Development of two coniferous stands impacted by multiple, partial fires in the Oregon Cascades : establishment history and the spatial patterns of colonizing tree species relative to old-growth remnant trees

Trees that survive disturbances can form a prominent legacy which may influence post-disturbance successional pathways. The effects of biological legacies on community dynamics is a critical question in ecology. In the present study, I examined two mapped stands in which old-growth remnant trees, survivors of partial fires, emerge above a lower canopy of mature trees which had regenerated after these fires. In the first part of this study, I reconstructed the history and patterns of the most recent fires and the establishment history of the post-fire regeneration. At the Eagle Rock study site, fires occurred in 1848, 1870 and 1892. At the Wolf Rock site, a fire burned in 1892, and fires in 1829 and 1896 appeared likely. Fires burned under the remnant trees, and no area remained unburned during the nineteenth century. Cohorts were layered and interspersed among each other rather than juxtaposed as discrete patches. Regeneration of both early seral Pseudotsuga menziesii and late seral Tsuga heterophylla was initiated by the fire events, and neither displayed continuous recruitment. At both sites, Pseudotsuga regenerated more quickly than Tsuga. The median establishment time for both Pseudotsuga and Tsuga was longer at Eagle Rock (south-facing) than at Wolf Rock (northwest-facing). In the second part of this study, I described the spatial patterns of colonizing tree species relative to the remnant trees. The spatial patterns of post-fire species were clearly dependent upon the remnant tree pattern. Species were typically dispersed away from remnant trees, but several species, Castanopsis and Cornus nuttallii at Eagle Rock and Tsuga at Wolf Rock, were aggregated around remnant trees. Tsuga patterns differed between sites. Consistent with its shade tolerance, Tsuga was independent of or aggregated around remnant trees at Wolf Rock, but was unexpectedly dispersed away from remnants at south-facing Eagle Rock. The within-group patterns of remnant trees were clustered, as were the patterns of almost all post-fire species. The clustering of post-fire species may reflect the spatial dependence of each species' pattern upon the clustered remnant tree pattern which ,itself, is the outcome of the patchy pattern of partial fire. The aggregation and dispersion of different post-fire species relative to remnant trees suggests that remnant trees or remnant-associated features from the pre-disturbance community differentially facilitate or inhibit colonizing species, thus influencing the direction of post-disturbance succession

Global Assessment of Extinction Risk to Populations of Sockeye Salmon Oncorhynchus nerka

BACKGROUND: Concern about the decline of wild salmon has attracted the attention of the International Union for the Conservation of Nature (IUCN). The IUCN applies quantitative criteria to assess risk of extinction and publishes its results on the Red List of Threatened Species. However, the focus is on the species level and thus may fail to show the risk to populations. The IUCN has adapted their criteria to apply to populations but there exist few examples of this type of assessment. We assessed the status of sockeye salmon Oncorhynchus nerka as a model for application of the IUCN population-level assessments and to provide the first global assessment of the status of an anadromous Pacific salmon. METHODS/PRINCIPAL FINDINGS: We found from demographic data that the sockeye salmon species is not presently at risk of extinction. We identified 98 independent populations with varying levels of risk within the species' range. Of these, 5 (5%) are already extinct. We analyzed the risk for 62 out of 93 extant populations (67%) and found that 17 of these (27%) are at risk of extinction. The greatest number and concentration of extinct and threatened populations is in the southern part of the North American range, primarily due to overfishing, freshwater habitat loss, dams, hatcheries, and changing ocean conditions. CONCLUSIONS/SIGNIFICANCE: Although sockeye salmon are not at risk at the species-level, about one-third of the populations that we analyzed are at risk or already extinct. Without an understanding of risk to biodiversity at the level of populations, the biodiversity loss in salmon would be greatly underrepresented on the Red List. We urge government, conservation organizations, scientists and the public to recognize this limitation of the Red List. We also urge recognition that about one-third of sockeye salmon global population diversity is at risk of extinction or already extinct

Interactions between a native sedge, Carex nudata, and physical river processes: a model of coupled biogeomorphic development

