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21.
22.
Climatic effect on lignin and polysaccharides in particle-size fractions of zonal steppe soils, Russia Zonal soils derived from similar parent materials are suitable for investigating the question, whether and how climate affects soil organic matter properties. For this reason we sampled 10 native surface (0—10 cm) and subsurface (ca. 50—60 cm) soil horizons in the native steppe and forest steppe of Russia. Polysaccharides and the vanillyl, syringyl and cinnamyl structural units of lignin (VSC) were determined in the fine earth (< 2 mm) as well as in clay (< 2 μm) and silt (2—20 μm) fractions. As the ratio of mean annual precipitation to potential evaporation (N/V) decreased, the concentrations of polysaccharides tended to decrease in the subsoil horizons. This was indicated most clearly for the silt fractions (r = 0.98**). In contrast, the VSC contents (in g kg—1 organic C) of the subsoils increased as N/V decreased (r = —0.92*), resulting in increasing VSC/polysaccharide ratios of the subsoil horizons with decreasing N/V ratio (r = —0.94*). It is suggested that production of polysaccharides or their transport into the mineral subsoil or both is favored at sites with wide rather than narrow N/V ratio, whereas lignin might be selectively enriched during intense soil organic matter decay at the Southern sites. 相似文献
23.
The present study examined the morphological and physiological effects of amorphous diatomaceous earth against the stored product pestsS. granarius, T. molitor andT. confusum. Diatomaceous earth, namely Fossil Shield® and Dryacide® increased the mortality rate of this insects. After contact with Fossil Shield® the individuals ofS. granarius had significant lost of weight and reduced their water content respectively. This showed that silica dusts break the water barrier of the cuticle. However, it increases the transpiration rate of water across the cuticle and the insect died past several times through dehydration. As well, an addition of food affected the effectiveness of dusts against insects. A lot of stored product beetles will be able to produce metabolic water of feed substrates. This ability protects and weaves contrary to the loss of water. Diatomaceous earth’s can be effective primarily through the sorptive properties of the hygroscopic particles. One day after dust treatment a significant weight loss ofT. molitor pupae was recorded. The exposure to the silica dust Fossil Shield® caused partly an incomplete metamorphosis and death of the individuals. Pupae dipped in Fossil Shield® or abrasive aluminium dust and rolled for further five minutes, reduced not significant higher their weight as unrolled exuvial stages. The morphological analyses of treated insects under the Scanning Electron Microscope showed, that the dust covered the hole integument. Partly, the silica particles sunk into the cuticle. After application of Fossil Shield® at the cuticle of adults,T. molitor, did not show any wax layer. Also it could not be found once blocked by stigma of the mealworm. The dust particles accumulated around the respiration openings and they partly overgrew. 相似文献
24.
A map of soil texture profiles was derived from readily available spatial data in combination with information from soil profiles using CART (classification and regression trees). The primary purpose was to provide a regionalized predictor for the vertical hydraulic conductivity profiles to be used as an input variable to an evapo‐transpiration model. In contrast to former studies, the texture of 110 soil profiles taken in the 10 km2 area was not averaged vertically but the profiles were grouped according to their hydraulic properties. Therefore, it was possible to include site specific profiles, e.g. with histic or argillic horizons. Despite of small sampling quantities (110 soil profiles grouped into 8 classes) a prediction probability of 60 to 70 % was achieved in most classes. The resulting map provides valuable information for the granulometric and hydrologic characterization of the study area.<?show $6#> 相似文献
25.
Velvetbean (Mucuna spp.) is a summer annual that has been used as a cover crop to reduce erosion, fix nitrogen and suppress weeds and plant-parasitic nematodes. Crude aqueous extracts (1:15 dry weight plant/volume water) were made from velvetbean plant parts, and various concentrations of the extracts were evaluated in vitro for toxicities to different stages of Meloidogyne incognita (Kofoid and White) Chitwood and for suppression of hypocotyl and root growth and inhibition of germination of tomato (Lycopersicon esculentum L.) and lettuce (Lactuca sativa L.). Germination was only affected by the full-strength extract from leaf blades. Lettuce root growth was the most sensitive indicator of allelopathic activity of the plant part extracts. Lettuce and tomato root growth was more sensitive to the extract from main roots than to extracts of other plant parts, with lethal concentration (LC50) values of 1.2 and 1.1% respectively. Meloidogyne incognita egg hatch was less sensitive to extracts from velvetbean than the juvenile (J2) stage. There was no difference among LC50 values of the extracts from different plant parts against the egg stage. Based on LC50 values, the extract from fine roots was the least toxic to J2 (LC50 39.9%), and the extract from vines the most toxic (LC50 7.8%). The effects of the extracts were nematicidal because LC50 values did not change when the extracts were removed and replaced with water. 相似文献
26.
