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1.
Many streams have been modified so extensively that river managers do not have clear reference conditions to frame targets for stream restoration. Large woody debris (LWD) has long been recognized as an important influence on both geomorphic and ecologic processes in stream channels; however, there have been few studies of LWD dynamics in New England. Although this region is heavily forested today, the forest is predominantly young (70–90 years old) regrowth following a historical episode of severe deforestation. This study presents the results of an extensive census of LWD and associated stream characteristics in over 16 river kilometres of northeastern Connecticut streams and represents the first reported inventory of wood loading and sorting in Southern New England. Results of this study indicate that wood loading and jam frequencies in the study region are low: 2.5–17.8 and 0.5–5.51 per 100 m, respectively. Orientation of LWD is predominantly parallel to flow, an indication that these streams are not retaining organic matter or sediment, which has important geomorphic and ecologic implications. Results imply that stream recruitment of LWD is still lagging from the massive forest conversions of the 18th and 19th centuries. Given the low wood loadings observed in the study reaches, manual wood addition and continued forest regeneration would likely improve both habitat diversity and organic matter and fine sediment retention in these systems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
N. E. Pettit D. M. Warfe M. J. Kennard B. J. Pusey P. M. Davies M. M. Douglas 《河流研究与利用》2013,29(7):864-875
The recruitment of wood from the riparian zone to rivers and streams provides a complex habitat for aquatic organisms and can influence both aquatic biodiversity and ecosystem function. The Daly River in the wet–dry tropics of northern Australia is a highly seasonal, perennially flowing sand‐bed river where surveys of river wood aggregations at the reach scale (~2 km) in 2008 and 2009 recorded densities of 37–78 km?1 and identified distinct types of river wood aggregations: key pieces, standing trees, fallen trees, wrack and single pieces. After larger than average flows in the 2008/2009 wet season, between 46% and 51% of the surveyed river wood had moved. The distribution of wood age classes indicated continual recruitment and slow turnover of wood within the river. Surveys of fish and habitat characteristics at the mesohabitat scale (~100 m) showed fish species richness; diversity and fish abundance were not correlated to the proportion of wood present. Fish assemblage structure was associated with wood cover as well as other environmental variables such as stream width and depth. The importance of in‐stream wood also varied for different species and age classes of fish. This study documents the dynamic nature of river wood aggregations and their complex and variable distribution and suggests their importance as fish habitat in this tropical river. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
3.
Historically, perceived increases in erosion and flooding levels have been attributed to in‐stream wood and used to justify its removal from streams and rivers around the world. More recently, recognition of the adverse morphological and biological impacts caused by this removal has led to rehabilitation projects that actively reintroduce wood to streams. However, a perception remains amongst some members of the general community that wood additions increase the likelihood of flooding and erosion in the target streams. To test whether there was a basis for this perception, we experimentally added wood to eight streams across southwest Victoria and Gippsland, Australia. The velocity, stage and bed and bank erosion rates were compared with those of unaltered reaches. We detected localized changes in the velocity and stage parameters but that these were unlikely to operate at the reach‐scale. Bed erosion rates, where maximum erosion was assumed if pins were not recovered, showed increased erosion due to wood additions but this was not supported by channel shape analyses, which identified short‐term increases in the variability of the channel shape, followed by longer‐term stability at treatment sites. We found no clear evidence of increased longer‐term rates of erosion or flooding associated with the introduction of wood to streams over the 18‐month study period. It remains important to carefully design rehabilitation works, but the lack of adverse effects on stream morphology and increased variability of the in‐stream environment suggests improved habitat diversity, supporting the use of wood addition as a stream rehabilitation technique. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
4.
