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Most research that has been done regarding Steller sea lions (SSLs; Eumetopias jubatus) has been during the breeding season. Adult SSLs are known to have high among-year breeding-season site fidelity, typically with movement away from breeding-season locations during non-breeding seasons. Using non-breeding-season sighting data of permanently marked SSLs from four areas in Alaska and broad-scale breeding-season sightings, we estimated among-year non-breeding-season site fidelity (i.e., the probability a SSL moves from its breeding-season location to a specific non-breeding-season area). Some SSLs, especially females, have high site fidelity to non-breeding-season areas; fidelity is markedly lower for males. We found no evidence that site fidelity varied among natal rookeries, but our sample sizes were relatively small, possibly limiting our ability to determine such effects. With our estimates of non-breeding-season site fidelity, coupled with previously demonstrated breeding-season site fidelity, we concluded that SSLs should be considered partial migrants (i.e., migratory behavior exhibited by only some individuals in a population) with at least some individual SSLs, particularly females, exhibiting migratory behavior.
A challenge modern-day ecologists and resource managers face is how to separate natural variations in populations from changes caused by human activities (e.g., climate change). Long-term monitoring programs provide valuable information to assist in this endeavor. This study details the initial findings of a long-term monitoring program initiated in 2004 to monitor changes in rocky intertidal communities within Redwood National and State Parks, located in northern California. Permanent plots were established at three sites using protocols developed by the Multi-Agency Rocky Intertidal Network, a consortium that monitors rocky intertidal communities along the western coast of North America. Replicate plots were established to monitor changes in abundance of key intertidal taxa, including mussels (Mytilus californianus), barnacles (Chthamalus dalli and Balanus glandula), red alga (Endocladia muricata), and rockweeds (Pelvetiopsis limitata and Fucus gardneri). Plots were sampled annually since they were established. Results from the first 15 years of this study indicate that all taxa exhibited substantial short-term (annual) variation, with barnacles and E. muricata exhibiting the most. For barnacles, such variations were correlated with measures of recruitment. Except for P. limitata, all other target taxa experienced at least one period of large-scale major change, where abundances decreased dramatically (> 50% of long term mean) and simultaneously in most plots. However, in almost all cases abundances recovered, resulting in no apparent long-term changes. For the few instances where long-term changes were detected, it is possible this result may be an artifact of the analytical methods used to assess them. The potential implications of this finding are discussed.
It is often assumed that dominant forest understory communities are predictably associated with overstory tree species, yet several long-term studies suggest that understory communities are more independent of overstory change. We use a 10-year dataset to explore variation in understory communities in a mature second-growth temperate forest in western Washington. We classify all recorded species into six growth-forms (graminoids, ferns, shrubs, subshrubs, saplings, herbaceous species), and introduced species (collectively grouped) to analyze responses to overstory productivity, stand age, canopy heterogeneity, soil type, stand type, and proximity to a canopy-gap forming pathogen (Phellinus sulphurascens), as well as overstory carbon (C) changes through the decade. Plant diversity and percent cover declined marginally through time (Shannon's H′ declined by 8% and percent cover by 4.5%), as plots remained dominated by the species Polystichum munitum and Gaultheria shallon. Species richness decreased significantly by 23% among years (mean plot richness was 10.02 in 2008 compared to 8.05 in 2018), and diversity, subshrubs, and shrubs generally declined with stand age. Shrubs were more abundant in conifer-dominated plots. Ferns, and changes in ferns, were associated with presence of P. sulphurascens, where cover increased in infected plots. Ordination results suggested community composition was correlated with changes in canopy cover (conifer forests) and stand age (deciduous forests). Changes in total plot C and canopy cover were also associated with diversity and total percent cover. Nevertheless, our results support incremental changes in understory communities on decadal time scales and limited predictability of the understory based on the overstory.
Riparian ecosystems are a critical ecological component in the Pacific Northwest. Many have been altered by human activities and need restoration. Establishing restoration objectives is daunting because of inherent spatial and temporal variation of geomorphology, disturbance regimes, and vegetation. We developed an analytical framework using geology and climate as the template for natural disturbance processes influencing riparian vegetation in northwest Oregon. We identified three ecoregions with contrasting geology and climate: Coast Range, with dissected topography and rain-dominated hydrology; West Cascades, with dissected topography and rain- and snow-dominated hydrology; and High Cascades, with undulating topography and snow-dominated hydrology. For all three, the most abundant stream reach type was small (< 15 m channel width) with wildfire the predominant natural disturbance. However, reaches affected by geomorphic disturbance were common for the Coast Range and West Cascades. Riparian vegetation dominated by large trees (≥ 51 cm diameter) was underrepresented compared to reference conditions for the Coast Range and West Cascades. Variation between subbasins in departure of current conditions from reference conditions was greatest in the West Cascades and negligible in the High Cascades. Vegetation in the Coast Range has moved in recent decades towards reference conditions. Wildfires since the latest remote-sensing-derived data (2017) may have altered riparian vegetation, affecting departure of current from reference conditions. Since the remote sensing of vegetation continues, it should be possible to assess these effects. Our results support restoration of riparian forests dominated by large trees in the Coast Range and West Cascades. Areas dominated by smaller trees may represent restoration opportunities.
