Movement patterns of southern redbelly dace,Chrosomus erythrogaster,in a headwater reach of an Ozark stream

Previous research on fish movement has focused primarily on recreationally important fishes in perennial streams; however, fewer studies have examined movement patterns of small‐bodied fishes in intermittent streams where abiotic and biotic conditions can be extreme compared with perennial systems. Using mark–recapture, we examined movement patterns of southern redbelly dace, Chrosomus erythrogaster, in an intermittent Ozark stream having both permanently connected and temporally isolated sections. Juvenile (60–88%) and adult (55–83%) residency rates were not significantly different for any mark–recapture sample, and movement was primarily within a section for both groups. Ontogenetic differences were detected for kurtosis, distance moved and population spread, with adults exhibiting greater variability in movement, moving more often and further. When considering only adults, there was a significantly higher number of individuals that exhibited intermovement from isolated sections compared with connected sections. In addition, a higher proportion of adults exhibiting intermovement moved to connected stream sections in May and July compared to January and March. Dace exhibited upstream bias in July, with 76% of emigrates moving to an upstream connected section. Although there were no statistically significant associations between the proportion of intermovers from connected and isolated sections and measured water quality and habitat variables, noteworthy trends were observed, and these trends were always stronger for connected sections. Understanding the factors that influence population dynamics in headwater streams is important for the survival and persistence of stream fish populations, especially considering the anticipated expansion of intermittent headwater streams as a result of future climatic changes.     

大豆叶面积垂直分布对产量及农艺性状的影响

于大豆开花期对亚有限大豆品种东农 594进行 3种密度、 8种组合的人工去叶裂区设计试验 ,评价了大豆垂直方向上不同叶层面积大小对产量及主要农艺性状的影响。试验结果表明 ,在大豆生育后期 ,中层叶片对产量及农艺性状有重大影响 ,上层次之 ,下层影响甚微。根据试验结果认为 ,大豆生育后期的中层叶片是决定产量的重要层次。大豆垂直叶面积分布最合理的类型与无限型大豆相类似     

土壤冻结过程中水分迁移动向的研究

土壤中除毛管水、重力水和薄膜水外,还有一种可供植物利用的水分,即上层滞水和冻结滞水。上层滞水是存在于土壤包气带中局部隔水层之上的自由水;冻结滞水是存在于季节冻土内的固态性水(那平山,1994)。两者常相伴存在于土壤中,冻结滞水的融化水滞留在土壤冻结层之上而形成季节性水资源。我国三北地区多属干旱、半干旱地带,年蒸发量大于年降雨量,日照强烈,气候干燥,土壤含水率很低,所栽幼苗往往因水分亏缺而难以成活。如果我们能够设法提高冻结滞水和上层滞水的含量,准确把握土壤上层滞水含量高峰的时机,并采用相应的造林技术措施,对提高春季…     

鸡败血支原体垂直传播模式及其阻断方法

以国际标准强毒Ｒ株人工感染非免疫产蛋鸡,定时扑杀,分别从鼻窦、眶下孔、气管、肺、气囊、卵巢和输卵管分离ＭＧ,并收集感染鸡所产蛋分离ＭＧ。结果表明,人工感染４８小时后上、下呼吸道及肺已被全面感染,９６小时气囊已被感染,１２０小时输卵管已能分离到ＭＧ,卵巢始终分离不到ＭＧ。人工感染鸡自１４４小时便能在其所产蛋中分离出ＭＧ。药物治疗能在７２小时内消除感染,油乳剂苗则需２４天后逐渐降低蛋内ＭＧ分离率,药物卵内注射、种蛋药浴、高温处理均能杀死卵内ＭＧ,但以研制的种蛋浸泡剂药浴效果为最好。     

