Flume experiments on wood entrainment in rivers

A flume experiment on entrainment of woody debris is carried out. Woody debris is modeled using smooth, cylindrical dowels, in touch with the flume bed. The water depth and velocity are evaluated that initiate the motion of the partially submerged dowels. On the basis of the experimental finding, a theoretical model of log entrainment is developed, providing in dimensionless form the equilibrium equation for incipient motion. The experiment shows that the equilibrium equation must keep into account the modification of the local water profile, affecting the force balance at incipient motion. This issue has been apparently neglected in the wood entrainment models so far developed. The entrainment model is less sensitive to the choice of the apparent drag coefficient. The capability of the model in predicting the critical log diameter for initiation of motion is discussed and compared with that from the recent entrainment model from Braudrick and Grant, 2000. The comparison shows interesting results and provide evidence of the needs for further studies on wood entrainment in rivers.     

A conceptual model for the longitudinal distribution of wood in mountain streams

Wood load, channel parameters and valley parameters were surveyed in 50 contiguous stream segments each 25 m in length along 12 streams in the Colorado Front Range. Length and diameter of each piece of wood were measured, and the orientation of each piece was tallied as a ramp, buried, bridge or unattached. These data were then used to evaluate longitudinal patterns of wood distribution in forested headwater streams of the Colorado Front Range, and potential channel‐, valley‐ and watershed‐scale controls on these patterns. We hypothesized that (i) wood load decreases downstream, (ii) wood is non‐randomly distributed at channel lengths of tens to hundreds of meters as a result of the presence of wood jams and (iii) the proportion of wood clustered into jams increases with drainage area as a result of downstream increases in relative capacity of a stream to transport wood introduced from the adjacent riparian zone and valley bottom. Results indicate a progressive downstream decrease in wood load within channels, and correlations between wood load and drainage area, elevation, channel width, bed gradient and total stream power. Results support the first and second hypotheses, but are inconclusive with respect to the third hypothesis. Wood is non‐randomly distributed at lengths of tens to hundreds of meters, but the proportion of pieces in jams reaches a maximum at intermediate downstream distances within the study area. We use these results to propose a conceptual model illustrating downstream trends in wood within streams of the Colorado Front Range. Copyright © 2009 John Wiley & Sons, Ltd.     

Processes and rates of sediment and wood accumulation in headwater streams of the Oregon Coast Range,USA

Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low‐order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was used to estimate the time since the previous debris flow and the time since the last stand‐replacement fire in unlogged basins in the central Coast Range of Oregon. Debris flow activity increased 42 per cent above the background rate in the decades immediately following the last wildfire. Changes in wood and sediment storage were quantified for 13 streams that ranged from 4 to 144 years since the previous debris flow. The volume of wood and sediment in the channel, and the length of channel with exposed bedrock, were strongly correlated with the time since the previous debris flow. Wood increased the storage capacity of the channel and trapped the majority of the sediment in these steep headwater streams. In the absence of wood, channels that have been scoured to bedrock by a debris flow may lack the capacity to store sediment and could persist in a bedrock state for an extended period of time. With an adequate supply of wood, low‐order channels have the potential of storing large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain. Copyright © 2003 John Wiley & Sons, Ltd.     

Efficient methods of discharge measurements in rivers and streams based on the probability concept

Regularities exist in fluid flows and can be represented by a set of constants. These constants are functions of the parameter of a probability distribution that exhibits resilience and stability under various flow conditions. Together, these regularities form a network and interact with each other, such that if one is known then the others can be determined from it. The regularities and their network explain the various fluid‐flow phenomena and can be used in analysis of rivers and streams. For example, they can be used as the basis to develop simple and efficient methods of discharge measurements as presented herein, which only require velocity sampling at a single point on a water surface or a few points on a single vertical. Because of their simplicity and the short time requirement, these methods can be easily automated for collecting discharge data in unsteady, high flows that are badly needed for real‐time flow forecasting and design of flood control structures, and for advancing the fundamental, scientific knowledge in hydrology. Copyright © 2005 John Wiley & Sons, Ltd.     

