Responses of microbial community structure to land-use conversion and fertilization in southern China

• Land conversion from paddy to vegetables significantly increased soil fungal PLFAs.
• Fertilization significantly increased total PLFAs and bacterial PLFAs.
• Soil physicochemical properties were responsible for the microbial community changes.

A short-term experiment was carried out in southern China to investigate the effects of land-use conversion from rice paddies to vegetable fields and fertilization on soil microbial community structure by analyzing soil phospholipid fatty acid (PLFA) profiles. A split-plot design with four replicates was adopted, in which land use (paddy and vegetable field) was the first-level treatment and fertilization (conventional fertilization and no fertilization) was nested as the second level. Our results showed that both land-use conversion and fertilization had significant effects on microbial community structure. After 2 years of land-use conversion, the total amount of PLFAs were 3.54 and 2.97 nmol g−1 for fertilized (V–F) and unfertilized (V–NF) vegetable fields, respectively, and 3.19 and 2.32 nmol g−1 for fertilized (R–F) and unfertilized (R–NF) rice paddies, respectively. Soil fungal PLFAs were 1.04 and 0.87 nmol g−1 for V–F and V–NF, respectively, which were significantly increased by 13.9 and 11.4 times compared with those of R–F and R–NF, respectively. The ratio of fungal to bacterial PLFAs significantly increased in vegetable fields compared with rice paddies. No significant differences were found in the total, bacterial, and actinomycetic PLFAs between vegetable fields and rice paddies. The application of fertilizer significantly increased the amount of total PLFAs and bacterial PLFAs. With land-use conversion and fertilization, soil physicochemical properties also changed, and microbial community structure showed a significant relationship with soil water content, NH4+-N, and pH, which explained the land-use conversion and fertilization effects on soil microbial community composition.