Large Wood Research Articles

Proactive river corridor definition: Recommendations for a process‐based width optimization approach illustrated in the context of the coastal Pacific Northwest

AbstractWe propose a holistic approach to define a river corridor as the minimum space needed to sustain key river functions based on an understanding of the desired functions of that corridor and the processes governing channel and floodplain formation. Giving such space is a fundamental nature‐based solution to river management, as it allows the river to use its own energy to maintain flood conveyance and habitat function. The review of existing river corridor concepts shows that these often focus on one or two potential functions of a river corridor and may not be well suited as tools to optimize eco‐geomorphic river function. We argue that evaluating the effects of river corridor width on multiple processes can provide an objective means to optimize delineation in areas where development encroaches onto floodplains and channel migration zones. Key processes are linked to channel migration and include floodplain rejuvenation, emergence of a dynamic patch mosaic of riparian habitat that sustains a functioning large wood cycle, and effects of constriction and confinement on channel dynamics and morphology. Quantification of these processes for an example river shows the most rapid gains for habitat and flood protection values up to the threshold for planform‐controlled conditions and an asymptotically reducing rate of gain in function above that threshold. For the example river, the threshold width approaching that asymptote is substantially more than its constrained condition but much less than the width of the floodplain and channel migration zone, offering a compromise for managing rivers with developed floodplains.This article is categorized under: Engineering Water > Sustainable Engineering of Water Water and Life > Nature of Freshwater Ecosystems Water and Life > Conservation, Management, and Awareness

Current progress in quantifying and monitoring instream large wood supply and transfer in rivers

AbstractLarge wood drives both the form and function of gravel‐bed rivers draining forested basins. Previously overlooked benefits of wood in rivers are now widely recognized. Together with flow and sediment regimes, the wood regime controls rivers' physical and ecological integrity. Yet large quantities of wood transported during floods can pose additional hazards, potentially damaging infrastructures like bridges or dams and exacerbating flooding. However, unlike the water and sediment regimes intensively studied over the past decades, the instream wood regime or budgeting has been only recently defined and thus is still rarely quantified. The instream wood budget describes the cascading processes from supply or recruitment, entrainment, and transport to deposition, storage and decay (i.e., fragmentation or decomposition). These processes show high spatial and temporal variability but can be characterized by magnitude, frequency, timing, duration and mode. Instream wood budgeting is challenging, primarily because of the lack of observations, monitoring stations, and standardized protocols to acquire data. This contribution reviews the most recent advances to quantify the different instream wood budget components, notably the wood supply, and transfer. Case studies showing applications of biogeochemistry, videography, artificial intelligence, numerical modelling or tracking illustrate the current progress. Because critical challenges remain, we identify and describe some of them and discuss how the wood in riverine sciences may develop in the future.

Survey on the natural resistance to decay of five hundred tropical wood species

The natural durability of wood species against rot has again become a matter of interest for the uses of wood as a natural material, while the use of synthetic fungicides is being debated. In the mid-20th century, many experimental studies were performed in Europe and North America, using different standardised protocols. More than five hundred tropical wood species were tested in France between 1955 and 1990, with a total of 9,842 wood samples tested. It would seem useful to allow free access to all the data from these tests in the interests of a more comprehensive study of the natural durability of large wood panels. The great majority (68%) of all these tests used two slightly different protocols with only a change in woodblock test dimensions. Roughly half of the species were tested under one of the two protocols, and the other half under the second. In addition, certain species were tested with both protocols. The dimensions of the test blocks, the fungal strain used, and the wood type (sapwood or heartwood) all give significantly different results, but the mean mass loss due to the 4 main fungal strains is a good predictor of the wood resistance to rot. Overall, mass loss for sapwood with each protocol is 45% higher than for heartwood of the same species. There is a significant positive correlation between the rot resistance of the sapwood and the heartwood, but the decrease in heartwood compared to sapwood is greater in durable wood species than in non-durable ones. Heartwood rot resistance was observed to be highly variable between trees of the same species, except in those classified as “very durable” and “non-durable”. This opens up possibilities for a classification of natural rot resistance for numerous useful types of timber that are often regarded as only moderately resistant because they include a small proportion of species with poor resistance. Each protocol group included over one hundred species for which density and chemical composition data were available. Density, lignin content, and extractive content have a similar and very significant influence on the rot resistance of the wood (R² around 0.25).

