Threats to at-risk salmonids of the Canadian Rocky Mountain region

Trout and charr, members of the salmonid family, have high conservation value but are also susceptible to anthropogenic threats in part due to the specificity of their habitat requirements. Understanding historical and future threats facing these species is necessary to promote their recovery. Of freshwater trout and charr in the Canadian Rocky Mountain region, westslope cutthroat trout (Oncorhynchus clarkii lewisi), bull trout (Salvelinus confluentus; a charr species) and Athabasca rainbow trout (Oncorhynchus mykiss) are of conservation concern. And indeed, range contractions and declining populations are evident throughout much of their ranges. Range contraction was most evident in the southern Alberta designatable unit (DU) of westslope cutthroat trout. Diminished populations were also evident in the downstream watersheds of the Alberta bull trout range, and throughout the Athabasca rainbow trout range. We assessed historical and future threats to evaluate the relative importance of individual threats to each DU and compare their impact among species. Individual threats fall into the broad categories of angling, non-native species and genes, habitat loss and alteration, and climate change. Severity of each threat varies by DU and reflects the interaction between species’ biology and the location of the DU. Severity of threats facing each DU has changed over time, reflecting extirpation of native populations, changes in management and industry best practices, expansion of non-native species and progressing climate change. The overall threat impact for each DU indicates a high probability of substantial and continuing declines and calls for immediate action.     

Effects of Two Underseed Species, Medicago polymorpha L. and Scorpiurus muricatus L., on the Yield of Main Crop (Durum Wheat) and Subsequent Crop (Teff) Under Humid Moisture Regimes in Ethiopia

Mixed cropping of leguminous underseed species and cereal crops may increase productivity and serve some additional purposes. Two leguminous weed species which are widely distributed in annual crops of the Ethiopian highlands have been studied with varying coverage in greenhouse trials in Ethiopia with regard to their suitability as underseeds and with wheat ( Triticum turgidum [L.] Thell. var. durum [Desf.] MacKey) as a main crop. The competitive effects of Scorpiurus muricatus L. on the grain yield of wheat were smaller than those of Medicago polymorpha L. (-14.1 % and -23.6 % respectively, compared with the underseed free control) which is mainly ascribed to differences in their speed of development and shoot height. The residual effects of the underseed's root masses on the grain yield of the successive teff crop (Eragrostis tef [Zucc] Trotter) were significantly higher with Scorpiurus muricatus (+99.3 %) than with Medicago polymorpha (+63.6 %). The results are discussed with regard to the specific site conditions in the cereal-dominated cropping systems of the Ethiopian highlands.     

梨幼树到结果初期春施15N–尿素的利用及其在土壤的残留与损失

2014—2016年,以‘黄冠’梨为材料,采用15N示踪技术研究了从幼树期到结果初期梨树对春季施用氮素的吸收利用及土壤残留与损失情况。研究结果表明,幼树期(2014—2015年)梨树生长以中心干和粗根等树体骨干结构建立为主,生长量相对较小;进入结果初期(2016年)后树体生长表现为树体骨干结构建立为主,枝梢等营养器官生长与产量形成并存,生长量大幅增加。整个试验期间,树体贮藏器官的标记氮素吸收量较大,其中幼树期中心干吸收量最大,结果初期粗根吸收量最大。0~100 cm土层标记氮素残留量随土层深度和施用年限增加逐渐降低,其中,施用标记氮素后第1年(2014年),土壤标记氮素残留量较高,残留率达63.61%,梨幼树对标记氮素利用率仅为3.25%。随后两年(2015—2016年)土壤残留量较低,树体对标记氮素利用率仅为0.51%和0.80%。试验结束时,幼树期到结果初期梨树对标记氮素的累计利用率为4.57%,土壤标记氮素残留量为20.34%,损失率达75.07%。     

超高效液相色谱-质谱/质谱法同时测定蔬菜中7种磺胺的残留量

为建立超高效液相色谱-质谱/质谱法(UPLC-MS/MS)同时测定蔬菜中7种磺胺残留量的方法。样品用1%乙酸乙腈提取，以C18色谱柱分离待测物，采用多反应监测(MRM)离子扫描模式，外标法进行定量，线性良好，相关系数均大于0.999。结果显示：7种磺胺的检出限为0.000 4～0.000 6 mg/kg，样品添加回收率为67.5%～94.1%，相对标准偏差均少于5.3%(n＝6)。该方法简单快捷、定量准确，可满足多种蔬菜中7种磺胺的残留检测要求。     

