Effects of Restoration Time on Microbial Diversity in Rhizosphere and Non-Rhizosphere Soil of Bothriochloaischaemum.

There is well-documented evidence that shows phytoremediation and restoration methods affect physical and chemical properties, enzyme activities, and microbial communities of soil. In this study, we investigated the response of soil microbial communities to restoration time. We found that arsenic content decreased gradually as restoration progressed. Total carbon (C) in shoots and total nitrogen (N) in roots of B. ischaemum both exhibited increasing trends with an increase in restoration time. The transfer factor of chromium was negatively correlated to C in shoots and positively correlated to sulfur in roots. Additionally, the transfer factor of lead had a remarkably positive correlation to the C/N ratio of roots. For soil enzymes, total N in soil was positively correlated to catalase and urease but negatively correlated to sucrose. Moreover, bulk soil bacterial composition was positively correlated to catalase, sucrase and phosphatase while fungal diversity was positively correlated to sucrose. This study found that restoration time plays the most significant role in bacterial and fungal composition and bacterial diversity, but it has no effect on fungal diversity in rhizosphere and non-rhizosphere soil. In addition, the driving factors of microbial composition and diversity varied in rhizosphere and non-rhizosphere soil among the different restoration time treatments.

[Characteristics of Soil Physicochemical Properties and Enzyme Activities over Different Reclaimed Years in a Copper Tailings Dam].

Mining for metal and mineral resources lead to the rapid rise of tailings dams and caused serious damage to the ecological environment of the mining area. Soil physicochemical characteristics and enzyme activities were important indexes for ecosystem functions, and they were also important factors in evaluating soil restoration qualities. We selected nine sub-dams of the Eighteen River copper tailings in Yuanqu County, and analyzed the relationship between soil physicochemical properties and soil enzyme activities. The results showed that there were great differences in soil physicochemical properties over different reclaimed years, and as the reclaimed years passed, soil nutrient contents significantly increased. There were significant negative correlations between catalase and the ratio of soil carbon and nitrogen, and urease was positively correlated to total nitrogen and soil moisture. Phosphatase and sucrose demonstrated no significant relationships with soil physicochemical factors. Copper content gradually accumulated in soil as the restoration period of sub-dams increased. Arsenic and cadmium content increased initially and then decreased before they gradually reached a stable level. In addition, there was no significant difference in zinc content among different sub-dams. Together, these results provide the ecological basis for further studies in soil ecosystem restoration and degradation mechanisms in copper tailings.

Ecological patterns and adaptability of bacterial communities in alkaline copper mine drainage.

Environmental gradient have strong effects on community assembly processes. In order to reveal the effects of alkaline mine drainage (AlkMD) on bacterial and denitrifying bacterial community compositions and diversity in tailings reservoir, here we conducted an experiment to examine all and core bacterial taxa and denitrifying functional genes's (nirS, nirK, nosZΙ) abundance along a chemical gradient in tailings water in Shibahe copper tailings in Zhongtiaoshan, China. Differences in bacterial and denitrifying bacterial community compositions in different habitats and their relationships with environmental parameters were analyzed. The results showed that the richness and diversity of bacterial community in downstream seeping water (SDSW) were the largest, while that in upstream tailings water (STW1) were the lowest. The diversity and abundance of bacterial communities tended to increase from STW1 to SDSW. The variation of bacterial community diversity was significantly related to electroconductibility (EC), nitrate (NO3-), nitrite (NO2-), total carbon (TC), inorganic carbon (IC) and sulfate (SO42-), but was not correlated with geographic distance in local scale. Core taxa from class to genus were all significantly related to NO3- and NO2-. Core taxa Rhodobacteraceae, Rhodobacter, Acinetobacter and Hydrogenophaga were typical denitrifying bacteria. The variation trends of these groups were consistent with the copy number of nirS, nirK and nosZΙ, demonstrating their importance in the process of nitrogen reduction. The copy number of nirK, nosZΙ and nirS/16S rDNA, nirK/16Sr DNA correlated strongly with NO3-, NO2- and IC, but nirS and nosZI/16SrDNA had no significant correlation with NO3- and NO2-. The copy numbers of denitrifying functional genes (nirS, nirK and nosZΙ) were negatively correlated with heavy metal plumbum (Pb) and zinc (Zn). It showed that heavy metal contamination was an important factor affecting the structure of denitrifying bacterial community in AlkMD. In this study we have identified the distribution pattern of bacterial community along physiochemical gradients in alkaline tailings reservoir and displayed the driving force of shaping the structure of bacterial community. The influence of NO3-, NO2-, IC and heavy metal Pb and Zn on bacterial community might via their influence on the functional groups involving nitrogen, carbon and metal metabolisms.