Wood In Streams Research Articles

Long‐term dynamics of large wood in old‐growth and second‐growth stream reaches in the Cascade Range of Oregon

AbstractWe quantified temporal dynamics of wood storage, input, and transport over a 24‐year period in adjacent old‐growth and second‐growth forested reaches in Mack Creek, a third‐order stream in the Cascade Range of Oregon. The standing stocks of large wood in the old‐growth reach exceeded those at the second‐growth reach by more than double the number of wood pieces and triple the wood volume. Annual inputs of large wood were highly variable. Wood numbers delivered into the old‐growth reach were 3× higher and wood volume 10× greater than in the second‐growth reach. The movement of number and volume of logs did not differ significantly between the two reaches over time. Less than 2% of the logs moved in most years, and the highest proportion moved in the year of the 1996 flood (9% in old growth and 22% in second growth). Most of the large wood aggregated as jams in both reaches. The second‐growth reach lacked major jams, but 29% of the logs in the old growth were in full‐channel spanning jams. Long‐term observations of annual storage, input, and movement reveal the temporal dynamics of wood rather than static representations of the characteristics of wood. Input events and transport of wood in Mack Creek were episodic and varied greatly over the 24‐year study, which illustrates one of the major challenges and opportunities for understanding the cumulative dynamics of wood in streams.

Large wood recruitment, retention and mobilization in low-order streams of the Brazilian Savanna

The delivery of wood to streams varies in space and time and may occur continuously or episodically. Once in a stream, wood may be retained or transported due to the balance between driving (water flow) and resisting forces (channel features and wood characteristics). Despite there being few studies directly measuring wood mobility, notable variations in annual transport rates and mean travelled distances have already been detected worldwide. In the tropics, due to wetter and warmer conditions and consequently higher decay rates and peak discharge, wood is believed that more readily degraded and transported downstream. However, there exists a knowledge gap regarding wood dynamics in tropical streams and even more considering tropical non-forested environments. In the present study, we aimed to document large wood (LW) recruitment, retention, and mobilization over a period of one year in eight low-order streams of the Cerrado (the South American Savanna) by tagging and tracing LW pieces. We detected high LW transport and recruitment rates in Cerrado streams, such that the total wood amounts remained constant over time. However, there were important differences between streams due to their distinct channel morphologies and the occurrence of episodic events. The LW length and diameter, original location and orientation were the most important factors in the prediction of the LW travelled distance, which ranged from zero to almost 100 m in one year. Our findings provide unprecedented information regarding wood mobility in tropical savanna streams in South America. To further advance knowledge about the dynamics of wood in Cerrado streams, future studies should characterize the great diversity of wood, especially with regard to densities that may strongly affect wood mobility. Furthermore, it is essential to perform long-term studies to document the dynamics of wood over years in these environments.

Fire severity influences large wood and stream ecosystem responses in western Oregon watersheds

BackgroundWildfire is a landscape disturbance important for stream ecosystems and the recruitment of large wood (LW; LW describes wood in streams) into streams, with post-fire management also playing a role. We used a stratified random sample of 4th-order watersheds that represent a range of pre-fire stand age and fire severity from unburned to entirely burned watersheds to 1) determine whether watershed stand age (pre-fire) or fire severity affected riparian overstory survival, riparian coarse wood (CW; CW describes wood in riparian areas), LW, or in-stream physical, chemical, and biological responses; and 2) identify relationships of LW with riparian vegetation and in-stream physical, chemical, and biological factors.ResultsAt higher fire severities, LW and CW diameter was smaller, but volume did not change in the first year post-fire. Larger size of CW in riparian areas versus LW in streams suggests potential future recruitment of larger-diameter wood into streams from riparian zones in severely burned watersheds. Fire severity exerted strong control on stream responses across watersheds, explaining more of the variation than stand age. At higher fire severities, riparian tree mortality, salvage logging, light, dissolved organic matter (DOM) concentrations, and fish densities were higher, whereas canopy cover, LW diameter, macroinvertebrate diversity, and amphibian density were lower. In watersheds with older stand ages, elevation and mean annual precipitation were greater but mean annual temperature, specific ultra-violet absorption at 254 nm, and phosphorus concentrations were lower. Overstory mortality in burned riparian areas was lower for red alder (12%) than western redcedar (69%).ConclusionsOur results link forested streams, fire, and LW by identifying key relationships that change with fire severity and/or watershed stand age. Severe fires burn more overstory riparian vegetation, leading to increased light, DOM concentrations, and macroinvertebrate and fish densities, along with reduced canopy cover, LW diameter, macroinvertebrate diversity, and amphibian densities. We highlight an important function of red alder in riparian zones—as a fire-resistant species, it may help facilitate a more rapid recovery for streams in fire-prone landscapes. Continued comprehensive aquatic and riparian ecosystem monitoring of these watersheds will aid in understanding long-term effects of post-fire management activities (salvage logging) on aquatic ecosystems.

