1. SEMIARID GRASSLAND: Soil and root-associated fungal communities Dominant root-associated fungi Methodology Bouteloua gracilis, B. eriopoda, Sporobolus cryptrandus and Yucca glauca roots were collected at the Sevilleta National Wildlife Refuge (SNWR). Roots were stained with modified Vierheilig and Piche (1998) protocol for the microscopy analysis. DNA was extracted and amplified with fungal specific primers ITS1-F and ITS4 and mycorrhizal specific primers NS31-AM1. PCR products were cloned using the TOPO-TA cloning kit (Invitrogen, Carlsbad, CA), and colonies with the inserts were amplified using rolling circle amplification (TempliPhi, Amersham, Buckinghamshire, England) and sequenced with BigDye® Terminator v1.1 Sequencing Kit (Applied Biosystems, Foster City, CA). Alpine Tundra libraries were obtained using 454. Clone libraries were analyzed with the programs DOTUR, UniFrac, and SONS. Phylogenetic trees were constructed using Parsimony analysis with PAUP. Acknowledgements This research was supported by the Sevilleta - National Science Foundation Grants DEB-0217774, DEB 0516113. Approximately 23 different orders were found A large number of sequences (52%) were novel (less than 97% similarity in GenBank) Fungal communities found in roots and soils were dominated by the order Pleosporales (53% of the sequences) Fungal communities were dominated by Ascomycota (83% of the sequences) S-Lifshuff P<0.0001 UniFrac significance P=0.01 Hypocreales Pezizales Filobasidiales Dothideales Soils Roots Sordariales Agaricales Xylariales Rarefaction curve of soil and root-associated fungal communities per sample Fungal community structure Roots were colonized by a unique community of endophytic fungi Other common orders were: Semiarid grassland fungal communities are dominated by dark septate endophytes (DSE) A fungal loop in semiarid grasslands * Novel Pleosporales sequences are shown in red A consortium of root-associated fungi The first three components of the PCA analysis explain 84% of the variation of the data. Fungal community of samples collected on January 2006, and May 2005 were more similar than the fungal community found in October samples. The second component (28.84% of the variation) separates N amended plots from control plots of May samples and the third component (14.78% of the variation) separates the fungal community found in N-amended and control plots for January samples. All seasons have in common a small core of endophytes. January endophytes are a subsample of the fungal community colonizing May samples (January samples shared 88% of the OTUs with May samples) Shared OTUs between N amendment and control treatments varies from 14% to 33% for the different seasons. Seasonal variation and N-amendment influence the structure of the fungal community colonizing B. gracilis roots Soil and endophytic fungal associations with grama at the Sevilleta LTER A ndrea Porras-Alfaro 1,2, Jose Herrera 3, Robert Sinsabaugh 2, Donald Natvig 2 1 Western Illinois University, 2 University of New Mexico, 3 Truman State University. Abstract Plant and soil fungi are fundamental in different ecological processes. However, our current knowledge of plant-associated and soil fungal communities is limiting our capacity of understanding main roles of fungi in ecosystems. The main objective of this research was to study diversity, composition and the effect of nitrogen fertilization on fungal communities at the Sevilleta semiarid grasslands. We collected plant-associated and soil fungal communities at the Niwot and Sevilleta LTER. Fungi were sequenced using fungal-specific primers. About 50% of the Operational Taxonomic Units were considered novel (less than 97% similarity with respect to sequences in the NCBI database). Rarefaction curves and diversity estimators do not show saturation. Root fungi were dominated by dark septate fungi and at least 10 different orders including endophytic, coprophilous, mycorrhizal (AMF), saprophytic and plant pathogenic fungi were found colonizing the roots of dominant plants. Major and most diverse groups belong to the order Pleosporales including potential novel families. Soil and root communities showed significant differences and AMF fungi were affected by nitrogen fertilization. Potential ecological roles of these symbionts, their diversity, and biogeographical distributions will be discussed. Arbuscular mycorrhizal fungi (AMF) (May 2005) Principal coordinate analysis of AMF fungal community colonizing B. gracilis roots in nitrogen (N) and control (C) plots. N-amended plot 2 was not included in this analysis because only 2 AMF sequences were recovered from this sample. Phylogeny of AMF colonizing B. gracilis roots. Total number of sequences of the OTUs calculated with DOTUR at 97% similarity are shown at the right. The high similarity among the root-associated fungal communities colonizing grasses at the Sevilleta supports the Threshold-Delay Nutrient Dynamics model in which plant responses to pulsed precipitation events are mediated by a fungal network (Collins et al. 2008, Green et al. 2008) Alpine tundra root-associated fungi are dominated by AMF and ericoid mycorrhizae (Order: Helotiales) Semiarid Grasslands Dominant communities included fungi from the order Pleosporales and Agaricales C: Control, N: Nitrogen.