Species turnover (β-diversity) in ectomycorrhizal fungi linked to NH4+ uptake capacity.
Ectomycorrhizal (EcM) fungal communities may be shaped by both deterministic and stochastic processes, potentially influencing ecosystem development and function. We evaluated community assembly processes for EcM fungi of Pseudotsuga menziesii among 12 sites up to 400 km apart in southwest British Columbia (Canada) by investigating species turnover (β-diversity) in relation to soil nitrogen (N) availability and physical distance. 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 (β(1/2) = 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 for Tomentella species. The lowest uptake rates of NH4+ were by nonmycorrhizal roots of axenically grown seedlings (10 nmol/m(2)/s), followed by Cortinarius species (60 nmol/m(2)/s). EcM roots from all sites displayed only marginal uptake of nitrate (8.3 nmol/m(2)/s). 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.
British Columbia Ministry of Forests, Lands and Natural Resource Operations, PO Box 9536, STN PROV GOVT, Victoria, British Columbia, Canada, V8W 9C4.
J M
JM
Kranabetter
Centre for Forest Biology, University of Victoria, PO Box 3020, STN CSC, Victoria, British Columbia, Canada, V8W 3N5.
B J
BJ
Hawkins
Biology Department, University of British Columbia, Okanagan Campus, Sci-385, 1177 Research Road, Kelowna, British Columbia, Canada, V4V 1V7.
M D
MD
Jones
Centre for Forest Biology, University of Victoria, PO Box 3020, STN CSC, Victoria, British Columbia, Canada, V8W 3N5.
S
S
Robbins
Natural Resources Canada, Pacific Forestry Centre, 506 Burnside Road West, Victoria, British Columbia, Canada, V8Z 1M5.
T
T
Dyer
Laboratory of Conservation and Utilization of Bio-resources, Yunnan University, 2# Cuihu Road North, Kunming, China.
T
T
Li
D064751:Ammonium Compounds / Q000378:metabolism*; D001955:British Columbia; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000145:classification* / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D058458:Nitrogen Cycle; D018517:Plant Roots / Q000382:microbiology; D028224:Pseudotsuga / Q000382:microbiology; D012987:Soil / Q000737:chemistry
D064751:Ammonium Compounds; D009566:Nitrates; D012987:Soil
ammonium; community assembly; fungal niche; nitrogen; species diversity