Variation in juvenile steelhead (Oncorhynchus mykiss) dispersal in relation to age and growth performance

Volitional dispersal is a ubiquitous strategy characteristic of species across major faunal groups. Dispersal during the juvenile life stage is of interest because early performance can be critical for determining future success (survival/reproduction). For salmonids, dispersal can influence local density, competition, individual growth and survival, though drivers of dispersal at meso-scales are rarely quantified. Here, we evaluate dispersal of tagged juvenile steelhead (Oncorhynchus mykiss) through habitat units in extended stream reaches (500 m) at sites across a watershed from July to October 2017. Our aim was to quantify the frequency and spatial extent of dispersal, identify links to biotic and abiotic factors, evaluate the implications for individual growth and test for associations between dispersal and migration initiation. Dispersal rates varied between sites, but were consistently higher for age 1+ than for age 0 steelhead (avg. 21% vs. 6% respectively). Age 1+ dispersal probability was positively correlated with time between recapture events and body mass, and negatively correlated with growth rate, maximum temperature experienced and age 1+ density. At sites where there appeared to be growth benefits to remaining sedentary compared to moving, proportionally fewer fish performed dispersal. We found no links between dispersal and timing or probability of migration initiation the following spring. Our results support the hypothesis that although dispersal over intermediate scales (10–1,000 m) might be rare, it could be an important strategy that permits fish to seek out better opportunities (foraging, shelter or otherwise) in underutilised areas.     

不同基质处理对淡水浇灌桐花树成苗率及幼苗生长的影响

为探索桐花树的淡水化人工培育技术以及筛选适宜的基质,以塘泥、黄心土、河沙和椰糠为试验材料,通过不同的配比组合成10种混配基质,并进行育苗试验,对桐花树的成苗率以及生长情况进行研究。结果发现,不同的混配基质对桐花树的成苗率、苗高、地径、根系生长、鲜重和干重等指标有明显的影响,其中以基质F（30%塘泥+50%黄心土+10%河沙+10%椰糠）综合得分最高,其平均苗高、地径、主根长、一级侧根数、全株生物量、成苗率分别比综合得分最低的基质高24.3%、11.1%、6.3%、6.5%、37.5%、2.0%。     

马铃薯组培苗时期不同LED光源处理对温室移栽后植株生长和微型薯结薯的影响

不同LED光源下培养的马铃薯组培苗在形态特征上差异明显,为探索这种差异是否会对其移栽后产生进一步影响,试验研究了100%红光(R)、100%蓝光(B)、100%绿光(G)、75%红光+25%蓝光(RB)、45%红光+35%蓝光+20%绿光(RBG)和100%白光(CK)6种光谱下培养4周的马铃薯组培苗温室移栽后植株的生长和结薯情况。试验结果表明,B处理的马铃薯组培苗移栽后缓苗期叶绿素荧光参数Fv/Fm和qP、结薯前期SPAD值及结薯期各器官生物量均始终高于CK和其他处理,且该处理下最大薯的干鲜重和有效微型薯占比分别较CK提高45.66%、45.09%和10.93%。R处理的组培苗移栽后结薯期地上部生物量显著高于CK,单株结薯数目提高29.60%,但有效微型薯占比较CK降低63.97%。G处理的组培苗移栽后生长和结薯指标均表现最差。组合光谱RB和RBG处理的组培苗移栽后的生长指标和微型薯产量及产量构成指标均与CK无显著差异。因此,单色红、蓝、绿光谱处理对马铃薯组培苗的影响会持续至其移栽后植株幼苗生长,甚至结薯期,组合光谱RB和RBG则不会。在马铃薯组培苗生产上,单色蓝光和单色红光作为照明光源具有潜在的应用价值,组合光谱RB和RBG可作为白色光源的替代光源。     

