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Species abundance-distribution relationship is currently a hot topic in community ecology. Previous studies have suggested that a positive abundance-distribution relationship is a widespread feature of ecological assemblage across a wide variety of organisms, but how this relationship varies among different functional groups remains unclear. In this study, the species abundance-distribution relationship in the tree layer, shrub layer, and herb layer were analyzed respectively in an oak forest (Quercus liaotungensis Koidz.), Beijing region, China. Ten transects were set up from the foot to the top of every west slope to create a continuous altitude gradient (1020– 1770 m). The width of each transect was 10 m and the length of each transect ranged from 80–200 m, depending on the altitude range and slope degree. This study area consisted of 119 quadrats, each 10 × 10 m2. Within each quadrat, three sub-quadrats (1m × 1m) were randomly selected for the inventory of herb layer. Our results showed that the relationship between local species abundance and the regional distribution was significantly positive while the frequency distribution was unimodal in the three layers, indicating that locally abundant species were widely spread whereas locally rare species had restricted regional distributions. Variance partitioning of species abundance showed that the contribution of environmental variation and spatial variation to regulating the species abundance-distribution relationship of different layers are different: the pure geographical variation decreased and the pure soil variation increased in the order of tree layer, shrub layer, to herb layer, while the response due to total soil variation was similar in all three layer communities. The distribution of tree layer and shrub layer are mainly influenced by large-scale factors while herb layer distribution is more likely determined by local-scale factors.
The improvement of soy sauce fermentation is restricted by the insufficient information on bacterial community. In this study, bacterial communities in the koji and mash stage were compared based on next-generation sequencing technology. A total of 29 genera were identified in the koji stage, while 34 in the mash stage. After koji stage, 7 genera disappeared and 12 new genera appeared in the mash stage. The dominant bacteria were Kurthia, Weissella and Staphylococcus in the koji stage and Staphylococcus, Kurthia, Enterococcus and Leuconostoc in the mash stage. The results provided insights into the microbial communities involved in soy sauce fermentation.
To quantify the emission of airborne aetinomycetes from the wastewater treatment plant (WWTP), the concentration and size distribution of airborne culturable actinomycetes were examined with a six-stage cascade impactor in a municipal WWTP with oxidation ditch process in Xi'an, China from June to July 2011. Simultaneously, characteristics of airborne bacteria were also measured to compare with data of actinomycetes. Similar to airborne bacteria, the concentration and size distribution of airborne actinomycetes were found to vary greatly at different phases of the wastewater treatment process. The mean concentration of actinomycetes in the WWTP ranged from 2139±229 at the sludge dewatering house (SDH) to 902±54 CFU∙m⁻³ at the effluent outlet (EO). The largest emission source of actinomycete aerosols was detected at the SDH, with 21-fold exceeding the permissible standards recommended in the literature. The particle size distributions showed that similar single-peak distribution patterns appeared for both airborne actinomycetes and bacteria. The count median diameter (CMD) of total actinomycetes and bacteria concentration were 2.3 and 3.2 µm in the WWTP, respectively. Although the total concentration of actinomycetes was smaller than that of bacteria in the present WWTP, the respirable fraction (particles smaller than 4.7 µm in aerodynamic diameter) for actinomycetes (81.9%) was higher than that for bacteria (64.6%). The results obtained in the present research suggest that more attention should be paid to the potential health risk related to actinomycetes in studies on wastewater treatments.
Tomato (Solanum lycopersicum L.) is one of the world’s most important cultivated vegetable. In the traditional cultivation methods, the excessive use of pesticides and fertilizers leads to an imbalance of nutrient elements in the soil, an increase in pests and diseases and a decrease in vegetable quality and yield. In the face of increasingly serious environmental and food problems, organic agriculture is considered to be an effective solution. In this experiment, the effects of organic cultivation patterns on the growth, quality, disease resistance in tomatoes, and the physical and chemical properties of soil were studied by different treatments. The results showed that the application of effective microorganisms (EM) bio-organic fertilizer in the cultivation process can significantly improve the yield, quality, and antioxidant enzyme activity of tomato. The use of straw mulching was found to significantly increase the growth, chlorophyll content, transpiration rate, and soluble sugar content of tomatoes. The application of EM bio-organic fertilizer or straw mulching significantly increased the activity of antioxidant enzyme and the expression of LeCHI gene in tomato leaves and enhanced tomato resistance to diseases. Organic production practices were found to significantly improve the soil.
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