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21.
Frank van Langevelde Jody A. Ettema Maurice Donners Michiel F. WallisDeVries Dick Groenendijk 《Biological conservation》2011,(9):2274-2281
During the last decades, artificial night lighting has increased globally, which largely affected many plant and animal species. So far, current research highlights the importance of artificial light with smaller wavelengths in attracting moths, yet the effect of the spectral composition of artificial light on species richness and abundance of moths has not been studied systematically. Therefore, we tested the hypotheses that (1) higher species richness and higher abundances of moths are attracted to artificial light with smaller wavelengths than to light with larger wavelengths, and (2) this attraction is correlated with morphological characteristics of moths, especially their eye size. We indeed found higher species richness and abundances of moths in traps with lamps that emit light with smaller wavelengths. These lamps attracted moths with on average larger body mass, larger wing dimensions and larger eyes. Cascading effects on biodiversity and ecosystem functioning, e.g. pollination, can be expected when larger moth species are attracted to these lights. Predatory species with a diet of mainly larger moth species and plant species pollinated by larger moth species might then decline. Moreover, our results indicate a size-bias in trapping moths, resulting in an overrepresentation of larger moth species in lamps with small wavelengths. Our study indicates the potential use of lamps with larger wavelengths to effectively reduce the negative effect of light pollution on moth population dynamics and communities where moths play an important role. 相似文献
22.
Nicola M. Hall Bocary Kaya Jan Dick Ute Skiba Amadou Niang Ramadjita Tabo 《Biology and Fertility of Soils》2006,42(3):224-230
The impacts of fallow on soil fertility, crop production and climate-forcing gas emissions were determined in two contrasting
legumes, Gliricidia sepium and Acacia colei, in comparison with traditional unamended fallow and continuous cultivation systems. After 2 years, the amount of foliar
material produced did not differ between the two improved fallow species; however, grain yield was significantly elevated
by 55% in the first and second cropping season after G. sepium compared with traditional fallow. By contrast, relative to the unamended fallow, a drop in grain yield was observed in the
first cropping season after A. colei, followed by no improvement in the second. G. sepium had higher foliar N, K and Mg, while A. colei had lower foliar N but higher lignin and polyphenols. In the third year after fallow improvement, a simulated rainfall experiment
was performed on soils to compare efflux of N2O and CO2. Improved fallow effects on soil nutrient composition and microbial activity were demonstrated through elevated N2O and CO2 efflux from soils in G. sepium fallows compared with other treatments. N2O emissions were around six times higher from this nitrogen-fixing soil treatment, evolving 69.9 ngN2O–N g−1soil h−1 after a simulated rainfall event, compared with only 8.5 and 4.8 ngN2O–N g−1soil h−1 from soil under traditional fallow and continuous cultivation, respectively. The findings indicate that selection of improved
fallows for short-term fertility enhancement has implications for regional N2O emissions for dry land regions. 相似文献
23.
Tillage systems influence soil properties and may influence the availability of applied and mineralized soil N. This laboratory study (20°C) compared N cycling in two soils, a Wooster (fine, loamy Typic Fragiudalf) and a Hoytville (fine, illitic Mollic Epiaqualf) under continuous corn (Zea mays) production since at least 1963 with no-tillage (NT), minimum (CT) and plow tillage (PT) management. Fertilizer was added at the rate of 100 mg 15N kg–1–1 soil as 99.9% 15N as NH4Cl or Ca(NO3)2 and the soils were incubated in leaching columns for 1 week at 34 kPa before being leached periodically with 0.05 M CaCl2 for 26 weeks. As expected, the majority of the 15NO3– additions were removed from both soils with the first leaching. The majority of applied 15NH4+ additions were recovered as 15NO3– by week 5, with the NT soils demonstrating faster nitrification rates compared with soils under other tillage practices. For the remaining 22 weeks, only low levels of 15NO3– were leached from the soils regardless of tillage management. In the coarser textured Wooster soils (150 g clay kg–1), mineralization of native soil N in the fertilized soils was related to the total N content (r2 0.99) and amino acid N (r2 0.99), but N mineralization in the finer textured Hoytville (400 g clay kg–1) was constant across tillage treatments and not significantly related to soil total N or amino acid N content. The release of native soil N was enhanced by NH4+ or NO3– addition compared to the values released by the unfertilized control and exceeded possible pool substitution. The results question the use of incubation N mineralization tests conducted with unfertilized soils as a means for predicting soil N availability for crop N needs. 相似文献
24.
