坡度和植被盖度对粉砂质河岸带坡面流侵蚀水动力特征的影响

揭示坡面水流水动力参数特征对于深入了解坡面土壤侵蚀的内在机制具有重要意义.本试验在黄河下游河岸带原生坡面上,采用野外模拟径流冲刷的方法,研究了4个坡度(5°、10°、15°、20°)和3个植被盖度(0%、15%、30%)在特定放水量(15 L·min^-1)条件下坡面薄层水流剥蚀土壤的水动力学过程,分析了径流剪应力(τ)、水流功率(ω)、径流能量(F)等水动力学参数的变化及其对坡度、植被盖度以及二者交互作用的响应差异.结果表明: 在坡度和植被盖度的影响下,τ、ω和F变化规律明显,坡度不变情况下,τ随着植被盖度的增加而增加,ω和F随着植被盖度的增加而减小;植被盖度不变情况下,τ、ω和F均随坡度的增加而增加.坡度小于10°时,坡度和植被盖度的变化对坡面土壤侵蚀的影响不明显;坡度大于10°时,相同坡度条件下植被盖度越大减蚀效果越明显,相同植被盖度下坡面侵蚀量随坡度的增大而增加.τ、ω均与土壤剥蚀率呈显著的线性关系,在土壤侵蚀发生时均存在临界剪应力和临界功率;F与土壤剥蚀率则呈现良好的对数关系.双因素方差分析表明,坡度和植被盖度对τ、ω和F的影响显著,两者的交互作用对ω影响显著,但对τ、F的影响不显著.     

近70年来不同地貌和植被类型区水沙特征演变及其对生态恢复的响应

黄土高原水土流失治理和退耕还林(草)等生态环境建设,对不同植被类型区和治理度下的水沙过程均产生了深刻的影响。以北洛河流域为例,基于1952—2019年实测水文数据,采用水文统计法,对比分析了上、中、下游等不同地貌和植被类型区生态恢复对水沙数量、径流调节、影响因素贡献等的影响及其差异。结果显示：(1)上、中、下游年均径流深分别为30、23、21 mm,产沙量为0.6、0.05、-0.02亿t。中游年均产流量占流域总水量的51%,上游年均产沙量占流域总沙量的90%以上。(2)上、中、下游径流深极显著减少,减少率分别为-0.28、-0.16、-0.43 mm/a;上游产沙量以0.02亿t/a速度极显著降低,中、下游产沙量不显著减少。(3)上、中、下游的削洪、补枯程度逐年代增加,与20世纪60年代比,21世纪10年代洪水期流量(Q₅)分别减少了63%、45%、60%,上游枯水期流量(Q₉₅)增加了68%,中游20世纪80年代枯水期开始产流。(4)与20世纪60年代比,上、中、下游21世纪10年代人类活动对产流量减少的贡献率分别为94.7%、26.7%...     

太平洋牡蛎同化率的研究

在室内实验条件下,研究了体重、饵料密度和质量对太平洋牡蛎同化率的影响.结果表明,太平洋牡蛎的滤水率、摄食率随个体的增大而增加,并且都符合幂函数模式:FR(IR)=aW^b.太平洋牡蛎同化率与其个体大小的关系不明显.饵料丰度和质量是影响太平洋牡蛎同化率的重要因素.随食物中有机物含量(POM/TPM)的增加,太平洋牡蛎的同化率也增加,随饵料密度的增加而降低.     

陕西黄龙山林区褐马鸡春季夜栖地选择

2006年4～6月,在陕西黄龙山林区,对褐马鸡(Crossoptilon mantchuricum)春季夜栖地的选择进行了研究.共记录到22个夜栖地,以夜栖树为中心做一个10 m×10 m样方,测定夜栖地海拔、坡向、坡度、坡位、地貌特征、夜栖树高度和胸径、乔木层盖度、乔木的数量、灌木层盖度、草本盖度、水源距离、人为干扰距离、林缘距离、栖枝高度和栖位上盖度等参数;通过9条样带测定54个随机样方,除栖枝高度和栖位上盖度外,指标相同.结果表明,褐马鸡春季夜栖地多偏向以坡度较大、山坡和山脊、接近水源、远离林边、人为干扰距离较远、乔木盖度和密度较大、栖树胸径较大、灌木层盖度和草本层盖度较小为主要特征的地方.主成分分析表明,前5个特征值的累积贡献率达到72.746%,可以较好地反映褐马鸡春季夜栖地生境特征.根据载荷系数绝对值大小,将褐马鸡春季夜栖地生境选择影响因子分别命名为地形和林下植被因子、气象因子、稳定性因子和水因子.影响褐马鸡夜栖地选择的关键因素是安全、舒适和栖息地转换的方便程度.     

