Exploring the potential for a multi-decadal midsummer streamflow reconstruction of the upper Samalá river basin in Guatemala using an Abies guatemalensis tree-ring chronology

The Samalá River in western Guatemala is critical for sustaining diverse agricultural production systems, from staple crop production in the upper basin to sugar cane in the lowlands. The streamflow from the Samalá River also supports hydroelectric power generation within the basin. The watershed is home to more than a hundred settlements including cities, towns, and villages, some of which have experienced extreme hydrological events, including destructive flooding from the river. However, the Samalá River streamflow record, only 38 years in length (1979–2016), is too short to assess the full range of hydrological variability for this economically important region, including Guatemala’s second largest city –Quetzaltenango. This paper presents a tree-ring based reconstruction of mean August streamflow for 125 years (1889–2013). Our results suggest that annual tree-ring width measurements from Abies guatemalensis are correlated with monthly mean streamflow records in the upper Samalá River basin. This association seems to be modulated in part by variability in the ENSO 3.4 region in the Pacific Ocean, suggesting decreased streamflow during the warm events of the sea surface temperature in the Pacific Ocean. The record indicates that single year events of low streamflow dominate the record. Nevertheless, a period of up to 8 consecutive years below-average streamflow is shown in the record between 1905 and 1912. Overall, this extended record of streamflow suggests that tree-ring studies in the area have the potential to provide useful inputs in the future that can be utilized by stakeholders and decision-makers within the Samalá watershed involving the management of discharge for crop irrigation, hydropower production, and disaster mitigation.     

基于雪岭云杉树轮宽度重建过去339年天山中部巴音布鲁克地区夏季NDVI

归一化差异植被指数(NDVI)被广泛应用于植被研究的各个领域,但由于观测时长较短,难以满足长时间尺度的研究需要。基于巴音布鲁克地区雪岭云杉建立了树轮宽度年表(STD),计算年表和NDVI同气象观测数据的相关系数。结果表明:树轮宽度指数和NDVI均与同时段的气象数据具有显著相关。结合宽度年表与6—8月NDVI间的显著正相关(r=0.7,P＜0.01,n=38),使用回归模型重建了研究区过去339年的夏季(6—8月)NDVI变化序列,在1680—2018年,重建序列有4个高植被覆盖时段(1738—1765、1786—1798、1964—1973和2000—2018年)和5个低植被覆盖时段(1690—1714、1825—1834、1850—1880、1895—1920和1945—1955年)。重建结果也反映了天山中部水文气候。与周边重建的对比显示,当开都河径流量增加,且研究区处于较为潮湿的环境时,植被覆盖相对较高,反之植被覆盖偏低。重建序列的极值也捕捉了历史文献中一系列自然灾害。混合单粒子拉格朗日综合轨迹模型(HYSPLT)后向轨迹模型和风场分析表明,NDVI异常受到西风带来的降水影响。     

An exploration of the controls of pre-instrumental streamflow using multiple tree-ring proxies

Previous studies have used tree-ring chronologies from several species to develop reconstructions of precipitation, temperature, streamflow and glacier mass balance for sites in Banff National Park, Alberta. This study examines the variability in a >300-year summer streamflow reconstruction for the Bow River at Banff in conjunction with changes in the major contributors to streamflow (glacier melt, winter and summer pecipitation). Reconstructed winter mass balance for Peyto Glacier is used as a surrogate for winter precipitation and April–August precipitation is reconstructed for Banff. Streamflow variability correlates most highly with winter precipitation and periods of high flow follow above average snowfall in the previous winter (high winter balance) and in some cases also with above normal summer precipitation. A clear response to changes in summer mass balance at Peyto Glacier (i.e. summer glacier melting) cannot be identified in this summer discharge record. Problems developing physically realistic flow reconstructions for snowmelt dominated rivers from summer sensitive tree-ring chronologies are also discussed.     

