Oregon Streams Research Articles

Backpack electrofishing can be used to collect adult lamprey

AbstractObjectiveWe describe a new method for collecting adult Pacific Lamprey Entosphenus tridentatus in wadeable streams using a backpack electrofisher with pulsed direct current at 300 V, 50 Hz, and a 4‐ms pulse width in a 150‐m2 reach of Eel Creek, a small dunal stream in Oregon, United States.MethodsThe 150‐m2 collection reach was predominately coarse substrate (20% boulders, 60% cobble, 15% pebbles, and 5% sand), whereas the substrate in the remainder of the 4.2‐km‐long Eel Creek is predominately sand and silt. The specific conductivity of the stream was 83.7 μS cm−1, water temperatures ranged from 8.9°C to 17.2°C, and water depth was less than 1.2 m. One person electrofished while gradually moving downstream, and up to six netters that were stationed up to 6 m away covered most of the channel width and caught the lamprey as they emerged from the substrate and floated or swam downstream.ResultWe collected 118 adult Pacific Lamprey (mean catch per unit effort = 29.5 lamprey h−1; range = 4–80 lamprey h−1) measuring 504 ± 54 mm TL (mean ± SD) over eight collection events during 2018–2021. Of these 118 fish, 117 were subsequently anesthetized, handled, tagged, and released within a few hours with no mortalities, external injuries, or abnormal behavior. One tagged lamprey (0.8% of all collected lamprey) died during a second collection 35 d later. The estimated peak power output was 267.7 μW cm−1, and the estimated mean body volume of the lamprey was 378 ± 68 cm3.ConclusionThe results suggest that backpack electrofishing is a useful method for collecting adult lamprey in streams with favorable habitat that concentrates them.

Implications of Metrics and Methodology for Juvenile Salmonid Monitoring in Western Oregon Streams

We attempted to determine whether electrofishing removal estimates or single-pass snorkeling was a more reliable method for Oregon Department of Fish and Wildlife (ODFW) monitoring of juvenile coho salmon (Oncorhynchus kisutch) and steelhead (O. mykiss) abundance and occupancy trends. Based on 1997 to 2000 data, we assumed abundance estimates from the method that tracked more closely with parental abundance would better approximate true juvenile abundance. Parental abundance from spawning ground surveys and juvenile abundance metrics unique to each method were estimated from 2000 to 2004 and 2007 to 2008. Parental abundance did not explain the variation in juvenile abundance from either method (r2 < 0.22), invalidating our assumption, but results had relevance for snorkel surveys used in ODFW monitoring. For both species, correlations between density (fish m2 -1) and abundance (quantity, based on fish km-1) estimates from snorkeling were weak (r < 0.379), but correlations between abundance estimates from both methods were strong (r > 0.846), implying abundance was more appropriate than density for ODFW monitoring. Neither method could sample all habitats, and annually variable proportions of coho salmon (15 to 47%) and steelhead (0 to 24%) abundance estimates obtained by electrofishing were in pools too shallow to meet the ODFW depth criterion for snorkeling. This resulted in lowering the criterion to ≥ 20 cm in 2010. The lower criterion, relative to original, has not shown differences in trends, but 30% more pools have been sampled, resulting in 23% higher abundance estimates with 10% proportionately smaller confidence intervals. These changes improved ODFW monitoring and related management decisions.

Quantitatively Estimating Carbon Sequestration Potential in Soil and Large Wood in the Context of River Restoration

Restoration aimed at rewetting the valley floor has the potential to increase organic carbon stock in the form of floodplain soil carbon, downed wood, and riparian vegetation. The primary goal of stream restoration is typically to restore habitat or maintain balance between natural ecosystem function and human land use. Although many benefits result from stream restoration, the carbon sequestration potential of different restoration approaches in diverse geographic settings has not yet been quantified. We investigate the carbon storage potential of restored stream segments (known as treatment segments) relative to otherwise analogous degraded and reference segments. We develop a conceptual framework to identify the conditions that maximize carbon storage in relation to characteristics of the river corridor and specific restoration practices and propose response surfaces for carbon storage. We illustrate application and quantification of the conceptual framework using data from a pilot study of treatment, degraded, and reference stream segments along two streams in Oregon, United States. The conceptual model is designed to help managers identify levels of hydrologic connectivity, channel and floodplain dynamics, floodplain vegetation, and other variables that may optimize carbon storage at a treatment site.

