Effects of Heavy Metals on Phyllosphere and Rhizosphere Microbial Community of Bothriochloa ischaemum

Abstract

Copper mining has resulted in severe damage to the ecological environment of mining areas. This study investigated heavy metal distribution in plants and compared the driving factors between aboveground and subsurface microorganisms, as well as the diversity in rhizosphere and non-rhizosphere soil microbial community response to heavy metal transfer factors in a copper tailings dam. We analyzed phyllosphere and soil microbial community using high-throughput sequencing and denaturing gradient gel electrophoresis, respectively. Although we detected chromium in aboveground and subsurface of Bothriochloa ischaemum specimens, no chromium was detected in soil. Total nitrogen was negatively correlated to the carbon and nitrogen ratios of plants and soil, respectively, while the total sulfur was negatively correlated to cadmium in roots. On the contrary, soil sulfur was positively correlated to cadmium in soil. Moreover, soil sulphur was the main influencing factor on the soil bacterial community, while ammonium nitrogen, total nitrogen, and zinc were the driving factors of fungi diversity in non-rhizosphere soil. Fungi diversity in the rhizosphere was significantly correlated to phosphatase, and fungi diversity in the non-rhizosphere was significantly correlated to sucrose enzymes. The transfer factor of lead was negatively correlated to rhizosphere fungi diversity, and the transfer factor of copper was significantly correlated to non-rhizosphere bacterial diversity. Results from this study may offer some scientific reference for the improvement of plant-microbe remediation efficiency. At the same time, this study could provide an ecological basis for further studies on soil ecosystem restoration and degradation mechanisms that are associated with copper tailings dams.