Decadal-scale changes in suspended wood after riparian recruitment in managed stands in headwater streams of coastal British Columbia,Canada

Large wood (LW) affects several ecological and hydrogeomorphic processes in streams. The main source of LW is riparian trees falling inside channels. However, in confined valley floors, falling trees are more likely to be suspended above the channel. Eventually, these suspended trees will decompose and break to finally fall into the channel to better provide functions for streams. We evaluated changes in wood decay, length, diameter, and suspended status (suspended or non-suspended) 17 years post-harvest and nine years after the first sampling occurred in 2006 in 12 headwater streams of coastal British Columbia, Canada. We also evaluated whether changes differed among riparian management treatments (no-harvest buffers of 10 and 30 m in width, thinning, and unharvested reference sites), and identified the factors affecting wood changes and suspended status. Wood pieces advanced in decay, became shorter, and 34% of them (n = 108) changed status from suspended to non-suspended. Non-suspended wood pieces were more decayed and shorter than suspended wood. Suspended wood was longer, thicker, less decayed, and represented 46.5% (n = 147) of the wood sampled in 2006. Our findings revealed limited influences of riparian management on many aspects of wood changes considered in this study. Changes in wood characteristics were more likely for pieces that were smaller in diameter, longer, and suspended closer to the water. The transition from suspended to non-suspended LW can be a long-term process that can increase wood residence time and reduce LW in-stream functions particularly in confined stream valleys. The suspended stage is also an important mechanism underlying time lags in stream ecosystem responses to riparian tree fall. © 2020 John Wiley & Sons, Ltd.     

Application of the new multimetric MMI_PL index for biological water quality assessment in reference and human-impacted streams (Poland,the Slovak Republic)

A new multimetric MMI_PL index, which is based on the macroinvertebrate composition and combines six single key metrics, has already been implemented in Poland according to the requirements of the EU Water Framework Directive. The objectives of our survey were to assess the biological water quality using the new multimetric MMI_PL index in both reference and human-impacted streams, to analyze whether the values of the new multimetric index properly reflect the ecological status of the water in upland and mountain streams as well as to determine which environmental factors influence the distribution of benthic macroinvertebrates and the values of the metrics. The study was carried out from 2007 to 2010 in three Ecoregions that were established by the EU WFD. A total of 60 sampling sites: 36 reference sites that were situated in the headwaters of mountain streams at mid- and high-altitudes and 24, human-impacted sampling sites were selected. The benthic macroinvertebrate surveys were supported by both a hydromorphological and macrophyte assessment according to the River Habitat Survey (RHS) and to the Macrophyte Methods for Rivers. Canonical correspondence analysis (CCA) showed that the values of the Habitat Quality Assessment (HQA) index, conductivity, pH and altitude were the parameters most associated (statistically significant) with the distribution of benthic macroinvertebrate taxa and the values of the metrics in both the reference and human-impacted (impaired) sections of the streams in Ecoregions 9, 10 and 14. The new MMI_PL index was useful for biological water quality assessment and was also important for separating both the reference and impaired sections of streams. The MMI_PL index and some key metrics performed contrary to what was expected in relation to the reference high-altitude siliceous streams (the High Tatra Mts., Ecoregion 10). Low values of multimetric index and key metrics did not properly reflect their high ecological status and pristine character as reflected by the hydromorphological (RHS) and macrophyte surveys or the physical and chemical parameters of the water.     

Wood storage in three mountain streams of the Southern Andes and its hydro‐morphological effects

This study analyses large wood (LW) storage and the associated effects on channel morphology and flow hydraulics in three third‐order mountain basins (drainage area 9–12 km²) covered in old‐growth Nothofagus forests, ranging from the temperate warm Chilean Andean Cordillera to the sub‐Antarctic Tierra del Fuego (Argentina). Amount, characteristics and dimensions of large wood (>10 cm diameter, >1 m long) were recorded, as well as their effects on stream morphology, hydraulics and sediment storage. Results show that major differences in LW abundance exist even between adjacent basins, as a result of different disturbance histories and basin dissection. Massive LW volumes (i.e. >1000 m³ ha^?1) can be reached in basins disturbed by fires followed by mass movements and debris flows. Potential energy dissipation resulting from wood dams is about a quarter of the total elevation drop in two streams, with a gross sediment volume stored behind wood dams of around 1000 m³ km^?1, which appears to be of the same order as the annual sediment yield. Finally, the presence of wood dams may increase flow resistance by up to one order of magnitude. Copyright © 2007 John Wiley & Sons, Ltd.     

