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1.
Cornus stolonifera, Salix petiolaris, and Spiraea alba
clones already located within the corridor of an electrical power line. To
establish the efficiency of treatments, we examined the statistical
differences of growth traits between species and treatments.
An analysis of the effects of layering shows, after the first growth season,
differences for all growth traits in only one species, Spiraea alba.
After the second growth season, we observed the development of new aerial
stems. Layering favors horizontal expansion of shrubs over height
development. The third year after treatment, the effect of layering is
reduced except for Cornus stolonifera, which continuously increases,
as shown by the significant progression of the clone issued from the layer
even five years after treatments. With the cutting back technique, we
expected a distinct vertical growth of the shrubs at the expense of
increasing the crown diameter. This technique would be best associated with
the rejuvenation of clones, followed by a layering of new shoots to allow a
horizontal expansion of the shrubs. Therefore, the formation of a dense shrub
community by layering should be considered a valuable approach for the
biological control of undesirable trees in powerline rights-of-way. 相似文献
2.
3.
Nugraha E. Suyatma Alain Copinet Lan Tighzert Veronique Coma 《Journal of Polymers and the Environment》2004,12(1):1-6
Biodegradable film blends of chitosan with poly(lactic acid) (PLA) were prepared by solution mixing and film casting. The main goal of these blends is to improve the water vapor barrier of chitosan by blending it with a hydrophobic biodegradable polymer from renewable resources. Mechanical properties of obtained films were assessed by tensile test. Thermal properties, water barrier properties, and water sensitivity were studied by differential scanning calorimeter analysis, water vapor permeability measurements, and surface-angle contact tests, respectively. The incorporation of PLA to chitosan improved the water barrier properties and decreased the water sensitivity of chitosan film. However, the tensile strength and elastic modulus of chitosan decreased with the addition of PLA. Mechanical and thermal properties revealed that chitosan and PLA blends are incompatible, consistent with the results of Fourier transform infrared (FTIR) analysis that showed the absence of specific interaction between chitosan and PLA. 相似文献
4.
Tree-based intercropping is considered to be a potentially useful land use system for mitigating negative environmental impacts from intensive agriculture such as nutrient leaching and greenhouse gas emissions. Rapid early growth of trees is critical for rapidly accruing environmental benefits provided by the trees. We tested the hypothesis that intercropping increases the growth and nutrient status of young hybrid poplars (Populus spp.), compared to a harrowing alley treatment (i.e., no intercrop), in two experimental sites (St-Rémi and St-Édouard) in southern Québec, Canada. Three hybrid poplar clones (TD3230, Populus trichocarpa × deltoides; DN3308, P. deltoides × nigra; and NM3729, P. nigra × maximowiczii) were planted at St-Rémi. Clones DN3333 and DN3570 were planted at St-Édouard. At St-Rémi, intercropping comprised a 4-year succession of three crops of soybean (Glycine max (L.) Merr.) and barley (Hordeum vulgare L.). At St-Édouard, intercropping comprised a 3-year succession of buckwheat (Fagopyrum esculentum Moench), winter rye (Secale cereale L.), and winter wheat (Triticum aestivum L.). At St-Rémi, four years after treatment began, leafless aboveground biomass of hybrid poplars in the intercropping treatment was 37% higher compared to that in the harrowing treatment. At St-Édouard, after the third growing season, leafless aboveground biomass of hybrid poplars in the intercropping treatment was significantly higher by 40%. Vector analysis of foliar nutrient concentrations and comparison with critical concentration values showed that N (both sites) and K (St-Édouard) were the most limiting nutrients. Hybrid poplar clones responded similarly to treatments, with no consistent differences in tree growth observed between clones. We conclude that tree-based intercropping systems may offer an effective means of improving the early growth of hybrid poplars planted to provide both environmental services and high-value timber. 相似文献
5.
Lefèvre G Bessière J Ehrhardt JJ Walcarius A 《Journal of environmental radioactivity》2003,70(1-2):73-83
In the goal of finding efficient scavengers for radioiodide in conditions (pH, pE) close to those encountered in deep geological sites, sorption of iodide ions on cuprous sulfide minerals (especially roxbyite, Cu(1.75)S) has been studied. Surface analysis by X-ray photoelectron spectroscopy has shown that commercial cuprous sulfides are covered by an oxidized overlayer (mainly in the form of CuSO(4)). Therefore, a synthetic procedure to get roxbyite (typically by mixing Na(2)S with an aqueous suspension of commercial Cu(2)O) was applied to produce pure samples with clean surfaces. Batch equilibration of cuprous sulfide particles suspended in aqueous solutions containing iodide species has revealed significant consumption of iodide. The sorption mechanism involves the formation of a surface complex via the exchange of surface hydroxyl groups by iodide anions, as highlighted by a transient pH increase during the immobilization process. Other copper and mixed copper-iron sulfides (e.g. CuS, CuFeS(2)), which are stable over wide pH and potential ranges are also likely to accumulate iodide species. Because of the specific interaction between iodide and copper(I) centers on the minerals, high distribution coefficients (>1000 ml/g) were observed. 相似文献
6.