冬小麦生长季不同灌溉模式对冬小麦-夏玉米产量与水分利用的影响

在华北平原黑龙港流域对冬小麦实行3种灌溉模式,研究了不同灌溉模式对冬小麦-夏玉米产量、耗水特性和水分利用效率的影响.结果表明:浇底墒水+拔节水处理(W2,75 mm+90 mm)和浇底墒水+拔节水+灌浆水处理(W3,75 mm+90 mm+60 mm)周年总产量均显著高于只浇底墒水处理(W1,75 mm),增幅分别为8.7%和12.5%.冬小麦全生育期对土壤水的消耗随灌溉量的增加而减少,夏玉米季总耗水量随冬小麦季灌溉量的增加而增加.W2处理冬小麦水分利用效率(WUE)比W3处理高11.1%,而其夏玉米水分利用效率(WUE)与W3处理差异不显著.W2和W1处理的周年水分利用效率(WUET)分别为21.28和21.60 kg.mm-1.hm-2,比W3处理分别高7.8%和9.4%.综合周年产量、耗水量和水分利用效率,W2是较好的节水丰产灌溉模式.     

不同降雨条件下坡长对喀斯特坡面土壤侵蚀的影响

基于2012-2014年对贵州省石桥小流域布设的5个坡长(5、10、15、20、25 m)径流小区的59次侵蚀性降雨条件下的产流产沙数据,分析不同降雨条件下喀斯特裸坡产流产沙与坡长的关系.结果表明:研究区坡面产流量随坡长的增加总体呈先减少后增加再减少的趋势,产沙量随坡长的增加先上升后下降.研究区59次侵蚀性降雨按降雨量...     

黄土丘陵区坡面植被盖度及其配置格局的水蚀效应模拟

黄土高原因土壤侵蚀严重被视为生态脆弱地带,探讨植被盖度及其所处坡位对土壤侵蚀的响应,对坡面侵蚀产沙的预测和调控具有重要意义。基于WEPP模型情景模拟,分析了分布广泛、耐旱性强的长芒草和典型恢复灌木植被柠条在不同雨强(0.5、1.0、1.5 mm/min)、不同植被盖度(20%、40%、60%、80%)和不同坡位(坡上、坡中、坡下)条件下的土壤侵蚀变化情况,运用双因素方差分析和相关贡献指数阐明坡面侵蚀产沙特征对坡位和植被盖度交互作用的响应,并提出植被配置的优化模式。结果表明:(1)提高植被有效覆盖度是减小土壤侵蚀的重要举措,且当植被分布在下坡位时坡面土壤侵蚀最少;(2)植被盖度可以有效减少产沙量。小雨强时,柠条和长芒草随盖度增加对泥沙的拦截率分别从38%增加到90%,64%增加到96%;中、大雨强时,植被盖度小于20%或者大于80%时,长芒草坡面产沙量大于柠条坡面。盖度为40%—60%时,长芒草坡面产沙量小于柠条坡面;(3)双因素方差分析表明:坡位和植被盖度对坡面侵蚀产沙量有极显著的影响(P0.001);当植被是长芒草时,坡位和植被盖度交互作用对坡面侵蚀产沙有显著影响(P0.01),植被是柠条时,坡位和植被盖度交互作用对坡面侵蚀产沙作用不显著;(4)通过模拟柠条和长芒草不同配置情景得出:长芒草分布在坡面下部产沙量较小,且当柠条和长芒草配比为1∶2时产沙量最小。     