Radial growth response of Populus xjrtyschensis to environmental factors and a century-long reconstruction of summer streamflow for the Tuoshigan River,northwestern China

Broad-leaved tree species have rarely been used in dendroclimatology and dendrohydrology in arid Central Asia. Core samples of Populus xjrtyschensis Ch. Y. Yang were collected along the Tuoshigan River in 2015. Correlation and response analyses indicate that the radial growth of P. xjrtyschensis shows a strong relationship to streamflow and a weak response to climate. We suggest that summer streamflow is a limiting factor for the radial growth of P. xjrtyschensis along the Tuoshigan River. Using tree-ring data from P. xjrtyschensis, we reconstructed the historical summer streamflow of the Tuoshigan River back to 1900. The reconstruction has an adjusted r² of 0.407 (1957–2006). Statistical verification methods and historical documents indicate that the reconstructed series is stable and reliable. The results reveal that the beginning of the 20th century and the end of the 20th century to the present experienced above average streamflow, while the mid-20th century was characterized by a long dry period. The reconstructed streamflow data series revealed 6-yr (99%), 11-yr (95%) and 17–25-yr (99%) cycles. We suggest that variability in summer streamflow of the Tuoshigan River may be related to solar activity and large-scale oscillations in the climate system.     

A dry season streamflow reconstruction of the critically endangered Formosan landlocked salmon habitat

This study presents a 259-year (1750–2008 CE) reconstruction for October to February (ONDJF) standardized streamflow index of the Chichiawan Stream, the sole habitat of the critically endangered Formosan landlocked salmon (Oncorhynchus formosanus) remaining natural population. The reconstruction was based on the earlywood ring-width variations of Taiwan Douglas-fir (Pseudotsuga wilsoniana), using ensemble empirical mode decomposition for chronology development. Results showed that a higher average ONDJF streamflow in the 1968–2008 period was positively associated with a wider Taiwan Douglas-fir earlywood ring. During that period, the average ONDJF streamflow was related to the Pacific Decadal Oscillation and El Niño-Southern Oscillation development. Spectral analysis indicated that the reconstructed index had significant peaks around 2∼7 years and less significant peaks around 20–35 years. Based on the derived and reconstructed indices, most of the average ONDJF streamflow between 1750 and 2008 was within the normal range. Furthermore, there was no statistical evidence to suggest that the flow regime of the last few decades had changed, which refuted the speculation that the dry season streamflow natural variability in the 1960s and 1970s might have contributed toward the critically endangered status of Formosan landlocked salmon. The results of this study will be useful for developing short- to mid-term strategies to protect the endangered species and manage water resources.     

水文变异下的黄河流域生态流量

使用t检验和Mann-Whitney U检验对黄河干流7个水文站月均流量进行水文变异分析,探讨了水文变异成因,在此基础上,确定变异前各月月均流量序列最适概率分布函数,将概率密度最大的月平均流量定义为河道内生态流量。经与Tennant法、最小月平均流量发和逐月径流法比较,考虑水文变异的河道内生态流量计算方法是可行、合理的。水文变异后,黄河干流7水文站月均流量普遍减少,月均流量满足河道内生态流量的频率降低。研究结果表明,人类活动是黄河生态系统水环境恶化的重要原因。在流域生态管理中,确保变异后生态流量满足频率与变异前相当。研究对于理解在当前气候变化与人类活动双重影响下,干旱半干旱区流域水资源科学管理具有一定理论与现实意义。     

A new 500-year reconstruction of Truckee River streamflow

The Truckee River Basin, located on the Nevada-California border, is an area of extreme hydrologic variability, being subject to both prolonged multi-decadal droughts and devastating floods; however, due to the brief instrumental record, understanding of the full range of this variability is limited. To assist local water managers assess the post-2000 drought in the context of historic droughts, this study revisits the first tree-ring reconstruction of Truckee River runoff: Hardman and Reil (1936). Incorporating their original 1930s tree cores as well as newly sampled material, three new site chronologies were developed and combined with other regional chronologies to produce a 1491–2003 reconstruction of Truckee River streamflow, an over 400-year extension of the instrumental record and 230 years longer than the previous reconstruction, providing new insights into the basin’s natural variability. In addition to evidence of extended droughts and extreme high streamflow years, this reconstruction shows a marked hydroclimatic shift centered around the 1850s. Prior to then, the Truckee River experienced decadal to multi-decadal periods of higher than average streamflow; subsequently, these periods have been decreasing in length with only two instances above three consecutive years of high streamflow since 1900. Whether this represents fundamental shift to a new hydroclimatic regime remains unclear. However, as global temperatures continue to rise, fewer long-term high streamflow episodes may have lasting impacts on water availability in the basin, raising the question further of whether the post-2000 drought is a new megadrought or a sign of aridification.     