Ecological Functions and Management of Large Wood in Fluvial Systems

Ecological Functions and Management of Large Wood in Fluvial Systems

Snow Avalanches as a Driver of Large Wood Dynamics in Mountain Streams

AbstractSnow avalanches are thought to influence large wood dynamics within mountain streams, but studies that explicitly quantify their impact are minimal. In three headwater catchments of the Frying Pan River, Colorado, USA, we found that wood loads in stream reaches intersected by avalanche pathways ranged from 220 to 8,500 m3/ha and were significantly greater than in non‐avalanched reaches. Inter‐catchment differences in the number of avalanche occurrences were not reflected in control reach wood loads, suggesting that elevated loads may be restricted to the general vicinity of the avalanche pathway. However, the sizable wood volumes in avalanche reaches generated notable geomorphic impacts, indicating that avalanches can create hotspots of in‐stream geomorphic complexity and influence the overall habitat mosaic of the stream ecosystem. Loads in avalanche reaches were moreover significantly greater than literature values for similar streams and recruitment processes, emphasizing the importance of snow avalanches as a wood recruitment mechanism.

Two‐Dimensional Numerical Modeling of Large Wood Transport in Bended Channels Considering Secondary Current Effects

AbstractThe modeling of large wood (LW) transport in rivers has received increasing interest from researchers in the last decade due to the widely recognized role of LW concerning flooding risk. For this purpose, few 2D depth‐averaged hydraulic models have been coupled with LW transport models. However, such models usually neglect the effects of secondary currents on LW trajectories in river bends. In this work, the model Iber‐Wood was enhanced to simulate the effects of secondary currents in river bends on LW trajectories. The proposed methodology presents a new formulation for considering secondary current effects on the flow field derived from the Manning formula and considers a new approach for reproducing the surface flow field that develops at channel bends. The enhanced model was tested to reproduce a series of laboratory experiments on wood transport in a sharp channel bend. The methodology introduces two new parameters in the model related to the secondary current effects, that is, the secondary current intensity and the adaptation length. These parameters were calibrated using available data from laboratory experiments. The good agreement between observed and simulated dowel trajectories in a sharp channel bend validated the proposed approach to simulate LW transport in the case of secondary currents.

Using Improved YOLOv5 Model to Detect Volume for Logs in Log Farms

<p>In this paper, we propose a new computer vision model called SE-YOLOv5-SPD for counting the number of log ends in large wood piles in log farms. This task traditionally requires a lot of manpower and previous computer vision methods struggle to detect logs in low pixels and small objects in images. Our model is based on the YOLOv5 model and incorporates the Squeeze-and-Excitation Networks (SENet) attention module and SPD-Conv (Space-to-Depth Convolution) module to improve accuracy. We also compare the performance of the SE attention module and SPD-Conv module to the CBAM attention module and Focus module using the SE-YOLOv5-SPD model. Results show that the SE-YOLOv5-SPD model can achieve excellent results of 0.652 in mAP50:95, 0.912 in mAP50, 0.968 in Precision, and 0.864 in Recall in a low-resolution environment with interference, which is significantly better than other models. Our findings indicate that the SE-YOLOv5-SPD model is a promising solution for counting the number of log ends in wood piles.</p> <p> </p>

Widespread wood placement and regrading drive lateral connectivity and reworking of the channel and floodplain in a valley bottom reset to Stage 0