云南纳帕海越冬黑颈鹤夜栖地特征

2009年11月至2010年4月对云南省香格里拉县纳帕海省级自然保护区越冬黑颈鹤(Grus nigricollis)的夜栖地的特征进行了调查.采用三角定位标图结合标志物校正法确定夜栖地方位,并进行实地校正.共记录夜栖地63个,均位于有水的斑块状沼泽中,基底大多有泥层,大部分(81.0%)有植被覆盖.夜栖地与人类活动区域和沼泽岸边有一定距离.与随机对照样地相比,夜栖地基底泥层较厚(Z=-2.365,P=0.018),明水面比例较大(Z=-3.086,P=0.002),离道路、村庄和农田较远(Z/t=-2.852～-2.334,P=0.008～0.020),水深在两者间有极显著差异(χ2=16.730,P=0.001).夜栖地利用前后对比发现沼泽斑块的面积有显著差异(t=2.977,P=0.021).主成分分析表明影响黑颈鹤夜栖地利用的因素依次为人类干扰、沼泽斑块大小和浅水环境状况.     

基于水蚀预报模型的黄土高原水平阶减流阻蚀效应模拟

黄土高原是我国土壤侵蚀最严重的地区,如何合理开展坡改梯工程对防治水土流失具有重要意义。本研究应用WEPP模型模拟坡面尺度降雨—侵蚀过程,模拟分析径流小区(10 m坡长)在不同坡度的水土流失特征和二阶、三阶水平阶在不同台面宽度(1,1.5,2 m)的减流阻蚀效应。结果表明:1)坡面尺度上,径流量和侵蚀量随坡度增加而增加。坡度达到20°时,径流量随坡度增加保持稳定,产沙量增加趋势渐缓;2)与坡面小区对比,二阶和三阶水平阶随台宽增加对地表径流调控率分别从6.5%增加到61.2%,从10.1%增加到69.7%;二阶水平阶在中(1.0 mm/min)、大(1.5 mm/min)雨强下,台面宽度大于1.5 m时产沙量小于坡面,泥沙调控率从1.1%增加到68.8%,三阶水平阶泥沙调控率从1.4%增加到82.3%;3)依据单位台宽减沙量,合理设计水平阶,使其减沙效益最大化。小雨强(0.5 mm/min)时,二阶、三阶水平阶的台面宽度达到1.5 m和1 m时可发挥优良的水土保持效果;中雨强(1.0 mm/min)时,台宽1.5 m的三阶水平阶效果最佳;大雨强(1.5 mm/min)时,则以2 m台宽的三阶水平阶效果更好。应用WEPP模型为定量评价工程措施的水土保持效益提供技术支撑。     

三峡水库支流拟多甲藻水华的形成机制

三峡水库支流的拟多甲藻水华发生已成为近年的常态,但是其发生机制依然不清楚。2009年到2011年期间,对拟多甲藻水华频发的童庄河回水区进行重点监测,并扩展到三峡水库长江干流及26条支流未淹没区和回水区浮游植物的四季调查。结果表明,四季调查中,拟多甲藻出现率、平均密度、最大密度和最大优势度,4月最高,相同季节,回水区最高。2—4月,童庄河回水区各点拟多甲藻密度均为升高到下降变化,最高密度自上游至下游大幅下降。2010年,拟多甲藻水华于2月最先在童庄河回水区上游出现,逐步向中下游发展,维持一定规模和时间后消退。与此同时,长江干流拟多甲藻出现率、密度和最大优势度大幅低于童庄河回水区。童庄河回水区发生(2005年、2007年和2010年)比不发生(2009年)拟多甲藻水华年份,三峡水库1—3月日出库流量(平均值4489.9—5623.3 m3/s)较小、1—2月水位日变幅(平均值0.148 m、0.246 m)和2月水位日升降(平均值-0.223 m)较大。研究认为,藻类在适宜水温时形成水华,2—4月支流回水区水温适宜、氮磷含量满足甲藻营养能力和生活习性需要。拟多甲藻能否形成水华,首先取决于回水区上游是否存在满足要求的水动力条件。其次,三峡水库出库流量、水位波动等水文条件,通过改变回水区上游水动力条件和回水区流速,影响水华能否形成及形成时间、程度、范围和维持时间。由于尺度效应不同,三峡水库相同水文条件对不同位置支流拟多甲藻水华形成的影响不一样。     