Passive Restoration of a Small Mountain Stream in Eastern Oregon

In this study, I documented the results of 11 years of passive restoration of a small mountain stream in northeastern Oregon. Removal of the main stressors on the system, grazing and agricultural practices, resulted in a strong recovery of the riparian vegetation over the middle two-thirds of the reach. Cover of trees and shrubs tripled, tree density increased sevenfold, and stream shading fourfold over the period 2007 through 2018. Average maximum daily stream temperature declined by 2.1 to 2.8 °C, and average maximum diurnal temperature range narrowed by 3.7 to 4.6 °C. Recolonizing American beavers (Castor canadensis) played an essential role in improving the condition of the streambed over 18% of the reach. Their dams and ponds initiated the process of streambed aggradation and transformed the single-thread, incised channel into a multi-thread configuration within beaver complexes. Vegetation expansion was much stronger in impounded than in un-impounded parts of the stream. Passive restoration was not effective in two sections, together comprising one-third of the reach. In the upper part of the stream, recovery stalled because of continued (unauthorized) trespass grazing during late summer and fall. The channelized lower section of the stream was too severely modified for measurable recovery to occur. I concluded that 11 years of passive restoration improved the functionality of the stream from 24% to 32%, and within beaver complexes, up to 57% of its pre-disturbance condition.

Lepidodermella weissi, new species (Gastrotricha: Chaetonotida: Chaetonotidae) from northwestern Oregon, U.S.A.

A new species of Lepidodermella (Gastrotricha: Chaetonotida: Chaetonotidae) is described from two streams in northwestern Oregon, U.S.A. This is the fourth species of freshwater gastrotrich reported from the Pacific Northwest region of the United States. The dearth of reports appears to be due more to a lack of study rather than a lack of gastrotrichs. Lepidodermella squamata is one of the species already reported from the Pacific Northwest, and occurs sympatrically with the new species described here. No other members of the genus have been reported from the Pacific Northwest. Three species of Lepidodermella have been reported previously from North America. The genus includes one marine species and 14 freshwater species. Lepidodermella weissi, new species, brings the number of freshwater species to 15 and can be distinguished from other freshwater members of the genus by the following characters: absence of parafurcal spines, absence of transverse anterior ventral plates, head width of less than 40 µm, head with five lobes, pharynx length 44 µm or less, adhesive tube length of 5 µm or more, more than 35 scales per middorsal column, presence of seven or fewer posterior midventral columns of scales, presence of a pair of posterior ventral plates, and the presence of several columns of spined scales between the ventral ciliary bands and the smooth scales of dorsum and sides.

Trematode parasites exceed aquatic insect biomass in Oregon stream food webs.

Although parasites are increasingly recognized for their ecosystem roles, it is often assumed that free-living organisms dominate animal biomass in most ecosystems and therefore provide the primary pathways for energy transfer. To examine the contributions of parasites to ecosystem energetics in freshwater streams, we quantified the standing biomass of trematodes and free-living organisms at nine sites in three streams in western Oregon, USA. We then compared the rates of biomass flow from snails Juga plicifera into trematode parasites relative to aquatic vertebrate predators (sculpin, cutthroat trout and Pacific giant salamanders). The trematode parasite community had the fifth highest dry biomass density among stream organisms (0.40g/m2 ) and exceeded the combined biomass of aquatic insects. Only host snails (3.88g/m2 ), sculpin (1.11g/m2 ), trout (0.73g/m2 ) and crayfish (0.43g/m2 ) had a greater biomass. The parasite 'extended phenotype', consisting of trematode plus castrated host biomass, exceeded the individual biomass of every taxonomic group other than snails. The substantial parasite biomass stemmed from the high snail density and infection prevalence, and the large proportional mass of infected hosts that consisted of trematode tissue (M=31% per snail). Estimates of yearly biomass transfer from snails into trematodes were slightly higher than the combined estimate of snail biomass transfer into the three vertebrate predators. Pacific giant salamanders accounted for 90% of the snail biomass consumed by predators. These results demonstrate that trematode parasites play underappreciated roles in the ecosystem energetics of some freshwater streams.

