دانلود گزارش کارورزی و کار آموزی

چکیده : 

This study was conducted to investigate the dynamic changes of bulk soil and microbial populations inthe surrounding plant rhizosphere under the influence of chloride de-icing salt. Each experimental plantwas given 0.25 L de-icing salt solution with an irrigation concentration of 200 g/L, once every 3 days for27 days. Samples were taken weekly from each soil layers (0–15 cm, 15–30 cm and 30–45 cm). The resultsrevealed that de-icing salt led to different effects in different soil layers in one month. A trend of increas-ing electric conductivity (EC) values, Na+concentrations, and Cl−concentrations in the upper soil layer,compared with the other two soil layers, was apparent, which proved a stronger effect of de-icing salt onthe upper soil layer. Soil cation exchange capacity (CEC) decreased with the accumulation of the de-icingsalt. Denaturing gradient gel electrophoresis (DGGE) analysis indicated that de-icing salt decreased theShannon diversity (H) and Evenness (E) of fungal populations in three soil layers and led to a decrease ofbacterial H in the upper soil layers. However, a contrary trend for H and E of bacterial populations wasseen in the middle and lower soil layers. Both the unweighted pair group mean average (UPGMA) clus-ter and canonical correspondence analysis (CCA) analysis indicated that the bacterial populations weremore stable than the fungal populations in response to salinity stress. CCA analysis showed the dynamicchanges of microbial populations and the soil properties (EC, CEC, Na+and Cl−) were strongly correla-tive. The microbial populations were obtaining a new dynamic equilibrium at the end of the study. Thedominant microbial populations were originally Crepidotus, Metarhizium, Penicillium and Acidobacterium,but converted to Pythium, Boletaceae, Cystofilobasidiales, Phacidium, Acidobacterium, Pseudomonas andChloroflexi with the addition of de-icing salt. The obtained results suggest that the uses of chemicalagents leading to soil salinization, such as de-icing salt, can destroy the micro-ecosystem of bulk soilsurrounding plant rhizosphere and influence soil health.