Northwest Science is happy to report on corrections for errors, typos, or other significant issues associated with previously published work. We received one such request for corrections from a previous issue while preparing our current issue.

The following corrections were reported for van Mantgem and Sarr (2015), Structure, Diversity, and Biophysical Properties of Old-Growth Forests in the Klamath Region, USA, in Northwest Science, 89(2), pages 170–181: The horizontal axis label for Figure 1 was incorrect. It should have shown “DBH class (cm)”. Additionally, the authors have reported that resurveys found mapping errors at a single plot (WHIS2). Removing this plot from spatial analyses did not change the patterns reported in the study.

Communities include habitat generalists whose resource use overlaps specialists. Habitat selection is a mechanism that allows competing species to coexist. Interspecific competition can facilitate coexistence directly or through promoting differential habitat selection. Habitat selection and interspecific competition can vary with population density; however, their roles in determining relative abundance of species across habitat space are poorly understood. We studied Peromyscus keeni, which flourishes in a range of habitats in southeastern Alaska, and Myodes gapperi, a specialist of mature coniferous forests in western North America, to elucidate how these mechanisms may facilitate coexistence in temperate rainforest. We used stepwise multiple regressions of minimum known alive (standardized to unit variance) across 1 ha grids during spring 1999–2000 and autumn 1998–2000 to determine contributions each variable, in each significant regression model, made to the variance in abundance for each species. We determined relative contributions of interspecific competition versus habitat selection in explaining species' habitat use among four different types of rainforest habitat. Intensity of interspecific competition (both directions) varied with population density and season. Habitat variables, rather than interspecific competition, explained variation in species' abundance at population peaks when intraspecific competition would be intense. Interspecific competition, with habitat, was significant at all other times. Our findings suggest habitat selection and interspecific competition explain variation in the abundance of both species among habitats, but contributions vary seasonally and with density. During spring, interspecific competition seemingly plays a greater role at higher densities, but during autumn interspecific competition increases its relative contribution as population density decreases.

The opossum shrimp Neomysis mercedis has expanded its range from the lower Columbia River upstream 695 kilometers into Lower Granite Reservoir where it is now very abundant. We studied Neomysis ecology in the reservoir during 2011–2015 to better understand the physical and biological factors that shape their distribution as well as their potential role in the food web. Benthic densities in offshore habitats ranged from 19 to 145 mysids m^-2 in shallow (2–12 m) water and from 3 to 48 mysids m^-2 in deep (> 12 m) water. Water velocity, depth, substrate, and seasonal interactions were important variables for explaining variation in Neomysis densities in offshore habitats. During spring, daytime densities in shoreline habitats (< 2 m deep) were variable, but nighttime densities generally decreased in summer following reproduction and as temperatures approached 23 °C. Neomysis were mainly collected from the water column during nighttime vertical tows in the downstream end of the reservoir when water velocities were low during summer and autumn. Reproduction occurred mainly in spring and early summer, but a second, smaller reproductive event was observed during autumn. The diet of Neomysis consisted primarily of detritus, rotifers, and copepods, but cladocerans were more prominent during summer and autumn. Physical factors like water velocity may have limited vertical migrations of Neomysis to feed in the water column and influenced use of different habitats in the reservoir. Neomysis are prey for a number of species, including juvenile salmon, but their relations are still largely unknown, and continued monitoring and research is warranted.

The purpose of this study was to determine physiological differences in drought response among Garry oak (Quercus garryana Douglas ex Hook. [Fagaceae]) seedlings from acorns collected at seven acorn collection sites in Washington state. Our objective was to aid in Garry oak restoration efforts by investigating potential differences in drought tolerance for seedlings grown from acorns collected at different sites. Acorns were collected from six sites east of the Cascades, and one site on Whidbey Island (Oak Harbor) west of the Cascades. Differences in morphological and photosynthetic characteristics observed for seedlings grown from acorns collected at these different sites became more pronounced after drought stress was induced by withholding water. Seedlings from acorns collected at the northernmost east-side site (Swauk Creek) were most susceptible to drought and had photosynthetic rates that were 35% lower under drought conditions than when well-watered. Seedlings from acorns collected at the site west of the cascades (Oak Harbor) were the least susceptible to drought and had assimilation rates under drought conditions that were similar to those when well-watered. Differences were also observed among seedlings from different sites in the occurrence of drought-induced loss of stem hydraulic conductivity and changes in leaf water potential and relative water content in response to drought. We conclude that seedlings grown from Garry oak trees at different sites across Washington State have distinct physiological responses to drought that may lead to differing survivorship when used in reforestation efforts and exposed to drought stress in the field.

Oregon white oak (Quercus garryana) habitat is a priority for conservation in the Pacific Northwest, with process-oriented management considered fundamental for the restoration of these ecosystems. Given that natural and anthropogenic processes operate across a wide spatial and temporal range, an historical perspective provides a more holistic understanding of the complex dynamics of these systems. To this end, we employed a multi-proxy approach to develop an environmental narrative of the Willamette University at Zena Forest (WUZ), Willamette Valley, Oregon between AD 1800 and 2014. We used historic written records, aerial photographs, ecological community characteristics, climate data, and dendrochronological data to investigate forest patterns and processes at the plot, stand, site, and regional scales. Our results illustrate temporal shifts in the importance of factors, including land use and ecological succession, in driving landscape change and forest development at WUZ. Critically, this narrative indicates that modern, patchwork vegetation patterns at WUZ are largely a consequence of anthropogenic practices that became increasingly targeted and intensive over the period of interest. This use of multiple proxy records provides a more comprehensive understanding of the dynamic ecological legacies and human-environment relationship necessary to guide restoration. Setting current management into a broader historical context enhances the efficacy of restoration efforts focused on improving the ecological health and function of oak habitat at WUZ, while contributing to the network of key sites maintaining these priority oak habitats in the Pacific Northwest.

