Ectomycorrhizal fungal communities of Swiss stone pine (Pinus cembra) depend on climate and tree age in natural forests of the Alps

Abstract

Background and Aims Pinus cembra represent a typical and important tree species growing in European subalpine and alpine habitats. The ectomycorrhizal (ECM) fungal communities associated to this tree under natural conditions are largely unknown. Methods In this study, we investigated the ECM fungal abundance and composition at four high-altitude sites (two northern-exposed and two southern-exposed habitats) in South Tyrol (Italy), and included also two different age classes of P. cembra. The ECM partners were characterized morphologically, and identified by rDNA ITS sequence analysis. Results The degree of mycorrhization in adult P. cembra was typically 100% in these natural habitats, with a total species diversity of 20 ECM species. The four high-altitude sites were similar concerning their species richness and mycobiont diversity, but they differed significantly in ECM species composition. Young P. cembra had a mycorrhization degree of 100% and a total of 10 species were observed. All mycorrhizal partners of naturally regenerated young P. cembra were only detected in one specific location, with the exception of Cenococcum sp. and Amphinema sp. which were detected at two sites. Young trees harbour a distinct ectomycorrhizal fungal diversity, which is clearly lower than the diversity detected in adult P. cembra trees. The P. cembra bolete (Suillus plorans) is the most important symbiotic partner of P. cembra at Southern Tyrolean high-altitude sites and is known for its strict, species-specific host association. Conclusions The ectomycorrhizal fungal community composition strongly depends on geographic region and on the slope exposure (north or south) of the site.

Swiss stone pine - portrait of a mountain forest tree

“…This enables the exchange of nutrients and sugars between the fungus and the host tree and is particularly important at the marginal sites of the occurrence of Swiss stone pine, where nitrogen-poor raw humus soils and rocky sites predominate. The diversity of the mycorrhizal fungal partners increases with the age of the Swiss stone pines, and their species composition varies according to site and exposure (Mandolini et al 2022). Frequently found is the stone pine bolete (Suillus plorans; Fig.…”

L'arole - portrait d'un montagnard

“…Cela facilite les échanges de nutriments et de sucres entre le champignon et l'arbrehôte, particulièrement importants sur des stations limitrophes de l'aire de l'arole, caractérisées par des sols d'humus brut pauvres en azote ou des sites rocheux. La diversité des partenaires mycorhiziens augmente avec l'âge des aroles, les combinaisons d'espèces variant en fonction de l'emplacement et de l'exposition (Mandolini et al 2022) En Suisse, l'arole a déjà subi des dégâts parfois étendus causés par de nombreux insectes, dont diverses espèces de pucerons, tenthrèdes, charançons, capricornes, scolytes et de teignes, tordeuses et pyrales (fig. 17).…”

Die Arve - Portrait eines Gebirgswaldbaums

“…Dies ermöglicht den Austausch von Nährstoffen und Zucker zwischen Pilz und Wirtsbaum und ist insbesondere an den Grenzstandorten des Arvenvorkommens wichtig, wo stickstoffarme Rohhumusböden und felsige Lagen vorherrschen. Die Vielfalt der Mykorrhizapilz-Partner wächst mit dem Alter der Arven und ihre Art-Zusammensetzung variiert je nach Ort und Exposition (Mandolini et al 2022). Häufig zu finden ist der Arvenröhrling (Suillus plorans; Abb.…”