Large wood in central Appalachian headwater streams: controls on and potential changes to wood loads from infestation of hemlock woolly adelgid

Large wood (LW) is an important component of forested headwater streams. The character of LW loads reflects a balance between adjacent valley processes that deliver LW to the channel (herein recruitment processes) and stream channel processes that either retain or transport LW through the reach (herein retention processes). In the central Appalachian Mountains, USA, LW characteristics in headwater streams located in eastern hemlocks (Tsuga candensis) forests are expected to change because of infestation of hemlock woolly adelgid (Adelges tsugae, HWA), an exotic, invasive insect. We examined LW characteristics in 24 headwater streams ranging from un‐infested to severe infestation, as determined by hemlock canopy health. The objectives of this work were to: (i) quantify wood loads; (ii) assess the relative importance of valley recruitment and in‐stream retention mechanisms in controlling reach‐scale wood loads; and (iii) assess if there was a detectable influence of HWA on LW loads. We hypothesized that LW loads would be similar to other forested streams in eastern USA and dominated by recruitment processes. In addition, higher LW loads would correspond with advanced HWA infestation. Mean wood frequency was 38 pieces/100 m ± 17 (standard deviation); mean wood volume was 3.69 m³/100 m ± 2.76. In general, LW load characteristics were influenced by both recruitment and retention parameters; jam (accumulations ≥ 3 pieces) characteristics were dominated by retention parameters. Results suggest that adjacent stand basal area influences LW loads and once LW is recruited to the channel, streams lack sufficient hydraulic driving forces, despite having lower resistance structures, to transport LW out of the reach. Sites in moderate decline had higher proportions of short (1–2 m and 1–4 m) and very long (>10 m) LW with higher frequency of jams that were low in volume. We present a hypothesized conceptual model of expected changes to LW loads associated with HWA infestation and hemlock mortality. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantifying the temporal dynamics of wood in large rivers: field trials of wood surveying,dating, tracking,and monitoring techniques

Wood plays an important role in stream ecology and geomorphology. Previous studies of wood in rivers have quantified spatial distributions but temporal dynamics remain poorly documented. The lack of such data is related to limitations of existing methods, especially when applied to large rivers. Five techniques are field‐tested to assess their utility for quantifying the temporal dynamics in rivers: repeated high‐resolution aerial surveys, the measurement of wood physical characteristics as proxies for ¹⁴C dating, passive and active radio frequency identification (RFID) tags, radio transmitters, and video. The spatial distribution of wood is surveyed using aerial imagery with a resolution finer than 0·10 m. The estimation of temporal trends by repeated aerial‐based surveys needs to consider vegetation growth and hiding. Wood residence times can be calculated using ¹⁴C analysis, but the assessment of wood physical characteristics including decay status and wood density offers a cheaper, if less accurate, alternative. Wood resistance to penetration is tested but results are not significant. Radio transmitters are reliable for multi‐year (～5 year) surveys and can be detected at 800 m. Passive RFID tags are limited by a read range of 0·30 m but are reliable for longer term (>5 year) studies. Active RFID tags combine a moderate read range (10–300 m) and low cost with in‐flood detection but require more testing. Video monitoring of wood passing on the surface of a river is successfully implemented. For a single flood on the Ain River (France), wood transport rates are an order of magnitude higher on the rising limb of the hydrograph than on the falling limb. Overall, the techniques improve the ability to gather the data needed to understand wood transfer processes and calibrate budgets of wood in rivers. Copyright © 2009 John Wiley & Sons, Ltd.     

Variation in riverine phosphorus between 1994 and 2003 as affected by land-use and loading reductions in six medium-sized to large German rivers

Land use and in-stream transformation exert great influence on concentrations and loads of phosphorus (P) in rivers. We aimed to display differences in the courses of total P (TP) and soluble reactive P (SRP) concentrations and loads in six medium-sized to large rivers in the central region of Germany, and to identify the reasons for different long-term trends. Therefore, we applied multivariate statistics to 10-year-time series (1994–2003) of TP, SRP, discharge (Q), water temperature (T), pH, dissolved organic carbon (DOC), total organic carbon (TOC), dissolved oxygen (DO), total iron (Fe), and total manganese (Mn). Statistical results were related to land use in the catchments of the rivers. TP concentrations ranged between 0.02 and 0.78 mg l⁻¹, and SRP concentrations ranged between 0.01 and 0.44 mg l⁻¹. Q correlated negatively with TP and SRP concentrations over the entire year. Furthermore, Fe correlated significantly and positively to TP and SRP and therefore, ferric hydroxides likely were the major P sorption sites. DOC showed significant positive correlation to SRP particularly in spring, indicating manure exposure in early spring as a major source of both, DOC and SRP. Significant negative correlations between DO and SRP in summer hint at internal P loading in rivers or in flushed lakes. Different forms of land use were the reasons of enhanced or retarded recovering from previous increases in P concentrations. High portions of arable land within some of the catchments impeded the process of decreases since 1996 because of remaining high-diffuse emissions from fertilized soils. Agricultural practices, exposing fertilizer to soils within the river catchments and high Q in early spring caused high TP and SRP loads to downstream systems, and evoked risks for downstream river reaches.     