In Canada, the western ridged mussel (WRM; Gonidea angulata, Lea) is only found within the Okanagan Valley, British Columbia, and is listed on both provincial and federal levels. A possible threat to this species is invasive plant (Eurasian watermilfoil, Myriophyllum spicatum, L.) control, through rotovation of the lake bottom. We investigated the impact of rotovation and found that: 1) Experimental rotovation resulted in WRM being crushed at the rotovation site while no mussels were crushed at the control site. One day after rotovation, we found significantly more dislodged WRM at the experimental than control site, which disturbs the natural behavior of the mussel. At the same time, we recovered significantly fewer live WRM at the experimental than the control site. This difference was likely explained by the burial of WRM, which we argue has a negative impact on mussel survival. Four months after rotovation, we recovered significantly fewer WRM at the experimental than control site, indicating that the rotovation had a long term negative effect on the mussel. 2) Surveys of WRM habitat showed that the mussel was more common at non-rotovation sites. At rotovation sites WRM was only found in areas that had not been rotovated recently or that are inaccessible to the rotovator. Overall, the experiment shows and the surveys indicate that rotovation has a negative impact on WRM. Based on these findings, resource managers should avoid using rotovation in areas where freshwater mussels are present.

From 1993 to 2007, we used single pass, September surveys to locate and measure fluvial bull trout (Salvelinus confluentus) redds in Rapid River, Idaho. Here we describe substrate sizes, redd dimensions, and water depths, velocities, and temperatures within and adjacent to 337 redds. Most (79%) spawning sites had fewer than 20% surface fines (< 2 mm) and mean, annual water depths and velocities ranged from 14.2–23.0 cm and 11.6–30.5 cm s^-1, respectively. Mean, annual completed redd total lengths and surface areas averaged from 1.03–1.47 m and 0.37–1.07 m^-2, respectively. Pea gravel (2 to < 8 mm) and gravel (8–64 mm) were dominant substrates (> 60%) in redds. Bull trout altered channel water depths and velocities during redd construction; pits averaged 5 cm deeper, leading tailspill edges 1.2 cm shallower, and tailspill crests 6.2 cm shallower than adjacent, undisturbed sites. Conversely, pit velocities averaged 2.1 cm s^-1 slower, tailspill edge velocities 2.3 cm s^-1 faster, and tailspill crest velocities 10.1 cm s^-1 faster than adjacent sites. Mean, annual pit water temperatures ranged from 4.5 to 7.7 °C. Water depths and water velocities over undisturbed sites adjacent to bull trout redds were significantly correlated with water depths and water velocities inside completed redds. Improving our understanding of fluvial bull trout redds will increase the accuracy of redd counts, especially in streams with sympatric, fall spawning salmonids. Data describing fine-scale characteristics of redds and adjacent sites will assist efforts to conserve and restore critical bull trout spawning habitats.

English laurel (Rosaceae: Prunus laurocerasus L.) is an evergreen shrub to small tree that is native to Asia but widely used in landscaping in temperate zones. In the Pacific Northwest this plant has become an important invasive species. However, surprisingly little is known about its ecology—in particular, its chemical defenses and interaction with herbivores and organisms of higher trophic levels. In the present field study, we quantitatively measured cyanogenesis (a constitutive direct chemical defense) and secretion of extrafloral nectar (EFN; an inducible indirect defense), and analyzed the effects of these defenses on insect herbivores (black vine weevil [Otiorhynchus sulcatus]) and predators (sugar ants [Tapinoma sessile]). To induce EFN production, English laurel leaves were mechanically damaged at different intensities and in a way to mimic feeding damage by the black vine weevil, which represents the only observed insect herbivore feeding on this plant at our study site near Portland, OR. While cyanogenesis was expressed at homogenously high levels (> 80 µmol CN^- g^-1 leaf fresh weight) among all experimental plants and was not affected by leaf damage, we found a significant positive correlation between damage, EFN production, and presence of ants. The number of vine weevils observed on experimental plants was significantly negatively correlated with EFN secretion and ant attraction. Our findings suggest that English laurel—beyond expression of cyanogenesis—efficiently utilizes indirect defense through ants in its invasive range. This protective mutualism may significantly contribute to the success of English laurel as an invasive species in native ecosystems of the Pacific Northwest.

We know little about the breeding behavior of most nocturnal raptors. Nest attendance and prey delivery rates can be used as indices of relative habitat quality or extent of parental care. We used video cameras to document and observe prey delivery rates, nest attendance and bout durations at two northern saw-whet owl (Aegolius acadicus) nests in two artificial nest boxes in north-central Oregon. We collected 858 hours of video surveillance between 21 March and 01 June 2014. The number of prey deliveries per night increased as the nesting season progressed: 1.25 during laying, 1.33 during incubation, and 4.0 during the nestling phase. Prey was delivered most often between 2100 and 2200. Nest attendance by females was high during pre-laying (97.8%), laying (97.9%) and incubation (98.2%), but decreased during the nestling phase (55.7%). Nest attendance was higher during diurnal hours than nocturnal hours across all nesting phases. Duration of off bouts (recesses) was similar during pre-laying and laying (26 min), decreased during incubation (19 min), then increased during the nestling phase (55 min). One of the nesting attempts was successful and the female abandoned the other clutch 22 days after initiation. The incubation and nestling periods were 30 days each.