No abstract

Knowledge of the community structure of ectomycorrhizal fungi among successional forest age-classes is critical for conserving fungal species diversity. Hypogeous and epigeous sporocarps were collected from three replicate stands in each of three forest age-classes (young, rotation-age, and old-growth) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) dominated stands with mesic plant association groups. Over four fall and three spring seasons, 48 hypogeous and 215 epigeous species or species groups were collected from sample areas of 6300 and 43 700 m2, respectively. Cumulative richness of hypogeous and epigeous species was similar among age-classes but differed between seasons. Thirty-six percent of the species were unique to an age-class: 50 species to old-growth, 19 to rotation-age, and 25 to young stands. Seventeen species (eight hypogeous and nine epigeous) accounted for 79% of the total sporocarp biomass; two hypogeous species, Gautieria monticola Harkn., and Hysterangium crassirhachis Zeller and Dodge, accounted for 41%. Average sporocarp biomass in young and rotation-age stands compared with old-growth stands was about three times greater for hypogeous sporocarps and six times greater for epigeous sporocarps. Average hypogeous sporocarp biomass was about 2.4 times greater in spring compared with fall and for epigeous sporocarps about 146 times greater in fall compared with spring. Results demonstrated differences in ectomycorrhizal fungal sporocarp abundance and species composition among successional forest age-classes.Key words: ectomycorrhizal fungi, sporocarp production, forest succession, Pseudotsuga menziesii, Tsuga heterophylla zone, biodiversity.

SliMMARYSeedlings of Abies grandis, Alnus rubra, Pinus ponderosa, Picea sitchensis, Pseudotsuga menziesii and Tsuga heterophylla were grown in monoculture and dual culture in the greenhouse and inoculated with spore slurries of 20 isolates representing 15 species of ectomycorrhizal hypogeous fungi {11 Rhizopogon species, Alpoz'a diplophloeus, Truncocolumella citrina, Melanogaster euryspermus and Zetleromyces gilkeyae). The primary objectives were to assess and compare the pattern of bost specificity between symbionts and to study the influence of neighbouring plants on ectomycorrhiza development. None of the fungai species had broad host range affinities. A variety of specificity responses were exhibited by the different fungal taxa, rangmg from genus-restricted to intermediate host range. In monoculture, nine species oi Rhizopogon (R. arctostaphyli, R. ellenae, R. flavofibrillosus, R. occidentalis, R. rubescens, R. smithii, R. suhcaerulescens, R. truncatus and R. vulgaris) formed ectomycorrhizas on Pinu.'! ponderosa whevess three Rhizopogon species {R. parksii, R. vinicolor and R. suhcaerulescens) formed ectomycorrbizas on Pseudotsuga menziesii. Truncocolumella citrina associated with Pseudotsuga menziesii and Alpozia diplophloeus with Alnus ruhra. Melanogaster euryspermus and Z. gilkeyae did not form ectomycorrhizas with any hosts. None of the fungi tested developed ectomycorrhizas on Ahies grandis, Tsuga heterophylla or Picea sitchensis in monoculture. In dual culture, the same nine Rhizopogon species that formed abundant ectomycorrhizas on Pinus ponderosa formed some ectomycorrhizas on secondary hosts such as Ahies grandis., Tsuga heterophylla, Pseudotsuga menziesii and Picea sitchensis. Similarly, Truncocolumella citrina formed abundant ectomycorrhizas on Pseudotsuga menziesii and low levels on the secondary hosts Abies grandis, Tsuga heterophylla and Picea sitchensis. Rhizopogon parksii and R. vinicolor only formed ectomycorrhizas on Pseudotsuga menziesii, and Alpova diplophloeus only formed ectomycorrhizas on Alnus rubra. The specificity pattern obtained by using this dual-culture approach is contrasted with previous pure-culture synthesis data and is discussed in terms of potential interplant linkages and community dynamics.

No abstract

No abstract

SUMMARYSeedlings of Pseudotsuga tnenziesii (Mirb.) Franco were grown for six-16 months in untrenched and trenched treatments in three 90-120-yr-old mixed forests dominated by Betula papyrifera Marsh, and P. menziesii in the southern interior of British Columbia. Each forest was characterized by mesic conditions and low light intensity (PAR < 200 ^mol m"^ s~^) in the understorey. The objective of the study was to evaluate the influence of overstorey tree roots on (i) ectomycorrhizal fungal composition, richness and diversity, and (ii) photosynthesis and growth of understorey P. menziesii seedlings. Seventeen ectomycorrhizal morphotypes were recognized on seedlings in the untrenched treatment, and nine in the trenched treatment over the three sites. Six types occurred in both treatments, of which on average Rhizopogon vinicolor Smith type was 20 times more abundant and Thelephora type six times less abundant in the untrenched as in the trenched treatment. Of types that formed strands or rhizomorphs, eight occurred in the untrenched treatment, where they occupied on average 23 % of root tips, and only four occurred in the trenched treatment over 4 % of the root tips. Mean richness, diversity, and evenness of ectomycorrhizal associates per seedling were approx. twice as great in the untrenched as in the trenched treatment.Net photosynthetic rate of P. menziesii seedlings was greater in the untrenched than in the trenched treatment in July and August, but not in September 1994. Height, diameter and biomass of seedlings did not differ between treatments, but height: diameter ratio was greater in the untrenched treatment at time of harvest. The effect of trenching on seedling performance was attributed mainly to differences in ectomycorrhizal colonization patterns because trenching had no significant effect on soil nutrient concentrations (total C, total N, NH^-N, available N, exchangeable Ca, exchangeable Mg, exchangeable K), C:N ratio, soil pH or light availability. Nor was there a significant difference in soil water in August, when seedlings in untrenched plots had higher net photosynthetic rates than those in trenched plots. Results suggest that influence of overstorey trees and pattern of ectomycorrhizal formation are important to P. menziesii seedling performance in deeply shaded forest environments.

No abstract

Post-fire Pezizales fruit commonly in many forest types after fire. The objectives of this study were to determine which Pezizales appeared as sporocarps after a prescribed fire in the Blue Mountains of eastern Oregon, and whether species of Pezizales formed mycorrhizas on ponderosa pine, whether or not they were detected from sporocarps. Forty-two sporocarp collections in five genera (Anthracobia, Morchella, Peziza, Scutellinia, Tricharina) of post-fire Pezizales produced ten restriction fragment length polymorphism (RFLP) types. We found no root tips colonized by species of post-fire Pezizales fruiting at our site. However, 15% (6/39) of the RFLP types obtained from mycorrhizal roots within 32 soil cores were ascomycetes. Phylogenetic analyses of the 18S nuclear ribosomal DNA gene indicated that four of the six RFLP types clustered with two genera of the Pezizales, Wilcoxina and Geopora. Subsequent analyses indicated that two of these mycobionts were probably Wilcoxina rehmii, one Geopora cooperi, and one Geopora sp. The identities of two types were not successfully determined with PCR-based methods. Results contribute knowledge about the above- and below-ground ascomycete community in a ponderosa pine forest after a low intensity fire.