Streamflow reconstruction of Eastern Himalaya River,Lachen ‘Chhu’, North Sikkim,based on tree-ring data of Larix griffithiana from Zemu Glacier basin

The relationship of streamflow records of the Lachen River with tree-ring parameters of total tree-ring width (TRW), earlywood width (EWW) and latewood width (LWW) chronologies of Larix griffithiana from Lachen, North Sikkim, Eastern Himalaya was generated. These chronologies correlate significantly with the observed discharge of the Lachen River where the EWW chronology explains 61.2% of the streamflow variance. Based on this result, Lachen River discharge for the period of previous year March to current year February was reconstructed using EWW chronology, which extends back to AD 1790. In the smoothed reconstructed data the period of extreme low streamflows were during AD 1791–1805, 1813–1822 and 1914–1925 and the extreme highs were during AD 1823–1835, 1879–1890, 1926–1946 and 1980–1989. The streamflow is also found to be lower than average during the monsoon failure (or East India Drought) of AD 1792–1796 and past great droughts of AD 1876–1878. The lower tree growth during AD 1816–1822 is consistent with that of the Tambora volcanic eruption of Indonesia in AD 1815. High spectral power at 4–8 years in the reconstructed streamflow is similar to that of ENSO range.     

水文变异条件下鄱阳湖流域的生态流量

受气候变化和人类活动综合影响,鄱阳湖流域水文状况发生变异。河流生态系统适应了变异前的水文状况,变异后势必会影响当地生态系统。基于此,采用8种变异检测方法对水文变异进行综合诊断,阐明水文变异原因。在此基础上,采用15种概率分布函数分别拟合5站各月变异前日流量序列,最终确定5站点各月最优分布函数及所对应的概率密度最大处的流量,即得河道内生态流量。研究表明:(1)抚河于1962年发生弱变异,赣江、修河于1968年发生中变异,信江、饶河于1991年发生弱变异;(2)变异后,赣江、信江、饶河、修河生态需水满足率平均上升11%,抚河生态需水满足率下降32%;(3)水文变异增加提高生态需水满足率,水利工程建设降低年均生态需水满足率、提高干季生态需水满足率。高森林覆盖率提高干季生态需水满足率,对年均生态需水满足率影响不明显。研究结果为鄱阳湖流域水资源管理及区域水资源规划与配置提供重要科学依据。     

Growing-season precipitation since 1872 in the coastal area of subtropical southeast China reconstructed from tree rings and its relationship with the East Asian summer monsoon system

Tree rings from temperate zones of the world have provided abundant palaeo- ecological and paleo-hydroclimatic information. However, tree rings from subtropical to tropical regions remain relatively scarce, which greatly limit our fully understanding about the climate change issues. In the present work, tree-ring-width (TRW) measurements of Masson pine from Fujian province, the coastal area of subtropical southeast China were successfully crossdated and a TRW STD chronology was developed from 1854 to 2012. Significantly positive correlation was identified between the tree rings and April–November total precipitation (r = 0.71, p < 0.01). The reconstructed April–November precipitation exhibited two comparatively wet (1876–1886 and 1957–1962) and one comparatively dry (1986–2004) periods. An evident drying trend since 1959 was seen and it was mitigated after 1993. Most of the extreme low-precipitation years in the reconstruction were supported by the historical records. As revealed by the spatial correlation patterns, our precipitation reconstruction was also consistent with other hydroclimatic records along the coastal areas of southeast China, proving its ability to capture the large-scale hydrological signal in southeast China (mainly refers to the south of the middle-lower reaches of Yangtze River). The reconstructed precipitation showed significant correlation with the East Asian summer Monsoon (EASM) index. Moreover, it also indicated simultaneous variation with the monsoon precipitation in North China on a decadal scale, implying that growing season precipitation variations in both regions were influenced by the EASM strength. This work highlights the potential of using tree-ring width to reconstruct precipitation in subtropical southeast China, while the relevant issues about precipitation variation in this region is far from resolved.     