Methodologies that have been developed to quantify large woody debris (LWD) have been largely tested and adapted for mountain streams of the Pacific Northwest, characterised by a very high density of LWD, composed of large pieces of wood. In French rivers, LWD studies have focused on larger systems presenting low density and discrete distributions of LWD accumulations, where existing methods could not readily be used. We thus propose an easy-to-use method to quantify LWD within such systems. After defining three representative types of LWD, the volume is obtained by representing each LWD accumulation by a simple geometric form in order to measure its height, width and length. A model is then built for the different accumulation types to estimate wood mass from the measured volume. Since the measured volume is a combination of air and wood, we quantified the proportion of air, which is, respectively, equal to 18, 90 and 93% for trunks, wood jams and shrubs. To understand variability in wood mass, we evaluated the influence of different factors on wood density (defined as the ratio between mass and volume). The main factor was found to be the water absorption capacity of the wood, whereas a lesser factor was the degree of wood decay. Most wood pieces were found to increase their mass by an average of 100% and more after only 24 h in contact with water. Moreover, the observed levels of water loss and water absorption during the first 24 h of removal or exposure to water imply major short-term variations in wood mass, which may have significant consequences for wood transport during flooding. © 1998 John Wiley & Sons, Ltd. 相似文献
5.
Channel‐spanning logjams completely span the active channel and create longitudinal discontinuities of the water surface and stream bed across at least two‐thirds of the channel width. These jams disproportionately affect channel process and form relative to smaller jams that do not span the entire channel width. We analyze a spatially extensive dataset of 859 channel‐spanning jams distributed along 124 km of 16 distinct rivers on the eastern side of Rocky Mountain National Park, Colorado, USA, with drainage areas spanning 2.6 to 258 km2 and diverse valley geometry and forest stand age. We categorized valley geometry in terms of lateral confinement (confined, partly confined, or unconfined), which correlates with gradient. Jams exhibit substantial downstream variability in spacing at channel lengths of 102–103 m. The number of jams within a reach is explained by a statistical model that includes drainage area, valley type (lateral confinement), and channel width. Longitudinal spacing of jams drops substantially at drainage areas greater than ~20 km2, although jam spacing exhibits tremendous variability at smaller drainage areas. We interpret the lack of jams at larger drainage areas to reflect increasing transport capacity for instream wood. We interpret the variability in jam spacing at small drainage areas to reflect local controls of valley geometry and associated wood recruitment and fluvial transport capacity. Our results suggest that management of instream wood designed to facilitate the formation of channel‐spanning jams can be most effectively focused on smaller drainage areas where these jams are most abundant in the absence of management that alters instream wood recruitment or retention. Unmanaged streams in the study region with drainage area <60 km2 have ~1.1 channel‐spanning jams per 100 m length of stream. The cumulative effects of these jams on instream storage of sediment and organic matter, hyporheic exchange, instream habitat, stream metabolism, and channel–floodplain connectivity are likely to be enormous. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
In‐depth knowledge of the fluvial corridor and surrounding slopes and forest vegetation is needed for a better understanding of wood recruitment or inputs to rivers. The information available in Central Spain on hydrogeomorphic processes and forest distribution enabled the evaluation of potential wood recruitment from three sources: landslides, bank erosion and fluvial transport during floods on a regional scale. The method presented here is based on a geographical information system (GIS) and on multi‐criteria and multi‐objective assessment using fuzzy logic principles. First, the areas potentially affected by landslides, bank erosion and floods were delineated, and a vegetation analysis was carried out to obtain the vegetation resistance and forest density. Several scenarios were proposed based on the process frequency and severity. Using this method, the volume of potentially available wood can be estimated for each scenario. Fourteen river basins in populated areas were selected for further analyses and field survey. Observations of in‐stream storage of woody debris and tree disturbances were used to interpret the woody debris dynamics throughout the watershed and validate the obtained results. This method offers a suitable approach to define a watershed's capacity to recruit wood material to streams by delineating the source areas and estimating the order of magnitude of the wood volume in each case. The results may be useful to characterize the dynamics of woody debris from the perspective of the potential hazard of its transport during floods, and they can also be used for forest and river management and restoration. