Variation in somatic cell counts of milk samples from individual cows     

Ola Syrstad  Ivar Rn 《Acta veterinaria Scandinavica》1979,20(4):555-561

Somatic cell counts of 2570 milk samples from 765 cows collected bimonthly from November 1975 to May 1976 were transformed to logarithmic values and analysed statistically. Components of variance were estimated as follows: Herds 0.033 (13 %), age groups 0.021 (8%), cows (within herds and age groups) 0.080 (31%), months 0.014 (6%), residual 0.107 (42%). Correction of actual cell counts for the influence of milk yield on the day of sampling led to only small changes in the magnitude of the various components. The coefficient of correlation between samples from the same cow was computed as 0.60 when the samples were from the same lactation, and 0.37 for samples from consecutive lactations.The proportionately small variation among herds as compared to the variation among cows of the same herd throws doubt on the efficiency of cell counting in samples of herd milk as a way of identifying cows with high cell counts.  相似文献   

A phenetic analysis of morphological variation in Citrullus lanatus in Namibia     

Gillian L. Maggs-Kölling  Sten Madsen  Jørgen L. Christiansen 《Genetic Resources and Crop Evolution》2000,47(4):385-393

Morphological data recorded from field trials using Citrullus lanatus germplasm collected in Namibia were used to analyse and compare the various morphotypes of this species. The experiment comprised wild types and local landraces as well as commercial cultivars. Cluster analysis supported the indigenous classification system used in Namibia, in which Citrullus types are distinguished based on gross morphology, ecology and usage and grouped into seed, cooking and fresh-eating (watermelon) types. Commercial watermelon cultivars formed a distinct cluster. Wide variation was found within the local types whereas the genetic basis of the commercial type appears to be narrow. The commercial cultivars were most closely related to local watermelon types and more distantly related to the wild types, whereas the cooking melons form an intermediate group.  相似文献   

Topophysis in Corymbia torelliana × C. citriodora seedlings: adventitious rooting capacity,stem anatomy,and auxin and abscisic acid concentrations     

Ivar Wendling  Peter R. Brooks  Stephen J. Trueman 《New Forests》2015,46(1):107-120

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Maturation and related aspects in clonal forestry—Part I: concepts,regulation and consequences of phase change     

Ivar Wendling  Stephen J. Trueman  Aloisio Xavier 《New Forests》2014,45(4):449-471

Progression from the juvenile to mature phase in woody plants is accompanied by changes in characteristics as diverse as adventitious rooting capacity, leaf morphology, canopy architecture, wood anatomy and reproductive development. Many concepts of phase change, the intensity and duration of changes that occur during the phase transition, and the practical consequences of plant maturation for growth and development, are poorly understood. Little is known about the physiological and environmental control of maturation in woody plants compared with herbaceous plants, and reliable markers of phase state have only been developed for a few species, mainly conifers. Understanding the mechanisms and forms of phase change is a prerequisite for achieving maturation or rejuvenation for applications such as seed production or clonal propagation. This review describes concepts, terminology and consequences of phase change, combining theoretical and practical aspects of tree maturation that relate to clonal forestry.  相似文献   

Is tree growth in boreal coniferous stands on mineral soils affected by the addition of wood ash?     

Staffan Jacobson  Hagos Lundström  Sten Nordlund  Ulf Sikström  Folke Pettersson 《Scandinavian Journal of Forest Research》2014,29(7):675-685

Increasing use of forest fuels for energy production is generating greater quantities of wood ash. In Sweden, it is recommended that this ash should be returned to the forest to counter soil acidification and avoid potential future nutrient deficiencies, but the effects on tree growth require clarification. Thus, 10 field experiments were established in Sweden in 1990–2006 to study the effects of adding wood ash of various origins, doses and combinations of both ash and nitrogen on stem growth in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst.) stands on mineral soil. Observations after 5–15 years show that growth responses were strongest when N was added, either alone or with wood ash. Growth responses to additions of wood ash without N were small and variable and statistically insignificant at all study sites. However, there were indications that adding wood ash may increase stem-wood growth at fertile sites and decrease it at less fertile sites. Hence, at fertile sites, it may compensate for the growth reductions that normally follow whole-tree harvests, at least temporarily, presumably due to its effects on soil N turnover. At less fertile sites, adding N is probably essential to counteract these growth reductions.  相似文献   

