Temporal Changes in the Ectomycorrhizal Community in Two Soil Horizons of a Temperate Oak Forest

Abstract

The species structure of an ectomycorrhizal (ECM) community was assessed monthly for 15 months in the two horizons (A1 and A2) of an oak temperate forest in northeastern France. Ectomycorrhizal species were identified each month by internal transcribed spacer sequencing. Seventy-five fungal symbionts were identified. The community was dominated by Tomentellaceae, Russulaceae, Cortinariaceae, and Boletales. Four species are abundant in the study site: Lactarius quietus, Tomentella sublilacina, Cenococcum geophilum, and Russula sp1. The relative abundance of each species varied depending on the soil horizon and over time. Some species, such as L. quietus, were present in the A1 and A2 horizons. C. geophilum was located particularly in the A2 horizon, whereas T. sublilacina was more abundant in A1. Some species, such as Clavulina sp., were detected in winter, while T. sublilacina and L. quietus were present all year long. Our results support the hypothesis that a rapid turnover of species composition of the ECM community occurs over the course of a month. The spatial and temporal unequal distribution of ECM species could be explained by their ecological preferences, driven by such factors as root longevity, competition for resources, and resistance to environmental variability.The fine roots of social tree species in temperate and boreal forests are symbiotically associated with fungi (52), forming composite organs called ectomycorrhizas (ECM). The ECM fungi play a crucial role in tree health by enhancing the nutrient acquisition, drought tolerance, and pathogen resistance of their hosts. ECMs efficiently take up water and organic and inorganic nutrients from the soil via the extramatricial mycelium and translocate these to colonized tree roots, receiving carbohydrates from the host in return (52). Most of the ectomycorrhizal roots are located in the top 20 centimeters of the soil, an area which is enriched in organic matter and where nutrients are concentrated (50). The ECM fungal community is species rich at the forest stand level, where hundreds of different fungal symbionts can be identified by morphotyping and DNA-based molecular methods (13,17,36,56).Beside its species composition, the structure is an important characteristic of the ECM community. Differences in ECM community structure on different scales are well documented: on the ecosystem scale (postdisturbance or postplanting successions) and along forest dynamics (4, 28, 56, 65), on the seasonal scale (6,8,20,33,54), and along spatial dimensions (vertical scale [13,14,24,49] and horizontal scale [36,58]). In a microsite or on a forest strand scale, species are distributed neither uniformly nor randomly but rather are aggregated in patches or distributed along gradients (9,12,19,24,44). The spatial heterogeneity of communities is important in terms of succession, adaptation, maintenance of species diversity, interspecific competition, and community stability (38). A spatial niche differentiation of ECM species and of ECM exploration types (1) could be du...

Potassium fertilization affects the distribution of fine roots but does not change ectomycorrhizal community structure

“…In contrast, the very abundant C. geophilum had no significant difference in occurrence in the Oi + Oe and Oa layers. This distribution has been shown in a number of studies (Baier et al 2006;Courty et al 2008) where the medium distance exploration types (L. rufus, C. neofurvolaesus, and C. delibutus) occur more often in the loose substrate horizons (Oi + Oe) than the more compact Oa layers. However, the short distance exploration type T. fibrillosa was also found preferentially in the Oi + Oe layer, suggesting that factors other than the compactness of the soil substrate may also be important, such as tolerance to fluctuations in soil temperature and moisture (Baier et al 2006).…”

“…Ectomycorrhizas can enhance K uptake and storage in roots by increasing the size of vacuolar pools and through increasing K influx rates and decreasing K efflux rates (Rygiewicz and Bledsoe 1984). In natural ecosystems, the fine roots of most trees are colonized by a large number of ectomycorrhizal fungal species (Erland and Taylor 1999;Courty et al 2008). Such investigations have shown that ectomycorrhizal communities in forests can be highly diverse, but these communities tend to be dominated by a few species and have a high number of rare species (Erland and Taylor 1999;Courty et al 2008).…”

“…In natural ecosystems, the fine roots of most trees are colonized by a large number of ectomycorrhizal fungal species (Erland and Taylor 1999;Courty et al 2008). Such investigations have shown that ectomycorrhizal communities in forests can be highly diverse, but these communities tend to be dominated by a few species and have a high number of rare species (Erland and Taylor 1999;Courty et al 2008). The ectomycorrhizal community structure is influenced by tree species (Lang et al 2011) and also by environmental factors such as nutrients (Jones et al 2012).…”

Below-ground ectomycorrhizal community in natural Tuber melanosporum truffle grounds and dynamics after canopy opening

“…This could be due to: (a) propitious weather conditions favour fruiting and the germinated spores colonise fine roots and form new ectomycorrhizas; and (b) the main shift in the relative abundance of T. melanosporum ectomycorrhizas from year to year occurs in autumn, when they have one of their two seasonal peaks (Bonet et al 2001), whereas the sampling has been performed in spring. The seasonal patterns of EM populations differ across species (Courty et al 2008) and our results indicate that the influence of weather is morphotype-specific. This could also contribute to changing the relative abundance of T. melanosporum ectomycorrhizas from one season to another.…”

“…Since the EM fungi differ in their preference for soil depth (Courty et al 2008), the EM community is likely to differ from that in wild truffières. In addition, the abundance of T. melanosporum ectomycorrhizas in our study is lower than generally reported in truffle plantations (which are usually established with nursery-inoculated seedlings on agricultural soils), and the richness of soil-borne EM fungi is higher (Sánchez-Durán et al 2009;Águeda et al, 2010).…”