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Riparian vegetation development and macroinvertebrate assemblages were studied in 16 streams formed between 35 and 230 years ago, following glacial recession in Glacier Bay National Park, southeast Alaska. Riparian vegetation established most rapidly in streams where flow variation in downstream reaches was buffered by a lake. Riparian vegetation development was positively correlated with lower bank stability, but was independent of stream age. Roots and branches of riparian vegetation trailing into streams (trailing riparian habitat—TRH) were shown to be an important habitat for a number of macroinvertebrate taxa. In young and unstable streams, TRH was colonized mainly by Plecoptera whereas in more stable lake‐influenced streams Simuliidae dominated. Significant coarse woody debris (CWD) accumulations were not observed until after approximately 130 years of stream development had occurred when certain channel features, such as gravel bars, were stabilized by dead wood. Where dead wood was present, opportunistic wood taxa were abundant, even in the younger streams. However, a xylophagous species, Polypedilum fallax, was not recorded until streams were over 100 years old. Two‐way indicator species analysis (TWINSPAN) using presence/absence of macroinvertebrate taxa on TRH, initially divided streams into lake and non‐lake systems, but subsequent divisions were consistent with differences in stream age. TWINSPAN of macroinvertebrate assemblages on dead wood again highlighted differences in stream age. Canonical correspondence analysis indicated that bed stability and stream age were the most important environmental variables influencing macroinvertebrate distribution on TRH. Trailing riparian habitat was most abundant in moderately unstable streams where it facilitates invertebrate colonization. CWD contributes markedly to channel stabilization, provides habitat for invertebrate xylophages, and confers additional habitat complexity. Maximum levels of CWD are predicted to occur in non‐lake streams after approximately 300 years, but at least a further 100 years will be required in stable streams below lakes where dead wood entrainment is not enhanced by flooding, channel migration and bank undercutting. A conceptual model summarizing the role of TRH and CWD on stream development in Glacier Bay is presented. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
Hydrogeomorphic and Biotic Drivers of Instream Wood Differ Across Sub‐basins of the Columbia River Basin,USA 
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下载免费PDF全文 N. Hough‐Snee A. Kasprak R. K. Rossi N. Bouwes B. B. Roper J. M. Wheaton 《河流研究与利用》2016,32(6):1302-1315
Instream wood promotes habitat heterogeneity through its influence on flow hydraulics and channel geomorphology. Within the Columbia River Basin, USA, wood is vital for the creation and maintenance of habitat for threatened salmonids. However, our understanding of the relative roles of the climatic, geomorphic, and ecological processes that source wood to streams is limited, making it difficult to identify baseline predictions of instream wood and create targets for stream restoration. Here, we investigate how instream wood frequency and volume differ between seven sub‐basins of the interior Columbia River Basin and what processes shape these differences within these sub‐basins. We collected data on wood volume and frequency, discharge and stream power, and riparian and watershed forest structure for use in modelling wood volume and frequency. Using random forest models, we found that mean annual precipitation, riparian tree cover, and the individual watershed were the most important predictors of wood volume and frequency. Within sub‐basins, we used linear models, finding that some basins had unique predictors of wood. Discharge, watershed area, or precipitation often combined with forest cover, riparian conifer, and/or large tree cover in models of instream large wood volume and frequency. In many sub‐basins, models showed at least one hydrologic variable, indicative of transport competence and one ecological variable, indicative of the reach or upstream watershed's capability to grow measurable instream wood. We conclude that basin‐specific models yield important insights into the hydrologic and ecological processes that influence wood loads, creating tractable hypotheses for building predictive models of instream wood. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
Large wood (LW) is a key component of stream habitats, and degraded streams often contain little wood relative to less‐impacted ones. Habitat rehabilitation and erosion control techniques that emphasize addition of natural wood in the form of individual elements or structures are increasingly popular. However, the efficacy of wood addition, especially in physically unstable, warmwater systems is not well established. The effects of habitat rehabilitation of Little Topashaw Creek, a sinuous, sand‐bed stream draining 37 km2 in northwest Mississippi are described herein. The rehabilitation project consisted of placing 72 LW structures along eroding concave banks of a 2‐km reach and planting 4000 willow cuttings in sandbars opposite or adjacent to the LW structures. Response was measured by monitoring flow, channel geometry, physical aquatic habitat and fish populations in treated and untreated reaches for 2 years before and 4 years after rehabilitation. Initially, LW structures reduced high flow velocities at concave bank toes. Progressive failure of the LW structures and renewed erosion began during the second year after rehabilitation, with only 64% of the structures and about 10% of the willow plantings surviving for 3 years. Accordingly, long‐term changes in physical habitat attributable to rehabilitation were limited to an increase in LW density. Fish biomass increased in the treated reach, and species richness approximately doubled in all reaches after rehabilitation, suggesting the occurrence of some sort of stressful event prior to our study. Fish community composition shifted toward one typical of a lightly degraded reference site, but similar shifts occurred in the untreated reaches downstream, which had relatively high levels of naturally occurring LW. Large wood is a key component of sand‐bed stream ecosystems, but LW addition for rehabilitation should be limited to sites with more stable beds and conditions that foster rapid woody plant colonization of sediment deposits. Published in 2006 by John Wiley & Sons, Ltd. 相似文献
11.