橡胶籽苗黑根病病原鉴定及生物学特性研究

橡胶籽苗黑根病严重影响橡胶育苗生产,本研究从感病籽苗中分离病原菌,经致病性的测定,病原的形态特征观察和菌丝体的ITS、RPB2、tub2等基因序列分析对比,鉴定病原菌为球毛壳菌Chaetomium globosum;生物学特性研究结果表明,该菌生长适应能力强,在10~35℃、pH 2~10范围内菌丝和子囊孢子能生长和萌发,全光照能减缓菌丝的生长,糖类营养物质有利于子囊孢子萌发,子囊孢子较耐高温,48℃持续20 min,50℃持续15 min,52℃持续10 min,以及54℃持续5 min时才能导致病原子囊孢子失活、死亡。在夏季大棚不育苗期间,采用高温闷棚杀死病原孢子,必要时在育苗期结合化学药剂防治,对该病害可取得较好的控制效果。     

内蒙古乌拉特高原荒漠原生树种蒙古扁桃容器育苗试验研究

蒙古扁桃是蒙古高原的一种孑遗植物,是国家三级保护植物,具有药用、饲用和巨大的生态价值。为了保护蒙古扁桃这一珍贵天然资源,开展了蒙古扁桃的容器育苗试验,总结繁育蒙古扁桃苗木的经验。试验在巴彦淖尔乌拉特后旗的呼和温都尔镇乌兰哈少嘎查进行。通过对蒙古扁桃容器育苗的试验,总结出了一套适用于西部干旱地区的蒙古扁桃繁育技术。     

铅(Pb2+)和镉(Cd2+)对火炬树种子萌发及幼苗生长的影响

【目的】研究不同浓度重金属铅(Pb^2+)和镉(Cd^2+)对火炬树Rhus typhina种子萌发及幼苗生长的影响,探索火炬树对重金属铅、镉胁迫的耐受程度及机理。【方法】采用培养皿滤纸发芽法,分别用不同浓度Pb^2+(300、600、900、1200、1500 mmol/L)、Cd^2+(140、280、420、560、700 mmol/L)溶液处理火炬树种子,测定种子发芽率、发芽指数、幼苗胚根长和茎长、硫代巴比妥酸(TBARS)含量、可溶性蛋白含量、超氧化物歧化酶(SOD)活性及过氧化物酶(POD)活性。【结果】与对照相比,不同浓度Pb^2+、Cd^2+均对火炬树种子的发芽率、发芽指数和幼苗生长有抑制作用,但低浓度Pb^2+可促进根长和芽长的伸长。随着Pb^2+和Cd^2+溶液浓度的增加,幼苗叶片中SOD活性和可溶性蛋白含量表现为先增加后降低,POD活性和TBARS含量均逐渐升高。其中,Cd^2+浓度为700 mmol/L时,发芽率、发芽指数、芽长和SOD活性达到最低值,而TBARS含量最高;Pb^2+浓度为1500 mmol/L时,根长达到最低值,POD活性达到最高值;Pb^2+浓度为600 mmol/L时,可溶性蛋白含量最高。【结论】Pb^2+浓度为300 mmol/L时会抑制火炬树种子萌发,但会促进幼苗生长,其余浓度Pb^2+、Cd^2+胁迫下,火炬树种子与幼苗受到一定影响,但是均较好完成了萌发与幼苗生长,并表现出多种积极的适应性特征,未出现无根苗现象,火炬树较其他木本植物对铅、镉2种重金属表现出更强的耐性。本试验结果可为今后选用火炬树作为重金属污染土壤的植物修复材料提供理论参考。     

五常市杂种落叶松幼龄期变异分析

以5年生36个杂种落叶松家系为材料,测定其树高、胸径生长性状,估算变异系数、遗传力和遗传增益,筛选出优良家系。结果表明:各家系的树高、胸径存在较丰富变异,树高变异系数小于胸径,树高、胸径极显著相关(P<0.01),家系间树高、胸径差异均达极显著差异水平(P<0.01)。以10%的入选率,初选出家系1317、1324、1318、和1327为优良家系,树高平均增益为15.98%,胸径平均增益为29.46%。     

