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Abstract
In this study we analyzed the spatial structure of ectomycorrhizal fungi present in the soils as resistant propagules (e.g. spores or sclerotia) in a mixed-conifer forest in the Sierra Nevada, California. Soils were collected under old-growth Abies spp. stands across approximately 1 km and bioassayed with seedlings of hosts that establish best in stronger light (Pinus jeffreyi) or that are shade-tolerant (Abies concolor). Ectomycorrhizal fungi colonizing the roots were characterized with molecular techniques (ITS-RFLP and DNA sequence analysis). Wilcoxina, five Rhizopogon species and Cenococcum were the most frequent of 17 detected species. No spatial structure was detected in the resistant propagule community as a whole, but P. jeffreyi seedlings had higher species richness and associated with seven Rhizopogon species that were not detected on A. concolor seedlings. We drew two conclusions from comparisons between this study and a prior study of the ectomycorrhizal community on mature trees in the same forest: (i) the resistant propagule community was considerably simpler and more homogeneous than the active resident community across the forest and (ii) Cenococcum and Wilcoxina species are abundant in both communities.
The authors gratefully thank a number of people for help with this study. Martin Bidartondo aided in collection of soils. Malcolm North aided access to Teakettle Experimental Forest and provided GPS coordinates for the sampling locations. Peter G. Kennedy and John J. Battles gave helpful comments on drafts of this manuscript. Thanks also are extended to Bitty Roy and two anonymous reviewers for suggestions that improved this paper. This research project was financed by a USDA competitive grant 2001-01217 from the Soil Biology Program to TDB.