Forestry influences on salmonid habitat in the North Thompson River watershed, British Columbia

Freshwater ecosystems that support juvenile salmonids can be degraded by human pressures such as forestry. Forestry activities can alter water temperatures and the delivery and storage of water, nutrients, wood, and sediment in streams, resulting in changes to the habitat, growth, and survival of juvenile salmon. Previous research on forestry impacts on habitat has focused on small, intensively monitored coastal systems. Here, we examined forestry activities, watershed characteristics, physical habitat, and stream temperature for 28 mid-sized tributaries of the North Thompson River to examine relationships between forestry and juvenile coho stream habitat in interior watersheds. Forest harvest had a positive correlation to maximum summer stream temperature. Streams with 35% of the riparian area harvested since 1970 had maximum summer temperatures 3.7 °C higher on average than those with 5% harvested. Stream gradient explained most of the variation in physical habitat and had negative correlations to pool cover, pool depth, and fine sediment cover. Taken together, these results indicate that watershed characteristics drive physical habitat, but forest harvest can be a primary driver of water temperatures.

Pool Formation and The Role Of Instream Wood In Small Streams In Predominantly Second-growth Forests.

Extensive and intensive forest harvesting during the 20th century often had, and continues to have, negative impacts on stream structure and ultimately fish. Loss of instream wood and pools has been identified as a pathway by which riparian forest management can negatively impacts salmonids. Passive riparian restoration (allowing forests and streams to recover through natural processes) through the use of riparian buffers when conducting forest harvests has often been employed to promote stream habitat recovery. In this study, we evaluate the effects of 25 years of passive restoration on instream wood and pool recovery in 74 reaches in small streams (1st through 3rd order) across three channel types (pool-riffle, step-pool, and cascade) in a predominantly second-growth forest. Gradient and stream size were the most important variables for determining pool density, while stream size was the most important variable for determining pool depth. Instream wood formed 39% of pools in pool-riffle, 30% of pools in step-pool and 25% of pools in cascade channels types. Instream wood volume had a significant (R2 = 0.261, P ≤ 0.001) positive relationship with pool volume in wood-formed pools. Dimensions of individual wood pieces were associated with their likelihood of pool formation: for each additional 1 meter length within the bankfull channel the odds of forming a pool increased by 25.6%, and for each additional centimeter in diameter the odds of pool formation increased by 2.0%. When compared with studies conducted in both second- and old-growth forests, we concluded that streams associated with second-growth forests hadve both reduced densities and sizes of instream wood and pools. Young forests are likely continuing to negatively impact stream habitat and fish populations. Because riparian zones in many forests are now dominated by relatively young forest stands, and given the timeline for recovery using passive restoration alone (e.g., 100 s of years in Pacific Coastal forests), active restoration could be explored to accelerate instream wood and pool recovery.

Wood stock in neotropical streams: Quantifying and comparing instream wood among biomes and regions.