Heike Kawaletz Inga Mölder Peter Annighöfer André Terwei Stefan Zerbe Christian Ammer 《Annals of Forest Science》2014,71(3):337-347
Context
Identifying the traits of exotic species may explain their invasiveness and help control the negative impacts of these species on native ecosystems. In this study, we investigated root competition as an important driver for the competitiveness of two exotic tree species in the seedling stage.Aims
In a pot experiment, carried out in Central Europe, we studied the effect of root competition of two exotic tree species (Prunus serotina Ehrh. and Robinia pseudoacacia L.) on biomass allocation of two native ones (Quercus robur L. and Carpinus betulus L.).Methods
Seedlings of these species were exposed to intra- and interspecific mixtures with and without the effect of root competition. For this, belowground plastic partitions were installed in the pots.Results
Competition intensity in the pots increased over time, irrespective of mixture type. However, this increase was much higher for the native species if mixed with the exotic species compared to monocultures or inter-native mixtures. In addition to ontogeny, competition affected biomass allocation patterns. Under root competition by the exotic species, the native species preferentially allocated their biomass to the roots. A higher allocation to the roots was mainly achieved at the expense of leaf and branch biomass.Conclusion
Root competition of P. serotina and R. pseudoacacia may be a reason for the lack of Q. robur and C. betulus in the seedling stage in natural environments where all four species occur. 相似文献27.
Brian Kronvang Inga K. Andersen Carl Christian Hoffmann Morten L. Pedersen Niels B. Ovesen H. E. Andersen 《Water, air, and soil pollution》2007,181(1-4):115-121
Water exchange, flow patterns and deposition of sediment and phosphorus were measured in cross-sections of a naturally functioning floodplain during one winter and in three restored floodplains following remeandering of formerly straightened and channelized rivers. Sediment and phosphorus depositional processes were studied, deploying artificial grass mats at different distances from the river channel. In addition, a mass-balance approach was applied on the experimental site. Our results show that the deposition of sediment and particulate phosphorus constituted 3,000–4,700 g DW m?2 and 1.2–7.3 g P m?2, respectively, on the four floodplains studied during a winter where flood duration lasted between 20 and 76 days. The storage efficiency for sediment ranged between 28–47 and 4.0–7.0% for phosphorus. 相似文献
28.
Stefan Fleck Inga Mölder Mascha Jacob Tobias Gebauer Hermann F. Jungkunst Christoph Leuschner 《Annals of Forest Science》2011,68(7):1173-1185
Introduction
Sight-based field measurements of tree crown projection area and canopy height are common praxis in forest science but difficult to validate. We quantified their measurement errors based on the virtual representation of an 11-species old-growth forest provided by high-resolution terrestrial LIDAR (light detection and ranging) measurements. 相似文献29.
Inga Moročko-Bičevska Jamshid Fatehi 《European journal of plant pathology / European Foundation for Plant Pathology》2011,129(4):567-577
Gnomonia fragariae is a poorly studied ascomycete, which was recently demonstrated to be a cause of severe root rot and petiole blight of strawberry.
The pathogen was genetically transformed with the GFP as a vital marker and hygromycin resistance gene. Several stable transformants
were obtained, which did not differ in their phenotype from the wild type isolate. Using one of the GFP-tagged isolates the
infection process and colonization of roots and petioles of host plant by the pathogen were studied. Fluorescence microscopy
examinations of the inoculated plants at different time points showed that plant infection occurs 24 h after inoculation and
intensively continues during first 3 days. The specific penetration sites on epidermal cells and preferences in colonization
for certain root and petiole tissues were observed. The pathogen intensively colonized and destroyed cortex of roots and petioles
and spread rapidly longitudinally within intercellular spaces. The petioles were colonized by the hyphae, which grew mostly
in the intracellular spaces of the cortical cells while in the roots the intracellular growth of hyphae occurred only in the
later stages of infection. The fungus was also capable to infect the vascular tissues of petioles although these were not
the primary tissues colonized by the pathogen. The mature ascomata were formed on the infected petiole bases several weeks
after the inoculation. This study presents a genetic transformation method for Gnomonia fragariae and it demonstrates details on infection process and colonization of root, crown and petiole tissues of strawberry by the
pathogen. 相似文献
30.
Andrej Rodionov Wulf Amelung Ludwig Haumaier Inga Urusevskaja Wolfgang Zech 《植物养料与土壤学杂志》2006,169(3):363-369
Black Mollisols are typically rich in charred organic matter, however, little is known about the zonal distribution of black C (BC) in steppe soils. In this study, we used benzene polycarboxylic acids (BPCA) as specific markers for BC in particle‐size fractions of depth profiles in several zonal soils (Greyzem, Phaeozem, Chernozem, Kastanozem) of the Russian steppe. In addition, liquid‐state 13C‐NMR spectra were obtained on the alkaline‐soluble soil organic matter (SOM). The results showed that both the content and depth distribution of BC varies in the different soil types; the concentration of BC in the bulk top soils being closely related to the aromaticity of the SOM (r2 = 0.98 for the native topsoils, 0.83 for top‐ and subsurface soils). Especially the Chernozems were rich in aromatic SOM, which partly contained more than 17% BC of total C, most of which being allocated in the mineral fractions. Long‐term arable cropping did not reduce the BC contents of the surface soil, though it did promote the enrichment of BC in the silt fractions. The same shift was detected as soil depth increased. We conclude that BC is not fully inert in these soils, but apparently can be preserved in the silt as decomposition of SOM increased, i.e., it accumulates exactly in that fraction, which has been formerly assigned to contain old, aromatic C. 相似文献