Impact of acid precipitation on freshwater ecosystems in Norway     

Richard F. Wright  Torstein Dale  Egil T. Gjessing  George R. Hendrey  Arne Henriksen  Merete Johannessen  Ivar P. Muniz 《Water, air, and soil pollution》1976,6(2-4):483-499

Extensive studies of precipitation chemistry during the last 20 yr have clearly shown that highly polluted precipitation falls over large areas of Scandinavia, and that this pollution is increasing in severity and geographical extent. Precipitation in southern Norway, Sweden, and Finland contains large amounts of H⁺, SO⁼ ₄, and NO^? ₃ ions, along with heavy metals such as Cu, Zn, Cd, and Pb, that originate as air pollutants in the highly industrialized areas of Great Britain and central Europe and are transported over long distances to Scandinavia, where they are deposited in precipitation and dry-fallout. In Norway the acidification of fresh waters and accompanying decline and disappearance of fish populations were first reported in the 1920s, and since then in Sørlandet (southernmost Norway) the salmon have been eliminated from several rivers and hundreds of lakes have lost their fisheries. Justifiably, acid precipitation has become Norway's number-one environmental problem, and in 1972 the government launched a major research project entitled ‘Acid precipitation — effects on forest and fish’, (the SNSF-project). Studies of freshwater ecosystems conducted by the SNSF-project include intensive research at 10 gauged watersheds and lake basins in critical acid-areas of southern Norway, extensive surveys of the geographical extent and severity of the problem over all of Norway, and field and laboratory experiments on the effect of acid waters on the growth and physiology of a variety of organisms. Large areas of western, southern, and eastern Norway have been adversely affected by acid precipitation. The pH of many lakes is below 5.0, and sulfate, rather than bicarbonate, is the major anion. Lakes in these areas are particularly vulnerable to acid precipitation because their watersheds are underlain by highly resistant bedrock with low Ca and Mg contents. Apart from the well-documented decline in fish populations, relatively little is known about the effects of acid precipitation on the biology of these aquatic ecosystems. Biological surveys indicate that low pH-values inhibit the decomposition of allochthonous organic matter, decrease the species number of phyto-and zooplankton and benthic invertebrates, and promote the growth of benthic mosses. Acid precipitation is affecting larger and larger areas of Norway. The source of the pollutants is industrial Europe, and the prognosis is a continued increase in fossil-fuel consumption. The short-term effects of the increasing acidity of freshwater ecosystems involve interference at every trophic level. The long-term impact may be quite drastic indeed.  相似文献   

Analysis of the genotype-by-environment interaction of spring barley tested in the Nordic Region of Europe: Relationships among stability statistics for grain yield     

Minna Nurminiemi  Sten Madsen  Odd Arne Rognli  Âsmund Bjørnstad  Rodomiro Ortiz 《Euphytica》2002,127(1):123-132

Variation in agronomic and quality characteristics was investigated in 220 Nordic spring barley cultivars across distinct environments (6 locations during 3 years) in the Nordic Region of Europe. The objectives of this research were to determine the importance of the genotype by environment interaction in all characteristics evaluated and to establish the relationship among different stability statistics for grain yield. Combined analysis of variance across locations indicated that both environments and genotype by environment interactions influenced significantly the cultivar phenotypes for all characteristics, irrespective of their type (row number) or earliness. The first two interaction principal component axes of the additive-main-effects-and-multiplicative-interaction (AMMI) model accounted together between 35% and 75% of the total genotype-by-environment interaction for all characteristics. Grain yield was, on average, higher in 2-row than in 6-row cultivars, which were significantly earlier in heading and grain maturity than the former. However, in some of the most northern locations, 6-row barley cultivars significantly outyielded on average 2-row barley lines. The genotype by location interaction variance (σ² _GL) accounted by each genotype was significantly associated to the deviation from regression (Tai's λ) while the coefficient of regression (β) was significantly correlated to the IPCA1 and IPCA2 of the AMMI model in 2-row, 6-row and early barley cultivars. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Genetic gains in Nordic spring barley breeding over sixty years     

Rodomiro Ortiz  Minna Nurminiemi  Sten Madsen  Odd Arne Rognli  Åsmund Bjørnstad 《Euphytica》2002,126(2):283-289