黄土高原流域水沙变化研究进展

人类活动和气候变化是影响流域水文过程的两大驱动因素,径流输沙是流域水文过程的总体反映,变化环境下径流输沙的变化规律与成因分析是水文学和全球变化研究的热点问题。黄土高原是我国水土流失最严重的地区。20世纪50年代以来,黄土高原地区开展了大规模的生态环境建设和水土流失综合治理,显著改变了流域土地利用和植被覆盖。下垫面条件改变与气候变化综合作用,使得流域水沙情势发生剧变。围绕黄土高原流域水沙变化的时空尺度特征与驱动机制,总结了径流输沙和水沙关系变化特征的研究结果,归纳了径流输沙变化的归因分析方法与人类活动和气候变化影响的贡献分割结果,探讨了气候变化、植被恢复、水土保持工程措施以及流域景观格局对水沙变化的影响机制。未来应加强流域水沙演变的时空尺度特征特别是水沙关系非线性特征的定量研究,阐明极端事件对水沙动态的影响与贡献;开展水沙变化影响机制的多要素综合解析,发展耦合地表覆被动态特征和气候变化的降雨-径流-输沙模型,揭示生态恢复与水沙演变过程互馈机制;开展未来气候变化、社会经济发展和生态建设工程情景下水沙动态的趋势预测,为黄土高原生态综合治理和水资源管理与黄河水沙调控提供策略建议。     

Unraveling past impacts of climate change and land management on historic peatland development using proxy‐based reconstruction,monitoring data and process modeling

Peatlands represent globally significant soil carbon stores that have been accumulating for millennia under water‐logged conditions. However, deepening water‐table depths (WTD) from climate change or human‐induced drainage could stimulate decomposition resulting in peatlands turning from carbon sinks to carbon sources. Contemporary WTD ranges of testate amoebae (TA) are commonly used to predict past WTD in peatlands using quantitative transfer function models. Here we present, for the first time, a study comparing TA‐based WTD reconstructions to instrumentally monitored WTD and hydrological model predictions using the MILLENNIA peatland model to examine past peatland responses to climate change and land management. Although there was very good agreement between monitored and modeled WTD, TA‐reconstructed water table was consistently deeper. Predictions from a larger European TA transfer function data set were wetter, but the overall directional fit to observed WTD was better for a TA transfer function based on data from northern England. We applied a regression‐based offset correction to the reconstructed WTD for the validation period (1931–2010). We then predicted WTD using available climate records as MILLENNIA model input and compared the offset‐corrected TA reconstruction to MILLENNIA WTD predictions over an extended period (1750–1931) with available climate reconstructions. Although the comparison revealed striking similarities in predicted overall WTD patterns, particularly for a recent drier period (1965–1995), there were clear periods when TA‐based WTD predictions underestimated (i.e. drier during 1830–1930) and overestimated (i.e. wetter during 1760–1830) past WTD compared to MILLENNIA model predictions. Importantly, simulated grouse moor management scenarios may explain the drier TA WTD predictions, resulting in considerable model predicted carbon losses and reduced methane emissions, mainly due to drainage. This study demonstrates the value of a site‐specific and combined data‐model validation step toward using TA‐derived moisture conditions to understand past climate‐driven peatland development and carbon budgets alongside modeling likely management impacts.     

Hydroclimatic variability of the upper Nazas basin: Water management implications for the irrigated area of the Comarca Lagunera,Mexico

Earlywood ring-width chronologies derived primarily from Douglas-fir trees were used to reconstruct winter–spring (November–May) precipitation and fall–spring (September–June) streamflow volumes for the period 1765–1993 in the forested upper Nazas watershed in Durango, Mexico. The tree-ring data were obtained from mixed conifer stands within or adjacent to the upper Nazas watershed. Precipitation data were derived from one of the longest regional records. The streamflow data were obtained from a guage located in the upper Nazas watershed. The Principal Component 1 (PC1) of nine residual earlywood chronologies accounted for 73% of the variance in November–May precipitation 1967–1993, and 64% for the total period with available data 1941–1993. The mean of three residual earlywood chronologies from Douglas-fir explained 51% of the normalized streamflow at Sardinas from 1971–1992. The 20th century was characterized by severe droughts, especially between 1950 and 1963 that also affected other regions of Mexico and the southwestern United States. Additional droughts of similar or greater magnitude occurred in the 1790s, 1810s, 1860–1870s and 1890–1910s. Similar periods of low flow occur in the September–June streamflow reconstruction between 1765 and 1993. These results indicate that tree-ring chronologies from this region document a high percentage of the precipitation and streamflow variance. Spectral analysis detected significant high periodicities in both records at peaks of 4 and 7 years that could be related to the ENSO frequency bands (approximately 4.0 and 6.25 years). Analysis of the reconstructed records show strong influence of ENSO on precipitation and streamflow amounts on an interannual basis. These results can provide significant inputs to decisions regarding management of water resources that are used to irrigate land in the Comarca Lagunera: specifically they indicate that water budgeting should be managed over longer time periods to account for this ENSO-related variability rather than on the year-to-year basis that is presently used.     

