Addition Of Large Woody Debris Research Articles

Reach-scale characterization of large woody debris in a low-gradient, Midwestern U.S.A. river system

Addition of large woody debris (LWD) to rivers has increasingly become a popular stream restoration strategy, particularly in river systems of the Midwestern United States. However, our knowledge of LWD dynamics is mostly limited to high gradient montane river systems, or coastal river systems. The LWD-related management of low-gradient, Midwestern river systems is thus largely based on higher gradient analogs of LWD dynamics. This research characterizes fluvial wood loads and investigates the relationships between fluvial wood, channel morphology, and sediment deposition in a relatively low-gradient, semiconfined, alluvial river. The LWD and channel morphology were surveyed at nine reaches along the Big River in southeastern Missouri to investigate those relationships in comparison to other regions. Wood loads in the Big River are low (3–114m3/100m) relative to those of higher gradient river systems of the Pacific Northwest, but high relative to lower-gradient river systems of the Eastern United States. Wood characteristics such as size and orientation suggest that the dominant LWD recruitment mechanism in the Big River is bank erosion. Also, ratios of wood geometry to channel geometry show that the Big River maintains a relatively high wood transport capacity for most of its length. Although LWD creates sites for sediment storage, the overall impact on reach-scale sediment storage in the Big River is low (<4.2% of total in-channel storage). However, wood loads, and thus opportunities for sediment storage, have the potential to grow in the future as Midwestern riparian forests mature. This study represents the first of its kind within this particular type of river system and within this region and thus serves as a basis for understanding fluvial wood dynamics in low-gradient river systems of the Midwestern United States.

Quantifying the role of woody debris in providing bioenergetically favorable habitat for juvenile salmon

The habitat complexity of a riverine ecosystem influences the bioenergetics of drift feeding fish. We coupled hydrodynamic and bioenergetic models to assess the influence of habitat complexity generated by large woody debris (LWD) on the growth potential of juvenile Chinook salmon (Oncorhynchus tshawytscha) in a river that lacked large wood. Simulations indicated how LWD diversified the flow field, creating pronounced velocity gradients, which enhanced fish feeding and resting activities at the sub-meter scale. Fluid drag created by individual wood structures increased under higher wood loading amounts, leading to a 5–19% reduction in the reach-averaged velocity. The reach-scale growth potential was asymptotically related to wood loading, suggesting that the river became saturated with LWD and additional loading would produce minimal benefit for the configurations we simulated. In the scenario we analyzed for illustration, LWD additions could quadruple the potential growth area available before that limit was reached for the configurations selected for demonstration. Wood depletion in the world's rivers has been documented extensively, leading to widespread attempts by river managers to reverse this trend by adding wood to simplified aquatic habitats. However, systematic prediction of the effects of wood on fish growth has not been previously accomplished. We offer a quantitative approach for assessing the influence of wood on habitat potential for fish growth at the microhabitat and reach-scales.

Restoration Monitoring on the McKenzie River, Oregon

In the spring of 2012, we, the Stream Stewardship Team from the University of Oregon’s Environmental Leadership Program (ELP), conducted post-monitoring surveys at a side channel of the Middle McKenzie River (side channel 4) to compare with baseline monitoring data collected by the 2011 ELP Restoration Stewardship Team. The goal of this restoration project was to enhance juvenile spring Chinook salmon (Oncorhynchus tshawytscha) rearing habitat within the channel. In 2011 the U.S. Forest Service placed large woody debris (LWD) in five sections of the channel after baseline monitoring to increase the complexity of the streambed within the channel and to create a distribution of sediment optimal for salmon spawning habitat. We conducted pebble counts, cross-channel surveys, and a longitudinal profile of the stream to observe changes since the addition of LWD. Median pebble size decreased downstream of the LWD placements at gravel count 1 and increased upstream at gravel count 2. The percent of embedded sediment decreased at both gravel count sites. We also detected noticeable changes in the stream morphology at four of the five cross-sectional surveys as well as along the longitudinal profile. Sediment size distribution and the formation of pools at the downstream end of the channel showed an initial change in stream morphology since 2011, but further monitoring is warranted in order to fully assess the effects of LWD on streambed complexity and salmon spawning habitat.

