Exploration type-specific standard values of extramatrical mycelium – a step towards quantifying ectomycorrhizal space occupation and biomass in natural soil

Abstract

The present study aims at providing standard values for the exploration type (ET)-specific quantification of extramatrical mycelium (EMM) of ectomycorrhizal fungi applicable to ecological field studies. These values were established from mycelial systems of ectomycorrhizae (ECM) synthesized in rhizotrons with near-to-natural peat substrate. Based on image analysis, the "Specific Potential Mycelial Space Occupation" (sPMSO), i.e. the ET-specific complete area that is covered by the EMM systems (mm 2 cm −1 ECM −1 ), and the "Specific Actual Mycelial Space Occupation" (sAMSO), i.e. the projection area of mycelial systems (mm 2 cm −1 ECM −1 ), were analyzed as an extension of a previously described approach. The "Specific Extramatrical Mycelial Length" (sEML) [m cm −1 ECM −1 ] and the "Specific Extramatrical Mycelial Biomass" (sEMB) (μg cm −1 ECM −1 ) were calculated for each of the ET via the proportion of hyphal projected area, hyphal length and biomass, the latter two being derived from previous measurements on Piloderma croceum, a "Medium-Distance" (MD)-ET. Both sPMSO and sAMSO were highest for the "Long-Distance" (LD)-ET, whereas those of the "Short-Distance" (SD)-ET and MD-ET were similar, although showing high variation. In contrast, mycelial density per occupied area of the MD-ET was twice as high as that of the LD-ET. Proportional to the sAMSO, the EMM length and biomass differed considerably between the three ET with values of the MD-ET being 1.9 times higher than those of SD-ET, and those of the LD-ET being 15 times higher than those of the SD-ET. These standards in relation to ECM length may ease quantification of mycelial space occupation and biomass in a relatively simple way. Thereby, the ET-specific contribution of EMM can be distinguishedalso of non-cultivable species-and up-scaling to large-scale estimation of cost/benefit relations is possible.

Environmental drivers of ectomycorrhizal communities in Europe's temperate oak forests

“…15 times more biomass than short‐distance exploration types (Weigt et al . ). The plasticity of these functional traits needs further investigation.…”

Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska

“…a). In the moist tussock tundra, all OTUs with EMM of the long-distance type, that has been hypothesized to play an important role in nutrient translocation and new root-colonization (Hobbie x0026; Agerer, 2010; Weigt et al ., 2011), were affiliated with Leccinum spp. that is specific to Betula nana in the Arctic.…”

How Ectomycorrhizae Structures Boost the Root System?

“…Mantle types are described in detail by Agerer (1987Agerer ( -2012Agerer ( , 1991Agerer ( , 1995Agerer ( , 2006) and Rambold (2004-2013) and divided into 16 types: nine plectenchymatous and seven pseudoparenchymatous. Laticifers, the latexcontaining, long, thick, scarcely branched hyphae, can occur in all of the mantle types (Agerer 2006).…”

“…Rhizomorphs are hyphae connected by various mechanisms and growing more or less parallel and more or less closely together over a greater distance (Agerer 1987(Agerer -2012, forming multi-hyphal linear aggregates (Agerer 1999). Based on structural, ontogenic, and functional similarities between all multi-hyphal linear aggregates, Cairney et al (1991) recommend that the term rhizomorph be used to describe all those structures, irrespective of their internal organization and their ontogeny (Agerer and Iosifidou 2004).…”

“…The extraradical mycelia of ectomycorrhizal fungi enormously increase the space plant roots occupy for water and nutrient gain (Cairney and Burke 1986;Leake et al 2004;Read 1992;Smith and Read 2008), but the costs for ectomycorrhizae are substantial (Rygiewicz and Andersen 1994;Weigt et al 2011). Therefore, the exploration types raise two different issues in the functioning of the mutualistic symbiosis: (1) the benefit for the plant as expressed by the range of soil occupation by the mycelium to explore and exploit the soil and finally transport water and nutrients to the roots and (2) the costs for the tree which are mainly expressed by the carbohydrates that have to be invested by the tree to support its fungal partner (Weigt et al 2012).…”