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41.
Context
Urban environments create a wide range of habitats that harbour a great diversity of plant species, many of which are of alien origin. For future urban planning and management of the green areas within the city, understanding of the spatial distribution of invasive alien species is of great importance.Objectives
Our main aim was to assess how availability of different ecosystem types within a city area, as well as several parameters describing urban structure interact in determining the cover and identity of invasive alien species.Methods
We studied the distribution of chosen invasive plant species in a mid-sized city in the Czech Republic, central Europe, on a gradient of equal sized cells from the city centre to its outskirts.Results
A great amount of variation was explained by spatial predictors but not shared with any measured variables. The species cover of invasive species decreased with increasing proportion of urban greenery and distance from the city centre, but increased with habitat richness; road margins, ruderal sites, and railway sites were richest in invasive species. In contrast, the total number of invasive species in cells significantly decreased with increasing distance from the city centre, but increased with habitat richness.Conclusions
Our results suggest that different invasive species prefer habitats in the vicinity of the city centre and at its periphery and the spatial structure and habitat quality of the urban landscape needs to be taken into account, in efforts to manage alien plant species invasions in urban environments.42.
Nitrogen leaching persists in mountain forests of Europe even in the presence of decreasing N depositions. We have hypothesized
that this leaching is linked to soil N transformations occurring over the whole year, even at 0°C temperatures. The aims were
to estimate (1) the effect of temperature on N transformations and (2) N pools and fluxes. The study sites are situated in
the Bohemian Forest (Czech Republic). Litter, humus, and 0–10-cm mineral layers were sampled in early spring, and the effect
of temperature on net nitrification, net ammonification, and microbial N immobilization were measured in a short-term incubation
experiment without substrate addition. Nitrogen pools were calculated from the concentrations of N forms in the soil and soil
pool weights, while daily N fluxes were calculated from daily net rates of processes and soil pool weights. Relationships
between temperature and net nitrification, net ammonification, and microbial N immobilization did not follow the Arrhenius
type equation; all processes were active close to 0°C, indicating that microbial N transformations occur over the whole year.
Microbial N immobilization rate was generally greater than N mineralization rate. The microbial N pool was significantly larger
than mineral N pools. Organic layers containing tens of grams of available N per square meter contributed more than 70% to
the available N in the soil profile. Daily N fluxes were related to N pools. On average, N fluxes represented daily mineral
and microbial N pool changes of 1.14 and 1.95%, respectively. The effect of microbial composition on the C/N ratio of microbial
biomass and respiration is discussed. 相似文献
43.
At cattle overwintering areas, inputs of nutrients in animal excrements create conditions favourable for intensive microbial
activity in soil. During nitrogen transformations, significant amounts of N2O are released, which makes overwintering areas important sources of N2O emission. In previous studies, however, increasing intensity of long-term cattle impact did not always increase emissions
of N2O from the soil: in some cases, N2O emissions from the soil were lower at the most impacted area than at the moderately impacted one. Thus, the relationships
between the level of long-term animal impact and potential production of N2O from soil by denitrification were investigated in field and laboratory experiments. Field measurements indicated that the
production of N2O after glucose and nitrate amendments was greater in severely and moderately impacted locations than in an unimpacted location,
while differences between the severely and moderately impacted locations were not significant. In laboratory experiments,
the potential production of N2O (measured as anaerobic production of N2O after addition of glucose and nitrate) was highest in the moderately impacted soil. Surprisingly, potential N2O production was lower in the most impacted than in the moderately impacted soil, and the net N2O production in the highly impacted soil was further decreased by a significant reduction of N2O to N2. The expected stimulating effect of an increasing ratio of glucose C to nitrate N on the reduction of N2O to N2 during denitrification was not confirmed. The results show that cattle increase the denitrification potential of the soil
but suggest that the denitrification potential does not increase indefinitely with increasing cattle impact. 相似文献
44.
Igor Koloniuk Josef Špak Karel Petrzik 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(3):447-450
The nucleotide sequence of the 3′-terminal part of the RNA1 genome segment of the M12 isolate of comovirus Turnip ringspot virus (TuRSV) was established. This isolate originated in 1989 in Moscow (Russia) from Chinese cabbage with Radish mosaic virus-like symptoms. Comparison of the M12 RNA polymerase amino acid sequence with that of Radish mosaic virus (RaMV) revealed
significant differences; these proteins are of different length and are only about 75% identical. On the other hand, the amino
acid sequence of the M12 RNA polymerase was more than 94% identical with that of TuRSV recently described in Toledo (USA).