Accurate assessments of genetic gains ensuing from plant breeding for the most important agronomic characteristics in Nordic spring barley (Hordeum vulgareL.) are not available. Hence this research was aimed to determine the rate of genetic improvement in the Nordic barley breeding pool. This study included 90, 2-row spring barley cultivars released (1942–1988) and29, 6-row spring barley cultivars released(1930–1991) adopted by Nordic farmers that were tested in four Nordic locations for three consecutive years. Relative genetic gain owing to plant breeding was 13% in2-row barley and 34% in 6-row barley for grain yield. The absolute gain for this characteristic was 13 ± 3 kg ha^-1 year ^-1 in 2-row barley, and22 ± 3 kg ha^-1 year^-1 in6-row barley. Improved yield was achieved in Nordic barley by reducing plant height(0.20 ± 0.04 cm year^-1 for 2-rowbarley and 0.16 ± 0.06 cm year^-1for 6-row cultivars), thereby reducing significantly lodging (0.5 ± 0.1%year^-1 and 0.4 ± 0.1year^-1), and increasing significantly the harvest index (0.0008 ± 0.0002year^-1 and 0.0018 ± 0.0002year^-1). Additionally, in 2-row spring barley cultivars resistance to powdery mildew (0.19 ± 0.08% year^-1)and thousand-kernel weight (0.07 ±0.03 g year^-1) were also significantly enhanced, whereas hectoliter weight was improved (0.06 ± 0.02 kg year^-1)in 6-row barley cultivars in the period investigated. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

First biogeographical survey of Artemia in Tanzania     

Frank Thomas Mlingi  Hieromin Amon Lamtane  Sebastian Wilson Chenyambuga  Ivar Lund 《Journal Of Applied Aquaculture》2020,32(3):278-290

ABSTRACT

In an Artemia survey conducted along the coast of Tanzania between March and July 2017, 32 salt pans in Tanga, Dar es salaam, Pwani, Lindi, and Mtwara were assessed. Of all visited salt pans, 16 (50%) had either Artemia biomass or cysts or both. Body length ranged from 4.0 mm to 9.5 mm, while the mean and modal lengths were 6.2 mm and 6.0 mm, respectively. Temperature ranged from 27.2°C to 48.7°C, salinity from 20 g L^?1 to >140 g L^?1, pH from 5.8 to 7.8, dissolved oxygen (DO) from 3.1 mg L^?1 to 4.9 mg L^?1, water depth from 10 cm to 75 cm and conductivity from 42.0 ms cm^?1 to 176.6 ms cm^?1. A bisexual population of Artemia franciscana is suggested. Observed cyst states included concave, biconcave, spherical and cracking cysts. This is the first to report on the occurrence of Artemia in Tanzania.  相似文献   

The suitability of anadromous Arctic charr as host and vector of the monogenean Gyrodactylus salaris     

R. Knudsen  P. Adolfsen  S. Sandring  R. Kristoffersen  S. Siikavuopio  A. Rikardsen 《Ecology of Freshwater Fish》2007,16(1):99-104

Abstract –  In 2000, the Atlantic salmon ( Salmo salar L.) stock in the river Signaldalselva, North Norway was found to be infected with the monogenean Gyrodactylus salaris (Malmberg). This river system has a multispecies fish community of nine species in total. Low densities of Atlantic salmon parr were found during electrofishing in October (2003) with a prevalence of 94% and a mean abundance of 848 G. salaris. This watercourse also holds a riverine stock of anadromous Arctic charr ( Salvelinus alpinus ), which is not common in Norway. Among the parr of Arctic charr, 64% were infested with an abundance of 23 parasites per fish. The most heavily infected 0+ and 1+ juvenile Arctic charr had 469 and 534 parasites, respectively, indicating that the parasites are able to reproduce on Arctic charr in the wild. There was little variation in the rates of infestation of Arctic charr along the studied stretch of the river, even in areas with very low densities of Atlantic salmon parr. The parr of anadromous Arctic charr seem to be suitable as long-term hosts for G. salaris . Moreover, a few (22%) infested adult sea-running Arctic charr were captured after ascending the river in the autumn, which shows that large fish may also act as carriers of G. salaris . However, no parasites were recorded on potential anadromous Arctic charr before descending during early spring (April 2003 and April 2004). Thus, it is still not clear whether anadromous Arctic charr are able to disperse the parasite between watercourses. So far, it is uncertain whether G. salaris may increase the mortality rates of Arctic charr and thereby be a threat to these unusual occurring riverine anadromous Arctic charr stocks.  相似文献