Do ectomycorrhizal exploration types reflect mycelial foraging strategies?

Area of Science:

• Ecology
• Mycology
• Forest Science

Background:

• Ectomycorrhizal (ECM) fungi form symbiotic relationships with trees, influencing nutrient cycling.
• ECM exploration types are hypothesized to reflect extraradical mycelial (ERM) spatial foraging and resource niches.
• Empirical data on the consistency of ECM foraging strategies within defined exploration types is limited.

Purpose of the Study:

• To investigate the actual soil foraging patterns of ECM fungi in relation to their established exploration types.
• To determine if ECM exploration types accurately predict the extent of extraradical mycelium proliferation in different substrates.
• To challenge and refine current understanding of ECM foraging strategies.

Main Methods:

• Root-excluding ingrowth mesh bags filled with six distinct substrates were incubated in mature Picea abies forests.
• High-throughput sequencing was employed to characterize ECM fungal communities within the ingrowth bags.
• ECM communities on adjacent fine roots were also analyzed for comparison after one growing season.

Main Results:

• Contrary to expectations, ECM genera associated with limited ERM production extensively colonized ingrowth bags.
• ECM genera typically linked to abundant ERM were found sparsely in ingrowth bags relative to their root abundance.
• Observed foraging patterns did not align with established ECM exploration type classifications.

Conclusions:

• Current assumptions linking ECM exploration types to specific soil foraging patterns appear to be inaccurate.
• The proliferation of ERM may be more strongly influenced by intergeneric differences in mycelial longevity and resource mobility.
• This study necessitates a re-evaluation of how ECM foraging strategies are understood and categorized.