Temporal shifts in intraspecific and interspecific diet variation among 3 stream predators

Intraspecific variation is increasingly recognized as an important factor in ecological interactions that can exceed the role of interspecific variation. Few studies, however, have examined how variation in intra- and interspecific resource use affect trophic interactions over time within a seasonally-dynamic food web. We compared diets with respect to predator body size and predator species identity over 3 seasons by collecting stomach contents from 2028 Reticulate Sculpin (Cottus perplexus), 479 Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii), and 107 Pacific Giant Salamanders (Dicamptodon tenebrosus) in western Oregon streams. In each season, predator body size was strongly associated with dietary composition and positively related to taxonomic breadth and the size of individual prey. Intra- and interspecific diet variation changed substantially across seasons, with much greater interspecific variation in spring than in summer and autumn. Interspecific differences in foraging mode (e.g., benthic vs drift feeding) were associated with predator-specific responses to a seasonal pulse in the availability of terrestrial thrip larvae (Thysanoptera) and contributed to temporal variation in trophic niche differentiation. These findings show that the relative magnitudes of intra- and interspecific diet differentiation can change over time in systems that receive seasonal resource pulses. Our results highlight the dynamic nature of food webs and the need to incorporate sampling over relevant temporal scales to understand species interactions.

Animal Track Accumulation on Streambanks of Four Eastern Oregon Streams

A 2-yr study of livestock/wildlife tracking was conducted on four streams in eastern Oregon. Binomial sampling of tracks proved to be an effective statistical method for monitoring the proportion of samples containing tracks on stream greenlines and testing the observed value against an established standard. Study results indicate that tracks are related to variables outside of the control of livestock grazing management.

Using Applied Science for Effective Watershed Restoration and Coho Salmon Recovery in Coastal Oregon Streams

Coos Bay, located on the southern Oregon Coast, is the largest estuary between the Columbia River and San Francisco Bay. Palouse and Larson Creeks in the northern section of Coos Bay are the two most productive streams for coho salmon. Such productivity occurs despite the pressure salmon habitats have experienced through a long history of anthropogenic alterations, and continue to face from the region’s robust industrial economy, including recreational and commercial fisheries, agricultural production, and forestry. Restoration efforts since the 1980s have helped mitigate environmental impacts, but the turn of the century brought a new era of coordinated research, monitoring, and restoration. Forming a multi-stakeholder partnership with the goal of restoring salmon runs, the local nonprofitnon-profit Coos Watershed Association and its partners worked together to learn about the strategies that coho use to survive in these altered landscapes and apply research findings to restore habitats. Specifically, they examined the most appropriate habitat restoration strategies for various life histories of coho salmon, while working within social and political constraints. As a result, these efforts over the past 35 years have led to a better understanding of salmon populations in Palouse and Larson Creeks and an effective restoration program that continues till today.

The importance of scale in understanding the effect of stream intermittence on aquatic macroinvertebrate diversity

AbstractBiotic richness in intermittent reaches (α‐diversity) is generally lower than in perennial reaches. However, variability among intermittent reaches (β‐diversity) is predicted to be higher. Yet how patterns in α‐ and β‐diversity scale up to influence stream network diversity is unclear and has received little attention. In addition, the timing of sampling relative to the resumption of flow in intermittent reaches should influence patterns in diversity. We predicted that early in the wet season, assemblages in intermittent reaches would be recovering from drying and have lower α‐diversity and higher β‐diversity relative to perennial reaches but that these patterns might not be reflected at the stream network scale. In contrast, we predicted that late in the wet season, assemblages in intermittent reaches would recover and α, β, and network diversity would be similar between intermittent and perennial reaches. These predictions were tested with macroinvertebrate assemblages in an eastern Oregon stream network. Early in the wet season, α‐diversity and network diversity were lower in intermittent than perennial reaches; however, β‐diversity was similar between the two types of reaches. Late in the wet season, both α‐diversity and β‐diversity were similar between intermittent and perennial reaches, suggesting recovery of intermittent reaches from drying. However, at the network scale, intermittent reaches continued to have lower diversity indicating a lack of recovery. Rare taxa were particularly vulnerable to flow intermittency. Our results indicate that a consideration of spatial scale, taxa abundance/rarity, and timing of sampling will improve our understanding of the effect of flow intermittence on diversity.

