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In this study, five mixed substrates – SSFGF, FSSGF, FSSFF, FSSFG, and FSFGF – consisting of fly ash, sludge, soil, fine cinder, gravels, and fine sand, were made in order to test the removal effect of lead. Multiple comparisons and analysis of variance were used to analyze physicochemical properties and the removal efficiency of lead. The test results showed that for five substrates, the effluent concentrations were not significantly different among 10 mg/L and 40 mg/L initial concentrations. For the other three initial concentrations (20 mg/L, 80 mg/L and 160 mg/L) from five substrates, it was significantly different. Moreover, when decomposition time was 0.25 h~48 h, the removal efficiency of Pb from the solution was better for substrate SSFGF-based wetland than those of the other substrate-based wetlands at low and medium initial concentrations (10 mg/L, 20 mg/L, 40 mg/L, and 80 mg/L), and then it was slightly better for substrate FSSFF-based wetland. At relatively high initial concentrations (160 mg/L), the removal efficiency was better for substrate FSSFF-based wetland than those of the other substrate-based wetlands, and then it was slightly better for substrate SSGFF-based wetland. Our study further suggested that SSFGF and FSSFF were the two relatively ideal substrate materials suitable for removal of Pb from a constructed wetland system.
C₃ desert plant Reaumuria soongorica (RS-C₃) and C₄ desert plant Salsola passerina (SP-C₄) may exist either in individual or in associated communities. Carbon isotope composition, leaf water potential, gas exchange and chlorophyll fluorescence characteristics of the individual and associated communities were compared with reveal, whether the associated growth represent an advantage under harsh habitat. The results showed that the δ¹³Cvalues of leaves ofRS-C₃ and SP-C₄ across different habitats fluctuated, respectively, from-24 to-27 ‰ and from-14 to-16 ‰. Leafwater potential of RS-C₃ was lower than SP-C₄ all day long, growing either individually or associated with the C₃ plant. When associated with the C₄ plant, the net photosynthetic rate of the RS-C₃ increased, and the photosynthetic rate of the partner SP-C₄ decreased. The transpiration rates of the associatedRS-C₃ and SP-C₄ were both lower than in their individual colonies. In associated communities, in RS-C₃, the maximal photochemical efficiency, the effective photochemical efficiency, the relative electron transport rate, the photochemical quenching of PS II increased, and the non-photochemical quenching of PS II decreased; all these parameters changed oppositely in the SP-C₄ plant.This shows that, in the associated community, the C₄ plants might facilitate adaptation of the RS-C₃, while SP-C₄ plant can adapt to the harsh environment through their own specialties. The association favored the expression of natural photosynthetic characteristics and survival of RS-C₃, while retarded the growth of SP-C₄. Associated growth decreases the transpiration rate of the whole community; it is conducive to improve its water use efficiency.
Alternate drought and flooding stress has become more prevalent during paddy growth stages as a result of climate change, especially in southern China. This study aims to assess the effect of alternate drought and flooding stress on water use, and nitrogen (N) and phosphorus (P) losses in paddy fields. Two controlled irrigation and drainage (CID) managements (namely drought at the beginning of growth stages followed by flooding (CID-1), and flooding at the beginning of growth stages followed by drought (CID-2) and one alternated wetting and drying (AWD) management were designed in specially designed experimental tanks with three replications in 2015 and 2016. Results showed that CID increased effective irrigation quantities and rainwater storage ability with a significant decrease in water use efficiency compared with AWD. For surface water, CID-1 significantly improved possible losses of nitrogen and phosphorus during the fertilizer application period over CID-2. For subsurface water, CID can significantly reduce the leaching losses of nitrate N and P compared with AWD. Meanwhile, CID-1 significantly increased the leaching losses of nitrate N at the former two growth stages compared to CID-2, yet no significant difference was found for ammonia N and P. Therefore, the application of controlled irrigation and drainage – especially for CID-1 – was an efficient method for obtaining high water quality and reducing eutrophication.
We used Populus cathayana, a native species with an extensive distribution in northern, central, and southwestern China, as a model species to detect the sex-specific differences in photosynthetic capacity, ultrastructure, nitrogen (N) metabolism, and nickel (Ni) accumulation and distribution in response to Ni stress. Exposure to 100 μM Ni²⁺ in a hydroponic system for 1 month significantly decreased the pigment content and the photosynthetic rate, caused visible impairment in cellular organelle structure, and induced obvious disturbance and imbalance in the N content of female plants, while male plants suffered a lower negative influence on all the above measured parameters. However, males accumulated a higher Ni concentration in both leaves and roots than females, while the transportation ratio of Ni from roots to shoots in males was slightly lower than that in females. Our results, therefore, suggest that males have a better tolerance capacity and a greater ability to remediate Ni-polluted soil than females. This greater tolerance capacity in males might be highly correlated with the better maintenance of N balance and more effective physiological detoxification responses (such as the response to proline) under Ni stress. The differences between the sexes in tolerance capacity to heavy metals should be verified after performing a field investigation using adult trees as materials in the future study.
Brown Eared-pheasant (Crossoptilon mantchuricum Swinhoe, 1863) is an endangered species endemic to China. Habitat management for Brown Eared-pheasant has to compensate the loss of natural forests and to improve their habitat quality. In this study, we applied a Habitat Suitability Index (HSI) model to analyze the habitat suitability and quality for the breeding populations of this species in Xiaowutaishan National Nature Reserve, North China. The Reserve (area 21833 ha) is located at 800–2882 m a.s.l. and high mountain and deep valley habitats as well as different types of mountain forest and alpine meadows occur there. We used six variables (vegetation type, canopy cover, altitude, exposure, slope gradient and position of slope) both in field observation and in the analysed model. According to the utilization rates of different habitat types by Brown Eared-pheasants, these variables were categorized into five classes (unsuitable, less suitable, moderately suitable, suitable, and highly suitable). Our results show that highly suitable, suitable, less suitable and unsuitable habitat accounted for 13.5%, 53%, 32%, and 1.5% of the entire reserve area, respectively. Our HSI model is well validated by the observed data. We expect this study can be useful as an example of successful model applying to the habitat management or population manipulation of the endangered species.
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