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To gain a better understanding of how rapidly microbial communities respond to different magnitudes of perturbation that mimic minor or catastrophic disturbances. Two montane sites in the western Cascade Mountains of Oregon with adjacent areas of forest and meadow vegetation were studied. A reciprocal transplant experiment evaluated both minor (soil cores remaining in the same vegetation type) or more severe disturbance (soil cores transferred to a different vegetation type). The biomass and composition of the bacterial and fungal communities were measured for 2 years following the establishment of the experiment. Minor disturbance (coring) had little impact on microbial biomass but transferring between vegetation type showed greater fungal biomass in soil incubated in the forest environment. The composition of bacterial communities was not influenced by coring but responded strongly to transfers between vegetation sites, changing to reflect their new environment after 2 years. Fungal community composition responded somewhat to coring, probably from disrupting mycorrhizal fungal hyphae, but more strongly to being transferred to a new environment. The response of the microbial community to major disturbance was rapid, showing shifts reflective of their new environment within 2 years, suggesting that microbial communities have the capacity to quickly adjust to catastrophic disturbances.

Canopy disturbances such as windthrow events have obvious impacts on forest structure and composition aboveground, but changes in soil microbial communities and the consequences of these changes are less understood. We characterized the densities of a soil-borne pathogenic oomycete (Pythium) and a common saprotrophic zygomycete (Mortierella) in nine pairs of forest gaps created by windthrows and adjacent forest understories. We determined the levels of Pythium necessary to cause disease by performing pathogenicity experiments using two Pythium species, a range of Pythium densities, and two common tree species (Acer rubrum and Prunus serotina) from the study sites. Three years post-disturbance, densities of Mortierella remained suppressed in soil from forest gaps compared to levels in intact forest understories while varying across sites and sampling dates. Pythium were infrequently detected likely because of soil handling effects. Expression of disease symptoms increased with increasing inoculum density for seedlings of P. serotina with each Pythium spp. having a similar effect on this species. Conversely, A. rubrum appeared resistant to the two species of Pythium. These results suggest that Pythium densities at sites where they were detected are sufficient to cause disease and possibly affect establishment of susceptible species like P. serotina. Because early seral environments have lower loads of the saprotrophic Mortierella, pathogen loads may follow a similar pattern, causing susceptible species to establish more frequently in those habitats than in late-seral forests. Forest disturbances that alter the disease landscape may provide an additional mechanism for explaining succession of temperate forests in addition to the shade-tolerance paradigm.

Meadows are natural dynamic features of forested mountain landscapes of the Pacific Northwest. Proportions of meadows and forests change with environmental conditions and disturbance history. We investigated the belowground microbial communities associated with these two vegetation types and how they change across the meadow–forest transition at two sites in Oregon. Soils were sampled along replicate transects extending from meadow into forest. We quantified total bacterial and fungal biomass using direct microscopy and described the composition of bacterial and fungal communities using a DNA-based fingerprinting technique. Bacterial biomass was similar in meadow and forest soils, but fungal biomass was significantly higher in forest soil. Meadow and forest soils had distinct communities of bacteria and fungi. Bacterial communities near the meadow–forest boundary reflected current vegetation, but fungal communities under meadow vegetation near the forest edge were intermediate in composition between those found in meadow and forest soils. The more gradual transition observed with fungal communities may reflect the influence of tree roots and their associated ectomycorrhizal fungi or possibly colonization by saprotrophic fungi associated with tree litter accumulating near the forest edge. Invasion of forest-associated fungi into the meadow soils may presage subsequent expansion of forest vegetation into meadows.

Little information exists on the re- sponses of soil fungal and bacterial communities in high elevation coniferous forest/open meadow ecosystems of the northwest United States of America to treatments that impact vegetation and soil conditions. An experiment was conducted in which soil cores were reciprocally transplanted between immediately adjacent forests and mead- ows at two high elevation (~1,600 m) sites (Car- penter and Lookout) in the H.J. Andrews Experimental Forest located in the Cascade Mountains of Oregon. Half of the cores were placed in PVC pipe (closed) to prevent new root colonization, whereas the other cores were placed in mesh bags (open) to allow recolonization by fine roots. A duplicate set of open and closed soil cores was not transferred between sites and was incu- bated in place. After 2 year, soil cores were removed and changes in fungal and bacterial bio- masses determined using light microscopy, and changes in microbial community composition determined by PLFA analysis, and by length het- erogeneity PCR of the internal transcribed spacer region of fungal ribosomal DNA. At both sites soil microbial community structures had responded to treatments after 2 year of incubation. At Carpen- ter, both fungal and bacterial community struc- tures of forest soil changed significantly in response to transfer from forest to meadow, with the shift in fungal community structure being accompanied by a significant decrease in the PLFA biomarker of fungal biomass,18:2x6,9. At Lookout, both fungal and bacterial community structures of forest soil changed significantly in response to open versus closed core treatments, with the shift in the fungal community being accompanied by a significant decrease in the 18:2x6,9 content of closed cores, and the shift in the bacterial community structure being accompanied by a significant increase in bacterial biomass of closed cores. At both sites, fungal community structures of meadow soils changed differently between open and closed cores in response to transfer to forest, and were accom- panied by increases in the18:2x6,9 content of open cores. Although there were no significant treat- ment effects on the bacterial community structure of meadow soil at either site, bacterial biomass was significantly higher in closed versus open cores regardless of transfer.