Simple measures of channel habitat complexity predict transient hydraulic storage in streams

Stream thalweg depth profiles (along path of greatest channel depth) and woody debris tallies have recently become components of routine field procedures for quantifying physical habitat in national stream monitoring efforts. Mean residual depth, standard deviation of thalweg depth, and large woody debris (LWD) volumes are potential metrics of habitat complexity calculated from these survey data. We used 42 intensive dye-transit studies to demonstrate the relevance of these easily measured channel habitat complexity metrics to transient hydraulic (“dead zone”) storage, a channel process important for biotic habitat as well as retention and “spiraling” of dissolved and particulate nutrients. We examined transient storage and channel morphology in small gravel and cobble-bedded upland streams (wetted width 2–5 m; slopes 2.6–8.3%) representing a wide range of flow stages, LWD loading, and channel complexity, including measurements before and after LWD was added to enhance fish habitat. While transient storage volume fraction decreased as flow stage increased in simple channels, those with complex morphology and well-developed riparian vegetation maintained high transient storage fractions even during storm flows. LWD additions increased transient storage and channel complexity over the 2 years of post-treatment measurements. We predict with considerable precision two different formulations of transient hydraulic storage fraction using single-variable linear regressions on residual depth (R 2 = 0.61–0.89), thalweg depth variance (R 2 = 0.64–0.91), or large woody debris volume (R 2 = 0.48–0.74). Demonstration of these likely causal associations contributes to understanding the process of transient storage and redefines the use of thalweg profile metrics as a new approach to quantifying morphologic and hydraulic complexity in streams.

Long-Term Effects of Large Woody Debris Addition on Stream Habitat and Brook Trout Populations

Abstract In this study, we resurveyed stream habitat and sampled brook trout Salvelinus fontinalis populations 6 y after large woody debris additions to determine long-term changes in habitat and brook trout populations. In a previous study, we added large woody debris to eight streams in the central Appalachians of West Virginia to determine whether stream habitat could be enhanced and brook trout populations increased following habitat manipulation. The large woody debris additions had no overall effect on stream habitat and brook trout populations by 6 y after the additions. The assumption that a lack of large woody debris is limiting stream habitat and brook trout populations was not supported by our results. In high-gradient streams, habitat complexity may be governed more by the abundance of boulders and large woody debris may have a lesser influence on trout populations.

Quantifying Macroinvertebrate Responses to In-Stream Habitat Restoration: Applications of Meta-Analysis to River Restoration

The assumption that restoring physical habitat heterogeneity will increase biodiversity underlies many river restoration projects, despite few tests of the hypothesis. With over 6,000 in-stream habitat enhancement projects implemented in the last decade at a cost exceeding $1 billion, there is a clear need to assess the consistency of responses, as well as factors explaining project performance. We adopted an alternative approach to individual case-studies by applying meta-analysis to quantify macroinvertebrate responses to in-stream habitat restoration. Meta-analysis of 24 separate studies showed that increasing habitat heterogeneity had significant, positive effects on macroinvertebrate richness, although density increases were negligible. Large woody debris additions produced the largest and most consistent responses, whereas responses to boulder additions and channel reconfigurations were positive, yet highly variable. Among all strategies, the strength and consistency of macroinvertebrate responses were related to land use or watershed-scale conditions, but appeared independent of project size, stream size, or recovery time. Overall, the low quality and quantity of pre- and post-project monitoring data reduced the robustness of our meta-analysis. Specifically, the scope and strength of conclusions regarding the ubiquity of macroinvertebrate responses to restoration, as well as the identification of variables controlling project performance was limited. More robust applications of meta-analysis to advance the science and practice of river restoration will require implementing rigorous study designs, including pre- and post-project monitoring replicated at both restored and control sites, collection of abiotic and biotic variables at relevant spatiotemporal scales, and increased reporting of monitoring results in peer-reviewed journals and/or regional databases.

Macroinvertebrate community response to large-woody debris additions in small warmwater streams

Half-logs are a common restoration tool used to provide cover for fish in degraded streams. These structures may also provide a stable substrate for biofilm production and aquatic macroinvertebrate colonization. Half-logs (N = 108) were installed into nine streams of the upper Wabash River basin, Indiana, in July 2003 to examine changes in aquatic macroinvertebrate community composition and functional guilds under varying land-use types. Following installation, half-logs were colonized and showed statistically significant increases in both relative abundance and taxa richness of macroinvertebrates over time. The number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa collected from half-logs, as a percentage of total community composition, was positively related to the percentage of canopy coverage across streams and the relative abundance of shredder taxa utilizing half-logs decreased significantly with increasing canopy coverage. Forest streams exhibited significantly lower relative abundances of individuals colonizing half-logs (mean = 14.9 taxa/0.25 m2) than fallow field and agricultural streams (mean = 29.5 and 33.1, respectively). The percentage of pollution-tolerant taxa using half-logs was highest in fallow field streams (mean = 18.4%), followed by forest and agriculture systems (mean = 15.9% and 13. 9%, respectively). These results indicate that half-logs were colonized by aquatic macroinvertebrates and exhibited changes in community composition and functional feeding guilds over time and across land-use types. The extent of colonization and use of half-logs was largely dependent upon the pre-existing in-stream habitat quality and the predominant land-use type.