Tjitske J. Geertsema Paul J. J. F. Torfs Joris P. C. Eekhout Adriaan J. Teuling Antonius J. F. Hoitink 《河流研究与利用》2020,36(7):1171-1182
Placement 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. 相似文献
12.
Benthic invertebrate communities were examined in Compensation Creek, a man‐made stream in south‐central Newfoundland, Canada. Samples taken in September 2006 and September 2007 from large woody debris (LWD) were compared with samples from benthic environments to determine whether LWD supported a more diverse and abundant invertebrate community. Benthic habitats in a nearby natural stream were also sampled. Taxa composition was similar between the man‐made and the natural stream, highlighting successful colonization for the majority of taxa. Within Compensation Creek, taxa richness was higher in benthic habitats than on LWD, likely influenced by the successional age of the stream and surrounding habitat. The more complex benthic substrate provided refugia and allowed for the accumulation of fine detritus as a food source. Scrapers were almost completely absent from LWD and collector‐gatherer abundance was greater in the benthos. Collector‐filterer abundance was more than six times greater near the pond outflow than farther downstream when discharge was high, but abundances were almost equal when discharge was reduced. Riparian vegetation has not fully established around the man‐made stream, whereas it is overhanging and extensive at the natural stream, leading to more leaf‐litter input for shredders. As the morphology of Compensation Creek changes, the invertebrate community will continue to develop and likely increase utilization of accumulated detritus at LWD. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
13.
It is well known that large woody debris (LWD) plays an important functional role in aquatic organisms' life. However, the influence of LWD on channel morphology and aquatic environments at watershed levels is still unclear. The relationships between wood and surface structure and aquatic habitat in 35 first through fifth order streams of southern interior British Columbia were investigated. Study streams in the channel networks of the study watersheds were classified into four size categories based on stream order and bankfull width: Stream size I: bankfull width was less than 3 m, Stream size II: 3–5 m, Stream size III: 5–7 m, Stream size IV: larger than 7 m. We found the number of functional pieces increased with stream size and wood surface area in stream sizes I, II and III (24, 28 and 25 m2/100 m2, respectively) was significantly higher than that in stream size IV (12 m2/100 m2). The contribution of wood pieces to pool formation was 75% and 85% in stream sizes II and III, respectively, which was significantly higher than those in stream size I (50%) and size IV (25%). Between 21% and 25% of wood pieces were associated with storing sediment, and between 20% and 29% of pieces were involved in channel bank stability in all study streams. Due to long‐term interactions, LWD in the intermediate sized streams (Size II and III) exhibited much effect on channel surface structure and aquatic habitats in the studied watersheds. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
14.
The natural tendency of woody debris to accumulate into complex debris jams has been adapted by the restoration industry because of the morphological and ecological benefits of these structures. While much work has been done on woody debris, there is a lack of understanding of the dynamics of debris jams including the controls on their formation and the associated changes in hydraulics. Treatment of jams as static structures, whose hydraulics may be described by that of a single‐solid object, prevents optimal success of wood‐based restoration projects. This paper reviews the state of the science on the initiation and accumulation of wood forming a debris jam. This review is used to develop a conceptual model of the evolution of a single debris jam focussing on the relationship between the structure and hydraulics and the feedback that exists between them. The proposed mechanisms behind debris jam evolution are supported by a case‐study of three natural jams. Incorporation of this model into restoration and management plans will result in more successful and cost‐efficient projects. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
15.