Valley bottom process reset, or the excavation of high surfaces and fill of incised channels combined with large wood addition, is a new method for creating multi-channel river-wetland corridors (also referred to as Stage 0 valley bottoms). Valley bottom process reset seeks to increase lateral flow and sediment connectivity, retain water and sediment, and kickstart geomorphic processes that may sustain aquatic and riparian habitat. This study uses this anthropogenic intervention to examine relationships among wood-induced hydraulic roughness, valley bottom topography, and geomorphic processes such as overbank flow and sediment transport, avulsion, sediment retention, and pool scour. Here, I present a 6-year case study of a two-phase valley bottom process reset along Deer Creek, Oregon. Kickstarting the floodplain reshaping processes required a substantial increase in roughness and hydrologic connectivity. The first phase of construction enhanced hydrologic but not sediment connectivity, failing to kickstart avulsion and floodplain reworking even during a likely 2- to 5-year recurrence interval flood. A second, more intensive phase of construction substantially reduced the threshold discharge necessary for overbank flow and floodplain reworking, as evidenced by the occurrence of these processes after only a <2-year recurrence interval flood. During this flood, a spatially distributed wood lattice rearranged into discrete jams that scoured pools, retained sediment, and drove geomorphically effective overbank flows. While valley bottom regrading likely contributed to these geomorphic effects, the spatial correlation between newly incised floodplain channels and areas of wood aggregation indicates wood's important role in driving floodplain reworking. I derive from these findings a conceptual model that details how wood drove floodplain reworking via two mechanisms: In-channel wood jams backwatered and constricted flow into the floodplain, and small wood jams formed in the floodplain forest further constricted flow through nascent channels to facilitate channel incision.

Protecting our streams by defining measurable targets for riparian management in a forestry context

Abstract Generally, governments and industry have implemented some degree of protection to reduce the impacts of forestry on aquatic ecosystems. Here, we consider the widespread application of streamside management in terms of riparian buffer retention to protect freshwaters from forestry practices across three jurisdictions with large and intensive forestry sectors (British Columbia, Finland and Sweden). This perspective was developed by working with researchers, practitioners and policymakers on mitigation measures to decrease the impacts of forestry on streams. We demonstrate that it is exceedingly rare for policies and guidelines to specify concrete objectives and measurable targets that can be assessed against riparian buffer management outcomes. Most often, policy objectives for riparian management prescribe ‘to prevent or mitigate impacts’, and this vagueness is insufficient to protect our waters. We argue that we should be clearer about the targets (outcomes) for riparian management and go beyond the simple idea that buffer presence, without further specification of its conditions, is always a successful protection strategy. One cannot measure the effectiveness of rules and guidelines without quantitative targets. Policy implications: In this paper, we suggest that locally developed and adjusted targets for riparian buffers must include quantifiable, measurable goals that specify what is supposed to be achieved and protected with respect to ecological functions, biological communities or other values. It should be relatively simple to move from current vague objectives such as ‘protect and prevent’ to a defined range of values for ecological parameters that buffers are supposed to provide. For example, these can include region‐specific shading levels and microclimate targets, large wood volumes, or riparian forest species composition. We stress that these targets must be developed through an open dialogue between agencies, practitioners, land owners and scientists. We acknowledge that there are trade‐offs between being too prescriptive and too vague. However, when excessively broad goals are the norm, we lose the capacity to effectively implement, monitor or evaluate the outcomes of protection measures.

