Does sand content in spawning substrate result in early larval emergence? Evidence from a lithophilic cyprinid fish

The spawning success of lithophilic salmonids is strongly influenced by the fine sediment content (“fines”) of spawning substrates, yet knowledge on the impacts of fines on the spawning of non‐salmonid lithophiles remains limited, despite their ecological and socio‐economic importance in European rivers. Consequently, the aim here was to use an ex‐situ experiment to investigate the impact of sand content on egg survival and timing of larval emergence of the surface‐spawning cyprinid European barbel Barbus barbus. Thirty incubator boxes within a recirculating system were filled with one of five experimental sediment mixtures (0%–40% sand by mass) that each contained 300 fertilised eggs at a depth of 50 mm. Emerged, free‐swimming larvae were captured and counted daily to assess grain‐size effects on larval survival and emergence. Specifically, total proportion of emerged larvae, cumulative daily proportion of emerged larvae and time required to reach 50% emergence were measured during the study. Whilst the proportion of sand in the sediments did not have a significant impact on egg‐to‐emergence survival (mean survival per treatment 75%–79%), it significantly affected the timing of larval emergence to the water column; early emergence was detected in treatments with elevated sand content (on average, 50% emergence after 12–13 days versus 19 days in the control). Similar to findings from salmonid studies, these results suggest high sand content in spawning gravels can influence timing of larval emergence and potentially cyprinid lithophilic fish survival.     

覆膜防沙治沙方法

沙漠、沙尘暴和沙化问题已经成为威胁人类生存的头号敌人，如何根治沙漠、沙尘暴和沙化是摆在人类面前的十分紧迫的任务。覆膜防沙治沙方法的研究和提出，成功地解决了人类面临的重大防沙治沙难题。为人类征服自然，征服沙漠树立了信心。介绍了覆膜防沙治沙的技术方式、方法、原理和覆膜栽培技术，供防沙治沙工程参考和推广。     

A new galago species for South Africa (Primates: Strepsirhini: Galagidae)

The primate fauna of South Africa has historically been viewed as comprising three diurnal cercopithecoid taxa – chacma baboons (Papio ursinus), vervet (Chlorocebus pygerythrus) and samango monkeys (Cercopithecus albogularis) – and two nocturnal lorisoid species – the thick-tailed greater galago (Otolemur crassicaudatus) and the southern lesser galago (Galago moholi). Here we report the positive identification of a third galago species within South Africa’s borders: the Mozambique dwarf galago or Grant’s galago, Galagoides granti (Thomas and Wroughton, 1907). The taxon was previously held to be restricted to Mozambique, eastern Zimbabwe, Malawi and Tanzania, but we have also observed it in the sand forest of Tembe Elephant Park and the Tshanini Community Reserve, near the Mozambique border. The species was formerly mistaken for Galago moholi, erroneously (we believe) extending the range of the latter species into northern KwaZulu-Natal. In South Africa the two small galagos are unlikely to have overlapping ranges: Galago moholi prefers dry savanna woodlands, whereas Galagoides granti is apparently confined to dry sand forest. However, both species may coexist with the larger and more widespread Otolemur crassicaudatus, an inhabitant of moist savanna, forest edge and thicket. The true South African ranges of both small galago species need to be ascertained.     

沙对高尔夫果岭坪床物理特性的影响

对28种沙与泥炭按75∶25混配而成的高尔夫果岭坪床材料的物理特性进行了评价。不同类型沙的粒径、均一性和形状有所不同。高尔夫果岭坪床的物理特性主要取决于所使用的沙的特性。对沙 泥炭混配的坪床来说,其导水率在95~827 mm/h范围内变化,总孔隙度变化范围为38.8%~47.2%,而通气孔隙度(在-3 kPa水势下)为0.9%~24.6%,毛管孔隙度(在-3 kPa水势下)为17.7%~42.1%。结果表明,排水速率和通气孔隙度与毛管孔隙度的平衡主要受沙的粒径大小的影响,起决定作用的是粒径最大和最小的沙所占的比例,而容重、总孔隙度和抗剪切强度取决于沙的均一性。当沙粒较圆且较为光滑时,坪床材料孔隙度趋向减少。沙表面越粗糙,坪床抗剪切能力就越强,而沙对坪床硬度的作用不显著。     