We conclude that TuRSV occurs in Europe as well as in America and probably represents a new species of the genus Comovirus. 相似文献
45.
Irena Mavrič Pleško Mojca Viršček Marn Saša Širca Gregor Urek 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(3):261-268
In 2003, Raspberry bushy dwarf virus was found for the first time in grapevine. Since this was the first report of a non-Rubus natural host, information about it is sparse. During this study the grapevine isolates were characterised biologically, serologically
and genetically and compared with known information about Rubus isolates. Infected plant material was used for mechanical inoculation of test plants, and for serological characterisation
with monoclonal antibodies. Most of RNA 2 was sequenced and compared with other sequences from the database. Grapevine isolates
infected Chenopodium murale systemically, which is not known for raspberry isolates. They were differentiated from Slovenian raspberry isolates with
three monoclonal antibodies using TAS-ELISA. Phylogenetic analyses clustered grapevine isolates separately from raspberry
isolates. Additionally, the virus was detected using nested RT-PCR in Longidorus juvenilis nematodes collected in an infected vineyard. Grapevine isolates of RBDV are distinct from raspberry isolates. 相似文献
46.
Jaroslava Přibylová Karel Petrzik Josef Špak 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(1):181-185
Four Rhododendron hybridum plants (from cvs Moravanka and Don Juan), all exhibited symptoms of shortened axillary shoots, reduced leaves with
vein clearing and yellowing, undeveloped flowers, and general stunting in a rhododendron nursery garden in southern Bohemia
in 2007. Electron microscopy examination of ultra-thin sections revealed the presence of numerous polymorphic phytoplasma-like
bodies in the phloem tissue of leaf midribs and petioles. The phytoplasma etiology of this disease was further confirmed by
polymerase chain reaction (PCR) using universal phytoplasma primers. Restriction fragment length polymorphism (RFLP) analysis
of amplification products obtained with a R16F2/R16R2 primer pair from all symptomatic plants indicated the presence of phytoplasma
from the 16SrVI-A subgroup. A detailed comparison of the amplified sequences and phylogenetic analysis confirmed that the
phytoplasma belonged to the subgroup 16SrVI-A (clover proliferation phytoplasma group). This is the first report of the natural
occurrence of ‘Candidatus Phytoplasma trifolii’ in plants of Rhododendron hybridum. 相似文献
47.
Václav Šíp Jana Chrpová Alžběta Žofajová Kateřina Pánková Martin Užík John W. Snape 《Euphytica》2010,172(2):221-233
Based on studies of the distribution of alleles at the important Rht and Ppd loci on wheat chromosomes 4B, 4D and 2D, different groups of winter wheat cultivars registered in the Czech and Slovak Republics
during the period 1976–2007 were examined for a range of agronomic traits using official data from multi-location trials.
Significant variation for all traits was detected among and between genotype groups. The frequent introduction of ‘Rht-D1b’ cultivars from the UK and Western Europe to the Czech Republic since 1995 has positively influenced lodging resistance and
undoubtedly also yielding ability, but negatively affected winter-hardiness and bread making quality. An improved opportunity
for earlier flowering cultivars with high winter-hardiness levels, in combination with high bread-making quality, can be obtained
with genotypes carrying the Xgwm261 allele 192-bp that is probably indicative of the presence of Rht8. While GA insensitive Rht genes caused approximately a 10 cm reduction of plant height, the 192-bp allele at Xgwm261 was not associated, in these conditions, with a significant reduction in plant height when compared to Xgwm261 alleles 165- and 174-bp. Likewise, the photoperiod insensitive allele Ppd-D1a did not have a significant effect on plant height and it had not adversely affected other characters. Later heading genotypes
carrying Xgwm261 alleles174- and 165-bp, often in combination with Ppd-D1b, could probably guarantee broader adaptability, which is highly desirable for changeable weather conditions. While the presence
of the 192-bp allele was clearly associated with suitability for cultivation in the warmer maize growing regions, this was
not so obvious for Ppd-D1a, particularly when combined with the 174-bp allele. GA responsive genes did not, apparently, influence adaptability to the
different growing conditions. These studies reveal that there were both shortcomings and benefits attributable to the use
of germplasm from different origins when introducing Rht and Ppd alleles. These results should be helpful to breeders in optimizing the choice of parents for crossing, and selection strategy
in these target environments. 相似文献
48.
