Response of soil micro-ecology to different levels of cadmium in alkaline soil.

Although the effect of heavy metal on soil microbial diversity was widely studied, the interaction among micro-ecological environment in heavy metal contaminated soil was less known. In this study, we systematically investigated the influence of cadmium (Cd) on soil micro-ecological environment (pH, nutrient content, soil enzyme activities, microbial biomass, bacterial and fungal diversities). Results showed that pH values slightly decreased with the Cd level increase, whereas the nutrient content including of Olsen-P (OSP), Alkeline-N (ALN), Olsen-K (OSK) and organic matter (OM) did not show significant difference in different treatments. In contrast to physicochemical properties, the biochemical qualities were easily influenced by Cd pollutant, resulting in soil microbial numbers and enzyme activities significantly decreased. High-throughput sequencing showed that microbial community composition was significantly affected by heavy metal. For bacteria, Actinobacteria abundance significantly decreased in Cd treated soil, corresponding to Proteobacteria and Firmicutes increased. For fungi, the most dominant phyla member (Ascomycota) was significantly decreased whereas Zygomycota significantly increased with Cd addition. These results further revealed the integral interrelation of micro-ecology environmental players under the stress of different Cd levels.