In grasslands, the interactions of foliar fungal diseases and their host plants are largely dependent on grazing by large herbivores. However, the relative importance of direct (i.e. pathogen removal) and indirect effects (i.e. via changes in plant community composition) of long‐term grazing on foliar fungal diseases remains largely unexplored, especially under varied grazing intensities. We conducted a 13‐year experiment to explore the effects of grazing intensity on foliar fungal diseases at both plant population and community levels in a semi‐arid grassland. We quantified the contributions of direct and indirect effects of long‐term grazing on community pathogen load. At the population level, the severity of five rusts and five powdery mildews decreased significantly as grazing intensity increased, whereas two leaf spots increased significantly in severity with increasing grazing intensity. Similarly, at the community level, the pathogen load of rusts and powdery mildews was negatively related to the increase in grazing intensity, whereas the pathogen load of leaf spots was positively related to grazing intensity. Overall, heavy grazing (i.e. 8.7 sheep/ha) significantly increased community pathogen load. Our SEM analysis showed that grazing indirectly increased the pathogen load of leaf spots by increasing disease proneness. Grazing decreased the pathogen load of rusts, but this could not be explained by changes in disease proneness. Overall, the indirect effects via changes in community composition of hosts resulting in the increase in community disease proneness outweighed the direct effect of grazing on community pathogen load. Synthesis and applications. Our study provides the first evidence that long‐term heavy grazing can indirectly increase community pathogen load by increasing the abundances of grazing‐tolerant hosts and decreasing the abundances of grazing‐intolerant hosts. These results provide empirical evidence that the pathogen load of foliar fungal diseases in grasslands can depend on the community context of hosts, which can, in turn, be controlled by large herbivores. We recommend that infectious diseases are considered when predicting the responses of grassland ecosystems to anthropogenic activities. Maintaining light to moderate grazing intensity or establishing an appropriate non‐grazing period could be an effective way to control foliar fungal diseases in grasslands.

Lespedeza davurica (Laxm.) is highly important for reducing soil erosion and maintaining the distinctive natural scenery of semiarid grasslands in northwest China. In this study, a pot experiment was conducted to investigate the effects of drought (20% water-holding capacity) on biomass and its allocation, root characteristics, plant hormones, and soil microbial communities and nutrients after L. davurica was grown in a greenhouse. Drought reduced the total biomass of L. davurica but increased the root:shoot biomass ratio. In addition, drought altered the composition and structure of microbial communities by limiting the mobility of nutrients in non-rhizosphere soils. In particular, drought increased the relative abundances of Basidiomycota, Acidobacteria, Actinobacteria, Coprinellus, Humicola and Rubrobacter, which were closely positively related to the soil organic carbon, pH, available phosphorus, ammonia nitrogen (N) and nitrate N under drought conditions. Furthermore, soil fungi could play a more potentially significant role than that of bacteria in the response of L. davurica to drought. Consequently, our study uncovered the effects of drought on the growth of L. davurica by altering soil microbial communities and/or soil nutrients, thus providing new insights for forage production and natural grassland restoration on the Loess Plateau of China.

The influence of antibiotic administration on the airway microbiota of healthy adults remains unknown. This study is a randomized, double-blind, placebo-controlled trial aiming to investigate the microbial shifts in airways after exposure to azithromycin among heathy adults.

Background Azithromycin, widely used in recent years, can change the airway microbiota in patients with chronic lung diseases. Little data exists regarding the effects of azithromycin administration on airway microbiota among healthy adults. Therefore, we conducted a randomized, double-blind, placebo-controlled trial to assess the process of variation and re-establishment of the airway microbiota after azithromycin exposure in healthy adults. Methods Forty-eight healthy volunteers were enrolled and randomly assigned into two groups. 500mg azithromycin or placebo was administered once daily for 3 days. We collected the induced sputum at the day before the drugs administration (D0), the day after the treatment course was completed (D4), 14 days, 30 days and 60 days post-dosing. 16S rRNA gene sequencing and quantification were applied to the induced sputum samples. We collected the environmental information including air quality data [particulate matter (PM 2.5 ) and PM 10 , air quality index (AQI) values] that might have an influence on the airway microbiota during the study. The subjects’ respiratory tract infection (RTI) events during sampling were recorded. Results Azithromycin didn’t alter bacterial load but significantly reduced species richness and Shannon index. Azithromycin exposure resulted in decrease in the detection rate and relative abundance of different families belonging to Veillonellaceae , Pasteurellaceae , Leptotrichiaceae , Neisseriaceae and Fusobacteriaceae . By contrast, the relative abundance of taxa belonging to Streptococcus increased immediately after azithromycin intervention. The shifts in the microbial community composition require about 14 days to recover while alpha-diversity recovered later. The high concentration of PM 2.5 contributed to a novel variability in microbial community composition of azithromycin group at D30 (30 days after baseline). The network analysis found that azithromycin altered the microbial interactions within airway microbiota. The influence was still obvious at D14 when the relative abundance of most taxa had returned to the baseline level. Conclusions Azithromycin has transient effect in airway microbiota of healthy adults and decreases the ability of the airway microbiota resilient from PM 2.5 stress. The influence of azithromycin on microbial interactions is noteworthy though the airway microbiota has returned to the near-baseline level.