Impacts of hydropeaking and thermopeaking on the downstream habitat in the Dal River,Korea

Dams located upstream only release water during the period of hydropower generation. This induces short-term fluctuations of water discharge in the downstream reach, which is called hydropeaking. As occurs quite often, if the temperature of the water released form the upstream dam is different from the water that is flowing in the downstream reach, the water temperature also tends to show short-term fluctuations, which is called thermopeaking. This study investigates the impacts of both hydropeaking and thermopeaking on the downstream habitat. The study area is a 2.3 km long reach located downstream from the Goesan Dam in the Dal River, Korea. To assess such impacts, this study conducted physical habitat simulations. The CMS-Flow model was used for the computation of the flow and water temperature, and the GEP model for the habitat simulation. Three physical habitat variables, flow depth, velocity, and water temperature, were used. The Zacco platypus was selected as the target fish in the study area. Simulation results indicated that the hydropeaking flows significantly reduced both the CSI and the WUA when compared with the natural flow regime. In addition, the use of the water temperature in the physical habitat simulations further decreased both CSI and WUA, indicating that thermopeaking is as important as hydropeaking in this type of assessment.     

Effects of temperature gradients resulting from reservoir discharge on Dorosoma cepedianum spawning in the Savannah River

Synopsis The timing and spatial pattern of gizzard shad, Dorosoma cepedianum, spawning were markedly affected by a temperature gradient caused by the release of hypolimnetic water from an upstream reservoir into the middle reaches of the Savannah River. During 1983 and 1984, a distinct thermal gradient occurred with the warmest temperatures at the downstream end of the 257 km study reach and the coolest temperatures at the upstream end. The occurrence of gizzard shad larvae indicated that spawning began at the sample stations farthest downstream and progressed upstream, peaking at each sample station when it warmed to approximately 19° C. The estimated difference in date of peak density of larvae between the upstream and downstream ends of the gradient was 23 days in 1983 and 35 days in 1984. Because of this pattern, densities of larvae were highest at the downstream end of the study area early in the spawning season and highest at the upstream end of the study area late in the spawning season.Photoperiod and daylength appeared unrelated to the patterns under study. Far-reaching effects of anthropogenic temperature changes on fish spawning and the distribution of larvae are probably common in rivers that receive hypolimnetic discharge.     

Assessing Habitat Suitability for Juvenile Atlantic Salmon in Relation to In‐Stream Restoration and Discharge Variability

In‐stream restoration often aims at increasing the availability of the stream habitat suitable for salmonid fishes, thus creating potential for increased fish abundance. We assessed the success of in‐stream restoration of River Kiiminkijoki, northern Finland, by combining River2D habitat hydraulic modeling and fish density monitoring at the same sites, with data from multiple restored and reference reaches for 3 years both before and after restoration. We modeled the effects of restoration on the area suitable (weighted usable area, WUA) for juvenile Atlantic salmon from post‐hatching to age‐1 fish. Wetted width in the restored reaches increased by 8.1% on average compared with only ?0.2% change in the reference reaches. Habitat time series across 10 years showed significant increases in the amount of suitable habitat under summer conditions for both age‐0 and age‐1 salmon. However, improvement of overwintering habitats was marginal or nonexistent. Densities of age‐1 salmon showed no response to restoration. Low river discharge during the winter was correlated with low salmon densities the following summer. It thus appears that variability in wintertime discharge, and associated high interannual variation of WUA values, overrode the almost 20% increase in average post‐ versus pre‐restoration summertime WUA. Our study shows that the combination of hydraulic modeling and biological monitoring is a promising approach to stream restoration assessment.     