I explored the effects of the riparian sedge, Carex nudata, on geomorphic processes in the Middle Fork John Day River, Oregon (MFJDR) as well as the environmental drivers of C. nudata’s distribution, building an integrative conceptual model of stream evolution in rivers with C. nudata.I investigated the environmental drivers of C. nudata distribution and tested the hypothesis that distribution is driven by stream power by conducting field sampling across 31 sites in the John Day and Santiam basins of Oregon. C. nudata abundance was inversely related with canopy cover and displayed a positive threshold response relative to stream power, mostly absent in streams with low stream power. Within the MFJDR, I used repeated topographic surveys and historic aerial imagery to investigate changes in channel morphology associated with C. nudata. Repeated surveys showed continuing bank erosion and small-scale changes such as scour in front of C. nudata fringes. Historic aerial imagery revealed that C. nudata islands most often originate from C. nudata fringes becoming detached from retreating banks rather than from initial establishment in midchannel positions. The continuing erosion of banks with C. nudata fringes raised the question of whether banks with C. nudata fringes are eroding at rates similar to banks without C. nudata. I addressed this question by establishing erosion pin arrays at 7 sites with C. nudata fringes and 7 without, measuring pins seasonally for 2 years. Erosion rates did not differ between sites with and without C. nudata. Furthermore, winter erosion was equal or greater than erosion during the spring snowmelt-driven peak flows pointing to the importance of winter processes such as freeze-thaw soil weakening that are likely independent of C. nudata patterns. I propose a conceptual model in which alternative pathways of channel development are possible after the establishment of C. nudata: 1) bank stabilization; 2) formation of a compound channel as banks retreat; 3) the formation of islands within the channel as banks retreat and scour occurs behind a C. nudata fringe. The potential for alternative pathways can lead to a diversity of channel forms, facilitating complexity, a key goal of river restoration

Distribution of epiphytic macrolichens in relation to remnant trees in a multiple-age Douglas-fir forest

Alternatives to clear-cutting are being implemented to increase biodiversity of managed forests in the Pacific Northwest. Lichens are an integral component of old growth, but lichen biomass develops slowly in forests. We evaluated the long-term potential of live tree retention for lichen conservation in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. We sampled lichen litterfall in a 2-ha stand that contained 200- to 600-year-old remnant trees scattered in a forest composed mostly of 100-year-old trees that established following fire. We used association, principal components, and regression analyses to relate lichen litterfall biomass to the proximity of remnant trees. Two epiphytic lichens were strongly associated with remnant trees: the foliose cyanolichen Lobaria oregana (Tuck.) Müll. Arg. and the fruticose green algal lichen Sphaerophorus globosus (Hudson) Vainio. Biomass of both species was highest near remnant trees, and biomass was slightly higher within groves of remnant trees than it was at the edges of these groves or near isolated trees. Lichens appear to have persisted on remnant trees through the last fire and are slowly recolonizing younger trees from this source of propagules. Retention of live trees, maintenance of hardwoods, and longer rotation periods have great potential to maintain old-growth-associated lichens in at least some managed forests

The Upcoming energy crisis

This project examined current reserves of fossil fuels and projected the lifespan before which they will be exhausted. In view of this fact and the effect fossil fuels have on the environment, we examined alternatives to these energy sources. While these alternatives presently are not economically competitive, advances in technology and rising energy prices may change this situation in the near future. Recommendations for an energy policy that will ensure ample, clean energy for the future generations have also been made

Range-wide map of assessed sockeye salmon and their IUCN status.

<p>Numbers displayed on map correspond to identification numbers for sockeye populations listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034065#pone.0034065.s001" target="_blank">Tables S1</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034065#pone.0034065.s002" target="_blank">S2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034065#pone.0034065.s003" target="_blank">S3</a>.</p

IUCN Red List criteria applied in the study.

a<p>Number of sockeye juvenile nursery lakes and distinct spawning regions within a population.</p><p>Quantitative criteria used in the study to determine extinction risk. CR = Critically Endangered, EN = Endangered, VU = Vulnerable.</p