Short-term effects of whole-tree harvesting on understory plant species diversity and cover in two Norway spruce sites in southern Norway     

Tonje Økland  Jørn-Frode Nordbakken  Holger Lange  Ingvald Røsberg  Nicholas Clarke 《Scandinavian Journal of Forest Research》2016,31(8):766-776

Effects of clear-cut harvesting on ground vegetation plant species diversity and their cover are investigated at two Norway spruce sites in southern Norway, differing in climate and topography. Experimental plots at these two sites were either harvested conventionally (stem-only harvesting) or whole trees including crowns, twigs and branches were removed (whole-tree harvesting), leaving residue piles on the ground for some months. We compare the number of plant species in different groups and their cover sums before and after harvesting, and between the different treatments, using non-parametric statistical tests. An overall loss of ground vegetation biodiversity is induced by harvesting and there is a shift in cover of dominant species, with negative effects for bryophytes and dwarf shrubs and an increase of graminoid cover. Differences between the two harvesting methods at both sites were mainly due to the residue piles assembled during whole-tree harvesting and the physical damage made during the harvesting of residues in these piles. The presence of the residue piles had a clear negative impact on both species numbers and cover. Pile residue harvesting on unfrozen and snow-free soil caused more damage to the forest floor in the steep terrain at the western site compared to the eastern site.  相似文献   

Granulomatous enteritis in rainbow trout (Oncorhynchus mykiss) associated with soya bean meal regardless of water dissolved oxygen level          下载免费PDF全文

P Mosberian‐Tanha  T Landsverk  C M Press  L T Mydland  J W Schrama  M Øverland 《Journal of fish diseases》2018,41(2):269-280

This study investigated morphological changes associated with soya bean meal‐induced enteritis (SBMIE) in distal intestine (DI) of rainbow trout (Oncorhynchus mykiss) fed a soya bean meal (SBM)‐based diet and exposed to normoxia or hypoxia created by optimal and low water flow rates, respectively. A 28‐day adaption period was followed by a 42‐day challenge period where 600 fish were subjected to dietary challenge and/or hypoxia. Twelve tanks each containing 50 juvenile trout were assigned randomly in triplicate to each treatment. Histopathological and immunohistochemical evaluation revealed pathological features that have not previously been described in association with SBMIE. Vacuolar degeneration of epithelial cells mainly at the base of mucosal folds, epithelial cysts, epithelial dysplasia, necrosis, shedding of necrotic cells, and granulomatous inflammation including infiltration of enlarged, sometimes finely vacuolated or “foamy” macrophages, multinucleated giant cells and increased proliferation of fibroblasts were observed. Acid‐fast bacteria were not detected in enlarged macrophages; however, these cells contained AB‐PAS‐ and sometimes cytokeratin‐positive material, which was interpreted to be of epithelial/goblet cell origin. Hypoxia did not affect the morphological changes in DI. These results suggest that SBM was associated with a granulomatous form of enteritis in DI of rainbow trout regardless of water oxygen level.  相似文献   

Functional amino acids stimulate muscle development and improve fillet texture of Atlantic salmon          下载免费PDF全文

T.‐K.K. Østbye  B. Ruyter  I.B. Standal  L.H. Stien  D. Bahuaud  J.‐E. Dessen  M.S. Latif  B. Fyhn‐Terjesen  K.‐A. Rørvik  T. Mørkøre 《Aquaculture Nutrition》2018,24(1):14-26

Sufficient firmness is essential for consumer appreciation and the suitability for processing of fish fillets. The objective of this study was to investigate the effect of functional amino acids (AA) on fillet texture and muscle development of Atlantic salmon. Triplicate net pens of 105 g salmon were fed a standard diet, or the same diet with added 15 g/kg arginine or 15 g/kg glutamate during a 5‐month rearing period. The growth rate and FCR (0.91–0.92) showed no significant dietary effects (body weight 864–887 g). Glutamate supplementation resulted in delayed postmortem glycogen degradation (pH drop) and rigour development, along with improved fillet firmness and intercellular myofibre integrity. An in vitro study with salmon myosatellite cells showed that exogenous glutamine or arginine increased the expression of muscle growth markers (myog, tnnl2, myl) at both 8 and 16°C culture temperature. The expression of a marker for proteolysis (ctsb), myl and myog were highest for the glutamine treatment at 16°C. Significant interaction between exogenous AA and temperature indicated elevated AA requirement when growth is accelerated. It is concluded that AA from the glutamate family are vital for fillet firmness. The dispensable glutamine and glutamate appear more critical compared to arginine, particularly during high‐performance periods.  相似文献   