We present evidence for historical change in a bumble bee community on Galiano Island, British Columbia, Canada, including the probable extirpation of three bumble bee species—Bombus insularis Smith, B. occidentalis Greene, and B. suckleyi Greene—as well as the disappearance of two species represented by singletons in the historical record: B. fervidus Fabricius and B. flavidus Eversmann. Evidence is based on a comparison of historical and contemporary species occurrence data, including recent data from intensive sampling targeting bumble bees using blue vane traps. The decline of B. occidentalis in southern portions of its range has long been observed, yet to our knowledge this is the first established case of its probable extirpation within an extensively surveyed part of its range. Results indicate that an additional species, B. vosnesenskii Radoszkowski, is a recent arrival on Galiano Island and has been expanding its range concurrently with the decline of B. occidentalis. Elsewhere in the region B. vosnesenskii has become a dominant species, particularly in urban environments. However, our data show it to be the least abundant species on this largely forested island. We also report patterns in the occurrence of B. sitkensis Nylander and B. vosnesenskii, suggesting that niche segregation may confound the effect of competitive exclusion previously reported for these species. Potential factors contributing to this likely case of bumble bee extirpation and subsequent colonization are discussed in the context of Galiano Island's historical land use and ecology. In conclusion, we assess the potential for community science to aid in the detection of ecological change via comparison of historical baseline and contemporary crowd-sourced biodiversity data.
The ringtail (Bassariscus astutus) is a species of conservation concern. Yet, little is known about basic ringtail ecology at the northwestern edge of its range, where the habitat differs considerably from its primary range in the southwestern United States. Diurnal rest sites, such as cavities in live and standing-dead trees, are an essential habitat element for ringtails and co-occurring mesocarnivores. Ringtails use diurnal rest sites as shelter during adverse weather conditions, refugia from predators such as the co-occurring fisher (Pekania pennanti), and dens to raise young. Understanding the forest conditions associated with rest sites selected by ringtails can inform forest management practices. We fixed very-high-frequency radio collars to 16 ringtails on the Hoopa Valley Indian Reservation in northern California to better understand the relationships between forest characteristics and fisher presence on ringtail rest-site use. We found that ringtails were more likely to select rest sites in mature older forests compared to oak woodland and open areas, and were less likely to select rest sites closer to perennial water sources. We did not detect an effect of fishers on the selection of rest sites. These results indicate that both late-seral and some early-seral forest conditions provide suitable habitat for ringtail rest sites and ultimately demonstrate that ringtails use a mosaic of seral stages in the forests of the Pacific Northwest.
We explored differences in bee communities between urban sites in the city of Salem, Oregon and nearby rural sites with restored areas. While cities provide habitat for some wild pollinators, urban bee communities tend to exhibit different compositions than rural ones, with urban communities particularly lacking ground-nesting and specialist oligolectic bees. We wanted to know whether these differences would still be present in a small city that is set in a heavily degraded rural landscape. We predicted that bees with narrow diet breadth would primarily use native floral resources. We found that urban and rural sites exhibited distinctly different bee community composition, both in 2018 and 2019. Bees that were indicators for rural areas tended to be large-bodied, ground-nesting, and have narrow diet breadth, but there were some surprising large-bodied ground nesters present in the city. The Bombus and Lasioglossum species that were the major drivers of the urban-rural differences were primarily associated with exotic plants in rural areas. Extreme specialist bees that used only one native plant genus were present only in rural restoration sites, but their numbers were too small to generate statistically significant patterns. Our results suggest that rural and urban land managers should be aware of the importance of the mass of floral resources provided by exotics and of the crucial importance of certain native plants that host specialist bees.
Hundreds of ant-nest bare-mineral-soil mounds, as well as ant plant litter ‘thatch’ mounds, are distributed across the sagebrush-steppe rangeland on Goodale’s Cutoff along the Oregon Trail near Arco, Idaho, adjacent to the northern boundary of Craters of the Moon National Monument and Preserve. US Natural Resources Conservation Service personnel and local landowners wanted to determine if these ants were exotic invasive pests that could damage rangeland pasture and grazing habitat or impact historic anthropogenic artifacts. Four species of native ants, Pogonomyrmex salinus, Formica limata, F. obscuripes, and F. ravida, which are common on the Snake River Plain of Idaho, were collected from different mounds. Another native ant, Solenopsis molesta, was foraging around the perimeter of one thatch mound. Additionally, a subterranean termite, Reticulitermes tibialis, common in the western United States and widespread within Idaho rangelands and mountains, was found foraging within both types of ant mounds. This study provides insight into ant and subterranean termite activity on the Snake River Plain.
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