New Phytologist
2001: 151(2): 543-550.


Do nutrient additions alter carbon sink strength of ectomycorrhizal fungi?

Bidartondo, M.I.1,Ek, H.2,Wallander, H.2 andB. Söderström2
1 University of California at Berkeley, Department of Environmental Science, Policy and Management, 321 Koshland Hall, Berkeley, California 94720-3102.
2Department of Microbial Ecology, Lund University, S 223 62 Lund, Sweden

Abstract
  • We examined carbon sink strength differences between ectomycorrhizal fungi in interaction with additions of ammonium and apatite (a phosphorus and calcium containing mineral).
  • We used Pinus muricata associated with Paxillus involutus and four suilloid isolates:Suillus pungens and members of three Rhizopogon section Amylopogon species groups.
  • Each association differed in ectomycorrhizal biomass, and mycelial growth rate, biomass and respiration.? P. involutus was most distinct:? 1) P. involutus produced the lowest biomass of ectomycorrhizal connections to P. muricata, but it extracted proportionally more carbon per connection; 2) transferred more than double the amount of ammonium per mycorrhizal biomass; 3) most rapidly and intensely colonized soil, but its mycelial respiration per biomass was lowest.
  • Ammonium addition resulted in a strong positive response in mycelial respiration by the suilloid fungi. Apatite addition resulted in a positive response in mycelial biomass production by the suilloid fungi. The high carbon cost of fungal ammonium uptake is suggested to be one explanation for reduced sporocarp production and mycelial growth commonly found after high levels of nitrogen addition.

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