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.

The effects of seasonal prescribed fire on the belowground ectomycorrhizal community and live fine root biomass were investigated before, 1 year after, and 2 years after prescribed underburning. Ectomycorrhizas were sampled from four replications of three treatments (fall underburning, spring underburning, and a nonburned control) in a randomized complete block design. Samples were separated in two subsamples representing the upper 5 cm and lower 5 cm of a soil core. Molecular tools were used to distinguish 140 restriction fragment length polymorphism (RFLP) species of fungi directly from the ectomycorrhizas. Prior to underburning, the number of RFLP species and amount of live root biomass were similar among treatment units and between upper and lower core samples. Fall underburning largely removed live root biomass to a depth of 10 cm and significantly reduced ectomycorrhizal species richness compared with spring underburning and the nonburned control for at least 2 years. RFLP species richness and live root biomass following spring underburning were generally similar to the nonburned treatment. The successful reintroduction of fire to the ecosystem to retain high species diversity of ectomycorrhizal fungi and achieve the desired future condition of large-tree ponderosa pine retention with low fuel loads may require more than underburning in a single season.Résumé : Les effets du brûlage dirigé saisonnier sur la communauté ectomycorhizienne dans le sol et la biomasse de racines fines vivantes ont été étudiés avant, 1 an après et 2 ans après un brûlage dirigé superficiel. Les ectomycorhizes ont été échantillonnées dans les quatre répétitions de trois traitements (brûlage automnal, brûlage printanier et témoin non brûlé) établis selon un dispositif en blocs aléatoires complets. Les échantillons ont été divisés en deux sous-échantillons représentant les parties supérieure (5 cm) et inférieure (5 cm) d'une carotte de sol. Des outils moléculaires ont été utilisés pour distinguer 140 espèces de champignons sur la base des RFLP directement à partir des ectomycorhizes. Avant le brûlage, le nombre d'espèces et la biomasse de racines vivantes étaient similaires entre toutes les parcelles expérimenta-les et entre les parties supérieure et inférieure des carottes de sol. Le brûlage automnal a pratiquement éliminé la biomasse de racines vivantes jusqu'à une profondeur de 10 cm et significativement réduit la richesse en espèces ectomycorhiziennes comparativement au brûlage printanier et au témoin non brûlé pendant au moins 2 ans. La richesse en espèces basées sur les RFLP et la biomasse de racines vivantes à la suite du brûlage printanier étaient généralement semblables au traitement non brûlé. La réintroduction réussie du feu dans l'écosystème dans le but de conserver une grande diversité d'espèces de champignons ectomycorhiziens et de recréer les conditions futures souhaitées pour conserver des pins ponderosa de forte dimension avec une faible quantité de combustibles pourrait exiger plus qu'un brûlage superficiel au cours ...

1.The obligate symbiosis formed between ectomycorrhizal fungi (EMF) and roots of tree species in the Pinaceae influences nutrient uptake and surrounding soil structure. Understanding how EMF respond to prescribed fire and thinning will assist forest managers in selecting fuel-reducing restoration treatments that maintain critical soil processes and site productivity. 2. The response of EMF species richness, live fine root biomass and duff levels to various forms and combinations of thinning and burning was investigated in mixed ponderosa pine and Douglas fir stands in the Blue Mountains of Oregon. The below-ground community composition and structure of EMF at the site was characterized using molecular methods. 3. The EMF community consisted of a large number of infrequently detected species. The distribution of a few abundant species ( Cenococcum sp., Piloderma sp., Rhizopogon salebrosus and Wilcoxina rehmii ) in a majority of the treatments both before and after treatment application demonstrates that some EMF species survive or rapidly re-establish after disturbance. 4. EMF species richness, live root biomass and duff levels were reduced significantly by prescribed fire treatments compared to the non-burned treatments. Synthesis and applications.These results indicate that prescribed fire results in a short-term reduction in EMF species richness and live root biomass and may influence whether managers can achieve the desired future condition of stands with large-tree retention and low fuel loads. EMF mortality and complete duff reduction after fire have been implicated with poor tree survival and slow stand recovery in forest ecosystems world-wide. The results of this study, along with the recovery potential of a site, and the impending risk of stand-replacing wildfire in stands differing in structure from historic conditions, bear consideration when reintroducing fire.

Seedlings oi Pseudotsuga menziesii (Mirb.) Franco, Pinus ponderosa Dougl. ex Laws, Arbutus fMeHSi' eiiV Pursh., and cuttings of Arctostaphylos uva-ursi (L.) Spreng were grown in monoculture and in conifer-hardwood dual-culture combinations in the glasshouse and inoculated with spore slurries of six Rhizopogon species. The primar\' objectives were to assess and compare the pattern of host specificity between symbionts and to study the infiuence of co-cultured plants on ectomycorrhiza development. The Rhisopogon spp. ranged from genus-specific to multiple-host compatible, ln monoculture, four

Aims Postfire logging recoups the economic value of timber killed by wildfire, but whether such forest management activity supports or impedes forest recovery in stands differing in structure from historic conditions remains unclear. The aim of this study was to determine the impact of mechanical logging after wildfire on soil bacterial and fungal communities and other measures influencing soil productivity. Methods We compared soil bacterial and fungal communities and biogeochemical responses of 1) soils compacted, and 2) soils compacted and then subsoiled, to 3) soils receiving no mechanical disturbance, across seven stands, 1-3 years after postfire logging. Results Compaction decreased plant-available N on average by 27% compared to no mechanical disturbance, while subsoiling decreased plant-available P (Bray) on average by 26% compared to the compacted and non-mechanically disturbed treatments. Neither bacterial nor fungal richness significantly differed among treatments, yet distinct separation by year in both bacterial and fungal community composition corresponded with significant increases in available N and available P between the first and second postharvest year. Conclusions Results suggest that nutrients critical to soil productivity were reduced by mechanical applications used in timber harvesting, yet soil bacteria and fungi, essential to mediating decomposition and nutrient cycling, appeared resilient to mechanical disturbance. Results of this study contribute to the understanding about impacts of harvesting fire-killed trees and bear consideration along with the recovery potential of a site and the impending risk of future fire in stands with high densities of fire-killed trees.