Growth release and growth inhibition of Pinus tabulaeformis forest in the Loess Plateau of western Shanxi Province,China北大核心CSCD

There has been increased focus on the impacts of climate change on vegetation growth, and human activities that interfere with the vegetation. Discussing the effects of climate change and thinning activity on forest growth is essential to expand plantation areas. In this study, the dendroecological method was used to analyze the radial growth of Pinus tabulaeformis to reveal the impacts of climate change and human activities on forest stand growth. These samples were derived from three different density areas of P. tabulaeformis forest at the Linfen City of Shanxi Province (the east of Loess Plateau). The correlation analysis between tree ring width index and climatic factors indicated that the growth of P. tabulaeformis was negatively related to precipitation in January and the monthly maximum temperature in December of the previous year, whereas positively correlated with precipitation in July and the monthly maximum temperature in October in that year. The phenomena of growth release and inhibition could be attributed to the impacts of climate change and thinning during 1978-2003. However, growth inhibition was closely related to unsuitable climatic conditions. Plot 1 showed a moderate growth inhibition period when the growth variation was less than -50%, and growth release was caused by thinning. The growth variation was greater than 47% in the period of growth release. Moreover, a slight growth release occurred due to tending in plot 2, and the rate of growth change exceeded 39%. A slight growth suppression induced by uncomfortable climatic condition caused growth variation less than -32% and a moderate growth release by the interaction of cutting and comfortable counterpart made variation rate larger than 75% in plot 3. The release effects of thinning can last for about 5 years. In summary, inappropriate climatic conditions can inhibit the growth of trees, and thinning can promote tree growth by about 5 years. The results can provide a reference for local forest management. © 2018 Science Press. All rights reserved.     

Chemical composition of the mycelium of Daldinia eschscholtzii北大核心CSCD

To investigate the chemical composition of the fungus Daldinia eschscholtzii, the compounds were separated by silica gel, Sephadex LH-20, and preparative chromatography. Their structures were identified by spectral methods. The MTT method was applied to measure the cytotoxicity of representative components. Eleven compounds were isolated and identified as 3β-hydroxyl-6,22-dien-5α,8α-peroxynitrite (1); ergosterol-9(11)-dehydroperoxide (2); mangiferonic acid (3); ergosta-4,6,8 (14),22-tetraen-3-one (4); (+)-syringaresinol (5); 3,5,3',5'-tetramethoxy-4,4,-diphenol (6); 5-methoxycoumarin (7); 5-hydroxy-2-methyl-4H-chromen-4-one (8); (2R,4R)-3,4-dihydro-5-methoxy-2-methyl-2H-1-benzopyran-4-ol (9); 2,3-dihydro-5-methoxy-2-methylchromen-4-one (10); and 7β-caruilignan C (11), respectively. Compound 4 showed inhibitory activity against H1299, H460, HGC-27, A5491, and MNK-45, with the IC50 value of 25.2 ± 2.9, 32.3 ± 4.2, 29.2 ± 1.2, 33.9 ± 3.7, and 18.0 ± 7.0 μmol/L, respectively. © 2018 Science Press. All rights reserved.     

Screening and degradation characteristics of a tetracycline-degrading bacterial strain北大核心CSCD

Tetracycline is widely used in livestock and poultry breeding industry, which can cause serious problems to the environment. Antibiotic pollution has become an important environmental issue. This study aimed to isolate and identify a well-functioning tetracycline-degrading bacteria strain from activated sludge and to investigate its optimum degradation conditions. The strain was identified through morphological features, Gram staining, and the sequence analysis of 16S rRNA. Furthermore, the temperature, initial pH of the medium, inoculation amount, and type of metallic salt were analyzed to investigate the tetracycline degradation performance of the isolated strain. Based on the single factor test, the method of response surface analysis was adopted to optimize the degradation condition. The strain was named TTC-1 and identified as Klebsiella pneumoniae. The optimum condition for tetracycline degradation was determined as follows: temperature of 34.4 °C, pH of 7.22, and MnSO4 concentration of 0.32 g/L. Under this optimum condition, the predicted tetracycline degradation rate was 93.77%, whereas the observed value was 94.26%. The experimental results showed that the proposed model had high accuracy. TTC-1 showed a good performance in degrading tetracycline, which can provide reference for the bacteria during the biological treatment of tetracycline containing wastewater. © 2018 Science Press. All rights reserved.     

A high-order well-balanced weighted compact nonlinear scheme for solving the pollutant transport model

Environmental Fluid Mechanics - Pollutant transport in flows may cause potential risk on the local ecological system and public health. Numerical prediction of pollutant transport driven by shallow...