Different influences of cadmium on soil microbial activity and structure with Chinese cabbage cultivated and non-cultivated

摘要

Purpose Cadmium (Cd) is a toxic heavy metal, accumulated in soil by anthropogenic activities and has serious effects on soil microbial activities in contaminated soils. Moreover, there is a lack of reliable data on the effects of Cd in the soil-plant system, since most of the information on Cd-microorganism interactions in soils are based on sewage sludge without plants. The main objective of this study was to assess the effects of Cd on soil microbial activities and community structure during growth of plant.rnMaterials and methods A greenhouse pot experiment was conducted to evaluate the impact of different concentrations of Cd on soil microbial activities during the growth of Chinese cabbage (Brassica chinensis) in two different soils. The field soils were used in this short-term (60 days) greenhouse pot experiment. The soils were spiked with different Cd concentrations, namely, 0, 1,3, 8, 15, 30 mgrnCd kg~(-1) oven dry soil, respectively. The experimental design was a 2 (soil) × 2 (vegetationon-vegetation) × 5 (treatments (Cd)) × 3 (replicate factorial experiment). After 60 days, the study was terminated and soils were analyzed for selected microbial parameters, such as, microbialrnbiomass carbon (C_(mic)), basal respiration and phospholipid fatty acids (PLFAs).rnResults and discussion Application of Cd at lower concentrations (1 and 3 mg kg~(-1)) resulted in a slight increase in C_(mic), whereas Cd concentrations >8 mg kg~(-1) caused an immediate significant decline in C_(mic), the ratio of C_(mic) to total organic C (C_(mic)/C_(mic)) decreased and the metabolic quotient (qCO_2, namely, the basal respiration CO_2/C_(mic)) increased with elevated Cd concentration. However, the impact on soil C_(mic) and basal respiration caused by Cd was dependent from plant cover or soil properties. The results of PLFAs showed relative increase in fatty acid indicators for fungi and actinomycetes and gradual increase in the ratio of Gram-positive to Gram-negative bacteria which were responsible for these differences with increasing Cd concentration in the planted and unplanted soils.rnConclusions Soil microbial parameters, including, soil C_(mic), the ratio of C_(mic)/C_(org), qCO_2, and community structure, may be sensitive indicators reflecting environmental stress in soil-Cd-plant system. However, further research work is needed for better understanding the changes in microbial community structure and actually impact on soil microbial community function.