气候变化对淮河流域中上游汛期极端流量影响的SWAT模拟

致洪暴雨主要是3天以上连续强降水,是淮河流域洪涝的直接原因。构建淮河流域中上游SWAT模型,用RegCM3在SRES A2排放情景下的模拟结果(2071-2100年)驱动SWAT模型,研究气候变化对淮河流域中上游汛期极端流量的影响。结果表明:(1)在SRES A2排放情景下,淮河流域中上游未来(2071-2100年)气温升高,降水量增加,降水的空间差异增大;颖河流域中游年降水量有较大幅度的减少,呈现暖干化的趋势;汛期极端过程降水增加,汛期最大9 d降水量平均增幅都在10%以上。(2)在SRES A2排放情景下的气候变化将导致淮河流域中上游汛期极端流量大幅度增加,干流5个水文站汛期最大9 d平均流量的增幅都在20%以上。(3)淮河流域中上游极端流量的概率分布更加集中,更大的极端流量出现的频率更高,研究流域下游更容易出现较大的极端流量。(4)研究流域下游极端流量概率对极端流量变化更敏感,下游也面临着更大的洪涝风险。     

Remarkable genetic divergence of Gymnodiptychus dybowskii between south and north of Tianshan Mountain in northwest China

Gymnodiptychus dybowskii is endemic to Xinjiang, China and has been locally listed as protected animals. To investigate its genetic diversity and structure, specimens were collected from six localities in Yili River system and Kaidu River. Fragments of 1092bp Cyt b gene were sequenced for 116 individuals. A total of 21 haplotypes were found in all samples, and no haplotype was shared between Yili River system and Kaidu River population. Sequence comparisons revealed 123 variable sites, with eight singleton sites and 115 parsimony informative sites. For all the populations examined, the haplotype diversity (h) was 0.8298 ± 0.0226, nucleotide diversity (π) was 0.2521 ± 0.1202, and average number of pairwise nucleotide differences (k) was 275.3369 ± 118.5660. AMOVA analysis showed that the differences were significant for total populations except for Yili River system populations. The pairwise F_st values revealed same conclusion with AMOVA analysis: Kaidu River population was divergent from Yili River system populations. The genetic distance between two groups was 0.108 and the divergence time was estimated at 5.4–6.6 Ma, the uplift of Tianshan Mountain might have separated them and resulted in the genetic differentiation. The neutrality test and mismatch analysis indicated that both two groups of G. dybowskii had went through population expansion, the expansion time of Yili River system and Kaidu River population was estimated at 0.5859–0.7146 Ma and 0.5151–0.6282 Ma, respectively. The climate changes of Qinghai-Tibetan Plateau might have influenced the demographic history of G. dybowskii.     

Tree-ring-based reconstruction of drought variability (1792–2011) in the middle reaches of the Fen River,North China

We developed a tree-ring chronology based on 52 ring-width series from 25 Pinus tabulaeformis trees at Tianlong Mountain (TLM) using the signal-free method. TLM is located in the middle reaches of the Fen River, North China, and is influenced by the East Asian monsoon system. Tree growth was highly correlated (0.789) with the Palmer Drought Severity Index (PDSI) from May to July and indicated a drought-stress growth pattern. Therefore, we developed a robust May-July PDSI reconstruction for 1792–2011 that explained 62.3% of the instrumental variance for 1951–2005. Severe drought years determined by the reconstruction are consistent with conditions reported in historical documents. The TLM PDSI reconstruction was consistent with other tree-ring-based hydroclimate reconstructions in North China; thus, it may accurately represent dry/wet changes that occur over a large area. Cyclical spectral peaks at 2–8 years in the reconstructed PDSI may indicate ENSO activity, as suggested by the positive correlation with the western Pacific sea-surface temperatures (SSTs) and the negative correlation with the eastern Pacific SSTs on the inter-annual scale.     