Large in-stream wood yield during an extreme flood (Storm Alex, October 2020, Roya Valley, France): Estimating the supply, transport, and deposition using GIS

During major floods, rivers erode their banks and thus recruit large wood pieces from the riparian zones. There is still a lack of knowledge about the transport of large wood, the volumes involved and the flux distribution, i.e. the large wood connectivity at catchment scale. During storm Alex (October 2020), the French Roya catchment (394 km2) experienced a paroxysmal morphogenic flood involving massive bank erosion. The riparian vegetation was largely recruited, with large wood contributing to logjams and bridge destruction. This paper presents a methodology for volumetric assessment of the large wood fluxes involved. Simple approaches are used to (i) quantify the inputs from stand density data from the national forest inventory and from source areas based on diachronic analysis of active channels highlighting the erosion of 87 ha of wooded areas; and (ii) quantify the volumes deposited via an exhaustive manual digitisation of 16,846 pieces of large wood deposited on 59 km of channels on the Roya and its tributaries. This catchment-scale, large wood connectivity analysis shows that the flood recruited and transported downstream a volume of around 14,000 m3 of large wood (uncertainty range: 7000–29,500 m3). Drone observations of the Roya River mouth in Italy and satellite images showing a raft of driftwood, several km long, drifting off the Roya River mouth in the aftermath of the flood corroborate our findings.

Method to evaluate large-wood behavior in terms of the convection equation associated with sediment erosion and deposition

Abstract. Recent flood hazards occurring in mountainous areas are often characterized by numerous amounts of sediment and large wood supplied from upstream, which often exacerbate flood disasters in downstream areas. This paper proposes a method for describing large-wood behavior in terms of the convection and storage equations, together with the governing equations for describing flood flows and channel changes associated with active sediment erosion and deposition. The proposed method is tested for its validity by simulating the phenomena occurring in an open channel with an erodible bed and flood flow with numerous amounts of sediment and large wood in the Akatani River flood disaster. As a result of calculations reproducing the open channel experiment, the applicability of the method is indicated as the percentage of wood pieces captured in the sediment deposition areas in the channel is within the range of the experimental results. The results of 2-D flood flow calculations with sediment and large wood in the Akatani River flood disaster suggested that large-wood deposition is reproduced where bed deformation is well reproduced. Overall, since the proposed method makes it possible to simulate the behavior of various amounts of large wood, it can be applied to the management of hazards in mountainous rivers such as the Akatani River.

Pyre wood fuel and food remains in a necropolis of Barcino (Barcelona, NE Iberian Peninsula): The case of Sant Antoni Market site (1st century CE)

Funerary cremations in Roman times were important rites of passage that involved the use of fire to accompany the dead into the afterlife. In the present study, we investigated the wood fuel that was used to build cremation pyres and the foodstuffs involved in offerings and funerary feasts in a necropolis of Barcino (present-day Barcelona), dated to the 1st century CE and located at the Sant Antoni Market site. Our approach began with the analysis of wood charcoal and fruit/seed remains, which were preserved over time through carbonisation. These archaeobotanical remains offer valuable insights into the selection of woody species and the condition of wood logs used for cremations. Additionally, they shed light on the food composition of offerings and feasts in this area of the Mediterranean coast, where data on such practices are scarce.The anthracological analysis of different combustion structures revealed that the principal taxon used for the stacks was evergreen oak, with deciduous oak playing a significant role during the initial use of the necropolis. Dendro-anthracological analysis indicated that medium to large diameters wood logs of deciduous oak obtained from mature individuals were commonly employed. Moreover, charcoal analysis suggested the use of pruning remains from fruit trees such as olive, grapevine, walnut, plums, and members of the apple family, providing evidence of arboriculture practices in the city. Additionally, various minor woody species (Aleppo and mountain pines, juniper, cypress, mastic, and rockroses) may have had several functions, including symbolic sensory aspects relating to smell and good flammability, the constitution of small objects or furniture placed on the stack (boxwood), and fire kindling or decoration (mastic, rockroses, honeysuckle, and laurustinus).Carpological analysis indicated that the most abundant offerings and/or feast remains consisted primarily of cultivated fruits such as figs, walnuts, and grapes, while pulses and cereals were comparatively scarce or absent. Finally, a noteworthy quantity of Arbutus berry remains was recorded, marking the first occurrence of such findings in similar Roman contexts to date.

