Ectomycorrhizal diversity, taxon‐specific traits and root N uptake in temperate beech forests

Abstract

Roots of forest trees are colonized by a diverse spectrum of ectomycorrhizal (EM) fungal species differing in their nitrogen (N) acquisition abilities. Here, we hypothesized that root N gain is the result of EM fungal diversity or related to taxon-specific traits for N uptake.To test our hypotheses, we traced 15 N enrichment in fine roots, coarse roots and taxonspecific ectomycorrhizas in temperate beech forests in two regions and three seasons, feeding 1 mM NH 4 NO 3 labelled with either 15 NH 4 + or 15 NO 3 À . We morphotyped > 45 000 vital root tips and identified 51 of 53 detected EM species by sequencing. EM root tips exhibited strong, fungal taxon-specific variation in 15 N enrichment with higher NH 4 + than NO 3 À enrichment. The translocation of N into the upper parts of the root system increased with increasing EM fungal diversity. Across the growth season, influential EM species predicting root N gain were not identified, probably due to high temporal dynamics of the species composition of EM assemblages.Our results support that root N acquisition is related to EM fungal community-level traits and highlight the importance of EM diversity for tree N nutrition.

Ectomycorrhizal fungi of Douglas‐fir retain newly assimilated carbon derived from neighboring European beech

“…In our study, we chose a 5-d chase period, which was shorter than turnover of ECM mycelia in soil (Ekblad et al, 2013) and sufficiently long to enable ECM-mediated nutrient uptake and translocation to leaves as observed for instance for nitrogen (Rivera Pérez et al, 2022;Khokon et al, 2023). Therefore, we presume that in our experimental setup, a putative CMN was stable and that 13 C would have been traceable in coarse roots or aboveground tissues of the recipients, if the uptake kinetics were similar to those of other ECM-delivered nutrients.…”

“…Most temperate forest trees associate with ectomycorrhizal (ECM) fungi (Martin et al, 2016) that provide them nutrients and water in exchange for photosynthetically fixed carbon (C; Smith & Read, 2008). In Central European forests, numerous ECM species co-exist (Buée et al, 2009;Nguyen et al, 2020;Khokon et al, 2023), showing a variable degree of host specialization (Lang et al, 2011;van der Linde et al, 2018;Voller et al, 2023). Ectomycorrhizal fungi enwrap the root tips with extraradical mycelium from which hyphae extend into the soil.…”

Sporocarp nutrition of ectomycorrhizal fungi indicates an important role for endemic species in a high productivity temperate rainforest

“…Endemism was still a significant predictor of nutritional status ( P = 0.03), supporting our conclusion of enhanced N status in numerous, unrelated species. A high capacity for NH 4 + exploitation and, perhaps for a few species, NO 3 − by nitrophilic EMF taxa likely underpins the often exceptional productivity of temperate forest ecosystems (Kranabetter et al ., 2015; Leberecht et al ., 2016; Anthony et al ., 2022; Khokon et al ., 2023).…”