The Effect of Large Woody Debris on Macroinvertebrate Communities and Epilithon Detritus Composition in a Channelized Headwater Stream

ABSTRACT Large woody debris (LWD) was placed in a channelized second order reach of Cedar Creek, Michigan, to determine if its presence would alter substrate composition and macroinvertebrate community. Pre- and pos-treatment cores were analyzed for macroinvertebrate composition, substrate particle sue, epilithon, and detritus development. The addition of LWD in experimental sections increased the number of macroinvertebrates by 19% and total biomass by 10%. Species richness and the Shannon-Wiener diversity index increased. Inorganic substrate composition and epilithon development were not altered; however, course particulate organic matter retention was significantly increased in larger particle size classes (> 4 mm).

Effects of Large Woody Debris Addition on Stream Habitat and Brook Trout Populations in Appalachian Streams

Large woody debris (LWD) was added to eight streams in the central Appalachians of West Virginia to determine if stream habitat could be enhanced and brook trout (Salvelinus fontinalis) populations increased. Brook trout populations were assessed one year prior to habitat manipulation and 3 years post-habitat manipulation. LWD was added by felling approximately 15 trees per 300 m stream reach. Four of the streams had LWD added to one 300 m reach with 300 m unmanipulated reaches upstream and downstream of the manipulated reach to observe within-stream effects of LWD additions on brook trout density. The remaining four streams had LWD added to three 300 m reaches and these streams were compared to those with only a single 300 m manipulated reach to observe the effects of the extent of habitat manipulation on brook trout density. New pools were formed by the addition of LWD, but overall pool area did not increase significantly in reaches where LWD was added. The relatively high gradient and coarse substrate of these streams may have precluded the added LWD from having a significant influence on stream channel morphology and habitat complexity. No pools were formed in the highest gradient stream, while the stream with the most pools formed had the lowest gradient. Brook trout populations fluctuated following habitat manipulations, and there was no overall effect of the LWD additions on within-stream variability in brook trout density. When there were significant differences among-streams with different extents of LWD additions, those streams receiving LWD additions over a large extent had the greatest brook trout densities. The full potential of added LWD to change stream habitat and influence on brook trout populations may take more time to develop than the 3 years post-manipulation period of this study.

Experimental provision of large woody debris in streams as a trout management technique

Abstract The natural stock of large woody debris (LWD) in the afforested Douglas River (Fermoy, Co. Cork) is very low relative to old‐growth forests, which seems to arise from deficiency both of supply and retention. Woody debris is important to the ecology and physical structure of forest streams, so its abundance is relevant to aquatic conservation and the maintenance and size of salmonid fish stocks. The physical characteristics and fish stocks of 16 contiguous segments of two 200 m stream reaches were surveyed in spring 1998 prior to the installation of 12 partially spanning debris structures on four of the segments. This study investigated the effect of debris structures on the heterogeneity of flow and substratum, and the distribution of brown trout (Salmo trutta), and assessed the potential use of woody debris manipulation as a tool in the management of forest streams. Surveys of stream habitat conditions over a 2 year period following the installation of woody debris showed a change in stream architecture. This created more suitable habitat for trout through development of additional pools in which beds of fine sediment developed, and constraining the main current, increasing the amount of eddies and slack water areas. There were significant increases in trout density and biomass in the debris segments relative to control segments without debris dams 1 and 2 years after debris addition, although trout condition was not modified by the addition of LWD. These results suggest that the addition of woody debris offers a positive and practical management technique for enhancing fish in plantation forest streams. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Ecosystem recovery in restored headwater streams: the role of enhanced leaf retention

Summary There is controversy over how the success of ecological restoration should be measured. Traditionally, emphasis has been placed on species diversity and other community attributes, whereas the restoration of ecosystem processes has received less attention. Here, we combine replicated field experiments and a field survey to provide an ecosystem‐level measure of stream restoration success. Numerous headwater streams in Finland, and in many other parts of the world, have been channelized for timber transport, resulting in channels with simplified structure and flow. Recently, programmes have been launched to restore these streams to their pre‐channelization condition. While the efficacy of restoration in improving fish habitat has been tested, little is known about effects on other stream biota or on the retention of leaf litter, despite its importance in trophic dynamics of forested headwater streams. Using a before‐after‐control‐intervention (BACI) designed experiment with multiple reference and experimental streams, we examined restoration‐induced changes in retention efficiency by conducting leaf‐release experiments before (1993) and after (1996) restoration. Substrate heterogeneity increased, but moss cover decreased dramatically following restoration. Retention efficiency in restored streams was higher than in channelized, but lower than in natural, streams. Algae‐feeding scrapers were the only macroinvertebrate group whose density increased significantly after restoration. Aquatic mosses were a key retentive feature in both channelized and natural streams, but their importance to retention was strikingly reduced by restoration. During restoration work, mosses are detached from large areas of the stream bed, exposing bare stone surfaces for colonization by periphytic algae. A more effective restoration technique would involve the use of moss transplants, or the addition of large woody debris, to increase retentiveness and thus enhance the availability of organic material to benthic consumers. This case study on rivers illustrates how restoration projects benefit from an ecosystem perspective and from measures of ecosystem processes in assessing restoration success.