Livestock Riparian Guidelines May Not Promote Woody Species Recovery Where Wild Ungulate Populations Are High

Stubble height, streambank alteration, and woody species use are indicators used to monitor livestock impacts on riparian areas in the western United States. Effects of wild ungulates on riparian conditions are often not monitored and assumed to be represented by indicators developed for livestock. We tested this assumption by evaluating effects of elk (Cervus canadensis) and mule deer (Odocoileus hemionus) on grazing indicators along Meadow Creek, a salmonid-bearing stream in northeastern Oregon. Wild ungulates reduced stubble height by 20% to 30%. Mean streambank alteration was 1.1% (ranged from 0.3–8%). Woody species use was negatively related to stubble height and positively related to streambank alteration (P < 0.05). Despite maintenance of stubble height and streambank alteration within regulatory guidelines, wild ungulate use of preferred woody species was moderate to high (>50%). Adherence to guidelines developed for livestock may not result in desired riparian conditions where wild ungulate populations are high.

Measurement of gas-exchange rate in streams by the oxygen–carbon method

The gas-exchange rate between streams and the atmosphere is needed to measure in-stream ecological processes and C processing in rivers and streams. Current methods include empirical relationships to hydraulics, direct injection of a tracer gas, and modeling based on O2 or C diel curves. All existing methods have strengths and drawbacks and most are limited to point measurements or are unable to measure diel variation in exchange rate. Researchers continue to search for better techniques, particularly for steep streams with high rates of gas exchange and low primary productivity. We present the O2−C (OC) method for calculating gas-exchange rates via simultaneous measurement of O2 and dissolved inorganic C (DIC). Gas-exchange rates are calculated by solving the combined stream transport equation for O2 and DIC. The output is a time-series of aeration rates at the same sampling frequency as the input O2 and C data. Field tests in a 4th-order montane stream in Oregon, USA, indicate that the method is suitable for stream reaches with high downstream gas-concentration gradients and saturation deficits. The mean modeled aeration rate adjusted to 17°C (3.25/h) agreed well with the value of 3.22/h from direct gas injection. Net ecosystem production calculated with the modeled aeration rate (−1.69 g O2 m−2 d−1) was consistent with the result obtained with direct gas injection (−1.60 g O2 m−2 d−1). An assumption of the model is a constant respiration quotient, but results indicated that the respiration quotient may be time variable. Sensitivity analysis indicated that application of the OC method is limited to reaches with a suitable change in combined O2 and CO2 concentration ≥ ∼4 μmol/L and combined O2 and CO2 saturation deficits ≈ 4 μmol/L, characteristic of smaller gaining streams. Preliminary application of the OC method indicates it could be useful to practitioners interested in continuous measurement of gas-exchange rates.

Suspended sediment and turbidity after road construction/improvement and forest harvest in streams of the Trask River Watershed Study, Oregon

AbstractTransport of fine‐grained sediment from unpaved forest roads into streams is a concern due to the potential negative effects of additional suspended sediment on aquatic ecosystems. Here we compared turbidity and suspended sediment concentration (SSC) dynamics in five nonfish bearing coastal Oregon streams above and below road crossings, during three consecutive time periods (“before”, “after road construction/improvement”, and “after forest harvest and hauling”). We hypothesized that the combined effects of road construction/improvement and the hauling following forest harvest would increase turbidity and SSC in these streams. We tested whether the differences between paired samples from above and below road crossing exceeded various biological thresholds, using literature values of biological responses to increases in SSC and turbidity. Overall, we found minimal increases of both turbidity and SSC after road improvement, forest harvest, and hauling. Because flow is often used as a surrogate for turbidity or SSC we examined these relationships using data from locations above road crossings that were unaffected by roads or forest harvest and hauling. In addition, we examined the association between turbidity and SSC for these background locations. We found a positive, but in some cases weak association between flow and turbidity, and between flow and SSC; the relationship between turbidity and SSC was more robust, but also inconsistent among sites over time. In these low order streams, the concentrations and transport of suspended sediment seems to be highly influenced by the variability of local conditions. Our study provides an expanded understanding of current forest road management practice effects on fine‐grained sediment in streams and introduces alternative metrics using multiple thresholds to evaluate potential indicators of biological relevance.