The effect of plant‐based diet and suboptimal environmental conditions on digestive function and diet‐induced enteropathy in rainbow trout (Oncorhynchus mykiss)          下载免费PDF全文

P. Mosberian‐Tanha  J.W. Schrama  T. Landsverk  L.T. Mydland  M. Øverland 《Aquaculture Nutrition》2018,24(1):112-122

This experiment investigated intestinal enteropathy and digestive function of rainbow trout challenged with soybean meal‐based diet (SBM) at optimal or suboptimal environments created by normal or reduced water flow, respectively. Oxygen level remained above 7 mg L^‐1 for optimal environment and between 4 and 5 mg L^‐1 for suboptimal environment. Triplicate groups of fish (mean body weight 74 g) were fed fishmeal‐based diet (FM) or SBM at optimal environment in period 1 (28 days). In period 2 (42 days), fish were subjected to a change from FM to SBM or remained on the same diet as used in period 1. The fish were also exposed to change from optimal to suboptimal environment or remained under optimal conditions. The fish subjected to change from FM to SBM, regardless of their environment, showed similar degree of enteropathy from day 14. Lipid and starch digestibility was lower in SBM‐fed fish at suboptimal environment compared to fish fed the same diet at optimal environment. Crude protein digestibility, however, was highest in SBM‐fed fish at suboptimal environment throughout period 2. In conclusion, in SBM‐fed rainbow trout, exposure to suboptimal environment did not change the degree of enteropathy; however, lipid and starch digestibility were further reduced.  相似文献   

Collar insertion depth effects on soil respiration in afforested peatlands     

A.?Jonay?Jovani-Sancho  Thomas?Cummins  Kenneth?A.?ByrneEmail authorView author&#;s OrcID profile 《Biology and Fertility of Soils》2017,53(6):677-689

Using collars for measuring soil respiration and its component fluxes in closed chamber systems relies on two main assumptions. Firstly, it is assumed that shallow collars prevent lateral soil gas leakage beneath the chamber’s walls and the underestimation of soil CO₂ fluxes, and secondly, the insertion of deeper collars excises all living roots and the autotrophic flux is eliminated. It was hypothesised that previous findings on collar insertion impacts on autotrophic and total soil respiration also apply to afforested peatlands. In these ecosystems, a large fraction of fine roots grow close to the soil surface. Therefore, the use of shallow collars may sever some fine roots and hyphae of mycorrhizal fungi, and therefore, it may lead to underestimation of total soil respiration. It was also hypothesised that this underestimation may be greater than a possible CO₂ leakage from lateral diffusion of soil gas as a result of not using collars. In this study, we measured soil CO₂ efflux in a Sitka spruce and a lodgepole pine plantation on blanket peat in southern Ireland. A surface collar (not inserted into the ground) and six insertion depths (5, 10, 15, 25, 35 and 45 cm) were established to assess the effect of the collar insertion depth on autotrophic and total soil respiration. The insertion depth of 5 cm reduced total soil respiration by 47 and 32% in the spruce and pine stands, respectively. Using nonlinear equations, it was estimated that a frequently used shallow insertion of 1.5 cm would have reduced this efflux by 35 and 20% in each stand, respectively. Moreover, it was demonstrated that this reduction was greater than a possible lateral soil gas leakage. These results suggest that the insertion of shallow collars should be avoided and surface collars permanently anchored in the soil should be used instead.  相似文献   

经济相对发达地区烟叶工场化烘烤模式的探索——以湖南省宁乡县为例     

张浩然  周冀衡  徐文军  何命军  张一扬  谢鹏飞  黄松青  张万良 《农学学报》2011,(1)

经济相对发达地区在经济基础、交通状况、烟农素质等方面优势明显,具备发展烟叶工场化烘烤的良好条件。以湖南宁乡为例,分析了工场化烘烤的运作模式和成本,认为劳动力价格较高、生产水平差异较大、烘烤技能不扎实、考核机制欠缺、服务方式存在缺陷是这类地区在推行工场化烘烤中值得关注的问题,然后提出了依托合作社解决用工困难、统一开展农事操作、加大烘烤培训力度等解决方案。  相似文献   

Autumn growth of Elytrigia repens,Cirsium arvense and Sonchus arvensis at high latitudes in an outdoor pot experiment     

