Data from: Species turnover (β diversity) in ectomycorrhizal fungi linked to NH4+ uptake capacity

We then examined functional traits for an N-related niche by quantifying net fluxes of NH4+, NO3- and protons on excised root tips from three contrasting sites using a microelectrode ion flux measurement system. EcM fungal communities were well aligned with soil N availability and pH, with no effect of site proximity (distance-decay curve) on species assemblages. Species turnover was significant (β1/2 = 1.48) along soil N gradients, with many more Tomentella species on high-N than low-N soils, in contrast to Cortinarius species.

Ammonium uptake was greatest in the spring on the medium and rich sites, and averaged over 190 nmol m−2 s−1 for Tomentella species. The lowest uptake rates of NH4+ were by non-mycorrhizal roots of axenically grown seedlings (10 nmol m−2 s−1), followed by Cortinarius species (60 nmol m−2 s−1). EcM roots from all sites displayed only marginal uptake of nitrate (8.3 nmol m−2 s−1).

These results suggest NH4+ uptake capacity is an important functional trait influencing the assembly of EcM fungal communities. The diversity of EcM fungal species across the region arguably provides critical belowground adaptations to organic and inorganic N supply that are integral to temperate rainforest ecology.

Usage notes

Ion flux results Net fluxes of H+, NH4+ and NO3- measured on ectomycorrhizal root tips using a microelectrode ion flux measurement system (MIFE). Roots were retrieved from three sites of contrasting soil fertility, both in the spring and fall of 2014. Non-mycorrhizal roots taken from axenically raised seedlings.

Dryad file.xlsx community similarity and distance measures Pair-wise comparisons of test sites for community similarity (Sorensen Bray-Curtis) with distance measures of mineralizable nitrogen and physical distance (km)