Instream wood plays important chemical, physical and ecological functions in aquatic systems, benefiting biota directly and indirectly. However, human activities along river corridors have disrupted wood recruitment and retention, usually leading to reductions in the amount of instream wood. In the tropics, where wood is believed to be more transient, the expansion of agriculture and infrastructure might be reducing instream wood stock even more than in the better studied temperate streams. However, research is needed to augment the small amount of information about wood in different biomes and ecosystems of neotropical streams. Here we present the first extensive assessment of instream wood loads and size distributions in streams of the wet-tropical Amazon and semi-humid-tropical Cerrado (the Brazilian savanna). We also compare neotropical wood stocks with those in temperate streams, first comparing against data from the literature, and then from a comparable dataset from temperate biomes in the USA. Contrary to our expectations, Amazon and Cerrado streams carried similar wood loads, which were lower than the world literature average, but similar to those found in comparable temperate forest and savanna streams in the USA. Our results indicate that the field survey methods and the wood metric adopted are highly important when comparing different datasets. But when properly compared, we found that most of the wood in temperate streams is made-up of a small number of large pieces, whereas wood in neotropical streams is made up of a larger number of small pieces that produce similar total volumes. The character of wood volumes among biomes is linked more to the delivery, transport and decomposition mechanisms than to the total number of pieces. Future studies should further investigate the potential instream wood drivers in neotropical catchments in order to better understand the differences and similarities here detected between biomes and climatic regions.

The role of large wood in streams as ecological corridors for wildlife biodiversity

The role of large wood in streams as ecological corridors for wildlife biodiversity

Taxonomy and ecology of Physisporinus forming synnema-like structures in freshwater environments

ABSTRACT Since 2011, we have collected fungi that form synnema-like structures (SSs) bearing many acanthophyses at the apex on water-splashed wood in streams in various regions of Japan. A provisional phylogenetic analysis of strains isolated from SSs based on their nrDNA sequences implied affinity with Physisporinus (Polyporales, Basidiomycota). However, it has not been reported that this genus forms SSs in freshwater habitats. We found a fungus forming not only SSs on the water-boundary part of wood but also resupinate basidiocarps with poroid hymenophores on nonsubmerged parts, and the morphological characteristics of the basidiocarps matched those of Physisporinus. Therefore, we investigated the relationship between SS-forming fungi and their sexual states by taxonomic approaches. Phylogenetic analyses based on nrDNA internal transcribed spacer (ITS) and large subunit (LSU) sequences indicated that SS-forming fungi diverged into five clades in Physisporinus. Each clade was discriminated by the color of SSs, morphology of acanthophyses, and cultural characteristics. Of the five clades, Clade 1, which consisted only of sequences of strains isolated from SSs and basidiocarps produced on rhizomorphs, was closely related to P. eminens and P. undatus, but the morphology of basidiocarps and the manner of basidiocarp development differed. Clade 5 was closely related to P. castanopsidis, P. crocatus, P. pouzarii, P. sanguinolentus, P. subcrocatus, P. tibeticus, and P. vitreus, but the basidiocarp morphology differed. Therefore, Clades 1 and 5 were described as two new species. Regarding Clades 2, 3, and 4, further taxonomic studies with additional specimens are required. SS and acanthophysis formation in wet habitats in streams and in culture could be recognized as new taxonomic and ecological characters of Physisporinus.