K S TØRRESEN  H FYKSE  T RAFOSS 《Weed Research》2010,50(4):353-363

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Quantitative trait loci (QTL) associated with resistance of rainbow trout Oncorhynchus mykiss against the parasitic ciliate Ichthyophthirius multifiliis     

R Jaafar  J Ødegård  H Mathiessen  A M Karami  M H Marana  L von Gersdorff Jørgensen  S Zuo  T Nielsen  P W Kania  K Buchmann 《Journal of fish diseases》2020,43(12):1591-1602

The parasitic ciliate Ichthyophthirius multifiliis has a low host specificity eliciting white spot disease (WSD) in a wide range of freshwater fishes worldwide. The parasite multiplies rapidly whereby the infection may reach problematic levels in a host population within a few days. The parasite targets both wild and cultured fish but the huge economic impact of the protozoan is associated with mortality, morbidity and treatment in aquacultural enterprises. We have investigated the potential for genetic selection of WSD-resistant strains of rainbow trout. Applying the DNA typing system Affymetrix^® and characterizing the genome of the individual fish by use of 57,501 single nucleotide polymorphisms (SNP) and their location on the rainbow trout chromosomes, we have genetically characterized rainbow trout with different levels of natural resistance towards WSD. Quantitative trait loci (QTL) used for the selection of breeders with specific markers for resistance are reported. We found a significant association between resistance towards I. multifiliis infection and SNP markers located on the two specific rainbow trout chromosomes Omy 16 and Omy 17. Comparing the expression of immune-related genes in fish—with and without clinical signs—we recorded no significant difference. However, trout surviving the infection showed high expression levels of genes encoding IgT, T-cell receptor TCRβ, C3, cathelicidins 1 and 2 and SAA, suggesting these genes to be associated with protection.  相似文献   

High salinity tolerance in eggs and fry of a brackish Esox lucius population     

A. T. JØRGENSEN  B. W. HANSEN  B. VISMANN  L. JACOBSEN  C. SKOV  S. BERG  D. BEKKEVOLD 《Fisheries Management and Ecology》2010,17(6):554-560

Abstract Knowledge on the biology and physiology of pike, Esox lucius L., populations inhabiting saline environments is scarce. An experimental setup was used to examine egg development and fry behaviour and growth under varying salinity levels in a brackish‐water pike population from the western Baltic Sea. Eggs and fry developed at 8.5 psu, which is higher than hitherto reported for other populations. Fry exhibited stress behaviour and reduced growth when subjected to salinities above 13 psu. This indicates that early life stages of E. lucius tolerate ambient salinity conditions equivalent to the natural environment in its nursery area in the Stege Nor lagoon. The population should therefore not be dependent on access to freshwater environments during spawning. However, the results also suggest that the population’s natural environment is on the margin of its physiological capacity. The results have significance for management of brackish‐water E. lucius populations, e.g. in relation to stocking strategies.  相似文献   

Influence of dietary menadione nicotinamide bisulphite (vitamin K3) and phylloquinone (vitamin K1) on Atlantic salmon (Salmo salar L.) tissue levels,determined by high‐performance liquid chromatography with fluorescence detection     

I.E. GRAFF  C. KROSSØY  K. GJERDEVIK  K. JULSHAMN 《Aquaculture Nutrition》2010,16(6):637-647

The aim of the present study was to investigate the retention of menadione nicotinamide bisulphite (MNB; vitamin K₃) and phylloquinone (vitamin K₁) in Atlantic salmon (Salmo salar L.). Another objective was to find a reliable method for determination of menadione in fish feed, and to include and validate more matrices in the methods for phylloquinone and menaquinones (vitamin K₂). Duplicate tanks of Atlantic salmon (～93 g) were fed four levels (0–1000 mg menadione kg^?1 feed) of MNB for 9 weeks. The concentration of menadione and phylloquinone in the feed and the concentration of phylloquinone and menaquinone‐4 (MK‐4) in the tissues were determined. The analysed concentration of dietary menadione found in feed indicated a substantial loss of MNB during feed production. This assumption was supported by screening 15 commercial fish feed samples which also revealed menadione concentrations far below the recommended level. MNB fed salmon showed only a minor increase in liver MK‐4 concentration, compared to salmon fed phylloquinone which had a considerably higher level of liver phylloquinone, indicating a higher retention of phylloquinone compared to menadione in Atlantic salmon. Due to highly varying stability and bioavailability of the different vitamin K derivatives, vitamin K supplementation in fish feed needs a revision.  相似文献