Beaver dams,streamflow complexity,and the distribution of a rare minnow,Lepidomeda copei

Freshwater fishes are threatened globally, and often too little is known about threatened species to effectively guide their conservation. Habitat complexity is linked to fish species diversity and persistence, and degraded streams often lack habitat complexity. Beaver Castor spp., in turn, have been used to restore streams and increase habitat complexity. The northern leatherside chub Lepidomeda copei is a rare, small‐bodied, drift‐feeding minnow that has anecdotally been observed to use complex habitats associated with beaver dams in the western United States. To investigate this anecdote, we conducted fish and habitat surveys, the latter focusing on quantifying habitat complexity, in a sub‐basin of the Upper Snake River Basin in the USA. Complementary generalised linear model and path analyses revealed that northern leatherside chub occurred more often at sites with complex streamflows, and streamflows were more complex when beaver dams were present and pools were deeper. Northern leatherside chubs were also more likely to occur when temperatures were warmer, aquatic macrophytes were abundant and stream channels were narrow and deep. The linkage between chubs, complex streamflows and beaver dams needs to be evaluated more broadly to completely understand its role in the rangewide status of the species. However, it does suggests that increased use of beaver reintroductions and dam analogues for stream restoration could be a boon for the northern leatherside chub, but such efforts should be monitored to determine their effectiveness to help adapt beaver‐based restoration approaches to best benefit the species.     

Changes in photosynthesis,growth, and sugar content of commercial sugarcane cultivars and Erianthus under flood conditions

Sugarcane (Saccharum spp.) is an economical crop in the tropical and subtropical countries. However, because of global climate change, flooding has become problematic, particularly during the rainy season, in Thailand. We investigated the effects of floods on three commercial sugarcane cultivars, namely NiF8, U-thong 6 (UT6), and U-thong 9 (UT9), as well as Erianthus spp. Growth was assessed using a pot experiment in a glasshouse with two treatments: (1) control and (2) 60 d of flooding followed by 30 d of normal conditions. In comparison with control, during prolonged flooding, Erianthus showed greatly decreased CO₂ assimilation, whereas NiF8, UT6, and UT9 showed slightly declined CO₂ assimilation. Growth in plants subjected to 60 d of flooding was less influenced by floods while sucrose content was not affected except in UT6. During flooding, some roots died, resulting in plants compensating adventitious roots to offset the negative effects of root death and to assist them in maintaining their growth, which appeared from the submerged nodes, with different characteristics for each cultivar. However, 30 d after draining, roots remained damaged, while adventitious roots died, resulting in lesser growth as compared with the control, but it did not significantly affect sucrose content and sugar yield. This study suggests that sugarcane plants need to produce the adventitious roots to compensate their roots’ death during flooding and require time to recover their root system after flooding for obtaining the optimum yield and quality at harvest.     

Impact of soil water content on maize responses to the plant growth-promoting rhizobacterium Azospirillum lipoferum CRT1

Members of the bacterial genus Azospirillum are root-associated bacteria that increase yield in cereals by promoting growth and alleviating drought stress. How plants integrate the many bacterium-derived growth-promoting stimuli with other environmental factors to generate a coordinated response remains unresolved. Using a commercial Azospirillum strain, A. lipoferum CRT1 and two host maize cultivars, it was observed that bacterization reduced the drought-induced increase in lateral root growth and enhanced the flood-induced increase in lateral root growth in the more drought- and flood-sensitive cultivar. In the other one, A. lipoferum CRT1 only elicited a moderate root growth response under low soil water potential. The photosynthetic potential and activity were increased in the earlier cultivar and decreased in the later one, irrespective of the soil water content. No impact of the bacterium was seen on the growth of the leaves of both cultivars under both stresses until the third leaf stage, therefore suggesting that it is a consequence of multiple primary adaptations to biotic and abiotic stresses. It is suggested that host–bacteria recognition leads to a stress-specific modulation of the root response and a differential stress-independent effect on photosynthesis. This is the first report of the impact of Azospirillum under flood conditions.     

湖北省分地区水灾损失等级划分初探

建立了湖北省分地区水灾损失灾度等级的划分标准。基于模糊模式识别理论，按最大隶属原则和择近原则对灾度等级进行了模糊综合评判。     

发展我国洪水保险的制度思考——美国洪水保险制度的借鉴与启示

洪水保险是一项重要的非工程防洪措施.美国是世界上最早建立国家强制性洪水保险体制的国家,经过艰难曲折的探索,闯出了一条成功之路.我国的洪水保险体制还处于积极探索阶段.中美两国尽管国情差异较大,但以洪水保险作为推进洪泛区洪水风险管理的经济手段,并以立法和国家计划等措施来保障实施的作法是值得借鉴的.本文就美国洪水保险制度的发展与沿革,寻找对我国建立洪水保险制度一些有益的启示,并就此提出了一些建设性意见.     

