Canadian Journal of Botany
1999. 77: 93-102.

Ectomycorrhizal fungi associated with Arctostaphylos contribute to Pseudotsuga menziesii establishment

Horton, Thomas R.1, Bruns, Thomas D.2, Parker, V. Thomas3

1 current address:
Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA

2 Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, California, 94720, USA

3 Department of Biology, San Francisco State University, San Francisco, California, USA
Chaparral on the central coast of California can occur as relatively stable patches of ectomycorrhizal Arctostaphylos directly adjacent to arbuscular mycorrhizal Adenostoma. Vegetation surveys and seedling survival assays show that Pseudotsuga establishes only in Arctostaphylos. We found no significant differences between Arctostaphylos and Adenostoma in allelopathy; light; temperature; or soil NH4+, NO3-, or K. Arctostaphylos soils tended to be higher in phosphate and were lower in pH, Ca, Mg, Ni and Cr than those from Adenostoma. After 1 year of growth of Pseudotsuga seedlings in an Arctostaphylospatch, 17 species of fungi colonized both Pseudotsuga and Arctostaphylos. Fifty-six of 66 seedlings were colonized by fungi that also colonized Arctostaphylos within the same soil core. Forty-nine percent of the Pseudotsuga ectomycorrhizal biomass was colonized by fungi that were also associated with Arctostaphylos within the same core. Another 12% was colonized by fungi known to associate with Arctostaphylos from different cores. After 4 months of growth, Pseudotsuga seedlings in four of five Arctostaphylosplots were ectomycorrhizal and colonized by fungi in Russulaceae, Thelephoraceae and Amanitaceae. Pseudotsuga seedlings in two of five Adenostoma plots were ectomycorrhizal but colonized by only two species of fungi in Thelephoraceae. These results provide compelling evidence that ectomycorrhizal fungi associated with Arctostaphylos contribute to Pseudotsuga seedling establishment.

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