Fertilizer value of nitrogen in hen and broiler manure after application to spring barley using different application timing

The nitrogen (N) fertilizer effect of layer hen and broiler manure applied at different times on spring barley yield was studied in seven Swedish field experiments during 2005–2008. Two experiments had parallel field incubations to study N release after fertilizer application. The effect of total N in manure on N offtake was 30–40% that of mineral N, except in a dry year, when the effect was very low. Although the relative proportions of ammonium N, uric acid N and other N differed between the hen and broiler manure, the effect of total N was similar for both. In field incubations, mineral N decreased from 75 to 60% of total N applied in hen manure, whereas it increased from 20 to 50% in broiler manure, because of net immobilization and release, respectively. The limited fertilizer nitrogen replacement value, corresponding to only 30–40% of total N, could be as a result of ammonia volatilization after rather shallow incorporation with harrow. Net N release from broiler manure lasted for 6–8 weeks after application, after which it generally ceased. In some cases, manure application in early spring gave better yield effects than application at sowing, probably because of better synchronization of the N release with crop N requirements. The residual N effect on the N offtake in crop in the year after manure application was on average 3% of the total N applied, equivalent to a fertilizer replacement value of about 6%.     

Genetic potential for residual feed intake and diet fed during early- to mid-gestation influences post-natal DNA methylation of imprinted genes in muscle and liver tissues in beef cattle

Discovery of epigenetic modifications associated with feed efficiency or other economically important traits would increase our understanding of the molecular mechanisms underlying these traits. In combination with known genetic markers, this would provide opportunity to improve genomic selection accuracy in cattle breeding programs. It would also allow cattle to be managed to improve favorable gene expression. The objective of this study was to identify variation in DNA methylation between beef cattle of differential pre-natal nutrition and divergent genetic potential for residual feed intake (RFI). Purebred Angus offspring with the genetic potential for either high (HRFI) or low (LRFI) RFI were prenatally exposed to either a restricted maternal diet of 0.5 kg/d average daily gain (ADG) or a moderate maternal diet of 0.7 kg/d ADG from 30 to 150 d of gestation. We performed DNA methylation analysis of differentially methylated regions (DMR) of imprinted genes (Insulin-like growth factor 2 (IGF2) DMR2, IGF2/H19 imprinting control region (ICR) and IGF2 receptor (IGF2R) DMR2) using post-natal samples of longissimus dorsi (LD) muscle taken from male and female calves at birth and weaning, and of LD muscle, semimembranosus (SM) muscle, and liver samples collected from steers at slaughter (17 months of age). Interestingly, for all three DMR investigated in liver, LRFI steers had higher levels of methylation than HRFI steers. In LD muscle, IGF2/H19 ICR methylation differences for heifers at birth were due to pre-natal diet, while for steers at birth they were mostly the result of genetic potential for RFI with LRFI steers again having higher levels of methylation than HRFI steers. While results from repeated measures analysis of DNA methylation in steers grouped by RFI revealed few differences, in steers grouped by diet, we found higher methylation levels of IGF2 DMR2 and IGF2R DMR2 in LD muscle of restricted diet steers at weaning and slaughter than at birth, as well as increased methylation in LD muscle of restricted diet steers compared with moderate diet steers at weaning and/or slaughter. Our results suggest that differential pre-natal nutrition, and divergent genetic potential for RFI, induces tissue- and sex-specific alterations in post-natal IGF2 and IGF2R methylation patterns and that these patterns can vary with age in Angus beef cattle.     

抗滑桩优化设计在滑坡治理中的应用研究

基于传统剩余推力法，提出了新的抗滑桩优化方法。以位于凉山彝族自治州某县城南的滑坡体为例，说明了主要治理方法。采用剩余推力法和新的抗滑桩优化方对该滑坡体天然状态工况进行了稳定分析。结果显示，在设计安全系数为1．15的情况下，该滑坡处于临滑状态，因此，须采取相应的加固措施，最后推荐了抗滑桩设计方案，已在凉山州某县城滑坡工程中成功实施。     

35CrMo旋转接头激光表面硬化技术的试验研究

用L9(34)正交试验法研究35CrMo旋转接头激光相变硬化工艺参数优化组合,分析了旋转接头激光相变硬化方法.试验结果表明:激光相变硬化层硬度比渗氮淬火提高了30%,耐磨性提高了1倍,表面残余应力为压应力;满足了旋转接头工作要求,为改进旋转接头表面处理方法提供了依据.