Impact of human activities on stonefly (Insecta,Plecoptera) ecological metrics in the Hron River (Slovakia)

A total of 57 stonefly species have been recorded in the Hron River. The natural gradient (slope and stream width) and pollution gradient of the river were defined using CCA based on physical, chemical and stonefly data. Stonefly metrics (abundance, richness/diversity, sensitivy/tolerance and functional metrics) were used to estimate the quality of the Hron River and the degree of proximity to its natural state. Similar results were obtained using two different methods. The first method was based on the homogeneity of variance and the interquartile range of different groups of stretches of the Hron River and the second was based on deviations from the expected values of biological metrics in a given stretch of the river. These values continuously decreased with increasing distance from the spring area, with the exception of the saprobic index, which increased in a downstream direction, and the stonefly average score, which did not change significantly along the whole river flow. The Stonefly Average Score (SAS) metric is universal for a variety of habitats such as the Hron River upstream and downstream, and is a reliable indicator of water quality and the natural course of a stream.     

Assessing the effect of Separation Levee Project on Chinese sturgeon (<Emphasis Type="Italic">Acipensor sinensis</Emphasis>) spawning habitat suitability in Yangtze River,China

Chinese sturgeon (Acipenser sinensis) is a protected anadromous fish species. The migration pattern of the fish has been blocked by the construction of Gezhouba Dam, reducing the natural spawning site length to less than 7 km along the Yangtze River. However, the fish has since established an alternative spawning ground in the narrow reach downstream of Gezhouba Dam. To enhance navigation, a Separation Levee Project (SLP) was implemented in the new-found spawning habitat of the fish. To therefore evaluate the effect of the SLP on Chinese sturgeon spawning habitat suitability, the conditions in the spawning habitat were simulated using River2D (a two-dimensional hydrodynamic model). Two main approaches (habitat kinetic energy and circulation metrics) were used in the simulation. The study showed that SLP only slightly changed the physical conditions in the spawning habitat. Using hydrodynamic simulation, the weighted usable area (WUA) before and after the SLP construction was also computed and habitat preference curve developed for water depth and velocity. On the average, SLP reduced WUA—a finding that was consistent with field-measured data. Based on WUA, the habitat conditions were more sensitive to SLP proximity than metrics based on velocity gradients. SLP posed detrimental impacts on the suitability of spawning habitats of Chinese sturgeon. The findings in this study provide further basis for the protection and restoration of Chinese sturgeon spawning habitats in especially the lower reach of Yangtze River.     

Contrasted impacts of climate change on stream fish assemblages along an environmental gradient

Aim To investigate the potential impacts of climate change on stream fish assemblages in terms of species and biological trait diversity, composition and similarity. Location One‐thousand one‐hundred and ten stream sections in France. Methods We predicted the future potential distribution of 35 common stream fish species facing changes in temperature and precipitation regime. Seven different species distribution models were applied and a consensus forecast was produced to limit uncertainty between single‐models. The potential impacts of climate change on fish assemblages were assessed using both species and biological trait approaches. We then addressed the spatial distribution of potential impacts along the upstream–downstream gradient. Results Overall, climate change was predicted to result in an increase in species and trait diversity. Species and trait composition of the fish assemblages were also projected to be highly modified. Changes in assemblages’ diversity and composition differed strongly along the upstream–downstream gradient, with upstream and midstream assemblages more modified than downstream assemblages. We also predicted a global increase in species and trait similarity between pairwise assemblages indicating a future species and trait homogenization of fish assemblages. Nevertheless, we found that upstream assemblages would differentiate, whereas midstream and downstream assemblages would homogenize. Our results suggested that colonization could be the main driver of the predicted homogenization, while local extinctions could result in assemblage differentiation. Main conclusions This study demonstrated that climate change could lead to contrasted impacts on fish assemblage structure and diversity depending on the position along the upstream–downstream gradient. These results could have important implications in terms of ecosystem monitoring as they could be useful in establishing areas that would need conservation prioritization.     