Vertical distribution of earthworms in grassland soils of the Colombian Llanos

 The vertical distribution of native earthworm species from natural and disturbed savannas in the Oxisols of the Colombian Llanos was assessed in a native savanna and in a 17-year-old grazed grass-legume pasture during a period of 17 months. Different patterns of vertical stratification were observed for all species with a strong migration of populations to deeper layers in the dry season. The correlation between the size of the earthworms and the average depth at which they were found was not significant (P>0.05), despite the fact that bigger species are located deeper in the soil. The living habits and adaptive strategies of the smallest species, Ocnerodrilidae n. sp., found in both ecosystems studied are responsible for this pattern. This endogeic species is associated with organic pools generated by an anecic species and further studies should assess the role of this species in ecosystem functioning. Mature worms of one anecic species were located deeper than immature ones in the soil (P<0.01). Soil moisture had an important effect on the vertical distribution of earthworms, although differences between immature and mature worms of the anecic Martiodrilus carimaguensis are likely to be of biotic origin. New data on the biology and ecology of these Neotropical species are shown. Received: 24 November 1999     

Movement of <Emphasis Type="Italic">Cucumber Mosaic Virus</Emphasis> Is Restricted at the Interface between Mesophyll and Phloem Pathway in <Emphasis Type="Italic">Cucumis figarei</Emphasis>

Viral movement in the leaf tissues of a resistant host, Cucumis figarei, inoculated with the pepo strain of Cucumber mosaic virus (CMV) and incubated at 24°C or 36°C was investigated by fluorescence in situ hybridization (FISH), leaf-press blotting, tissue printing and immunogold-silver staining techniques. Observation by FISH revealed that at 24°C most infection sites with CMV at 0.01 mg/ml or 0.1 mg/ml were limited to a single cell during the incubation period, that the number of infection sites increased from 24hpi (hours post inoculation) to 80 hpi in the leaves inoculated with CMV at 0.5 mg/ml, and that the size as well as the number of infection sites rapidly increased with time in the leaves inoculated with CMV at 2.0 mg/ml. These results suggested that one factor for the resistance of C. figarei at 24°C might be an inhibition of viral movement in and out of the infection sites. Leaf-press blotting and tissue blotting indicated that CMV remained in the infection sites at 24°C, whereas it spread from the inoculated leaves to other parts of the plants through vascular systems at 36°C. Immunogold-silver staining demonstrated that at 24°C CMV infected bundle sheath (BS) cells in minor veins, whereas at 36°C it invaded not only BS cells, but also phloem parenchyma (PP)/ companion cell (CC) or PP/intermediary cell (IC) complexes in minor veins in the regions with chlorotic symptoms. These results indicated that at 24°C CMV had difficulty in passing through the interface between BS and PP/CC or PP/ IC complexes and that viral entry from mesophyll to the phloem pathway was inhibited in the inoculated leaves. Received 26 August 1999/ Accepted in revised form 14 December 1999     

Movements of the yellowfin shiner, Notropis lutipinnis

Abstract— Yellowfin shiner, Notropis lutipinnis , movements were observed in two streams located near Clemson, South Carolina (USA). Subcutaneous paint tags were used to associate fish with the pools in which they were initially captured, tagged and released. Few mortalities related to marking techniques were observed in both captive and field-tagged fish. Tag longevity varied among paint colors used and anatomical locations marked. Movements were inferred from recaptured fish collected over a 12-month period. Recaptures within release pools were proportionally greater than movements outside release pools, although the sampling technique used likely overestimated recaptures within release pools. Recaptures outside release pools were more frequent in late spring and early summer, coinciding with the N. lutipinnis spawning season. The linear home range estimate for this species was 42.9 ± 79.0 m, although this represents a minimum estimate because complex movements by individual fish could not be detected.     

中国温带半干旱、干旱区山地气候垂直带谱研究

本文在讨论了山地垂直气候带研究方法的基础上，充分利用地学分析、气候遥感信息复合和地形气候学分析的优势，成功地完成了三者的匹配与结合，给出了大兴安岭、阴山、贺兰山等山地垂直气候带谱的基本特征。