Seasonal, soil type, and alternative management influences on microbial communities of vegetable cropping systems 总被引:15,自引:0,他引:15
Microbial community responses to alternative management may be indicative of soil quality change. In this study, soils were collected from research plots over 2 years and from commercial grower fields over 1 year. Treatments at the sites included 1-9 years of either winter cover cropping or winter fallow practices. Soils were assayed for microbial fatty acid methyl esters (FAMEs), direct count microscopy and Biolog substrate utilization potentials to assess management and environmental influences on soil communities. The strongest influence was season. Soils in early spring (prior to termination of the cover crop) utilized fewer carboxylic acids and generally were enriched in eukaryotic FAMEs, whereas proportionally more bacterial FAMEs were detected in soils at canopy closure and harvest of the summer vegetable crop. Within a season, community FAME and Biolog patterns were related to field properties. FAME profiles from grower fields in early spring and harvest were correlated significantly with soil texture, cation exchange capacity, and carbon content. Changes in community structure and Biolog potential occurred in some soils in response to winter cover crops, although effects were not observed until cover crop incorporation. Greater amounts of fungal and protozoan FAME markers were detected in some cover-cropped soils compared to winter fallow soils. Cover crop residues increased FAME diversity at one research station and Biolog diversity at two research stations and the grower fields. Although seasonal and field-dependent factors are major determinants of microbial community structure, shifts can occur as soil physical and chemical properties change in response to alternative practices, as demonstrated by this study. 相似文献
25.
The distribution of inoculated Escherichia coli cells and indigenous bacteria in a silt loam soil and a sandy soil was studied using fluorescence microscopy techniques. Ethidium bromide stained inoculated cells against the soil and resin background. Satisfactory results were also obtained with epifluorescence microscopy of samples stained with calcofluor white M2R (CFW) and 4′,6-diamidino-2-phenylindole (DAPI). Indigenous soil bacteria were visualized in soil thin sections, after staining with ethidium bromide, using fluorescence microscopy. The density of these bacteria was estimated to be 107-108 cells/cm3. Inoculated E. coli cells, stained with one of the green fluorochromes (fluorescein isothiocyanate (FITC), 5-(4,6-dichlorotriazinyl)aminofluorescein, or eosin Y), could be clearly distinguished in sandy soil thin sections. Confocal laser scanning microscopy with 3D image reconstruction was also successfully applied to characterize distribution of E. coli introduced to soil. The fate of introduced bacteria and the location of indigenous bacteria in soil can be confirmed using the microscopic techniques described in this paper. 相似文献
26.
Abstract. The accuracy of a ThetaProbe (Delta-T Devices Ltd, UK) to obtain repeated measures of soil water content in pot plants was tested. This alternative to balance determinations led to a large underestimation of water content, varying from 12.2 to 21.8% of the total water content, depending on soil type. 相似文献
27.
28.
29.
Isolation and identification of goose parvovirus in the UK 总被引:2,自引:0,他引:2
30.
Prevalence of antibodies to bluetongue virus and Anaplasma marginale in Montana yearling cattle entering Alberta feedlots: Fall 2001
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Van Donkersgoed J Gertonson A Bridges M Raths D Dargatz D Wagner B Boughton A Knoop D Walton TE 《The Canadian veterinary journal. La revue veterinaire canadienne》2004,45(6):486-492
A serologic survey was conducted in yearling cattle imported into Alberta feedlots from Montana during October 2001 to estimate the prevalence of antibodies to bluetongue virus (BTV) and Anaplasma marginale in Montana yearling cattle. The apparent prevalence of antibodies to BTV when the competitive enzyme-linked immunosorbent assay (cELISA) was used was 0.37% (21/5608). Test positive cELISA samples were also all positive when tested by virus neutralization (VN) and they reacted to 1 or more BTV serotypes, including 2, 10, 11, 13, and 17. The apparent prevalence of antibodies to A. marginale when a recombinant cELISA (rcELISA) was used with a positive cutoff at 30% inhibition was 1.93% (108/5608). When the rcELISA positive cutoff was at 42% inhibition, the apparent prevalence was 0.73% (41/5608). After the reported sensitivity and specificity of the test had been accounted for, the A. marginale antibody results were consistent with a population that was either free of exposure or had a very low prevalence for A. marginale. 相似文献