Tineke H. Jones Alain Houde Elyse Poitras Pierre Ward Michael W. Johns 《Food and environmental virology》2009,1(2):57-65
There are increasing concerns of zoonotic transmission of some animal enteric viruses, such as calicivirus, hepatitis E virus,
and rotavirus, which are closely related to human pathogenic strains. Most enteric viruses are detected by molecular techniques
because they cannot be cultured. Surrogates such as F-RNA coliphages are cultivable but few molecular methods exist. Individual
real-time TaqMan RT-PCR assays for the replicase gene of F-RNA coliphage genogroups I and IV were developed and multiplexed
with a real-time TaqMan RT-PCR assay for feline calicivirus as a sample process control for the simultaneous detection and
enumeration of genogroup I and IV F-RNA coliphages. Genogroup IV were successfully detected with the multiplexed assay in
80% of fecal samples that contained F-RNA coliphage levels ≥3.2 log plaque forming units (pfu). F-RNA coliphage were at or
below the limit of detection in most fecal samples when levels were ≤4 log pfu/g. 相似文献
7.
The Mantophasmatodea is the most recently discovered insect order. The fossil records of all other ‘polyneopteran’ orders
extend far in the past, but the current absence of pre-Cenozoic fossils of the Mantophasmatodea contradicts a long evolutionary
history, which has to be assumed from the morphological distinctness of the group. In this paper, we report the first Mesozoic
evidence of a mantophasmatodean from the Middle Jurassic of Daohugou, Inner Mongolia, China. Furthermore, the new fossil shares
apomorphic characters with Cenozoic and recent Mantophasmatodea, suggesting a longer evolutionary history of this order. 相似文献
8.
It is well known that arboreal ants, both territorially dominant species and plant ants (e.g., species associated with myrmecophytes or plants housing them in hollow structures), protect their host trees from defoliators. Nevertheless, the presence of an induced defense, suggested by the fact that the workers discovering a leaf wound recruit nestmates, is only known for plant ants. Based on the results from a field study, we show here (1) that colonies of Azteca chartifex, a territorially dominant, neotropical arboreal ant species, mostly selected Goupia glabra (Goupiaceae) trees in which to build their principal carton nests and (2) that plant signals induced workers to recruit nestmates, which patrol the leaves, likely providing the plant with a biotic defense. Furthermore, the number of recruited workers was clearly higher on G. glabra, their most frequently selected host tree species, than on other tree species. These results show that contrary to what was previously believed, induced responses are also found in territorially dominant arboreal ants and so are not limited to the specific associations between myrmecophytes and plant ants. 相似文献
9.
Demetres Briassoulis Cyril Dejean Pietro Picuno 《Journal of Polymers and the Environment》2010,18(3):364-383
The critical review of norms and standards and corresponding tests to determine the compostability of biodegradable plastics,
possibly applicable also to biodegradable agricultural plastics, shows that many norms concerning testing and labelling of
compostable plastics have been established at the international level. Some of them are about plastic materials, some others
are about products like packaging. The media and conditions of testing cover mainly the conditions designed for industrial
composting facilities, and only a few concern home composting conditions. Considering that the end of life management of biodegradable
agricultural plastic products will be done at the farm to reduce the management of the waste and also its cost, only a few
of these norms are considered to be suitable for adaptation to cover also biodegradable agricultural plastic products. The
biodegradability validation criteria under composting conditions, such as the threshold percentage of biodegradation and disintegration,
the time and temperature, and the ecotoxicity, are presented for the main norms and standard testing methods. Based on these
different norms and their content, a list of specs and technical requirements that could be adapted to meet farm composting
conditions for agricultural compostable plastics is proposed. These requirements may be used as criteria for the establishment
of a new integrative norm for agricultural compostable plastics. 相似文献
10.
In French Guiana, parabiotic societies (natural mixed colonies) are frequently found in ant gardens. Crematogaster limata parabiotica (Myrmicinae), often associated with Camponotus femoratus (Formicinae), was found for the first time in parabiosis with ponerine ants: Pachycondyla goeldii and Odontomachus mayi. A detailed study of the relationships between Cr. l. parabiotica and O. mayi showed that each species is aggressive towards allospecific or conspecific individuals belonging to another colony, but tolerates
allospecific individuals from the multi-species society. Studies of cuticular substances of the four ant species were made
using gas chromatography. The results showed that each species, living alone or in parabiosis, possesses a specific chemical
profile. Thus, the ants are able to recognise nestmate and non-nestmate individuals of the associated species, even though
their cuticular profiles are different. The hypothesis that the nestmate allospecific profile is learned is suggested to explain
this pattern of recognition.
Received: 5 June 1996 / Accepted after revision: 17 October 1996 相似文献