Severely burned wood from wildfires has low functional potential in streams

Abstract More frequent and more severe forest fires mean more severely burned wood in streams. Instream wood provides habitat complexity, alters geomorphology, retains organic and inorganic material, promotes hyporheic flow and acts as substrate for biofilm and invertebrates. However, little is known about instream wood functions in fire‐prone biomes and how they combine with wood burning levels to guide postfire management efforts. Over 3 years, we tracked instream wood following forest fires in central Portugal. We examined for the first time the influence of burning level, season and a large suite of driving factors on the likelihood of four different functions having primary ecological consequences—retention of organic matter, serving as substrate for aquatic biota, being key pieces forming wood jams and deflecting flow including pool habitat formation. One of the main ecological functions of wood in rivers is to provide substrate for vegetation, periphyton, biofilm and oviposition. Our results show that this can be negatively affected when the wood is severely burned. Except for jam formation, the probability of each stream wood function changed markedly with season and the probability of non‐function was nearly twice as high in the Euro‐Mediterranean dry season than in the wet season. More anchored and decayed wood increased the probability of all functions, whereas the effect of submergence depended on the function. Challenging the ‘size paradigm’ that larger sized pieces provide more function, our data suggest that the effect of size is function‐specific. Synthesis and applications. We show how postfire stream restoration success can be maximized by selecting the most appropriate wood and taking advantage of attribute‐function relationships. We urge managers to refrain from removing wood or to selectively remove the most severely carbonized only, allowing the persistence of great potential to provide substrate for stream biota. The non‐attraction of severely burned wood as substrate can be compensated for by other wood with attributes enhancing this function, such as wood deeper within the bankfull area, and with large diameters. These results will help to inform successful management, as is increasingly asked from restoration ecology.

<p><strong>Two new species of <em>Minimelanolocus</em> (Herpotrichiellaceae, Chaetothyriales) from submerged wood in Yunnan, China</strong></p>

During a survey on diversity of freshwater fungi along a north-south latitudinal gradient in Asia, three fresh specimens of Minimelanolocus were collected from submerged wood in streams in northwestern Yunnan Province, China. Based on their distinct morphological features and phylogenetic analyses of combined ITS, LSU and SSU sequence data, Minimelanolocus nujiangensis and M. clavatus are described as new species and M. submersus was recollected from Yunnan, China. Illustrations and descriptions with notes of the three species are provided. This study increases the known diversity of Minimelanolocus and enriches freshwater fungal resources.

Loading of stream wood following the 2016 Chimney Tops 2 Wildfire: Great Smoky Mountains National Park, Tennessee, USA

AbstractLarge wood drives physical and ecological processes in river systems, but the relative roles of continuous individual tree mortality versus episodes of mass mortality in wood recruitment are not well understood. Here, the 2016 Chimney Tops 2 wildfire, a rare severe wildfire in the eastern United States, was used as a case study for examining the role of mass tree mortality in wood loads of streams in Great Smoky Mountains National Park (GSMNP), Tennessee. Wood surveys were conducted on four reaches in two drainage systems affected by the fire to ascertain the total frequency and volume of burned and unburned wood pieces and jams. Relative to unburned wood, the Chimney Tops 2 fire resulted in a major influx of burned wood to the study reaches, with large percentages of individual pieces (average of 47% by frequency, 48% by volume) and jams (average of 72% by frequency, 93% by volume) exhibiting burn marks. Burned wood pieces had a larger diameter than unburned pieces (p = .065). Results suggest that rare mass‐mortality events like the Chimney Tops 2 wildfire could play a major role in wood dynamics of mountain streams in humid forested regions.

Linking instream wood recruitment to adjacent forest development in landscapes driven by stand-replacing disturbances: a conceptual model to inform riparian and stream management

Instream wood plays an important role in stream morphology and creation of fish habitat in conifer forests throughout the temperate zone. In some regions, such as the US Pacific Northwest, many streams currently have reduced amounts of instream wood due to past management activities (timber harvest, wood removal, etc.). These reductions exist against a backdrop of naturally dynamic amounts and distributions of instream wood, which likely fluctuate over time based in part on the stage of development (disturbance and succession) in adjacent riparian forests. Despite many studies on both forest development and instream wood accumulation, the linkages between these processes have not been fully described, particularly as they relate to stream restoration needs. In this paper, we combine literature on forest development, disturbance, and processes that drive instream wood recruitment to more explicitly connect the temporal dynamics of stream wood inputs with the dynamics of adjacent riparian forests. We use moist forests of the Pacific Northwest as an exemplary system, from which to draw broadly applicable patterns for landscapes influenced by stand-replacing disturbance regimes. This conceptual model highlights a U-shaped pattern of instream wood recruitment, in which instream wood is highest after a stand-replacing disturbance and during the old-growth stage, and lowest through the middle stages of forest development (currently the most abundant stages in many landscapes as a result of past forest management practices). This mid-successional period of scarce wood is likely exacerbated in streams with a history of wood removal. The U-shaped pattern suggests that, without higher-than-average levels of disturbance, many streams in landscapes dominated by mid-successional second-growth forests (∼30–80 yr old) will be deficient of instream wood until forest stands are over 200 years old. As such, the balance between the predominant riparian conservation strategy of passive restoration (e.g., unharvested riparian reserves) and the alternative of active restoration (e.g., wood additions and (or) riparian stand treatments) should be carefully considered, depending on management objectives, site context, and potential tradeoffs over time.