欧美国家针叶树容器苗生产与启示

针叶树是芬兰、瑞典、挪威、美国、加拿大等欧美国家主要的商品林树种。容器苗是针叶树重要的育苗类型。与裸根苗比较，容器苗具有育苗周期更短、造林季节可延长、苗木适应性更广、苗木质量更一致的优点。因此，容器育苗成为精准林业发展的必然趋势。为了借鉴欧美容器育苗的技术方法，提高我国容器苗的质量，为我国针叶树容器苗发展提供参考，文中主要从4个方面综述了欧美国家检测与提高苗木质量的方法，即列举了针叶树常用的苗木质量检测指标，总结了育苗容器与育苗基质的改良进展，介绍了养分、水分、光照与温度等培养条件的优化手段，简要概述了容器苗病虫害防控的进展，提出了我国相关树种容器苗生产的启示与借鉴。     

Effects of dietary Bacillus pumilus on growth performance,innate immunity and digestive enzymes of giant freshwater prawns (Macrobrachium rosenbergii)

The present study was conducted to investigate the effects of Bacillus pumilus on the growth performance, innate immunity and digestive enzymes of the giant freshwater prawn, Macrobrachium rosenbergii. Prawns (mean weight: 1.81 ± 0.01 g) were fed different levels of B. pumilus at doses of 0, 1 × 10⁷, 1 × 10⁸ and 1 × 10⁹ CFU/g to produce one control group and three experimental groups (G1, G2 and G3), respectively. After a 60‐day experimental feeding period, the results showed that the final weight, weight gain rate (WGR) and specific growth rate (SGR) were significantly higher in experimental groups than in the control (p < 0.05), whereas these improvements did not differ significantly (p > 0.05) among experimental groups. The improvements in phagocytic activity, respiratory burst (RBs) activity and the activity of catalase (CAT), nitric oxide synthase (NOS) and acid phosphatase (ACP) were significantly higher in G2 and G3 than in the control and G1 (p < 0.05). Further, the activity of CAT, NOS and ACP significantly increased with an increase in the dietary level of B. pumilus (p < 0.05). The activity of phenoloxidase (PO) in G3 was significantly higher than that in the control (p < 0.05). The activity of amylase was significantly higher in the groups G2 and G3 than that in the control group. G3 improved the activity of protease compared with the control (p < 0.05). In conclusion, the results of this study indicated that the potential use of B. pumilusat a dose of 1 × 10⁸ CFU/g feed could improve the growth, immunity and digestive enzymes of M. rosenbergii.     

Effects of chromium yeast,tributyrin and bile acid on growth performance,digestion and metabolism of Channa argus

A 60‐day feeding trial was carried out to evaluate the effects of chromium yeast (CY), tributyrin (TB) and bile acid (BA) on the snakehead (Channa argus). The control (CT) group was fed the basal diet, and the experimental groups were fed 200 mg/kg CY (concentration: 1,000 mg/kg), 2.5 g/kg TB (purity: 45%) or 1 g/kg BA (purity: 30%) in addition to the basal diet. The addition of CY, TB and BA statistically increased the weight gain rate, and specific growth rate, whereas the feeding rate and feed conversion ratio were significantly reduced (p < 0.05). When compared with the CT group, TB elevated the serum glutathion peroxidase (GSH‐Px) activity; and BA reduced low density lipoprotein cholesterol (LDL‐C) contents significantly (p < 0.05). The three feed additives reduced intestinal malonaldehyde (MDA) levels dramatically. Tributyrin significantly enhanced intestinal trypsin and pepsin activities (p < 0.05). The activity of fructose‐1,6‐bisphosphatase and pyruvate carboxylase in the group fed CY was significantly lower than in the CT group. In conclusion, dietary inclusion of the three additives enhanced growth performance of C. argus. Dietary supplementation of CY affected protein, glucose and lipid metabolism. Diets with TB levels improved intestinal digestive enzyme activity and antioxidant capacity. The addition of BA improved glycolipid metabolism.