Large Wood and Instream Habitat for Juvenile Coho Salmon and Larval Lampreys in a Pacific Northwest Stream

AbstractThe influences of large wood on Pacific salmon are well‐studied, but such studies on nonsalmonid species such as lampreys are uncommon. To address this need, we evaluated the potential effects of large wood on larval lampreys (Pacific Lamprey Entosphenus tridentatus and potentially Western Brook Lamprey Lampetra richardsoni) as well as on juvenile Coho Salmon Oncorhynchus kisutch in a small, coastal, Oregon stream. Our objectives were to (1) identify instream habitat characteristics associated with the presence of larval lampreys and abundance of juvenile Coho Salmon and (2) evaluate how these characteristics were associated with instream wood. To address habitat use, we quantified presence of larval lampreys in 92 pools and abundance of juvenile Coho Salmon in 44 pools during summer low flows. We focused on a study reach where large wood was introduced into the stream between 2008 and 2009. Results indicated that presence of larval lampreys was significantly associated with the availability of fine sediment and deeper substrate. The abundance of juvenile Coho Salmon (fish per pool) was strongly associated with pool surface area and to a weaker extent with the proportion of cobble and boulder substrates in pools. Pools with wood, regardless of whether they were formed by wood, had significantly greater coverage of fine sediment, deeper substrate, and greater pool surface area. Taken together, these results suggest that instream wood can provide habitat associated with the presence of larval lampreys and greater abundance of juvenile Coho Salmon.Received September 11, 2016; accepted March 25, 2017 Published online May 31, 2017

Wild ungulate herbivory suppresses deciduous woody plant establishment following salmonid stream restoration

Domestic and wild ungulates can exert strong influences on riparian woody vegetation establishment, yet little is known about how wild ungulate herbivory affects riparian restoration in the absence of cattle. We evaluated elk (Cervus elaphus) and mule deer (Odocoileus hemionus) impacts on the establishment of deciduous woody riparian plantings along 11km of Meadow Creek, a steelhead (Oncorhynchus mykiss) and Chinook (Oncorhynchus tshawytscha) salmon stream in northeastern Oregon, USA. We compared survival and growth between protected and unprotected plantings (from wild ungulates), and assessed the contribution of the plantings to the total deciduous woody cover after two growing seasons. Riparian use by wild ungulates was estimated by tracking a subset of the deer and elk populations using global positioning system telemetry collars. Elk riparian use was 11 times greater than deer, and in contrast to elk, deer were functionally absent from greater than 50% of the restored reach. Wild ungulate herbivory decreased planting survival by 30%, and growth by 73%, and was most detrimental to cottonwood (Populus balsamifera; increased likelihood of mortality by 5 times and suppressed growth by more than 90%). Herbivory impacts resulted in survival rates below regional criteria (50%) for restoration success after only two growing seasons. Naturally recovering shrubs accounted for 99% of the deciduous woody cover, and were mostly composed of the same species or genera as those planted. Our results suggest that wild ungulate herbivory can impede riparian restoration along salmonid streams by suppressing woody plant establishment and recovery.