Use of Strong Habitat–Abundance Relationships in Assessing Population Status of Cryptic Fishes: An Example Using the Harlequin Darter

AbstractUnderstanding trends in abundance is important to fisheries conservation, but techniques for estimating streamwide abundance of cryptic fishes with strong habitat–abundance relationships are not well established and need further development. We developed techniques for addressing this need using the Harlequin Darter Etheostoma histrio, a small, cryptic freshwater fish associated with submerged wood in streams. Our objectives were to (1) determine how Harlequin Darter abundance and the amount of submerged wood were related at sampled sites and (2) use this relationship to estimate Harlequin Darter abundance at unsampled sites and extrapolate Harlequin Darter abundance estimates and associated uncertainty streamwide. We conducted a mark–recapture study to estimate abundance of Harlequin Darters in 25‐m stream reaches at 24 sites in Big Escambia Creek (BEC) and 18 sites in Pine Barren Creek (PBC) (Escambia River tributaries in northwestern Florida). The number of wood pieces (submerged wood ≥1.5 m long and ≥0.25 m in circumference) in both creeks was counted and mapped using side‐scan sonar and a geographic information system. Harlequin Darter and wood data were used in a Bayesian multinomial mixture model to estimate site abundance of Harlequin Darters, to determine the relationship between wood and Harlequin Darter abundance, and to extrapolate Harlequin Darter abundance streamwide. We found a positive relationship between wood and Harlequin Darter abundance in both creeks, and there were more wood pieces in PBC than in BEC. Streamwide abundance of Harlequin Darters was greater in PBC than in BEC. The extrapolated streamwide abundance estimates were 9,369 Harlequin Darters (95% credible interval = 6,668–13,402) in PBC and 7,439 Harlequin Darters (95% credible interval = 4,493–11,226) in BEC. Our methods effectively estimated abundance of a small, cryptic fish that uses complex wood habitat. In addition, our findings may assist in the conservation of the Harlequin Darter.

Wood‐induced backwater effects in lowland streams

AbstractPlacement of wood in streams has become a common method to increase ecological value in river and stream restoration and is widely used in natural environments. Water managers, however, are often hesitant to introduce wood in channels that drain agricultural and urban areas because of backwater effect concerns. This study aims to better understand the dependence of wood‐induced backwater effects on cross‐sectional area reduction and on discharge variation. A newly developed, one‐dimensional stationary model demonstrates how a reduction in water level over the wood patch significantly increases directly after wood insertion. The water level drop is found to increase with discharge, up to a maximum level. If the discharge increases beyond this maximum, the water level drop reduces to a value that may represent the situation without wood. This reduction predominately depends on the obstruction ratio, calculated as the area covered by wood in the channel cross section divided by the total cross‐sectional area. The model was calibrated with data from a field study in four lowland streams in the Netherlands. The field study showed that morphologic adjustments in the stream and reorientation of the woody material reduced the water level reduction over the patches in time. The backwater effects can thus be reduced by optimizing the location where wood patches are placed and by manipulating the obstruction ratio. The model can function as a generic tool to achieve a stream design with wood that optimizes the hydrological and ecological potential of streams.

