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• Forest structure recovered within 25 years after selective logging. • Fungi were found to be more susceptible than bacteria to forest conversion. • Fungi affected C-, N- and P-cycling, but bacteria only affected C-cycling. • Fungi may play a more important role in aboveground-belowground linkages during forest conversion compared with bacteria. Forest conversion can affect the diversity and community structure of soil bacteria and fungi. However, little is known about the impact of forest conversion on aboveground-belowground linkages and associated nutrient cycling. To address this research gap, we investigated the aboveground and belowground recovery, the specific responses of bacterial and fungal communities and the associated nutrient cycling in the conversion from artificial Chinese fir forests to broad-leaved conifer-mixed forests at 5-yr-, 10-yr- and 25-yr-old stands after selective logging. Bacterial and fungal community structures were analyzed using high-throughput sequencing of the 16S rRNA and ITS genes. Six microbial enzyme activities involved in the cycling of C, N and P were studied. Our results showed that the aboveground forest structure was recovering towards native evergreen broad-leaved forest after selective logging. The alpha-diversity of fungal community was significantly increased across the chronosequence of logging, but the alpha-diversity of bacterial community was not. Fungal community composition and structure changed during forest conversion, whereas the bacterial community showed slight changes in unique taxa. Neither bacterial nor fungal community structures changed towards the similar pattern as native evergreen broad-leaved forest across 25 years. These results indicated that fungi were more susceptible to forest conversion than bacteria. Furthermore, compared with bacteria, fungi were more strongly affected by soil properties, such as NH 4 +-N, pH, AK and TOC. Structural equation modeling indicated that fungi had strong impacts on C-, N- and P-cycling but that bacteria only affected C-cycling. Overall, the fungal community may play a more important role in the aboveground-belowground linkages and C-, N-, and P-cycling compared with the bacterial community during forest conversion. [ABSTRACT FROM AUTHOR]

• Prolonging the rotation of Eucalyptus plantations improve the soil quality. • Physicochemical properties and biological characteristics have interrelated relationships. • Bacterial and fungal community structure show diverse trends with forest age growth. • Microbial community structure could be a sensitive indicator of soil quality. Eucalyptus is widely cultivated in southern China as a short-rotation fast-growing species for timber production. However, this kind of business model has aroused widespread concern on soil quality. This study aimed to determine the cutting period of Eucalyptus plantation by comparing the effects of different cultivation years on soil quality. Four Eucalyptus stands, including 2-, 6-, 10-, and 15-year-old (abbreviated as 2 yr, 6 yr, 10 yr, and 15 yr, respectively) were used, and 25 soil physicochemical and biological indicators were determined. Results showed that the soil texture of the 10 yr and 15 yr plantations significantly improved. Soil organic matter, macronutrients, enzyme activity, and microbial biomass decreased significantly at 6 yr and then increased at 10 yr. However, the contents of available nutrients and the activities of urease and catalase decreased again at 15 yr. Redundancy analysis showed that the contents of total phosphorus, available phosphorus, available potassium, available zinc, and available calcium considerably influenced the soil bacterial community, whereas the contents of total nitrogen and available nitrogen greatly affected the fungal community. Meanwhile, pH and soil texture exerted a significant impact on microbial community structure. Bacterial diversity showed an increasing trend with the rotation period, whereas the fungal diversity ranked by 2 yr > 6 yr < 10 yr > 15 yr. The relative abundances of soil major microbial taxa were closely related to the soil physicochemical properties and were roughly similar to ecological strategy. These results suggest that cultivation period significantly affected the soil quality. Thus, we propose to extend the rotation period of Eucalyptus plantation to 10 yr. Extending the cultivation period to 10 yr significantly improved soil quality, but the available nutrients and enzyme activity of the 15 yr plantation showed a decreasing trend. Microbial community structure may be a sensitive indicator of soil quality in Eucalyptus plantations. [ABSTRACT FROM AUTHOR]