Introducing indices to assess the effects of in-stream large wood on water and sediment connectivity in small streams

Large wood (LW) can have significant effects on channel hydraulics by creating hydraulic resistance that decreases reach-average flow velocity and transport capacity, further influencing water and sediment connectivity. Although some case studies have already explicitly dealt with LW considering its effects on connectivity, a conceptualization as well as standardized methods or protocols to assess their effects on water and sediment connectivity in river systems are still missing. The relationship between in-stream LW depositions and their hydraulic function and the related potential effects on water and sediment connectivity can be quantified through drag force. However, such drag analyses are very data-demanding, time consuming and therefore often not practicable. Especially in river management, often simple and fast screening approaches are needed to get a system-wide overview on location, type and the potential effects of LW depositions. In this paper, we introduce a simple LW in-stream dis-connectivity index as well as a LW sediment retention potential index for streams narrower than log length calculated based on visually estimated field-derived parameters. Both indices have been applied in two mixed-load streams in an Austrian national park. The newly developed indices have shown to provide a simple means to quantify and compare the effects of LW on water and sediment connectivity and sediment retention potential between different river systems. Moreover, it has been demonstrated that information derived from the indices as well as on type and location is valuable for place-based river management, e.g. related to river sediment, habitat and flood control. Although we were able to show a clear relationship between the conceptual considerations of the proposed indices and the data derived from field surveys, the presented approach further needs to be tested and evaluated by interested scientists and practitioners in different environmental settings supported and corroborated by more quantitative data.

Sunken trees in the deep sea link terrestrial and marine biodiversity.

Wood in the deep sea serves as a substantial food source in an otherwise barren environment, forming specialized, endemic, and diverse community assemblages. This biodiversity reliance on a terrestrial source creates a linkage by which anthropogenic impacts on land can alter the deep oceans. Knowledge of the alpha- or beta-diversity of entire wood-fall communities, and wooden drivers of each would elucidate the terrestrial and deep-sea linkage. We report on a multifactorial experiment in the deep ocean in which alpha- and beta-diversity of 43 wood falls and 11 tree species are quantified over time, wood density, and wood size. We tested multiple hypotheses seeking to link how biodiversity on land may impact the biodiversity in the deep oceans. A tremendous biodiversity occurred among these wood falls in the deep Gulf of Mexico; 114 invertebrate species from 10 phyla. Time, wood hardness, and wood size all impacted various components of community structure. In many cases, these effects were additive. Species occurring on softwoods versus hardwoods and small versus large wood falls were compositionally different. Although various processes can control community structure, this experiment suggests a strong influence of environmental filtering and host specificity of wood-fall invertebrates suggesting an intimate coupling to tree biodiversity and biomass on land.

Fuzzy-logic indicators for riverbed de-clogging suggest ecological benefits of large wood

Rivers provide dynamic habitats with ecological niches, particularly in their mobile sand, gravel, and cobble riverbed patches that create an active hyporheic zone. Natural or artificial deposition of fine sediment may clog the porous matrix of the hyporheic zone, impairing exchange processes between the subsurface and surface water. Clogging reduces the permeability of the sediment matrix, thus degrading the ecological functionality of the hyporheic zone. Once clogged, the ecological functions may be recovered through active stream restoration, which requires considerate site assessment. To this end, clogging is typically assessed by expert opinion of substrate characteristics including grain size characteristics, porosity, hydraulic conductivity, and interstitial oxygen content. To overcome limitations of expert assessment, such as subjectivity expressed in noisy decision-making, this study introduces a novel fuzzy-logic method based on physically sound rules. The method provides quantitative indicators for clogging and declogging to evaluate the effectiveness of stream restoration. We applied the fuzzy-logic method to test whether the placement of large wood, a common restoration practice, can locally prevent or reduce clogging. Two measurement series from before and after a morphologically effective flood suggested that large wood placements perpendicular to the flow generate elevated amounts of declogging. The tested logs caused a greater amount of declogging within their region of influence than observed at a reference point. The effect was stronger for a log emergent at baseflow. The declogging assessment showed that the novel fuzzy-logic indicators can reasonably overcome subjective judgment by accounting for multi-variate quantitative changes rather than individual parameter trends.