Large wood as a confounding factor in interpreting the width of spring-fed streams

Abstract. Spring-fed streams throughout volcanic regions of the western United States exhibit larger widths than runoff-fed streams with similar discharge. Due to the distinctive damped hydrograph of spring-fed streams (as compared to large peaks visible in the hydrographs of runoff-fed streams), large wood is less mobile in spring-fed than runoff-fed stream channels, so wood is more likely to remain in place than form logjams as in runoff-fed streams. The consequent long residence time of wood in spring-fed streams allows wood to potentially have long-term impacts on channel morphology. We used high-resolution satellite imagery in combination with discharge and climate data from published reports and publicly available databases to investigate the relationship between discharge, wood length, and channel width in 38 spring-fed and 20 runoff-fed streams, additionally responding to a call for increased use of remote sensing to study wood dynamics and daylighting previously unpublished data. We identified an order of magnitude more logjams than single logs per unit length present in runoff-fed streams as compared to spring-fed streams. Histograms of log orientation in spring-fed streams additionally confirmed that single logs are immobile in the channel so that the impact of single logs on channel morphology could be pronounced in spring-fed streams. Based on these observed differences, we hypothesized that there should be a difference in channel morphology. A model for stream width in spring-fed streams based solely on length of wood is a better model than one derived from discharge or including both discharge and wood length. This study provides insights into controls on stream width in spring-fed streams.

Country‐wide analysis of large wood as a driver of fish abundance in Swedish streams: Which species benefit and where?

Abstract Rivers are heavily affected by human impacts that threaten many fish species. Among restoration measures, the addition of large wood (LW) in streams has been shown to increase fish abundance, yet which species benefit from LW, to what extent relative to other drivers, and which factors influence LW quantity is not clear, and these uncertainties limit our ability to use LW as an effective restoration measure. Here, a time series (from 1993 to 2016) of electrofishing data, including 3641 streams across Sweden, was used to investigate the beneficial effects of LW on the abundance of juvenile brown trout, Salmo trutta, juvenile Atlantic salmon, Salmo salar, and juvenile and adult sculpins, Cottus gobio and Cottus poecilopus, while accounting for other abiotic and biotic factors, and the drivers of LW abundance at a country‐wide scale. Large wood benefitted brown trout, and the effects were greater with decreasing shaded stream surface. LW effects were comparable in magnitude to the positive effects of average annual air temperature and the negative effects of stream depth and predator abundance – factors where the influence was second only to the negative effects of stream width. LW did not benefit salmon abundance, which was correlated positively with stream width and negatively with altitude, nor did it benefit sculpin abundances, which mainly decreased with annual average air temperature and altitude. The quantity of LW strongly diminished with stream width, and, to a lesser extent, with stream depth, altitude, annual average air temperature, and forest age, whereas it increased with stream velocity, slope, and forest cover. The results suggest that LW can be used as an effective restoration tool for brown trout in shallow and narrow streams, especially in areas with little shade. Here, the addition of LW may help to alleviate the impacts of forest clearance and climate change.

If a tree falls in an urban stream, does it stick around? Mobility, characteristics, and geomorphic influence of large wood in urban streams in northeastern Ohio, USA

Large wood influences geomorphological, ecological, and biogeochemical functions of streams, but in urban areas it is also considered an unaesthetic hazard. Quantifying the abundance and mobility of in-stream wood along an urban intensity gradient, and understanding the relationship between wood dynamics and stream reach, network, and watershed characteristics allows for a stronger understanding of the potential benefits and hazards of wood in urban streams. Repeat wood surveys were conducted at 11 stream reaches in the Cleveland, Ohio area, where wood removal is not practiced and forested riparian zones exist. Study reaches span a gradient of impervious surface cover and extent of the stream network with a forest buffer. Channel morphology and sediment size were also measured. Stream hydrology does not change when imperviousness is 12–40% in this region, so quantification of impervious surfaces stands in for a broader suite of urban impacts.Wood abundance decreases – and mobility increases – as urban intensity in the watershed and along the stream network increases. Jams become smaller and less stable, but the size and orientation of individual wood pieces do not change along an urban gradient. Over the 6-month study period, wood mobility exceeded 100% in some of the most urbanized streams and transport distances are inferred to be on the order of 100s of meters. There was a positive correlation between jam spacing and pool spacing, and finer sediment sizes occurred in some wood-associated deposits, but overall geomorphic effects are limited. Where reaches are confined, wood abundance is suppressed, but impervious surfaces and the extent of forest along the stream network are stronger predictors of wood dynamics than reach scale characteristics. These results emphasize the importance of situating understanding of reach-scale wood dynamics in the context of larger scale phenomena.