Both mycorrhizal fungi and systemic fungal endophytes in the Order Clavicipitales have been extensively studied. Compared to these groups, root-associated fungal endophytes have received very little attention, even though they seem common in many ecosystems. Based on published reports, comparisons between host colonization by the root endophytes and mycorrhizal fungi from various habitats suggest that endophytes are possibly as abundant as mycorrhizas (Mandyam and Jumpponen 2005). As more reports that document the abundance of root endophytes in different habitats become available, a better understanding of the ecology and functions of these endophytes seems not only logical but critical. The term ‘endophyte’ is used to describe either bacterial or fungal intracellular symbionts of plants that do not cause any visible signs of tissue damage or adverse effects on the host (Petrini 1991; Wilson 1995; Stone et al. 2000; Schulz and Boyle 2005). Fungal root endophytes are a paraphyletic group primarily occurring in the Ascomycota, although some examples also exist for Basidiomycetous endophytes (see Verma et al. 1998; Barazani et al. 2005). In this group, we usually include all root-inhabiting fungi that are considered non-mycorrhizal based on the morphology of the colonized host roots and on fungal structures produced in colonized roots typically considered indicative of dark septate endophytes (DSE). We also include fungi that produce hyaline structures when colonizing hosts intracellularly (O’Dell et al. 1993; Barrow and Aaltonen 2001; Ohki et al. 2002; Narisawa et al. 2003), but do not form typical DSE structures. These hyaline fungi can routinely be isolated from the roots of many plant species. Well-studied systemic and foliar endophytes of grasses, such as Acremonium sp., Epichoe sp. and Neotyphodium sp., will be excluded from this discussion. Many of the studies of fungal root endophytes have either made no effort to identify the fungi or have focused on one fungus isolated at a single site. This gives the impression that the species diversity of fungal root endophytes is low. Phialocephala

Hypogymnia imshaugii is one of the most common, conspicuous and morphologically variable epiphytic lichens of the Pacific coastal states and provinces. The species varies greatly in morphology and chemistry, suggesting multiple closely related species or one or more phenotypically plastic species. We sought to determine whether additional ecologically meaningful species might be present within the H. imshaugii complex. Improving our species concepts could potentially improve ecological inferences based on community sampling. Three relatively well-defined genetic groups and one residual group in the H. imshaugii complex were detected with haplotype networks based on the ITS locus; however, phylogenetic reconstructions on combined ITS, mtSSU, GPD1 and TEF1 loci did not reflect this pattern. At present, we have insufficient evidence to support defining any of these groups as new taxa. The four major chemotypes in H. imshaugii differed in frequency among the genetic groups. None of the genetic groups...

We inferred phylogenetic relationships using Bayesian and maximum likelihood approaches for two genera of lichenized fungi, Hypogymnia and Cavernularia (Parmeliaceae). Based on the combined ITS and GPD1 dataset from 23 species (49 specimens) of Hypogymnia and two species (8 specimens) of Cavernularia, we conclude that Hypogymnia is paraphyletic, and that it should include Cavernularia to retain its monophyly. Hypogymnia hultenii ( = Cavernularia hultenii) and H. lophyrea ( = C. lophyrea) are accepted here. Five species of Hypogymnia represented by more than a single individual were found to be monophyletic and significantly supported. The phylogeny reflects a statistically significant biogeographic pattern where continental-scale endemic taxa tend to occur within the same phylogenetic group. Sorediate taxa, which have worldwide or broader geographical ranges than affiliated species lacking soredia, are spread across the phylogenetic tree. Hypogymnia contains three species pairs: H. krogiae and ...