Pengelolaan Sumber Daya Alam Hutan Studi Kasus : Hutan Kota Tinjomoyo Kota Semarang

Forest is a stable ecosystem, which has a balance between producers, consumers and decomposers. Where, the forest itself has the ability to provide unlimited natural resources. However, optimal and sustainable forest management and utilization is needed in order to have a forest that has adequate environmental carrying capacity, with the aim of guaranteeing the role and existence of the forest. The Tinjomoyo City Forest which is located in Semarang City has an area of ​​57 ha, with the area of ​​green space in Semarang City being 10,966 ha, out of the 37,367 ha area of ​​Semarang City. Thus, it has reached 30% of the need for green space in the City, if based on Law no. 41 of 1999. Therefore, because the position of the City of Semarang, which has a large green space, has complied with the Law, it is very important to maintain its existence. In this research, it was carried out by direct observation method, which included observation, inventory, and volume calculation. After carrying out an inventory and data processing, it was found that the Tinjomoyo City Forest had a volume of wood reserves of 4,548,600 m3. So with the knowledge of these large enough wood reserves, it is necessary to maintain, manage and utilize forest resources optimally and sustainably. With the aim, to maintain the availability of wood reserves in the Tinjomoyo City Forest.

Identifying bridges prone to instream wood accumulation: insights from bridges across the UK

Accumulation of instream large wood (i.e., fallen trees, trunks, branches, and roots) at bridges during floods may exacerbate flooding, scour and cause structural failure. Yet, explaining and predicting the likelihood of a bridge trapping wood remains challenging. Quantitative data regarding wood accumulation at bridges are scarce, and most equations proposed to estimate the accumulation probability were derived from laboratory experiments, and include variables such as flow velocity, Froude number, and approaching wood volume or size which are difficult to obtain. Other evaluations based on technical reports and information regarding wood removal have been proposed but are mostly qualitative. Until now, a data-driven approach combining multiple quantitative accessible variables at the river reach and catchment scales remains lacking. As a result, the controlling parameters explaining whether a bridge is prone to trap wood are still unclear. This work aims to fill this gap by analysing a database of 49 bridges across the United Kingdom (UK) classified as prone and not prone to wood accumulation. The database contained information regarding the geometry of the bridge (i.e., number of piers and pier shape) and we added parameters describing the upstream river channel morphology, the riparian landcover, and high-flow characteristics. We applied multivariate statistics and a machine learning approach to identify the variables that explained and predicted the predisposition of bridges to wood accumulation. Results showed that the number of bridge piers, the unit stream power, the pier shape, and the riparian forested area explained 87% of the total variability for the training dataset (0.87 training accuracy), and the selected model had a testing accuracy of 0.60 (60%). Although limited by the sample size, this study sheds light on the identification of bridges prone to wood accumulation and can inform bridge design and management to mitigate wood-related hazards.

Experimental study on potassium catalyzed gasification of large particle size biomass with CO2

Candlenut wood with large particle size is selected to investigate the biomass gasification catalyzed by potassium. The sample pore structure, the spatial distribution of potassium, and the effects of potassium salt species on the biomass gasification with CO2 are examined. The results show that the large particle candlenut wood exhibits obvious spatial anisotropy and that the pore structure is mainly distributed along the axial direction. Large particle candlenut wood has a more uniform distribution of potassium salts along the axial direction. Part of the potassium salt releases outward during the gasification, which reduces the potassium salt content in the sample center. The average potassium contents of sample loaded with KCl and biochar of sample loaded with KCl are 9.273% and 7.745%, respectively. The synthesis of polycyclic aromatic hydrocarbons in tar could be inhibited by potassium, which could also catalyze the gasification and methane removal reactions of biochar and facilitate the formation of CO and H2. Compared to raw sample (28.99%), the syngas yields from the gasification of sample loaded with KCl, sample loaded with K2CO3, and sample loaded with K2SO4 are 40.22%, 52.16%, and 41.72%, separately. The catalysis of potassium is closely related to its occupation of the active sites on biochar. The chemical bonds formed by potassium and biochar are repeatedly broken and formed during the gasification, which promotes the decomposition of organic matter. Compared with KCl and K2SO4, K2CO3 has a better catalytic effect.