Macrophyte-based bioindication in rivers - A comparative evaluation of the reference index (RI) and the trophic index of macrophytes (TIM)

Submerged macrophyte vegetation has been mapped in four calcareous groundwater-fed streams in Bavaria (southern Germany) in order to compare and assess two different methods of river bioindication. The first one, the trophic index of macrophytes (TIM), is a tool to assess the trophic status of running waters. In contrast, the reference index (RI) is an ecological index which evaluates the difference between a reference community and the actual submerged vegetation, depending on the river type, as required by the Water Framework Directive. Water nutrient concentrations were measured once at selected sites in all water courses.The TIM reflects water phosphorus concentrations, accounting also for nutrients enrichment in the sediment, and is not influenced by shading, depth, substrate and flow velocity of the water course. The TIM is very sensitive to small variations in P concentration when the P level is low, while the index tends to a maximum as soluble reactive phosphorus (SRP) and total phosphorus (Ptot) exceed a certain value.The RI indicates river ecological status which is not only influenced by trophic status but by every factor leading to a deviation of the actual macrophyte community from the reference community. In the investigated rivers the RI indicated reduced flow velocity caused by milldams and shading by riparian vegetation, in addition to trophic status.In rivers that are at the boundary between two different river types, classification of river type can play a crucial role for river status assessment. Incorrect classification of river type can lead to both, a “too good” and “too bad” assessment.     

Intra‐annual variability in the non‐advective heat energy budget of Devon streams and rivers

The nature of intra‐annual variability in the non‐advective heat fluxes affecting streams and rivers in Devon, UK was investigated through detailed monitoring of study reaches in an upland moorland catchment, below a regulating reservoir, and flowing through deciduous woodland and coniferous forest during the period May 1995 to April 1996. A clear pattern of seasonal variation was evident, whereby net radiation provided a heat source during the summer but a heat sink in the winter, as incoming short‐wave radiation declined and outgoing long‐wave radiation increased. Sensible transfer added heat to the study reaches in the summer but removed it during the winter, and bed conduction acted as a heat sink in the summer period but as a heat source in the winter months. Friction and evaporation added and removed heat, respectively, from the study reaches throughout the year, but the magnitude of these fluxes reflected seasonal variations in discharge and in wind speed. Water temperature generally followed the net non‐advective heat energy budget, which was positive in summer but negative in winter. Although a general pattern of seasonal variability in the non‐advective heat energy budget was evident, detailed differences in the nature and extent of intra‐annual variability were apparent between the study reaches and particularly between forested and non‐forested sites. Copyright © 2004 John Wiley & Sons, Ltd.     

Decadal changes in distribution and frequency of wood in a free meandering river,the Ain River,France

This study examined the temporal dynamics and longitudinal distribution of wood over a multi‐decadal timescale at the river reach scale (36 km) and a meander bend scale (300–600 m) in the Ain River, a large gravel‐bed river flowing through a forested corridor, and adjusting to regulation and floodplain land‐use change. At the 36 km scale, more wood was recruited by bank erosion in 1991–2000 than since the 1950s. The longitudinal distribution of accumulations was similar between 1989 and 1999, but in both years individual pieces occurred homogeneously throughout the reach, while jam distribution was localized, associated with large concave banks. A relationship between the mean number of pieces and the volume recruited by bank erosion (r² = 0·97) indicated a spatial relationship between areas of wood production and storage. Wood mass stored and produced and channel sinuosity increased from 1993 to 2004 at three meander bends. Sinuosity was related to wood mass recruited by bank erosion during the previous decade (r² = 0·73) and both of these parameters were correlated to the mean mass of wood/plot (r² = 0·98 and 0·69 respectively), appearing to control wood storage and delivery at the bend scale. This suggests a local origin of wood stored in channel, not input from upstream trapped by preferential sites. The increase in wood since 1950 is a response to floodplain afforestation, to a change from braided to meandering channel pattern in response to regulation, and to recent large floods. We observed temporal stability of supply and depositional sectors over a decade (on a reach scale). Meander bends were major storage sites, trapping wood with concave banks, also delivering wood. These results, and the link between sinuosity and wood frequency, establish geomorphology as a dominant wood storage and recruitment control in large gravel‐bed rivers. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydraulic characteristics and habitat suitability in presence of woody debris: A flume experiment

