A Study On English–chinese Translation Of Business Textbook Based On Newark's Text Typology Theory

Bio-available nitrogen in primary successional series is one of the key limitations for ecosystem development. N-fixing microorganisms often serve as early and abundant colonizers in these N-deficient terrestrial ecosystems and are tightly linked to the accumulation of soil N. Consequently, diazotrophic communities are a primary driving force for the improvement of substrate nutritional status and other physiochemical characteristics which facilitate recolonization of plants and other macroorganisms during later successional stages.Based on detailed ecological surveys and the landscape pattern, we selected the bare tailings (BT), algae crust (AC), moss/algae crust (AMC), moss crust (MC) and vegetated area (VEG) as succession series of copper mine tailings at Tongling, Anhui Province, P.R. China. An undisturbed off-site control area (CK) with good soil structure and high herbaceous diversity was chosen for comparison purpose.The abundance and diversity of N-fixing community along the succession series of mine tailings were determined using multiple molecular approaches including terminal restriction fragment length polymorphism (TRFLP), clone library analysis and real time quantitative PCR (qPCR) of the nifH gene. The main results were summarized as follows:1) In general, the diazotrophic diversity was lowest in BT, and there was an increase in the BSCs followed by a decrease in site VEG. Nitrogen-fixing microorganisms detected are mainly affiliated with the Proteobacteria and Cyanobacteria, with the former present in all series while the latter exclusively associated with the BSCs. It is likely that nitrogen-fixng Cyanobacteria are the dominant N suppliers in the BSCs, a crucial stage during the primary succession.2) Real-time PCR revealed that diazotrophs were abundant in the copper mine tailings. The nifH gene number ranged from 5.06×10~5(BT)to 3.47×10~8(CK)copies per gram of soil (dried weight).Variations in the nifH gene abundance showed a significant positive correlation with changes in soil C and N concentrations (p < 0.01) and a negative correlation with heavy metal (Cu and Zn) concentrations (p < 0.05). Overall, the number of nitrogen fixing bacteria increased with the progressing succession. This could be attributed to the new environmental niches and especially nutrient resources opened by the BSCs and plants in the later successional stages.3) Primary succession was a process with soil development. In newly unvegetated and nitrogen-deficient tailings, diazotrophs played an important role in accumulating soil N, which was indispensible for further recolonization of biological soil crusts (BSCs) and plants.This represents the first report using cultivation-independent molecular approaches to elucidate the diazotrophic diversity and community structure evolution associated with a successional series of mine tailings. Our findings could be of importance in developing ecological theory and restoration practice in mine tailings.