半荒漠地区绿洲混播牧草

在甘肃河西半荒漠地区建植绿洲人工草地对6种混播牧草群落稳定性进行了研究.结果表明,混播组合T6(无芒雀麦-紫花苜蓿型)和T5(紫花苜蓿-草地早熟禾型)在群落稳定性及抗杂草的竞争力等方面表现均佳.在水热条件适宜情况下刈割频率为4～5次/年.T6的全年牧草产量可达126.9 t/hm2,根积累量232.6 t/hm2.茎叶比为1.09.叶面积指数7.0.通径分析表明,叶面积指数对产量的影响最大(决定系数0.859 5).通过草地植物多样性保护、控制叶面积指数和维持草地营养平衡等调控措施,可使群落获得较高的稳定性.群落的多样性指数(y)与均匀度指数(x)相关极显著(r=0.718 4,P<0.01).     

Soil, site and management components of variation in species composition of agricultural grasslands in western Norway

A partitioning of the total variance in species composition of grasslands associated with increasing fertilizer inputs (unfertilized pastures, artificially fertilized hay meadows and intensively cultivated grassland) in western Norway was undertaken. The partitioning was carried out with (partial) constrained ordinations (canonical correspondence analysis) and associated Monte Carlo permutation tests. Explained variation was high (0·651), with soil chemistry, management and site explaining 0·271, 0·228 and 0·052 of the variation, respectively, and the interaction between soil and management explaining 0·100 of the variation. However, much of the measured soil chemistry was considered to be an effect of management. The soil chemistry variable explaining most variation was extractable P content, associated with high soil extractable P contents in the intensively cultivated grassland due to high fertilizer applications. However, soil extractable P content did not explain differences in species composition when grasslands with smaller differences in fertilizer inputs (meadows vs. pastures) were compared. Total soil C and N contents and C:N ratios explained significant variation between all grassland types. Lowest levels of these variables were measured in the grassland with the highest fertilizer inputs, suggesting that total soil N content cannot be used as a predictor of fertility. Significantly higher soil N contents were measured in grasslands of low productivity, probably due to a low decomposition rate of stress‐tolerant plants and the consequent low availability of soil N and accumulation of soil organic matter. Ellenberg N values reflected soil chemical differences in this study with high Ellenberg N values reflecting high Ca, Mg and P contents and pH values and low total C and N contents and C:N ratios.     

Fine structure of the reindeer cornea in normal conditions and in keratitis

The fine structure of the reindeer cornea in normal conditions and in spontaneous keratitis was described. There were more layers of squamous and fewer layers of polyhedral cells than in pigs, cattle and horses.Mild cases of corneal opacity just had some swollen superficial epithelial cells.When fully developed the keratitis had all the characteristics of an acute inflammation. Swelling or shrinking of the epithelial cells with or without degenerative nuclear changes were common. A striking alteration of the epithelial cells was the irregular appearance of the filaments which was frequently observed. In some cases there was pronounced intercellular oedema with desquamation of the superficial squamous cells and occasional neutrophils in the intercellular space. The stroma was the site of oedema, infiltration of leukocytes and vascularization.The aetiology and pathogenesis of the disease are not yet established but experimental research on these problems is in progress.     

Seroprevalence of Salmonella spp. in Wild Reindeer (Rangifer tarandus tarandus) in Iceland

Veterinary Research Communications -     

Influence of distance to forest edges on natural regeneration of abandoned pastures: a case study in the tropical mountain rain forest of Southern Ecuador

In spite of its high diversity the forests in Southern Ecuador are highly endangered by deforestation. One of the main reasons for the loss of forests is the conversion into pastures. Due to their fast degradation, the pastures are abandoned after several years and form an increasing area of unproductive land. The remoteness from existing forest edges is discussed as one reason for the very slow natural reforestation of these areas. In this study we analyzed the regeneration of a secondary forest after approx. 38 years of succession in relation to the distance from the surrounding forest. We revealed that regeneration was rather slow. Especially larger trees with dbh > 10 cm were very scarce. Only Dioicodendron dioicum, Graffenrieda emarginata and Clusia sp. achieved larger diameters. The basal area of the secondary forest is still far beyond the original level in the primary forest. The number of species on plot level and the Shannon index were significantly lower in the secondary forest compared to the primary forest. The total number of species decreased from 47 to 31 with increasing distance from the forest edge and the similarity of species composition to the upper story declined to a level of 56.4 (Sörensen). Alzatea verticillata, Macrocarpea revoluta and Palicourea andaluciana had significantly higher abundances in the succession stages than in the natural forest. The most abundant species in all regeneration plots, G. emarginata and Purdiea nutans, seem to be generalists as they did not show preference either to natural forest or successional stages.     

驯鹿头髓解剖

运用大体解剖的方法对驯鹿头骨进行了形态学观察，并将其与双峰驼牛、马的头骨进行了比较。结果表明：驯鹿的梨骨特别发达。泪骨，额骨和鼻骨之间围成一个狭长的筛鼻甲窦（部）。下凳骨比牛、马、驼窄而长，下颌角钝圆。泪骨的形态较特殊，颜而形成纵形深窝，泪孔有两个，位于眶缘上，并有尖状的泪突分开，眶缘与颧骨交界处有一个深切迹，无泪囊窝。     

Adaptation and evaluation of the integrated farm system model to simulate temperate multiple-species pastures

Whole-farm simulation provides a tool for predicting the effects of farm management strategies on farm productivity and profitability. One such model, the Integrated Farm System Model (IFSM), was modified to allow representation of up to four forage species coexisting in a pasture mixture. The model was calibrated to simulate net herbage accumulation (NHA) observed during six periods of a 2002 experiment in a 3-species pasture in Pennsylvania, USA, composed of orchardgrass (Dactylis glomerata L.), white clover (Trifolium repens L.), and chicory (Cichorium intybus L.). The model also predicted sward botanical composition, total annual NHA, crude protein (CP), and neutral detergent fiber (NDF). Sensitivity analysis showed that predictions of NHA were most sensitive to both chicory and orchardgrass specific leaf area and partitioning of photosynthate to the shoot, as well as chicory photosynthetic efficiency. The model was evaluated against data from the same 3-species pasture in 2003 as well as a 2-species pasture (lacking chicory) from the same experiment in 2002 and 2003. Predictions of total annual NHA in 2- and 3-species pastures were within ±18% of observed values, though predictions of within-season NHA were less accurate. Predictions of botanical composition tended to remain within ±15% of observed values by species. Predictions of within-season CP and NDF concentrations in the whole sward tended to remain within ±22% and ±15%, respectively. Given the generality and realism required of IFSM, the degree of precision in the modified pasture submodel is acceptable for achieving IFSM’s primary goal of comparing the effects of different management scenarios on forage productivity and the long-term profitability and environmental impact of farms.     

北方干旱区优良牧草抗旱性和抗寒性研究进展

干旱和低温是制约北方干旱区栽培草地发展的限制因子。文章对北方干旱区常见的紫花苜蓿、羊草、老芒麦、垂穗披碱草、无芒雀麦和冰草6种牧草的抗寒性、抗旱性的研究进展进行了分析,并从外部形态、生产力、生理生化指标等方面,就不同牧草品种对低温和干旱的适应性以及反馈机制进行了综述,最后对牧草抗性未来的研究方向进行了展望。     

南山草场两种牧草害虫的调查报告

以南山草场的人工草场为例,记述了酿成牧草重灾的害虫粘虫和蛴螬的一般发生情况,为害程度及防治措施,并对今后的防治工作,提出了以生物防治为主,物理防治为辅的建议。