The natural flow regime of rivers has been altered throughout the world in a variety of ways, with many alterations resulting in reduced flows. While restoring impaired systems remains a societal imperative, a fundamental understanding of the effects of reduced flows on river ecosystem structure and function is needed to refine restoration goals and guide implementation. We quantified the effects of chronic low flows on snag‐dwelling macroinvertebrate community structure and production in a low‐gradient river. Macroinvertebrates commonly associated with flowing water (e.g. passive filter‐feeders (PFF)) and higher quality habitats (e.g. Ephemeroptera, Plecoptera and Trichoptera (EPT)) had significantly higher abundance and biomass, and showed trends of higher production, in faster flowing reaches upstream of a hydrologic disconnection created by a drainage ditch. The presence of EPT and PFF groups resulted in a significantly more diverse community composed of larger‐sized individuals compared with downstream, low‐flow reaches, where smaller‐bodied taxa (e.g. small crustaceans), and groups reflective of degraded conditions (e.g. Oligochaeta, Isopoda and Chironomidae) dominated production. Multivariate analyses suggested that differences between these two disparate communities were driven by water velocity and organic matter resources. Mean estimates of total community production did not differ significantly between the two reaches, however, there were areas in low‐flow reaches that attained high secondary production because of patchily distributed and highly productive chironomids. Results demonstrate that long‐term reductions in flows, even in a low‐gradient river, can lead to significant shifts in macroinvertebrate communities, ultimately influencing energy flow pathways in stream food webs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
16.
Large wood, both live and dead, is essential for producing complex habitat in many streams, especially in forested watersheds that support salmonid populations. The addition of engineered wood structures is a common approach taken in many streams where past watershed management practices have resulted in reduced wood loading. We examined six 300‐m stream reaches in the Lagunitas Creek watershed, Northern California, to determine (i) the distribution of large wood in the bankfull channel and 10‐year floodplain, (ii) the influence of large wood on the size and distribution of pools and (iii) whether streams with engineered wood structures had greater diversity of pool habitat to support salmonid populations. We found that the amount of large wood in the bankfull channel and the amount available for recruitment from the 10‐year floodplain were highly variable among and within reaches examined and largely dependent on the local geomorphic setting. Stream reaches with engineered wood structures had elevated pool frequencies relative to reaches without these structures, suggesting a higher capacity to support salmonids during critical life stages. Among large wood pieces that had a strong influence on pool formation, 23% had an attached root wad and 66% were part of a cluster. All of the study reaches we examined had lower volumes of large wood in their bankfull channels than similar stream types with natural wood‐loading levels, suggesting that increased additions of large wood could provide ecosystem benefits over time. These principles can be understood and transferred effectively to other watersheds using a framework of wood‐loading process domains. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
Round gobies have had significant impacts on benthic fish and invertebrate communities in nearshore habitats of the Great Lakes. As round gobies have become more abundant in lake habitats, there has been an expansion of their populations into tributary streams and rivers. We compared stream invertebrate and fish communities in New York tributaries to Lake Erie with round gobies present and absent. Four of six benthic invertebrate metrics differed between streams with and without round gobies. Streams with round gobies present had reduced Shannon diversity, EPT richness, and EPT/chironomid ratios, and increased macroinvertebrate density relative to streams without round gobies, but there was no difference in non-Diptera density, or total taxa richness. None of the four fish metrics examined differed between streams with and without round gobies. However, darters occurred in all streams lacking round gobies, but did not occur in any streams with round gobies. Comparisons with historical fish and macroinvertebrate distributional data support our suspicion of goby-induced community changes. In these New York streams, round gobies seem to have had significant impacts on invertebrate communities via their consumptive behavior, whereas the impacts on fish communities are less evident. If round gobies continue to expand their distribution inland, the resultant alterations in macroinvertebrate communities may impact the suitability of tributary streams as spawning and nursery habitat for several sport fish species and for energy dynamics in tributary streams. 相似文献
18.