Algirdas Augustaitis Ingrida Augustaitienė Almantas Kliučius Gintaras Pivoras Dalia Šopauskienė Raselė Girgždienė 《European Journal of Forest Research》2010,129(3):431-441
The multiple-stressor effects of air pollution, nutrient and water availability are the key issues of present forest ecosystem
research. However, too little is known about the seasonal effect of pollutants on tree crown defoliation and their interaction
with changes in climate. Therefore, data on seasonal variation in air pollution, including surface ozone, deposition of acidifying
compounds and meteorological conditions, were tested against pine defoliation to identify the periods when the effect of the
considered contaminants is most pronounced. The findings of the study revealed that a higher level of air concentrations of
acidifying pollutants and their deposition was observed during the dormant period, with the exception of only ΣNH4+ air concentrations and their monthly deposition. An increase in precipitation over the vegetation period and mean monthly
temperature from September to December, as well as a decrease in temperature and precipitation over the remaining months of
the dormant period represented the climate change condition over the 14-year period in the observed region. Detected changes
in the considered parameters during the dormant period were found to be most significant to changes in pine crown defoliation.
Therefore, we concluded that climate changes, if they occur by the detected scenarios, should mitigate the negative effect
of air pollutants and acid deposition on pine crown condition. 相似文献
49.
Alisa Šehić Jelena Vasiljević Igor Jordanov Andrej Demšar Jožef Medved Ivan Jerman Marija Čolović Fiona Hewitt T. Richard Hull Barbara Simončič 《Fibers and Polymers》2018,19(6):1194-1206
This research investigated the influence of two flame retardant (FR) mixtures consisting melamine cyanurate (MeCy) and aluminum diethylphosphinate (AlPi), and MeCy and sodium aluminosilicate (SASi) at different weight ratios, on the flammability, thermal behavior and mechanical properties of polyamide 6 (PA6) composite yarns produced by meltspinning. The morphological and chemical properties of PA6/FR filaments were investigated by scanning electron microscopy and Fourier-transform infrared spectroscopy, flame retardancy by vertical burning test UL-94, thermal behavior by thermogravimetric and differential scanning calorimetric analyses, and mechanical properties by tensile tests. The results indicate that within the UL 94 V2 rating, the composite yarns differed significantly from each other in their burning and dripping behavior. The incorporation of both mixtures, MeCy+AlPi and MeCy+SASi, into the PA6/FR yarns significantly decreased the afterflame time relative to pristine PA6, confirming a lower production of flammable volatiles. This phenomenon was attributed mainly to MeCy, which caused an immediate extinguishment of the flame after the withdrawal of the igniting flame. Compared to one component MeCy, the incorporation of the MeCy+SASi mixture enhanced the thermooxidative stability of the PA6/FR yarns because of their additive effect at higher concentrations. In contrast, an antagonistic effect was obtained for the MeCy+AlPi mixture, irrespective of the concentration. Since the incorporation of MeCy+SASi did not drastically reduce the tensile properties of filaments, this mixture enables the production of the PA6/MeCy+SASi composite yarns with the enhanced flame retardancy and thermo-oxidative stability. 相似文献
50.
Eva Švecová Giuseppe Colla Paola Crinò 《European journal of plant pathology / European Foundation for Plant Pathology》2017,147(1):27-41
A new longidorid nematode, Longidorus persicus n. sp., is described and illustrated from a population extracted from soil associated with wild rose (Rosa sp.) naturally growing in the mountains close to the village of Cheshmeh-e-Nezamei near the city of Gilan-e-Gharb, Kermanshah province, western Iran. The new needle nematode is characterised by a large body size (6550–7763 μm), an anteriorly flattened lip region, ca 13 μm wide, distinctly set off from body contour by a depression, amphidial fovea large, pocket shaped, slightly asymmetrically bilobed, a moderately long and flexible odontostyle ca 86 μm long, stylet guiding ring located at ca 25 μm from anterior end, posterior arrangement of the pharyngeal gland nuclei, vulva almost equatorial (49–54 %), tail short, about 3/4 of its width, dorsally convex-conoid, with rounded terminus, with a c’ ratio ca 1.3, bearing three pairs of caudal pores and male rare (ratio 1:10 females) with spicules ca 46 μm long. Integrative diagnosis was completed with molecular data obtained using D2-D3 expansion segments of 28S rDNA, ITS1-rDNA, and partial 18S-rDNA. The phylogenetic relationships of this species with other Longidorus spp. using D2-D3 expansion segments and partial 18S-rDNA indicated that L. persicus n. sp. clustered together with L. perangustus and L. euonymus: both of them sharing an anteriorly flattened lip region and distinctly set off from body contour by a depression. 相似文献