烷基-二醇基硅胶填料的合成及对莠去净类除草剂的在线分离

三步合成了烷基-二醇基硅胶(ADS)色谱材料，首先用γ-缩水甘油醚氧丙基三甲氧基硅烷把功能基团键合到硅胶基体上，再把该环氧化硅胶与硬脂酸反应以制备酯型十八烷基反相填料，最后在20MPa压力下装成色谱预柱(35×4.6mm I.D)。用该预柱通过六通阀后接ODS分析柱(250×4.6mm I.D)，构成中心切割二维HPLC。该系统能对具有一定疏水性的化合物进行在线富集，实现环境及生物复杂样品直接进样分离分析。使用该系统对尿中的莠去净和西玛津残留进行了分离分析，以含有0.1%乙酸的酸性水缓冲液对加标尿液中莠去净类化合物保留在预柱上，干扰分析的大分子被排阻而无保留通过，其它干扰分子保留小而通过，再切换六通阀，以乙腈和0.1%乙酸水溶液进行梯度洗脱，进而在下一级ODS分析柱上进行分离（紫外检测225nm），两种除草剂的分离分析取得了良好的定性定量结果     

外加剂和掺和料对砂浆性能影响的

当前，在水工棍凝土工程中，抹而砂浆的强度和抗渗性能越来越受到人们的重视通过对比试验，研究了减水剂、引气剂单掺、复掺及与硅粉、粉煤灰复掺，对砂浆强度和抗渗性能的影响，并从机理方面分析它们改善砂浆性能的原因结论是:减水剂、引气剂与硅粉、粉煤灰适当配比复掺，对砂浆的强度和抗渗性能的改善显著     

人工降雨条件下不同坡度红壤坡面迳流泥沙变化特征研究

在人工模拟降雨强度为1.44 mm/min的条件下,研究了不同坡度(β)红壤近似裸地坡面迳流、泥沙的变化特征,研究结果表明:①地表迳流量随坡度的增大而迅速增加。②当β≤23°时,土壤侵蚀量随坡度的增大而迅速增加;当25°≤β≤40°时,土壤侵蚀量随坡度变化较小。③坡面土壤侵蚀的临界坡度则介于23°~25°之间。④坡度与侵蚀量关系可用函数表示为:S=199.1×L1.65×tan1.4β(0°≤β≤23°)。     

复合硅改性热处理杨木的制备及性能

[目的]针对木材树脂改性剂释放甲醛不环保,无机改性材吸湿性高等问题,将廉价易得的硅石粉溶液化,再有机杂化,制得高渗透、环保、防火的水溶性木材复合硅改性剂,通过真空加压浸渍处理和热处理联合改性,可以有效提高木材的物理力学和阻燃等性能.[方法]分别制备硅油复合硅改性剂(SC2)和偶联剂杂化硅改性剂(HS2),对人工林杨木进...     

4种荒漠植物种子出苗和幼苗生长对沙埋深度的响应

通过室内试验测定了黑果枸杞、沙冬青、沙蒿、霸王4种荒漠植物的种子生理特征以及沙埋深度（0、1、2、3、4、5 cm）对4种荒漠植物种子出苗及幼苗生长的影响。结果表明,体积较大的沙冬青和霸王种子萌发率与其重量、含水量、形状及活性间存在正相关关系;体积较小的黑果枸杞、沙蒿萌发率与种子重量、含水量、形状之间为正相关关系,与种子活性负相关。随着沙埋深度增加,4种植物种子出苗率下降、首次出苗时间延迟,茎高、绝对株高和根长及根冠比总体呈先增大后减小的趋势;幼苗生长方面,黑果枸杞和沙蒿分别适宜于1～2、0～1 cm的浅层沙埋,均在沙埋深度5 cm时种子几乎不萌发;沙冬青、霸王则适宜于3～4 cm较深层沙埋,在沙埋0 cm时均不萌发。此外,在荒漠区采用这4种植物进行植被恢复时,除考虑种子自身性状外,还应充分考虑当地的沙埋、降雨等条件,以提高出苗率、增大幼苗定植率。