Fine stream wood decreases growth of juvenile brown trout (Salmo trutta L.)

In this study, the growth rate, gut fullness, diet composition and spatial distribution of brown trout was compared between artificial channels with and without fine wood (FW). Access to FW resulted in significantly lower brown trout growth rates over the study period from late summer to early winter as water temperatures declined from 17 °C to 1 °C. Access to FW resulted in minor differences in occurrence of the most common taxa found in brown trout diets, except for chironomid larvae which were found in c. 60% of the brown trout guts from control treatments but in only 30% of the guts from FW treatments in early winter. Diet consisted primarily of case-bearing and free-living Trichoptera larvae, Asellus, chironomid and Ephemeroptera larvae. Brown trout gut fullness was not significantly affected by access to FW bundles. Brown trout aggregated among FW but were more evenly distributed in channels lacking it. Our results suggest that juvenile brown trout use FW as a shelter at a wide range of water temperatures, and that this behaviour may result in reduced growth rates during their first fall and the onset of their first winter. We also show that prey availability and the composition of brown trout diet changes from late summer to early winter and that FW has a small but significant effect on brown trout diet composition.

Effects of A Severe Drought On Summer Abundance, Growth, and Movement of Cutthroat Trout In A Western Oregon Headwater Stream

Winter snowpack depth, snowmelt timing, and snowmelt duration are projected to change in the future, leading to increased frequency and severity of drought in the Pacific Northwest. In summer 2015, stream flows throughout the Pacific Northwest were at record low levels because of low winter snowpack conditions consistent with these climate projections. We explored effects of the 2015 low-snowpack-associated drought on Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) abundance, growth, and movement patterns in two 100m reaches ( 350 y old forests) of an unnamed perennial western Oregon headwater stream before (2 y) and during a severe drought. We found that the abundance of Cutthroat Trout declined substantially during the drought year, regardless of habitat availability, riparian forest age, or stream wood structure. Fish growth during summer was consistently negative during all 3 y of the study in both reaches. During the drought year, estimated abundance and total biomass of Cutthroat Trout declined in both reaches compared to the 2y prior. In all 3 y, the majority (76%) of fish in the reach with a young riparian forest stand moved >2 m from their release point. In contrast, across the 3 study years, only 26% of fish on average moved >2 m from their release point in the old-growth reach, which had more large wood and pool area. Across both reaches, in the non-drought years, most fish moved into pools (32.4%), but some moved to riffles (23.3%). During the drought year, of the fish that were recaptured, only upstream movement to pools were observed. There were no observed movements of recaptured fish to riffles. Overall, study results suggest that increasing severity of summer drought in the Pacific Northwest is likely to reduce the abundance of fish in small headwater streams, and the remaining fish preferentially use pool habitats such as those found in structurally complex streams.

Helminthosporium submersum sp. nov. (Massarinaceae) from submerged wood in north-western Yunnan Province, China

The diversity of lignicolous freshwater fungi of China is currently being studied. In this paper, we report on nine collections of asexual morphs of Helminthosporium from submerged wood in rivers and streams in west to north-west Yunnan Province, China. The taxa are characterized based on morphology and phylogenetic analyses of ITS, LSU, SSU, RPB2 and TEF1α sequence data. A new species, Helminthosporium submersum, is described and illustrated with notes on taxonomy and phylogeny. Molecular data for Helminthosporium aquaticum and H. velutinum are provided.