Effectiveness of large woody debris in stream rehabilitation projects in urban basins

Urban stream rehabilitation projects commonly include log placement to establish the types of habitat features associated with large woody debris (LWD) in undisturbed streams. Six urban in-stream rehabilitation projects were examined in the Puget Sound Lowland of western Washington. Each project used in-stream log placement as the primary strategy for achieving project goals; none included systematic watershed-scale rehabilitation measures. The effectiveness of LWD in these projects was evaluated by characterizing physical stream conditions using common metrics, including LWD frequency and pool spacing, and by sampling benthic macroinvertebrates. In all project reaches where pre-project data existed, pool spacing narrowed after LWD installation. All project sites exhibited fewer pools for a given LWD loading, however, than has been reported for forested streams. In project reaches where the objective was to control downstream sedimentation, only limited success was observed. At none of the sites was there any detectable improvement in biological conditions due to the addition of LWD. Our results indicate that, although LWD projects can modestly improve physical habitat in a stream reach over a time scale of 2–10 years, they apparently do not achieve commensurate improvement in biological conditions.

Influence of large woody debris on stream insect communities and benthic detritus

We examined the extent to which benthic detritus loadings and the functional feeding group structure of stream insect communities respond to channel modifications produced by experimental addition of large woody debris (LWD, entire logs) to Stony Creek, Virginia. Benthic detritus loadings per sample did not change after LWD additions, but large increases in pool habitats created by LWD increased net detritus by an estimated 27 kg (25%) in the 250 m of stream receiving LWD. A large increase in the proportional area of pool habitats may result in a dominance of collector-gatherers and corresponding decreases in shredders and scrapers. Functional feeding group community structure in pools was similar spatially and temporally. Riffles were spatially convergent, but differed temporally. Community structure was significantly different between pools and riffles. The results indicate possible large scale influences in overall community structure due to channel alterations by LWD, but little within-habitat change.

Applying geostatistics to quantify distributions of large woody debris in streams

Large woody debris (LWD) strongly influences morphology and aquatic habitat in streams within forested watersheds. Previous studies have used data to describe spatial distributions of LWD in qualitative terms. We used high-resolution spatial data collected from a forested stream in western Oregon to conduct three geostatistical analyses. The data were collected at five time periods prior to and following the addition of LWD into the stream. Each analysis is examined for its potential and shortcomings in quantifying distributions. Our findings indicate that semi-variograms, when used with a raster spatial data structure, can be useful quantitative descriptions of LWD distributions.

Response of Juvenile Coho Salmon and Steelhead to Placement of Large Woody Debris in a Coastal Washington Stream

Abstract Many fish habitats have been altered in Pacific Northwest streams and rivers over the past century by a variety of land use practices, including forestry, urbanization, agriculture, and channelization. There are research and management needs for evaluation of the effectiveness of rehabilitation projects intended to enhance stream fish habitat recovery. The response of populations of juvenile coho salmon Oncorhynchus kisutch and steelhead O. mykiss to addition of large woody debris (LWD) was tested in North Fork Porter Creek (NFPC), a small coastal tributary of the Chehalis River, Washington. The NFPC was divided into three 500-m study sections; two sections were altered with two approaches (engineered and logger's choice) to adding LWD, and the third was kept as a reference site. Immediately after LWD addition, the abundance of LWD pieces was 7.9 times greater than the pretreatment level in the engineered site and 2.7 times greater in the logger's choice site; abundance was unchanged in the refer...

Effects of large woody debris placement on stream channels and benthic macroinvertebrates

Large woody debris (LWD) was added as an experimental stream restoration technique in two streams in southwest Virginia. Additions were designed to compare human judgement in log placements against a randomized design and an unmanipulated reach, and also to compare effectiveness in a low- and a high-gradient stream. Pool area increased 146% in the systematic placement and 32% in the random placement sections of the low-gradient stream, lending support to the notion that human judgement can be more effective than placing logs at random in low-gradient streams. Conversely, the high-gradient stream changed very little after LWD additions, suggesting that other hydraulic controls such as boulders and bedrock override LWD influences in high-gradient streams. Logs oriented as dams were responsible for all pools created by additions regardless of stream or method of placement. Multiple log combinations created only two pools, while the other seven pools were created by single LWD pieces. Total benthic macroinvertebrate abundance did not change as a result of LWD additions in either stream, but net abundances of Plecoptera, Coleoptera, Trichoptera, and Oligochaeta decreased, while Ephemeroptera increased significantly with the proportional increase in pool area in the low-gradient stream.