Mat-forming ectomycorrhizal (EcM) fungi represent a prevalent constituent of many temperate forest ecosystems and create dramatic changes in soil structure and chemistry. EcM mat soil have been shown to have increased microbial respiration rates and have been hypothesized to harbor unique assemblages of fungi and bacteria. The objectives of this dissertation were to characterize and examine the fungal and bacterial communities associated with EcM mats in old-growth forests of the H.J. Andrews Experimental Forest located in the Oregon Cascades. Additionally, this work assessed the application of traditional, emerging, and novel molecular sampling techniques for determining microbial communities of environmental samples. This research investigated the microbial communities associated with two common EcM mat genera found in old-growth Douglas fir stands in the Pacific Northwest; Piloderma (Atheliales, Basidiomycota) and Ramaria (Gomphales, Basidiomycota). Soil samples were collected from Piloderma and Ramaria mats and surrounding non- mat soil for molecular analysis of nucleic acids. First, a comparative study was conducted to determine the most appropriate rDNA molecular sampling technique for microbial community characterization. Two next-generation sequencing methods, Roche 454 pyrosequencing and Illumina-based environmental sequencing, the latter developed by the author, were compared to a more traditional sequencing approach, i.e., Sanger sequencing of clone libraries. These findings informed the subsequent sampling of the fungal ITS and bacterial 16S rDNA fragment with 454 pyrosequencing to determine the microbial communities within mat and non-mat soils. Second, this work utilized a pyrosequencing approach to explore fungal community structure in EcM mat and non-mat soils. This work concluded that differences in microbial communities do exist between Piloderma mat, Ramaria mat, and non-mat soils, but the differences are largely quantitative with relatively few distinct taxonomic shifts in microbial constituents. Piloderma, Ramaria and Russula, in addition to being the dominant taxa found on mycorrhizal root tips, were found to be the most abundant taxa in bulk soils within their respective mat types or non-mat sample. The background fungal communities within the EcM mats in this study exhibited considerable taxonomic overlap with the exception of Piloderma vs. non-mat comparisons; Russula species dominated nonmat soils but tended to be excluded or significantly underrepresented in Piloderma mats. Lastly, this study explored the bacterial communities associated with Piloderma and Ramaria mats using lower- coverage 454-Jr pyrosequencing. Bacterial communities exhibited significant structure as a function of mat-type, soil horizon and pH, but this finding should be interpreted with respect to the nonrandom distribution of Piloderma-mats in the O- horizon and the Ramaria-mats in the A-horizon, and the tendancy for EcM mats to be more acidic than surrounding soils. Nonetheless, the total microbial (bacterial and fungal) community was typically dominated by the mat-forming taxa, or Russula, in the case of non-mat soils. While the presence of Piloderma mats did enrich or restrict some bacterial groups, soil pH was also found to be a significant driver of bacterial richness and taxonomic diversity. Fungal and bacterial richness were also found to be positively related to one another, regardless of soil horizon or EcM mat type. This work, taken together, contributes to the understanding of hyperdiversity and heterogeneity of microbial communities of temperate forest soils and highlights the potential for fungal and bacterial communities to be influenced by the presence of EcM mats. / Graduation date: 2012

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The work was development in Forestry Fepagro, Santa Maria, RS and in Laboratory of Biology and Microbiology of Soil and Environment Prof. Marcos Rubens Fries, from Department of Soil of Federal University of Santa Maria. First, the objective was to identify mycorrhizal associations in six native forestry species of Rio Grande do Sul State. This research was conducted in tree seasons of the year, in six native forestry species of State of Rio Grande do Sul. The roots were processed and analyzed according to mycorrhizal colonization type. The sporocarps found of native ectomycorrhizal fungi were identified, isolated and multiplied. The studies species were