Effects Of Secondary Plants On Soil Microbial Community Structure And Metabolism In Xinjiang Earthquake Fault Zone

The aim of this study was to investigate the effects of secondary plants on Soil microbial community structure and metabolism in Xinjiang earthquake fault zone. The rhizosphere soils collected from 13 different secondary plants were studied by testing soil chemical properties and employing terminal restriction fragment length polymorphism (T-RFLP) and BIOLOG techniques. Unplanted soil in the same depth served as control. The investigated contents and results showed that:1. Soil pH, organic matter, total nitrogen, available nitrogen, available phosphorus and available potassium were measured according to the standard soil analysis methods (DB/6500 B11). The results showed that the soils were alkaline (pH=8.04-8.51), Analysis of variance(ANOVA) indicated that chemical properties of 13 rhizosphere soils were significantly different (p<0.05). The pH in most (9) rhizosphere soils were higher than control; soil nutrients among the different plants varied widely, the overall trend showed rhizosphere soil nutrients were higher than control, and soil nutrients contents in the rhizosphere of Achillea millefolium and Eremopyrum orientale were relatively high, while the one in Sabina pseudosabina were low. The results presumed that the vegetation restoration improved the soil nutrients in varying degrees.2. T-RLFP technique were used to study bacterial community structures in rhizosphere soil of secondary plants, we choosed universal primers 8F/1492R to amplify bacterial 16SrDNA, and Hhaâ… , Rsaâ… enzymes to digest. As a result, the different plants changed the composition of dominant bacterial groups in soil and increased the sorts of dominant bacterial groups. Achillea millefolium and Eremopyrum orientale had the most significant effects. Proteobacteria accounted for the largest proportion (49.55%) in the soil. Canonical correspondence analysis (CCA) showed that the distribution of dominant bacterial groups was negatively correlated with pH significantly (Hhaâ… digestion: r =- 0.82, p <0.001; Rsaâ… digestion: r =- 0.76, p <0.05). These results suggested that vegetation restoration increased soil bacterial diversity, and had influence on the structures of soil bacterial communities. The distribution of dominant bacterial groups was also related to soil pH.3. T-RLFP technique were used to study archaeal community structures in rhizosphere soil of secondary plants, we choosed universal primers 21F/958R to amplify archaeal 16SrDNA, and Hhaâ… , Rsaâ… e nzymes to digest. The results showed that archaea were found only in thoes rhizosphere soils of Salix vistita, Salix rectijulis, Eremopyrum orientale, Seriphidium nitrosum, Geranium sibiricum, Spiraea media, Galium verum and Rosa spinosissima. Results in the detection of archaea showed that the similarities of archaeal communities among different rhizosphere soils were low. Crenarchaeota and Euryarchaeota were the main groups. Canonical correspondence analysis (CCA) showed that the distribution of dominant archaeal groups was positively correlated with soil organic matter (Hhaâ… digestion: r = 0.94, p<0.001; Rsaâ… digestion: r = 0.74, p<0.05). Correlation analysis showed that soil available phosphorus content was positively correlated with all diversity indices of archaeal communities (p<0.05), and total nitrogen content showed a significant positive correlation (p<0.05) to the evenness index in Hhaâ… Digestion results. The results showed that the vegetation restoration can enrich archaea at 0-20 cm soil. Because of the differences of plants, archaeal community presented very differently. Soil organic matter and available phosphorus also affected the distribution of archaea.4. We selected 3 dominant secondary plants from each herbaceous and shrubs, and used BIOLOG technique to study microbial communities metabolic function. As a result, the average well color development(AWCD)of 6 rhizosphere samples were distinctly(p<0.05) different, and higher than control. Secondary plants had no significant(p>0.05) impact on richness of carbon source utilization, but changed the dominance and evenness (p<0.05). The principal component analysis (PCA) showed that the utilization of carbon sources were different among samples. Those differences were mainly attributed to the use of carbohydrates, amino acids and carboxylic acids. As appearance of plants, the types of carbon sources utilized by microorganisms were changed from phenol to carbohydrates and carboxylic acid. In addition, available potassium content in soil was negatively correlated with the use of polymers (-0.84) and amines(-0.83). These results suggested that the secondary plants can significantly enhance the ability of microorganisms to carbon source utilization, and change the types of carbon sources utilized by microorganisms. The utilization of some carbon sources were affected by available potassium content.