Effects of plant species coexistence on soil enzyme activities and soil microbial community structure under Cd and Pb combined pollution.

The relationship between plant species coexistence and soil microbial communities under heavy metal pollution has attracted much attention in ecology. However, whether plant species coexistence could offset the impacts of heavy metal combined pollution on soil microbial community structure and soil enzymes activities is not well studied. The modified ecological dose model and PCR-RAPD method were used to assess the effects of two plant species coexistence on soil microbial community and enzymes activities subjected to Cd and Pb combined stress. The results indicated that monoculture and mixed culture would increased microbe populations under Cd and Pb combined stress, and the order of sensitivity of microbial community responding to heavy metal stress was: actinomycetes > bacteria > fungi. The respirations were significantly higher in planted soil than that in unplanted soil. The plant species coexistence could enhance soil enzyme activities under Cd and Pb combined. Furthermore, planted soil would be helpful to enhance soil genetic polymorphisms, but Cd and Pb pollution would cause a decrease on soil genetic polymorphisms. Mixed culture would increase the ecological dose 50% (EDs50) values, and the ED50 values for soil enzyme activities decreased with increasing culture time. The dehydrogenase was most sensitive to metal addition and easily loses activity under low dose of heavy metal. However, it was difficult to fully inhibit the phoshpatase activity, and urease responded similarly with phosphatase.

Spatial characteristics of soil enzyme activities and microbial community structure under different land uses in Chongming Island, China: geostatistical modelling and PCR-RAPD method.

Information about soil enzyme activity and soil DNA as indicators of how land use affects soil quality remains unknown for alluvial island. The purpose of this study was to investigate the effects of land use on enzyme activities and soil gene diversity in the Chongming Island, Shanghai, China, with the aim of providing further knowledge about the problems related to soil quality and its evolving spatial characteristic on the Chongming Island. The results indicate that land use causes an important change of organic matter, with either causing a small decrease or an increase in the absolute enzyme activity. With increased management intensity, there is an increase in the number of soils with high organic matter content and a decrease in the soils with low organic matter content. The effect on enzyme activity varies depending on the type of land use or management and the type of enzyme. The orders of the number of gene polymorphic bands under different land uses were as follows: agriculture soil>commercial soil>industrial soil>wetland. The complexities of the behaviors of the soil enzymes indicate that genetic analysis and biomarkers in conjunction with geostatistics method will be a powerful and accurate indicator to evaluate soil quality under land use.