Effects of nitrogen and phosphorus addition on soil microbial community composition in temperate typical grassland in Inner Mongolia

Nitrogen and phosphorus addition is a main measure to improve plant growth and soil properties. However, little is known about the relationship between nitrogen and phosphorus addition and soil microbial community composition in temperate typical grassland in Inner Mongolia. In this paper, two single factor experiments were conducted respectively to investigate the influence of different nitrogen rates (0, 56, 112, 224, 392, 560 kg N hm^-2 a^-1) and different phosphorus rates (0, 15.5, 31, 62, 93, 124 kg P hm^-2 a^-1) addition on soil microbial community composition of temperate typical grassland in Xilinguole, Inner Mongolia, China. During the 6-year experimental period, increasing nitrogen rate increased the total numerical values of PLFA biomarker, actinomycete PLFA biomarker, bacteria PLFA biomarker, and the ratios of G⁺ / G^-, but did not have significant effect on the numerical values of fungal PLFA biomarker. Increasing nitrogen rate decreased the ratios of fungi/ bacteria. Total numerical values of PLFA biomarker, bacteria PLFA biomarker, actinomycete PLFA biomarker, fungi PLFA biomarker and fungi PLFA biomarker/ bacterial PLFA biomarker ratio had the highest values at the P3 (62 kg P hm^-2 a^-1)phosphorus addition treatment. The results indicated that nitrogen and phosphorus addition could greatly affect soil microbial community composition in temperate typical grassland.