Araucaria angustifolia (Bertol.) Kuntze), Enterolobium contortisiliquum (Vell.) Morong.), Peltophorum dubium (Spreng) Taub.), Tabebuia chrysotricha (Mart. ex DC.) Standl.), Tabebuia impetiginosa (Mart.) Standl.), Apuleia leiocarpa (Vogel) J.F. Macbride). The forestry species didn t show ectomycorrhizal colonization in native conditions, although, it was found in some sporocarps near to some plants. It was observed the presence of associations with endomycorrhizal fungi in all species. The following study had the objective to test the possibility to form associations with ectomycorrhizal fungi and Apuleia leiocarpa and, in the fungi isolated UFSM RA 2.8 and UFSM RA 3.6 from Fepagro Forestry, respectively. These fungi were classified as Suillus sp. and Scleroderma sp. respectively. The fungi UFSC Pt 116 (Pisolithus microcarpus) and UFSC Pt 24 (Pisolithus sp.), were from of Federal University of Florianópolis, including the treatment without fungi. In Apuleia leiocarpa the fungi UFSM RA 3.6 was substituted by UFSC Sc 124 (Scleroderma sp.) fungi. It was analyzed seedling length, brash mass of aerial part and root, dry mass of part aerial, length and root and mycorrhizal colonization. It was observed the formation of ectomycorrhizal association in little plants of Apuleia leiocarpa and in Peltophorum dubium when inoculated with the ectomycorrhizal fungi Suillus sp.(UFSM RA 2.8). Furthermore, the results showed the best development in Apuleia leiocarpa in high plants, brash mass of aerial part and root, dry mass of part aerial. The Apuleia leiocarpa showed ectomycorrhizal association with isolated UFSM RA 2.8, in vitro . The Peltophorum dubium showed evidence that is possible have ectomycorrhizal associations with the isolate UFSM 2.8 in laboratory conditions. / O trabalho foi desenvolvido na Fepagro Florestas, Santa Maria RS e no Laboratório de Microbiologia e Biologia do Solo e do Ambiente Prof. Marcos Rubens Fries, do Departamento de Solos da Universidade Federal de Santa Maria. Primeiramente, o objetivo foi realizar um levantamento da ocorrência bem como a identificação das associações micorrízicas em seis espécies florestais nativas presentes no Estado do Rio Grande do Sul. O estudo foi conduzido em 3 épocas do ano com a coleta de amostras de solo, raízes e esporocarpos dos fungos. As raízes foram processadas e analisadas quanto ao tipo de colonização micorrízica. Os esporocarpos fungos ectomicorrízicos nativos encontrados foram identificados, isolados e multiplicados. As espécies estudadas foram o pinheiro-do-paraná (Araucaria angustifolia (Bertol.) Kuntze), timbaúva (Enterolobium contortisiliquum (Vell.) Morong.), canafístula (Peltophorum dubium (Spreng.) Taub.), ipê-amarelo (Tabebuia chrysotricha (Mart. ex DC.) Standl.), ipê-roxo (Tabebuia impetiginosa (Mart.) Standl.), grápia (Apuleia leiocarpa (Vogel) J.F. Macbride). As espécies florestais estudadas não apresentaram colonização ectomicorrízica a campo, entretanto, foram encontrados esporocarpos próximos de algumas plantas. Observou-se a presença de associações com fungos endomicorrízicos em todas as espécies. Posteriormente, estudou-se a possibilidade de formar associações com fungos ectomicorrízicos, grápia e canafístula. Foram utilizados os seguintes isolados: na grápia os fungos utilizados foram os isolados UFSM RA 2.8 e UFSM RA 3.6 oriundos da Fepagro Florestas, Santa Maria-RS, classificados como Suillus sp. e Scleroderma sp., respectivamente e os isolados UFSC Pt 116 (Pisolithus microcarpus) e UFSC Pt 24 (Pisolithus sp.), oriundos da Universidade Federal de Florianópolis, mais a testemunha sem fungo. Na canafístula o fungo UFSM RA 3.6 foi substituído pelo fungo UFSC Sc 124 (Scleroderma sp.). As avaliações foram: altura de planta, massa verde da parte aérea, massa verde radicular, massa seca da parte aérea e colonização micorrízica. Ocorreu a formação de associação ectomicorrízica nas plântulas de grápia e indícios desta formação com a canafístula quando inoculadas com o fungo ectomicorrízico Suillus sp. UFSM RA 2.8. Além disso, os resultados mostram que ocorreu melhor desenvolvimento nas plântulas de grápia quanto a altura de plantas, massa verde radicular e da parte aérea, e massa seca da parte aérea. A grápia apresentou associações ectomicorrízicas com o isolado UFSM RA 2.8, in vitro . A canafístula apresentou características morfológicas evidenciando uma possível associação ectomicorrízicas com o inóculo UFSM RA 2.8 em condições de laboratório.