Data from a flume experiment were used to explore the modified hydraulic conditions and habitat suitability in streams where feeding of large woody debris (LWD) is present. Feeding of LWD was simulated by insertion of wood dowels with varying diameter and length. Two processes were mimicked, namely (i) lumped LWD load, and (ii) distributed LWD load. Lumped load may occur for wood coming either from upstream or from a tributary, and entering the stream of interest in one only section. Distributed load occurs for wood entering along the considered stream, in several sections. Distributed wood income resulted in homogeneously increased bed roughness, leading to increased flow depth and decreased velocity, whereas lumped input of wood from upstream resulted in larger local clustering and change of the flow properties, but with less influence on the distributed hydraulic properties. A method is proposed to predict bulk flow properties in presence of LWD. Then, a simple approach is used based upon the concept of wetter usable area WUA to investigate modified habitat conditions for fish species in presence of woody debris. An application to a real world case study from the literature is then shown, where increasing density of wood increases habitat availability for colonization by fish guilds.     

新疆艾比湖主要入湖河流同位素及水化学特征的季节变化

通过野外调查取样和室内测试分析,利用水文化学以及氢氧稳定同位素技术,分析艾比湖主要入湖河流氢氧同位素及水化学的组成特征,并探讨其季节性变化.结果表明：地表水水质指标高值多出现于博乐市、温泉市和精河县及艾比湖湿地附近,主要污染为水体富营养化、工矿业污染以及有机质污染,其污染程度夏、秋季高于春、冬季.河水的δ¹⁸O与δ²H存在明显的线性关系,其相关指数为夏季（R²=0.99） > 春季（R²=0.98） > 秋季（R²=0.96） > 冬季（R²=0.90）,均沿当地大气降水线分布,受西北干旱区强烈的蒸发作用影响,各季节河流斜率均小于8,氘过量参数值多为正值.博尔塔拉河与精河地表水体δ¹⁸O值整体上表现为沿流程逐渐偏正的趋势,博尔塔拉河水体氢氧同位素与高程相关指数表现为春季（R²=0.70） > 冬季（R²=0.57） > 夏季（R²=0.45） > 秋季（R²=0.30）,精河因其海拔差异不大,流程简短,与高程相关性低.博尔塔拉河和精河氢氧同位素与氯化物、硫酸盐、五日生物需氧量等指标间存在相关性,且在夏、秋季最大,相关系数R>0.75,与总磷、Cu²⁺、色度、浊度等指标基本都不显著相关,相关系数R<0.25.     

Estimation of water clarity in Taihu Lake and surrounding rivers using Landsat imagery

In China, the increase in exogenous-source pollutants from rivers is one of the most important causes of lake eutrophication. The application of remote sensing technology to water quality monitoring of rivers connected to these lakes has special significance for lake management at regional scales. Many research studies have estimated water clarity using Landsat imagery. However, most of this work focused on lakes or reservoirs, for which abundant water-only pixels (i.e., pure pixels of water, PPW) were available. Few of these studies have addressed rivers, especially rivers with an average width less than 100 m. In our study, we sought to determine whether water clarity in the rivers connected to Taihu Lake could be estimated using Landsat imagery. We obtained 18 Enhanced Thematic Mapper Plus (ETM+) images from 2009 for 13 rivers ranging from an average of 37.3 to 173.6 m wide. Three field campaigns conducted in May 2009, September 2009, and January 2010 were used to obtain field measurements of Secchi disk depth (SDD). Our results suggested that the widely used model, a(TM1/TM3) + b(TM1) + c, was suitable for the estimation of SDD for Taihu Lake. The brightness of the panchromatic band of ETM+ showed significant correlations with TM1, TM3 and TM1/TM3 (p < 0.001). As a result, SDD in the lake could also be estimated using the Landsat panchromatic band. The multispectral image of ETM+ did not provide adequate PPW for estimation of water clarity in rivers. However, PPW derived from the panchromatic image captured about 93% of the variation in SDD, on average, for the every worst-case scenario in the 13 rivers. Using the PPW in rivers, a significant correlation was found between the brightness of the panchromatic image and SDD (R² = 0.64, p < 0.001). Our results demonstrate that the panchromatic image of Landsat, but not the multispectral image, can be used to estimate water clarity in rivers with an average width greater than 40 m in the Taihu basin.     

