Notoginseng (Panax notoginseng), a valuable herbal medicine, has high death rates in continuous cropping systems. Variation in the soil microbial community is considered the primary cause of notoginseng mortality, although the taxa responsible for crop failure remains unidentified. This study used high-throughput sequencing methods to characterize changes in the microbial community and screen microbial taxa related to the death rate. Fungal diversity significantly decreased in soils cropped with notoginseng for three years. The death rate and the fungal diversity were significantly negatively correlated, suggesting that fungal diversity might be a potential bioindicator of soil health. Positive correlation coefficients revealed that Burkholderiales, Syntrophobacteraceae, Myrmecridium, Phaeosphaeria, Fusarium, and Phoma were better adapted to colonization of diseased plants. The relative abundance of Fusarium oxysporum (R = 0.841, P < 0.05) and Phaeosphaeria rousseliana (R = 0.830, P < 0.05) were positively associated with the death rate. F. oxysporum was a pathogen of notoginseng root-rot that caused seedling death. Negative correlation coefficients indicated that Thermogemmatisporaceae, Actinosynnemataceae, Hydnodontaceae, Herpotrichiellaceae, and Coniosporium might be antagonists of pathogens, and the relative abundance of Coniosporium perforans was negatively correlated with the death rate. Our findings provide a dynamic overview of the microbial community and present a clear scope for screening beneficial microbes and pathogens of notoginseng.

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a b s t r a c tConcentration-and flux-based O 3 doseeresponse relationships were developed for poplars in China. Stomatal conductance (g s ) of five poplar clones was measured to parameterize a Jarvis-type multiplicative g s model. The maximum g s and other model parameters varied between clones. The strongest relationship between stomatal O 3 flux and total biomass was obtained when phytotoxic ozone dose (POD) was integrated using an uptake rate threshold of 7 nmol m À2 s À1 . The R 2 value was similar between flux-based and concentration-based doseeresponse relationships. Ozone concentrations above 28 e36 nmol mol À1 contributed to reducing the biomass production of poplar. Critical levels of AOT 40 (accumulated O 3 exposure over 40 nmol mol À1 ) and POD 7 in relation to 5% reduction in total biomass for poplar were 12 mmol mol À1 h and 3.8 mmol m À2 , respectively.