基于多水文改变指标评价东江流域河流流态变化及其对生物多样性的影响

新丰江、枫树坝和白盆珠3座大型水库的建立对东江流域河道流量和河流流态过程有了较大改变,威胁河道下游生态系统的健康。基于广义指标生态剩余和生态赤字评价了东江流域受水库影响后流域生态需水需求目标总的盈余和缺失变化过程,基于IHA32指标计算的Do和DHRAM评价了水库对下游河段河流水文过程总的改变程度以及威胁河道生态系统健康的风险性大小,并进一步分析了对河道生物多样性的影响。研究结果如下:(1)水库对流量历时曲线(FDC)有显著影响,曲线上部下降,尾部上升,尤其体现在秋季和冬季。降水对年与夏季生态剩余影响较大,水库对各季节生态剩余和生态赤字均有较大影响:秋季和冬季生态赤字几乎为0,生态剩余显著增加。生态剩余和生态赤字与大部分IHA中32个指标具有很强的相关性,可作为衡量东江流域年和季节径流变化的生态指标。(2)龙川、河源、岭下和博罗4站点总体改变程度分别为58.48%、54.04%、54.32%和52.47%。河流流态变化导致总季节生态剩余增加并维持在较高水平,进一步引起河流生物多样性下降,并维持在较低水平。龙川和河源两站河流流态的变化对河流生态系统造成了高风险性影响,岭下和博罗两站则为中等风险。     

An improved reconstruction of May–June precipitation using tree-ring data from western Turkey and its links to volcanic eruptions

We developed a high quality reconstruction of May–June precipitation for the interior region of southwestern Turkey using regional tree-ring data calibrated with meteorological data from Burdur. In this study, three new climate sensitive black pine chronologies were built. In addition to new chronologies, four previously published black pine chronologies were used for the reconstruction. Two separate reconstructions were developed. The first reconstruction used all site chronologies over the common interval AD 1813–2004. The second reconstruction used four of the chronologies with a common interval AD 1692–2004. R ² values of the reconstructions were 0.64 and 0.51 with RE values of 0.63 and 0.51, respectively. During the period AD 1692–1938, 41 dry and 48 wet events were found. Very dry years occurred in AD 1725, 1814, 1851, 1887, 1916, and 1923, while very wet years occurred in AD 1736, 1780, 1788, 1803, and 1892. The longest dry period was 16 years long between 1860 and 1875. We then explored relationships between the reconstructed rainfall patterns and major volcanic eruptions, and discovered that wetter than normal years occurred during or immediately after the years with the largest volcanic eruptions.     

Long-term trends in streamflow from semiarid rangelands: uncovering drivers of change

In the last 100 years or so, desertification, degradation, and woody plant encroachment have altered huge tracts of semiarid rangelands. It is expected that the changes thus brought about significantly affect water balance in these regions; and in fact, at the headwater‐catchment and smaller scales, such effects are reasonably well documented. For larger scales, however, there is surprisingly little documentation of hydrological change. In this paper, we evaluate the extent to which streamflow from large rangeland watersheds in central Texas has changed concurrent with the dramatic shifts in vegetation cover (transition from pristine prairie to degraded grassland to woodland/savanna) that have taken place during the last century. Our study focused on the three watersheds that supply the major tributaries of the Concho River – those of the North Concho (3279 km²), the Middle Concho (5398 km²), and the South Concho (1070 km²). Using data from the period of record (1926–2005), we found that annual streamflow for the North Concho decreased by about 70% between 1960 and 2005. Not only did we find no downtrend in precipitation that might explain this reduced flow, we found no corresponding change in annual streamflow for the other two watersheds (which have more karst parent material). When we analyzed trends in baseflow (contributions from groundwater) and stormflow (runoff events linked to specific precipitation events), however, we found that in spite of large increases in woody plants, baseflow for all the watersheds has remained essentially consistent or has increased slightly since 1960. At the same time, stormflows were of smaller magnitude. Animal numbers have declined precipitously in the latter half of the last century. We suggest that these lower stormflows result from generally higher soil infiltrability due to generally improving range condition. There is no indication that the decline in streamflow is related to diminished groundwater flows caused by extraction of subsurface water by woody plants.     

Temporal and spatial distribution of young Brachyplatystoma spp. (Siluriformes: Pimelodidae) along the rapids stretch of the Madeira River (Brazil) before the construction of two hydroelectric dams

Monthly (April 2009 to May 2010) bottom‐trawl sampling for Brachyplatystoma species along the rapids stretch of the Madeira River in Brazil revealed that Brachyplatystoma rousseauxii larvae and juveniles were present in low abundances in all areas and during all hydrological periods. The presence of larvae and juveniles throughout the hydrological cycle suggests asynchronous spawning in the headwaters of the Madeira River.