河流大型底栖动物对环境压力的响应:以太湖、巢湖流域为例

为了解河流大型底栖动物对环境压力的响应关系,以人类干扰程度不同的太湖流域和巢湖流域为研究区,系统调查区域内河流大型底栖动物,结合水体、沉积物理化数据及生境质量状况,运用空间分析和多元统计分析等方法,探讨了大型底栖动物多样性及典型物种对关键环境因素的响应规律.结果表明,太湖流域和巢湖流域的环境质量和大型底栖动物群落结构均差异较大,巢湖流域的生境质量优于太湖流域,巢湖流域平原区部分点位的水体营养盐(特别是氮浓度)高于太湖流域平原区.巢湖流域丘陵区的敏感型物种(主要为水生昆虫)密度远高于太湖流域丘陵区,太湖流域丘陵区的耐污型物种(寡毛纲)平均密度稍高于巢湖流域丘陵区,而巢湖流域平原区的寡毛纲霍甫水丝蚓(Limnodrilus hoffmeisteri)和苏氏尾鳃蚓(Branchiura sowerbyi)平均密度远高于太湖流域平原区.广义加性模型建立的响应关系曲线表明,栖境多样性和总氮浓度可以作为生物多样性的指示因子.铜锈环棱螺(Bellamya aeruginosa)、椭圆萝卜螺(Radix swinhoei)、河蚬(Corbicula fluminea)、霍甫水丝蚓、苏氏尾鳃蚓、黄色羽摇蚊(Chironomus flaviplumus)等特征物种与特定环境因子的响应关系显著,这些物种也可以作为环境监测的指示物种.底栖动物环境梯度的响应曲线能够定量地描述底栖动物群落对环境因子的响应关系,有利于深入了解水体水质、营养状态及生境质量与大型底栖动物群落结构的相关关系,进而预测不同人为干扰下大型底栖动物群落结构的变化趋势和演替过程.     

Implementation and validation of video monitoring for wood budgeting in a wandering piedmont river,the Ain River (France)

The transport of wood in rivers during floods is an important process that underlies differences in habitat and morphology between water courses and regions. Quantitative data are needed to properly address management objectives and balance wood budgets. In this study we use a streamside video camera to detect wood passage and measure quasi‐instantaneous rates of wood transport in the Ain River, France. The objectives are to verify the procedure, describe the relation between wood transport and discharge, and construct and validate a wood budget for the reach upstream of the camera. Verification of the procedure includes tests of detection frequency, wood velocity, and piece size. A log base two transformation is proposed to classify wood by piece length. It was found that a wood transport threshold occurs at approximately two thirds of the bankfull discharge. Wood transport follows a positive linear relation with discharge up to the bankfull discharge but is both more variable and less sensitive to discharge when the floodplain is inundated. Transport rates are approximately four times higher on the rising limb of the hydrograph than on the falling limb. Wood transport estimates from a three‐stage rating curve are two to 10 times higher than those from a wood budget using local and aerial surveys of upstream dynamics. Future work should address uncertainties related to wood diameter measurements, sampling length and frequency, and antecedent floods. Copyright © 2012 John Wiley & Sons, Ltd.     

淠河流域河源溪流鱼类空间分布格局及主要影响因素

淠河是安徽省内淮河右岸最大的支流,也是淮河中游重要的水源地.为了解淠河流域河源溪流鱼类的空间分布格局及其主要影响因素,本研究于2015年4—5月对6条河源溪流鱼类及其环境因子进行了调查.研究结果表明,6条溪流共采集鱼类19种,其中杂食性种类占57.9%,肉食性和植食性种类分别占26.3%和15.8%.所有种类中,宽鳍鱲(Zacco platypus)是主要优势种,绿太阳鱼(Lepomis cyanellus)为研究区域首次报道的外来入侵种.就6条溪流各样点的平均值而言,淠河西部3条溪流鱼类种类数及个体数均明显高于东部3条溪流,但重量却并没有类似趋势.Sorensen相似性分析表明,6条溪流鱼类组成具有较高相似性,且相对较小值主要位于高、低海拔溪流之间.除趋势对应分析二维空间排序与相似性分析结果一致.Pearson相关分析表明,影响鱼类种类数的主要是局域栖息地参数(包括海拔、流速、底质、水深、河宽和电导率)和溪流的空间位置参数(溪流级别、流量量级和下游量级);影响鱼类个体数和重量的均仅有局域栖息地参数中的底质因素.本研究结果可为淠河流域鱼类的保护和管理提供重要的基础资料.