Drought causes alterations in the abundance of fungi and bacteria in soil, which could affect community level microbial carbon use efficiency (CUE) and the capacity to store C in soil. We examined drought effects (implemented with rainout shelters) on microbial community composition, enzyme activity, and CUE during a dry summer and wet winter in a seminatural grassland in Australia. Drought caused small increases in CUE in both dry and wet seasons. However, CUE was much higher in the wet winter than in the dry summer. Seasonal variation in CUE were related to changes in microbial community composition where CUE was negatively associated with fungal abundance and fungi:bacteria ratio. Moreover, CUE was negatively related to β-glucosidase and peroxidase activity, suggesting that increased abundance of fungi that invest more C in the production of these enzymes resulted in the reduced CUE. Overall, our results suggest that seasonal variation in CUE could be driven by changes in microbial community composition, and that seasonal effects are larger than effects caused by drought in this grassland.

干旱导致土壤中真菌和细菌的丰度发生变化，这可能会影响社区一级的微生物碳利用效率（CUE）和在土壤中存储C的能力。在澳大利亚的半自然草原，在干燥的夏季和潮湿的冬季，我们研究了干旱（采用防雨棚）对微生物群落组成，酶活性和CUE的影响。在干旱和潮湿季节，干旱导致CUE略有增加。但是，在潮湿的冬季，CUE比干燥的夏季要高得多。CUE的季节性变化与微生物群落组成的变化有关，其中CUE与真菌的丰度和真菌：细菌的比率呈负相关。此外，CUE与β-葡萄糖苷酶和过氧化物酶活性呈负相关，这表明在这些酶的生产中投入更多C的真菌的丰度增加导致CUE降低。总体而言，我们的结果表明，CUE的季节变化可能是由微生物群落组成的变化驱动的，并且该季节的影响大于干旱造成的影响。