Ectomycorrhizal fungal succession coincides with shifts in organic nitrogen availability and canopy closure in post-wildfire jack pine forests.
Successional changes in belowground ectomycorrhizal fungal (EMF) communities have been observed with increasing forest stand age; however, mechanisms behind this change remain unclear. It has been hypothesized that declines of inorganic nitrogen (N) and increases of organic N influence changes in EMF taxa over forest development. In a post-wildfire chronosequence of six jack pine (Pinus banksiana) stands ranging in age from 5 to 56 years, we investigated EMF community composition and compared shifts in taxa with detailed soluble inorganic and organic N data. Taxa were identified by internal transcribed spacer rDNA sequencing, and changes in community composition evaluated with non-metric multi-dimensional scaling (NMDS). Dissimilarities in the community data were tested for correlations with N variables. We observed a successional shift along NMDS axis 1 from such taxa as Suillus brevipes and Thelephora terrestris in sites age 5 and 11 to species of Cortinarius and Russula, among others, in the four older sites. This change was positively correlated with soluble organic N (SON) (r(2) = 0.902, P = 0.033) and free amino-acid N (r(2) = 0.945, P = 0.021), but not inorganic N. Overall, our results show a successional shift of EMF communities occurring between stand initiation and canopy closure without a change in species of the dominant plant-host, and associated with SON and free amino-acid N in soil. It is uncertain whether EMF taxa are responding to these organic N forms directly, affecting their availability, or are ultimately responding to changes in other site variables, such as belowground productivity.
Department of Forestry and the Ecology, Evolutionary Biology and Behavior Program, Michigan State University, 126 Natural Resources, East Lansing, MI 48824, USA. leduc.stephen@epa.gov
Stephen D
SD
LeDuc
Erik A
EA
Lilleskov
Thomas R
TR
Horton
David E
DE
Rothstein
D044822:Biodiversity; D021903:DNA, Ribosomal Spacer / Q000737:chemistry; D005390:Fires; D038821:Mycorrhizae / Q000145:classification / Q000235:genetics / Q000502:physiology*; D058458:Nitrogen Cycle; D028223:Pinus / Q000378:metabolism / Q000502:physiology*; D011157:Population Dynamics
D021903:DNA, Ribosomal Spacer