The Biological Sediment Tolerance Index: Assessing fine sediments conditions in Oregon streams using macroinvertebrates

Fine sediments in excess of natural background conditions are one of most globally common causes of stream degradation, with well documented impacts on aquatic communities. The lack of agreement on methods for monitoring fine sediments makes it difficult to share data, limiting assessments of stream conditions across jurisdictions. We present a model that circumvents these limitations by inferring fine sediments in Oregon streams through sampling of macroinvertebrates. Tolerances to fine sediments (<0.06mm diameter) were calculated for 240 macroinvertebrate taxa, from a calibration dataset of 446 sites across Oregon, as well as an independent validation dataset of 50 samples. Weighted averaging methods were used to infer fine sediment levels in streams by weighting the tolerances of modeled taxa observed in a sample by their abundances. The final model, the Biological Sediment Tolerance Index (BSTI), showed a strong relationship to measured fine sediments (calibration r2=0.49, validation r2=0.58). Root-mean-squared-error was small in the calibration dataset (2% fines), but larger in the validation dataset (14% fines). Repeatability was assessed by examining variability in BSTI at 14 sites across Oregon. Because field methods for sampling macroinvertebrates are standardized across resource agencies in Oregon and the responses of macroinvertebrates represent the actual effects of fine sediments on stream ecosystems, the BSTI may offer water resource managers’ a cost-effective method for assessing fine sediment conditions in their ongoing efforts to improve water quality across the state.

Salty Salamander: Occurrence of aDicamptodon tenebrosusin a Tidal Stream

Amphibians, due to their highly permeable skin and egg membranes, are generally considered osmotically challenged animals and, thus, highly sensitive to brackish and saline environments (Shoemaker and Nagy 1977; Duellman and Trueb 1994). Due to their intolerance of salt water, amphibians have long been mostly discounted from occurring in areas directly influenced by the ocean (Darwin 1872), and notes of salamanders in these habitats are rare (Neill 1958). On 14 May 2012, we observed a larval Dicamptodon tenebrosus (Coastal Giant Salamander) in the tidal area of Hunter Creek, Curry County, Oregon (UTM Zone 10, 382898.3E, 4693923.4N, WGS84), 177 m from the Pacific Ocean. The animal was active, appeared in good body condition, and had a snout-vent length of 5.5 cm and a total length of 9.7 cm (Fig 1A). We found the salamander in a shallow sand and rock pool on the edge of the stream (,30 cm deep), with a salinity of 1.0 ppt. Freshwater is generally ,0.5 ppt; brackish water is 0.5 to 20 ppt; sea-water typically averages 35 ppt (Boaden and Seed 1985). We measured salinities of up to 1.4 ppt in this area on other days, and these concentrations have been found to be detrimental to caudate amphibian embryonic and larval survival and development (Hopkins and others 2013a, 2013b, 2014). The water temperature at the time of our observation was 14.26C. This area of the stream is devoid of riparian and aquatic vegetation, except for some algae growing on the rocks, and is essentially on a sandy and rocky beach (Fig. 1B, 1C). Affected dramatically by the tides, the water level of this habitat changes by almost 1.0 m between high and low tides (Fig. 1B, 1C). A dead sea-star (Forcipulatida, Pisaster spp.) was located a few meters away from the salamander. This habitat is also affected by coastal storm events, which sometimes lead to sea-water washing through this area (Fig. 1D). As we only found 1 individual D. tenebrosus in the tidal area of this stream, it is possible that these storm events may prevent a larger population from inhabiting this habitat due to temporarily increased salinity beyond this species’ tolerance level, or simply because the lack of vegetation and cover in this habitat renders it unsuitable. It is also possible that this individual may have been washed downstream due to spring flooding, and may be sensitive to increased salinity levels, as was found for Ambystoma gracile (Northwestern Salamander) in British Columbia, where larvae were found dead or dying in a tidal area with presumably increased salinity (Carl 1949). The D. tenebrosus that we found in the tidal area did not, however, appear to be dead or dying, and may have been more salt-tolerant than the individuals observed by Carl (1949). Ferguson (1956) also found 1 larval D. tenebrosus approximately 20 m from the edge of the high tide area of a coastal stream in Lincoln County, Oregon, but salinity was not measured. To the best of our knowledge, salinity tolerance in D. tenebrosus has not yet been experimentally determined, and more work clearly needs to be done to determine tidal habitat utilization and salt tolerance in this species. Although reports of salamanders in tidal habitats in the Pacific Northwest are rare, Ferguson (1956) found Taricha granulosa (Roughskinned Newts) in the tidal area of a stream in southern Oregon, and we also found a large breeding group (over 60 individuals) of this species in the same tidal area as the Dicamptodon we observed (Hopkins and Hopkins, pers. obs.). Batrachoseps relictus (Relictual Slender Salamanders) were reported on a beach in California (Moss Landing, Monterey County) under driftwood near the tide line (Licht and others 1975; B Bury, pers. comm.), as was B. pacificus (Channel Islands Slender Salamander) in the Channel Islands (Hansen and others 2005). Batrachoseps relictus was experimentally determined to be physiologically adapted to the increased salinity in this habitat (Licht and others 1975). GENERAL NOTES