Germination ecology of seeds of the annual weeds Capsella bursa-pastoris and Descurainia sophia originating from high northern latitudes

Low temperatures may inhibit dormancy break in seeds of winter annuals, therefore it was hypothesized that seeds of Capsella bursa‐pastoris and Descurainia sophia that mature at high latitudes in late summer–early autumn would not germinate until they had been exposed to high summer temperatures. Consequently, germination would be delayed until the second autumn. Most freshly matured seeds of both species collected in August and September in southern Sweden were dormant. After 3 weeks of burial at simulated August (20/10°C) and September (15/6°C) temperatures, 28 and 27%, respectively, of the C. bursa‐pastoris and 56 and 59%, respectively, of the D. sophia seeds germinated in light at 15/6°C. In contrast, in germination phenology studies conducted in Sweden, only a few seeds of either species germinated during the first autumn following dispersal. However, there was a peak of germination of both species the following spring, demonstrating that dormancy was lost during exposure to the low habitat temperatures between late summer and early autumn and spring. Nearly 100% of the seeds of both species subjected to simulated annual seasonal temperature changes were viable after 30.5 months of burial. In the burial study, exhumed seeds of C. bursa‐pastoris were capable of germinating to 98–100% in light at the simulated spring–autumn temperature regime (15/6°C) in both spring and autumn, while those of D. sophia did so only in autumn. In early spring, however, seeds of D. sophia germinated to 17–50% at 15/6°C. Thus, most seeds of these two annual weeds that mature in late summer do not germinate in the first autumn, but they may do so the following spring or in some subsequent autumn or spring.     

基于北斗的大坝连续压实监控系统研究及应用

针对目前在大坝碾压施工过程中,传统施工质量控制方式难以满足日益提高的对高坝施工技术的需要,基于北斗卫星导航系统(BDS)和地理信息系统(GIS),对大坝碾压施工质量实时监控技术进行研究。通过安装在碾压机械上的加载设备及振动传感器采集数据,在集成软件处理并记录该碾压机械碾压施工过程,实现对碾压过程全程、全自动的实时监控。将研究结果应用于平桥水库面板堆石坝碾压施工过程中,结果表明,系统实现了对大坝碾压施工过程压实质量参数的有效监控,为大坝高质量、高强度施工提供保障,为工程管理提供便利和依据。     

深厚覆盖层上混凝土防渗墙服役性能分析

【目的】研究混凝土面板砂砾石坝防渗墙的应力变形及实际防渗效果,为高寒地区深厚覆盖层类似工程的设计与施工提供依据。【方法】以青海省纳子峡混凝土面板砂砾石坝为研究对象,在防渗墙施工及运行初期(2012-05-2018-01)对其进行应力监测、变形监测、渗流监测,对所得监测数据进行统计分析,进而评价防渗墙的实际工作状态。【结果】纳子峡混凝土面板砂砾石坝防渗墙各测点应力及变形表现稳定,在施工期防渗墙钢筋的应力变化因受地面施工等因素影响主要承受拉应力,且向上游侧倾斜;在水库运行期间(2014-09-2018-01),墙体受到来自上游的水压力,主要承受压应力,且向下游侧倾斜;布置在墙体上游侧的渗压计渗透压力远大于下游侧各测点,表明防渗墙防渗效果良好,渗透压力受测孔孔内水位影响,且随库水位表现出一定的周期性变化规律,库水位每抬升(或下降)1 m,墙体下游侧各测点渗透压力增加(或减小)约0.6 kPa。【结论】纳子峡大坝混凝土防渗墙在其施工及运行初期应力变形较为稳定,防渗效果良好,能为大坝的安全提供保障。     

基于标准化降水指数的西藏昌都市旱涝时空特征

旱涝灾害是昌都市主要自然灾害,了解昌都市旱涝时空分布特征,对减轻该区域旱涝灾害损失、合理利用水资源和生态屏障建设有重要意义。利用1981—2015年昌都市7个气象站的逐月降水数据,采用标准化降水指数(SPI),分析昌都市旱涝变化特征。结果表明:昌都市旱涝变化具有明显的阶段性特征,1981—1995年旱涝交替发生,1996—2004年雨涝频繁,2005年以后以干旱为主;春夏两季降水呈弱增加趋势,春夏旱减少,秋季降水呈弱减少趋势,秋旱增加,冬季则无明显的变化;北部、中部和南部在2002年以前,旱涝存在一致性,2002年后存在较大的差异;20世纪80年代中期旱涝变率最大,旱涝转换频繁,21世纪初早期变率最小,3个区域的旱涝变率总体上与全市相似,2011年以后,南部区域变率较高,旱涝交替频繁。     

牧草柳枝稷种子破休眠技术的研究

柳枝稷switchgrass (panicum virgatum)的种子属深度休眠。本文探索了后熟化(干藏),冷冻层化(湿润冷藏),磨擦,浸泡,以及植物生长调节剂GA和ABA对破除种子休眠的影响。