Host and tissue variations overshadow the response of boreal moss‐associated fungal communities to increased nitrogen load

Abstract

Human activity has more than doubled the amount of nitrogen entering the global nitrogen cycle, and the boreal forest biome is a nitrogen-limited ecosystem sensitive to nitrogen load perturbation. Although bryophyte-associated microbes contribute significantly to boreal forest ecosystem function, particularly in carbon and nitrogen cycling, little is known about their responses to anthropogenic global change. Amplicon pyrosequencing of the ITS2 region of rDNA was used to investigate how fungal communities associated with three bryophyte species responded to increased nitrogen loads in a long-term fertilization experiment in a boreal Picea abies forest in southern Norway. Overall, OTU richness, community composition and the relative abundance of specific ecological guilds were primarily influenced by host species identity and tissue type. Although not the primary factor affecting fungal communities, nitrogen addition did impact the abundance of specific guilds of fungi and the resulting overall community composition. Increased nitrogen loads decreased ectomycorrhizal abundance, with Amphinema, Cortinarius, Russula and Tylospora OTUs responding negatively to fertilization. Pathogen abundance increased with fertilization, particularly in the moss pathogen Eocronartium. Saprophytic fungi were both positively and negatively impacted by the nitrogen addition, indicating a complex community level response. The overshadowing of the effects of increased nitrogen loads by variation related to host and tissue type highlights the complexity of bryophyte-associated microbial communities and the intricate nature of their responses to anthropogenic global change.

RNA‐based analyses reveal fungal communities structured by a senescence gradient in the moss Dicranum scoparium and the presence of putative multi‐trophic fungi

“…Mosses are widely distributed across diverse terrestrial biomes (Lindo & Gonzalez, ), where they play key roles in ecological processes including carbon and nutrient cycling (Brown & Bates, ; Turetsky et al ., ; Lenton et al ., ). Fungi associated with mosses include diverse parasitic, pathogenic, commensal, mutualistic and saprotrophic taxa (Redhead, ; Carleton & Read, ; Martínez‐Abaigar et al ., ; Davey & Currah, , ; Kauserud et al ., ; Davey et al ., , , ; Stenroos et al ., ). Whereas ecto‐ and endo‐mycorrhizal fungi can associate with mosses (Parke & Linderman, ; Davey & Currah, ; Zhang & Guo, ; Anderson et al ., ), typical mycorrhizal interactions between mosses and fungi are not common.…”

“…(, ) compared ergosterol concentrations as an indicator of fungal biomass in the green (living) and brown (senescent) tissues of several moss species and noted that Basidiomycota fungi of the genera Galerina and Mycena were more prevalent in brown, dead tissues (Davey et al ., ). A subsequent study (Davey et al ., ) based on amplicon sequencing data showed that distinct fungal communities occurred in photosynthetic and senescent tissues. There is a need to determine which fungi are active in each specific tissue layer, and across layers, to understand the symbiotrophic–saprotrophic continuum and the importance of multitrophism in plant–fungal symbioses.…”

A novel experimental system using the liverwort Marchantia polymorpha and its fungal endophytes reveals diverse and context‐dependent effects

“…For a few liverwort hosts, mutualistic mycorrhiza‐like relationships have been demonstrated with Glomeromycotina (Humphreys et al ., ; Field et al ., ), Mucoromycotina (Field et al ., ,b; Field et al ., ), and the ascomycete ericoid mycorrhizal fungus Pezoloma ericae (Kowal et al ., ). Surveys of fungal communities in bryophytes reveal considerable diversity beyond these focal mutualist taxa (Davis & Shaw, ; Davey et al ., , ; Knack et al ., ), but experiments have not explored the functional impacts of this wide range of additional endophytes.…”

Differential gene expression associated with fungal trophic shifts along the senescence gradient of the moss Dicranum scoparium

“…The taxonomic classification of fungal nutrient transporter and CAZy RNA revealed increase proportions of Basidiomycota toward the bottom layer of gametophytes, which is concordant with the results based on nrRNA data (Chen et al ., ). The healthy photosynthetic (top) portion of gametophytes are dominated by ascomycetes, especially members of Pezizomycotina (U'Ren et al ., ; Davey et al ., , ; Chen et al ., ). This might suggest that basidiomycetes are better adapted to colonize senescent/decomposing tissues of plants, where they can successfully compete with ascomycetes as decomposers of the soil litter (Voříšková and Baldrian, ).…”

“…1). It is known to harbour a high diversity of fungi (U'Ren et al, 2010;Davey et al, 2017;Chen et al, 2018). These features make D. scoparium an ideal system to study the capacity of fungi to switch function or for a mycelium to have multiple functions simultaneously.…”