Investigating organic matter in Fanno Creek, Oregon, Part 3 of 3: Identifying and quantifying sources of organic matter to an urban stream

• Continuous fluorescence monitor used to calculate annual organic carbon loads. • Annual organic carbon load was approximately 324 tonnes of C. • First autumn storm mobilized ∼3× higher carbon concentrations than other storms. • Organic matter in Fanno Creek mostly a terrestrial source, likely riparian litterfall. The sources, transport, and characteristics of organic matter (OM) in Fanno Creek, an urban stream in northwest Oregon, were assessed and quantified using: (1) optical instruments to calculate transported loads of dissolved, particulate, and total organic carbon, (2) fluorescence spectroscopy and stable isotope ratios (δ 13 C, δ 15 N) to elucidate sources and chemical properties of OM throughout the basin, and (3) synoptic sampling to investigate seasonal and hydrologic variations in the characteristics and quantity of OM. Results from this study indicate that of the roughly 324 (±2.9%) metric tons (tonnes, t) of organic carbon exported from the basin during March 2012 to March 2013, most of the OM in Fanno Creek was dissolved (72%) and was present year-round at concentrations exceeding 3–4 milligrams of carbon per liter, whereas particulate carbon typically was mobilized and transported only by higher-flow conditions. The isotopic and fluorescence characteristics of Fanno Creek OM indicate that the carbon originates primarily from terrestrial inputs, most likely riparian vegetative biomass that enters the stream via litterfall and overland transport and then travels through the system episodically as a result of hydrologic processes. The amount of OM exported from the Fanno Creek drainage over the course of a year in this study is consistent with previous estimates of annual riparian litterfall in or near the creek. Although the creek channel is actively eroding, most bank material has too little OM for that to be a dominant source of OM to the stream. Fluorescence data revealed that the OM contains primarily humic and fulvic-like components that become less aromatic as the OM moves downstream. The most significant seasonal variation was associated with OM transported in the first storms of the autumn season (fall flush). That material was characteristically different, with a larger fraction of microbially derived OM that probably resulted from an accumulation of easy-to-mobilize and decomposing material in the streambed during previous months of summertime low-flow conditions. The first fall flush produced the highest concentrations of OM of the entire year, and the resulting load of mobilized and decomposing OM resulted in a significant oxygen demand immediately downstream in the Tualatin River.

Assessing the utility of green LiDAR for characterizing bathymetry of heavily forested narrow streams

Stream depth and bathymetry in forested environments is difficult and costly to measure in the field, but critically important for stream-dwelling organisms. Green (bathymetric) LiDAR can be used to characterize stream bathymetry, but little is known of its ability to accurately characterize stream bathymetry in narrow (width less than 5 m), heavily forested streams. We compared digital elevation models (DEMs) derived from green and near-infrared (NIR) LiDAR to field measurements in a narrow, forested stream in Oregon, USA, as well as comparing the two DEMs to each other along the length of the stream and to estimates of leaf area index. Our results suggest that green LiDAR may be limited in accurately characterizing the bathymetry of narrow streams in heavily forested environments due to difficulty penetrating canopy and interactions with complex topography.

Scouleria siskiyouensis(Scouleriaceae), A New Rheophytic Moss Endemic To Southern Oregon, USA

Scouleria siskiyouensis Shevock & D. H. Norris, a new species restricted to rivers and streams in southwestern Oregon is described and illustrated. This species appears related to the widespread S. aquatica Hook. in Drummond of western North America but is distinguished by a combination of features including lamina bistratose except for a few cells at immediate leaf margin unistratose, leaves lanceolate to ovate-lanceolate and with leaf apex acute to acuminate.