Introducing large woody debris into streams is a common practice in restoration projects. Beyond the complexity of flow patterns and sediment movements in streams where woody debris are found or placed, it seems that our understanding of the basic hydraulics of large roughness elements in small channels remains limited. Underestimating the drag force affecting large roughness elements can compromise the success of stream restoration projects. Results from a simple experimental setting confirm that drag force estimates based on approaches developed for small cylinders are not valid when applied to large cylinders. Indeed, the classic drag force equation that uses an empirical drag coefficient is found to significantly underestimate measured drag forces, even when corrected for the ‘blockage ratio’. In contrast, application of specific momentum can yield good estimates of the drag force. A dimensionless depth is defined in a 1D context as a function of the flow depth, critical flow depth and cylinder diameter. A cylinder is considered to be ‘large’ when this dimensionless depth is smaller than 2. In this instance, a relationship is established to estimate the upstream flow depth and the drag force acting on the cylinder. This research bridges the small roughness element theory widely recognized in hydraulic engineering with the theory applicable to large, flow controlling structures such as weirs. From a practical perspective, this research can be used to assist in the design of engineered large woody debris structures. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
19.
The objective of this paper is to determine the alteration of the taxonomic composition and functional structure of macroinvertebrate community associated with a massive growth of the invasive algae Didymosphenia geminata downstream of a mountain reservoir (Pajares Reservoir, La Rioja, Northern Spain). As the massive growth of the alga disappears a few kilometres downstream of the reservoir associated with the input of nutrients from a nearby village sewage, we may compare the community composition between nine stations in three different conditions: three stations heavily affected by the presence of D. geminata, three further downstream stations without the algal massive growth but affected by river regulation and three control stations (unregulated and without the algae). Results show a significant disturbance of the composition and structure of macroinvertebrate community in sites affected by the stream flow regulation downstream of the dam compared with unregulated streams, but the alterations are more dramatic in the area where the growth of D. geminata is massive because of the total substrate occupation by the algal filaments. Scrapers and others invertebrates living on the coarse substrate are especially affected at such sites. Moreover, an important increase in the relative abundance of chironomids is associated with the algal massive growth, especially in case of Eukiefferiella devonica and Cricotopus spp., reducing the assemblage diversity and leading to the taxonomic and functional homogenization of the community. Changes in the reservoir management (such as releasing the water from surface rather than from the hypolimnion) may be useful to control the massive growth of D. geminata and thus reducing the effects of river regulation on macroinvertebrate assemblage composition. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
20.
In‐channel large woody debris (LWD) promotes quality aquatic habitat through sediment sorting, pool scouring and in‐stream nutrient retention and transport. LWD recruitment occurs by numerous ecological and geomorphic mechanisms including channel migration, mass wasting and natural tree fall, yet LWD sourcing on the watershed scale remains poorly constrained. We developed a rapid and spatially extensive method for using light detection and ranging data to do the following: (i) estimate tree height and recruitable tree abundance throughout a watershed; (ii) determine the likelihood for the stream to recruit channel‐spanning trees at reach scales and assess whether mass wasting or channel migration is a dominant recruitment mechanism; and (iii) understand the contemporary and future distribution of LWD at a watershed scale. We utilized this method on the 78‐km‐long Narraguagus River in coastal Maine and found that potential channel‐spanning LWD composes approximately 6% of the valley area over the course of the river and is concentrated in spatially discrete reaches along the stream, with 5 km of the river valley accounting for 50% of the total potential LWD found in the system. We also determined that 83% of all potential LWD is located on valley sides, as opposed to 17% on floodplain and terrace surfaces. Approximately 3% of channel‐spanning vegetation along the river is located within one channel width of the stream. By examining topographic and morphologic variables (valley width, channel sinuosity, valley‐side slope) over the length of the stream, we evaluated the dominant recruitment processes along the river and often found a spatial disconnect between the location of potential channel‐spanning LWD and recruitment mechanisms, which likely explains the low levels of LWD currently found in the system. This rapid method for identification of LWD sources is extendable to other basins and may prove valuable in locating future restoration projects aimed at increasing habitat quality through wood additions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献