DAYTIME RESTING ACTIVITY OF AEDES AEGYPTI AND CULEX QUINQUEFASCIATUS POPULATIONS IN NORTHERN MEXICO.

Aedes aegypti and Culex quinquefasciatus are disease vectors distributed throughout much of the world and are responsible for a high burden of vector-borne disease, which has increased during the last 2 decades. Most pathogens vectored by these mosquitoes do not have therapeutic remedies; thus, combating these diseases is dependent upon vector control. Improvements in vector control strategies are urgently needed, but these hinge on understanding the biology and ecology of Ae. aegypti and Cx. quinquefasciatus. Both species have been extensively investigated, but further knowledge on diel resting activity of these vectors can improve vector surveillance and control tools for targeting resting vector populations. From April to December 2021, we determined outdoor daytime resting habits of Ae. aegypti and Cx. quinquefasciatus male, female, and blood-fed female populations in Reynosa, Mexico, using large red odor-baited wooden box traps. The daytime resting activity for Ae. aegypti males, females, and blood-fed females was restricted to a period between 0900 h and 1300 h, with a peak at 0900 h, while the resting activity of Cx. quinquefasciatus male, female, and blood-fed females was between 0700 h and 1100 h, with a peak at 0700 h. A generalized additive model was developed to relate relative humidity and temperature to resting Cx. quinquefasciatus and Ae. aegypti male, female, and blood-fed populations caught in traps. This study advances the understanding of outdoor resting behavior for 2 important vector mosquito species and discusses future studies to fill additional knowledge gaps.

Large wood supports Elwha revegetation by reducing ungulate browsing

IntroductionThe increasing number of dams approaching obsolescence drives a need for knowledge about riparian restoration associated with dam removal. Restoring woody vegetation on exposed reservoir beds following dam removal is essential to stabilizing sediment, reconnecting riverine and terrestrial systems, and providing future sources of shade, nutrients, and wood. Revegetation after dam removal on many rivers can be challenging due to rapidly drying sediment, low sediment nutrient content, and heavy ungulate browse pressure. Revegetation in Elwha River restoration, the largest dam removal to date, used large woody debris (LWD) to mitigate moisture and nutrient limitation but ungulate browsing has constrained woody plant growth in many coarse sediment deposits. We evaluated potential for LWD to reduce ungulate browsing following Elwha dam removal.MethodsWe studied LWD mitigation of browsing in the largest former reservoir and a comparable valley upriver with a natural floodplain. We measured browse intensity in randomly located plots stratified by four levels of LWD extent, from no LWD to complete LWD enclosure.ResultsLWD reduced browse intensity four-fold in the former reservoir, but only in plots fully surrounded by LWD. Partial LWD enclosure provided little browse reduction. We obtained similar results in the upriver valley, where browse intensity was somewhat lower except within wood clusters. Wood-mediated browse reduction was slightly greater in the former reservoir than in the upriver valley. Protection from browse was greatest for plant species preferred by ungulates.DiscussionThese results suggest forest restoration after dam removal can be expedited by surrounding young trees with large logs. Planting within LWD clusters or placing LWD clusters in restoration sites can facilitate establishment of forest islands in strategic locations. These forest islands can support dispersal of seeds and marine derived nutrients, reconnect established forest to the river, and potentially advance restoration by decades.