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Wildfire could result in dramatic changes to soil temperatures and environments, with immediate, short- or long-lasting impacts on soil microbes. However, relatively little research has documented how fire disturbance, soil depth, time variation and their interactions affect soil microbial communities in wet conditions. This study investigated a severe wildfire influenced on bacterial and fungal communities at four soil depths (0–5, 5–10, 10–15 and 15–20 cm) after two quarters (with similar precipitation and exactly during the rainy season). Soil sampling was conducted in a burned site relative to an undisturbed contiguous site in the North China artificial Pinus tabulaeformis forest. Results indicated that fire had significant effects on bacterial and fungal richness, diversity, composition and structure, including most impacts on the surface mineral soil (0–5 cm) within the first period post-fire and minor impacts on the subsoils (5–20 cm) up to the second period. The microbial richness and some dominant taxa in the undisturbed soils changed with time and depth, suggesting spatiotemporal variation in soil microbial communities although the effects of rainfall were weakened. These differences in microbes between burned and undisturbed soils were mainly driven by soil pH, whereas organic matter and available potassium mediated the distribution of microbial communities along depth and time, respectively. In addition, fungal community was more sensitive to fire and time than bacterial community but an opposite result was found in depth. Nevertheless, soil microbes showed some signs of adaptation to fire. This work advocate that non-intervention should be considered in the short term after a fire or low-intensity water replenishment in the case of aridity. • Fire could affect the microbes of subsoils within short-term recovery period. • Spatiotemporal variations were found in soil microbial communities. • Soil pH, OM and AK mediated microbes along fire, depth and time, respectively. • Fungi showed differential sensitivities to context compared with bacteria. • Soil microbes showed some signs of adaptation to fire. [ABSTRACT FROM AUTHOR]

Carbon source and influent COD/N (chemical oxygen demand: total nitrogen) pose distinct effects on nitrogen removal efficiency and microbial community structure of constructed wetlands. To investigate the interactive effect of carbon source with COD/N on nitrogen removal and microbial community structure in subsurface flow constructed wetlands, glucose (C 6 H 12 O 6) and sodium acetate (C 2 H 3 NaO 2) were used to determine five COD/N ratios in nine groups of constructed wetlands divided into glucose constructed wetlands and sodium acetate constructed wetlands. Results showed that efficiency in COD removal increased with COD/N, and peak value reached 92.7%. Interactive effect of carbon source with COD/N on system pH and ammonium removal was notably significant. Differences in ammonium removal performance between treatments were achieved by the variation of influent COD/N ratio and the change of system pH resulted from different carbon sources, and the result suggested that glucose was a better choice at high COD/N ratio. System microbial community structure was significantly affected by carbon source, influent COD/N ratio and their interaction. Microbial biomass in constructed wetlands significantly increased with increasing COD/N ratio. Higher density and diversity of fungus were observed in glucose constructed wetlands, particularly at COD/N ratio of 7 and 10. Evaluation of treatment ability of constructed wetlands (CWs) mainly focuses in effectivity in nitrogen removal. However, variation in carbon source (CS) and influent COD/N ratio significantly affect the nitrogen removal and systems microbial community structures. However, to date, simultaneous discussion of CS and COD/N ratio in CW system is limited, especially when the COD/N ratio is more than 15. Particularly, there have been no reports on the interaction between CS and COD/N ratio on nitrogen removal and microbial community structure in CWs using a comprehensive analysis involving two-way analysis of variance and principal component analysis. The main objective of this research was to investigate effects of carbon source (CS) and COD/N ratio on system performance, microbial community structure, and interaction between CS and COD/N ratio on nitrogen removal. Results showed that efficiency in COD removal increased with COD/N, and peak value reached 92.7%. Interactive effect of CS with COD/N on system pH and NH4+-N removal was notably significant. Differences in NH4+-N removal performance between treatments were achieved by the variation of influent COD/N ratio and the change of system pH resulted from different CSs, and the result suggested that glucose was a better choice at high COD/N ratio. System microbial community structure was significantly affected by CS, influent COD/N ratio and their interactions. Microbial biomass in CWs significantly increased with increasing COD/N ratio. Higher density and diversity of fungus were observed in GWs, particularly at COD/N ratio of 7 and 10. Image 1 • Interactive effect of carbon source with influent COD/N was notably significant. • Efficient NH 4 +-N removal achieved in glucose wetlands (GWs) at high COD/N. • COD removal rate for sodium acetate wetlands (YWs) was lower than GWs. • Richer fungi biomass and diversity was featured in YW biofilms than GWs. [ABSTRACT FROM AUTHOR]