPN) dilution method. Propagule number was low in early successional sites and was progressively higher in sites of 3yr and over. Results of spore counts and MPN analysis showed similar patterns. In all sites, earthworm cast material contained higher numbers of spores and infective propagules than nearby field soil. These differences were significant in sites of 5 yr and over. There was a positive relationship between MPN of propagules and spore counts in cast material, but spore counts underestimated total propagule numbers. It is suggested that, due to feeding on senescing roots, earthworms concentrate mycorrhizal propagules in their cast soil. Due to the fact that surface worm casts were more abundant in early succession, the deposition of propagules was comparable to that in older communities. Earthworms may therefore be important agents in the distribution of mycorrhizal fungi, and thereby influence plant establishment in early succession.