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941.
Billy Nzau Matondo Michaël Ovidio Pascal Poncin Tampwo Alain Kakesa Lunkayilakio Soleil Wamuini Jean -Claude Philippart 《Fisheries Science》2007,73(5):1137-1146
ABSTRACT: Hybridization success at early developmental stages and larval resistance to osmotic, thermal and fasting tests in roach Rutilus rutilus , silver bream Blicca bjoerkna , common bream Abramis brama and their F1 hybrids were investigated. Results revealed that hybrid survival rates were similar to parents. At the eyed embryo stage, however, a maternal effect was observed as a general trend during hatchling and larval stages. After these stages, hybrids displayed a higher survival rate than their parents. Under stress tests, no survival was observed after 40 min for osmotic and thermal shocks and after 24 days for the prolonged fasting test in these species and their F1 hybrids. The median survivals of hybrids were intermediate between the two parents. For total mortality, hybrids were also affected by a maternal effect but to the advantage of the hybrids. 相似文献
942.
943.
No��mie Gaudio Philippe Balandier Gwena?l Philippe Yann Dumas Fr��d��ric Jean Christian Ginisty 《European Journal of Forest Research》2011,130(1):77-89
Depending on its developmental and morphological characteristics, shrubby or herbaceous understorey vegetation interacts differently with tree seedlings during the regeneration process. In acidic temperate forests, three common understorey plant species??Calluna vulgaris (L.) Hull, Pteridium aquilinum (L.) Kuhn in Kersten, Molinia caerulea (L.) Moench??are known to rapidly colonize forest gaps. Therefore, they often develop at the expense of light-demanding Scots pine (Pinus sylvestris L.) seedlings. An experiment was set up in a nursery in central France to mimic early competition occurring in a newly created gap between Scots pine seedlings and these three common understorey species (young forest-harvested individuals planted at 5 densities from 0 to 57 plants m?2). Pine seedling survival and growth (height, diameter, shoot and root biomass) and a functional trait (leaf mass on an area basis, LMA) were measured for 2 years, and cross-analysed against plant density, plant cover and available light. When understorey plant density increased, pine seedling diameter growth and biomass were negatively affected by all three plant species; height growth only slowed beneath Pteridium. These negative effects were closely linked to competition for light beneath Pteridium and Molinia. The application of the Beer?CLambert law gave an extinction coefficient k that was high for Pteridium, intermediate for Molinia and much lower for Calluna. LMA was confirmed as an effective foliar trait to reflect the degree of stress undergone by pine seedlings. 相似文献
944.
Jaume Gort-Oromi Lauri Mehtätalo Heli Peltola Ane Zubizarreta-Gerendiain Pertti Pulkkinen Ari Venäläinen 《Annals of Forest Science》2011,68(7):1233-1243
• Introduction
The objective of this work was to study how spacing and genetic entry and/or origin group affect radial growth (ring width and cumulative diameter development) and ring density from pith to bark in Scots pine (Pinus sylvestris L.) and in what sense their annual variability could be explained by the climatic variables. The spacing trial was located in central Finland, with current stand density range of 2,000–4,000 trees per hectare. All the six genetic entries had Kanerva pine (plus tree S1101) as a father tree, whereas the mother tree represented Finnish plus trees from southern, central and northern Finland. 相似文献945.
Jean Trap Fabrice Bureau Marthe Akpa-Vinceslas Thibaud Decaens Michaël Aubert 《Annals of Forest Science》2011,68(3):595-606
Introduction
We investigated changes in humus morphology and soil potential net N mineralization pathways along a pure beech even-aged forest chronosequence, composed of four stages (15, 65, 95, and 130 years old) on Luvisol. 相似文献946.
• Introduction
Size-density relationships define the maximum number of stems that even-aged stands of a given species can hold in relation to the mean size of trees. They are used to derive stand density measures and are useful tools used to control tree mortality. 相似文献947.
• Introduction
Xeric (trailing) forest range limits are particularly vulnerable to impacts of predicted climate change. Regional modelling studies contribute to the identification of potential local climatic threats and may support appropriate management strategies. 相似文献948.
Rosalía Núñez-Pastrana Guadalupe Fabiola Arcos-Ortega Ramón Armando Souza-Perera Carlos Alberto Sánchez-Borges Yumi Elena Nakazawa-Ueji Francisco Javier García-Villalobos Adolfo Alberto Guzmán-Antonio José Juan Zúñiga-Aguilar 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(4):669-683
949.
Claude Husson Bruno Scala Olivier Ca?l Pascal Frey Nicolas Feau Renaud Ioos Beno?t Mar?ais 《European journal of plant pathology / European Foundation for Plant Pathology》2011,130(3):311-324
Decline induced by Chalara fraxinea is an emerging disease that severely affects ash stands in Europe. The disease appears to have an invasive spread from East to West of Europe in the last decade. The teleomorphic stage, Hymenoscyphus pseudoalbidus, that occurs as apothecia on ash rachis in the litter was recently described. The origin of ash decline remains unclear as a cryptic species, H. albidus, a long-established fungus in Europe, could be present in the same niche, and as in Switzerland, H. pseudoalbidus was shown to have been present long before the recent epidemic outbreak. In France, the emerging disease is very recent and clearly restrained to Northeastern France. We thus collected isolates from infected hosts and from apothecia/ash rachis both inside and outside the infected area in France in order to compare them on the basis of pathogenicity towards ash seedlings and sequences of the ITS regions and of three single-copy genes. We showed that two population types exhibiting about 2% base pair polymorphism in the sequences analysed were present in Northern France. The first type, corresponding to H. pseudoalbidus, was present on rachis and infected hosts only in Northeastern France and showed strong pathogenicity towards ash seedlings in inoculation tests. By contrast, the second type, which corresponds to H. albidus, was present throughout Northern France and showed no pathogenicity towards ash seedlings. Our study confirms the results of Queloz et al. (2010) who presented molecular evidences for the existence of two cryptic species, H. albidus and H. pseudoalbidus. The results strongly suggest that Chalara fraxinea/H. pseudoalbidus is a recent invader in France. 相似文献
950.
Ladislav Hn
l 《Pedobiologia》2004,48(4):647-381
Soil nematodes were studied in 39- and 49-year-old “red” dumps mainly composed of Fe2O3 waste pyrite remnants from production of sulphuric and other acids, and in a 84-year-old “white” dump mainly composed of CaCO3 material from soda production. The youngest stage of spontaneous biological succession contained moss–lichen patches which were mainly inhabited by bacterivorous nematodes (Acrobeloides nanus, Panagrolaimus rigidus, Rhabditis terricola, Bursilla monhystera) in very low abundance (about 50×103 ind m−2). Invasion of grass resulted in increase of bacterivorous nematodes up to several millions ind m−2 but with considerable seasonal fluctuations. Nematode assemblages diversified in sites colonized by various deciduous trees and Paratylenchus straeleni was the dominant plant parasitic nematode. In site with stabilized grass carpet on the “white” dump dominant nematodes were Geocenamus quadrifer and Pungentus engadinensis. Eudorylaimus spp. first appeared in 49-year-old dump but their populations remained very low (1–9×103 ind m−2). Some species found in control deciduous forests on natural soils (e.g. Xenocriconemella macrodora, Cephalenchus hexalineatus, Tylolaimophorus minor, Ogma menzeli, Hoplotylus femina) did not colonize deposits. Natural succession of nematodes on chemical waste materials was very slow and even after about 80 years their communities under deciduous trees showed many differences from those in nearby semi-natural mixed forests. 相似文献