Physical habitat simulation for a fish community using the ANFIS method

This study presents physical habitat simulations for the fish community in a reach of the Dal River, Korea. The study reach is 2.3 km long, located downstream from the Goesan Dam. The reach is gravel-bed, including a bend. A riffle is present at the apex of the bend, and pools are located before and after the riffle. Field monitoring revealed that five fish species are dominant, namely Zacco platypus, Coreoleuciscus splendidus, Zacco temminckii, Pungfungia herzi, and Acheilognathus yamatsute, and account for 78% of the total fish community. These five fishes, which include both lotic and lentic fishes, were selected as target species. The Center for Computational Hydroscience and Engineering 2D (CCHE2D) model, a 2D shallow water equation solver, and the Adaptive Neuro Fuzzy Inference System (ANFIS) method were used for hydraulic and habitat simulations, respectively. The Mahalanobis distance method was used for identifying outliers in the monitoring data. It was shown that the ANFIS method combined with data quality assessment predicts the Composite Suitability Index (CSI) better than the method without it. The CSI distributions in the study reach are presented for various flows. It was found that the distributions of the combined CSI predicted by the ANFIS method are higher than those predicted by the conventional multiplicative aggregation method with Habitat Suitability Curves (HSCs). In addition, it was revealed that the discharge that yields the maximum Weighted Usable Area (WUA) for the whole fish community is more than twice the discharge yielding the maximum WUA for a single target species. This increased discharge leads to a 58% increase in the maximum WUA for the fish community.     

黄河流域鱼类食性同资源种团的时空变化

鱼类资源保护是黄河流域生态保护和高质量发展的重要环节.通过历史资料整理和野外调查发现,1960-2019年,黄河流域共分布鱼类16目35科201种.其中,鲤形目物种数最多,占比60.7％;鲈形目次之,占比10.0％.1960-1980年分布鱼类15目28科182种;1980-2019年分布鱼类10目23科112种.源区...     

Interim Hydrologic Responses to Phase I of the Kissimmee River Restoration Project,Florida

Hydrologic conditions were evaluated during a 10‐year Interim Period following completion of Phase I of the Kissimmee River Restoration Project and initiation of environmental water releases from upstream to provide adaptive management of flow to the Phase I area. Phase I construction backfilled 13 km of flood control canal C‐38 and redirected flow into 22 km of reconnected river channel. Evaluations focused on five restoration expectations (performance measures) based on pre‐channelization hydrologic data for the Kissimmee River. Environmental releases resulted in more continuous discharge from upstream, but did not affect the magnitude of discharge. After backfilling of C‐38, water levels in the Phase I area varied with discharge and periodically inundated the floodplain. However, the long, annual recession event, characteristic of pre‐channelization, was not reestablished; instead, most Interim Period years had multiple events with shorter durations and faster recession rates. Mean channel water velocity increased during the Interim Period but was not always in the desired range. Hydrologic conditions throughout much of the Phase I area were affected by the backwater effect of the downstream water control structure. Four expectations showed improvements in terms of number of years met; however, none met the expectation targets. The inability to meet expectation targets reflects in part the incomplete or interim status of the restoration project.     

White sturgeon (Acipenser transmontanus) passage at the Dalles Dam, Columbia River, USA

White sturgeon (Acipenser transmontanus) ≥95 cm TL were monitored using acoustic and radio telemetry at a large hydroelectric dam (the Dalles Dam) on the Columbia River, during March 2004 through November 2005 to determine timing and routes of passage and to characterize general movements. Transmitters were surgically implanted into 148 fish during the study; 90 were released into the tailrace and 58 into the forebay. We documented 26 passage events by 19 tagged fish: eight upstream via fish ladders and 18 downstream, mostly through open spill gates. During the study 17 fish entered the two ladders one or more times; 11 entered only the east ladder, three entered only the north ladder, and three entered both ladders at sometime. Residence time within the ladders by individual fish was variable, ranging from about 1 min to nearly 6 months (median = 7.7 h). Only six fish successfully ascended the east ladder, one fish twice. We could not unequivocally determine which fish ladder one fish used to pass upstream. Differences in construction between the north and east fish ladders may account for the greater success of the east fish ladder in passing sturgeon upstream. Changes to operations at hydroelectric dams to benefit migrating anadromous salmonids may influence upstream or downstream passage by white sturgeon. Altering patterns and timing of spill discharge, altering fish ladder entrance attraction flows, and the use of lights, sound, and partial barriers to direct other species of fish to preferred passage routes have unknown effects on sturgeon passage. A better understanding of the consequences to the metapopulation of increasing or precluding upstream or downstream passage is needed.