Effects of phosphorus addition on soil microbial biomass and community composition in a subalpine spruce plantation

• P addition exerted the specific influences on soil microbial community composition.
• High level P addition increased soil microbial biomass via improving soil C availability and pH.
• Soil microbes were insensitive to the elevated P availability.

Phosphorus (P) availability is expected to affect soil microbial community. However, our knowledge about the responses of soil microbial biomass and community composition to P availability is still limited. In this study, we established field plots with addition of 0, 5 (LP), 15 (MP) and 30 (HP) g P m−2 yr−1 in a subalpine spruce plantation and investigated the responses of soil microbes. Chloroform fumigation-extraction and phospholipid fatty acids (PLFA) analysis were used to determine soil microbial biomass and community composition, respectively. After two growing seasons of P addition, the HP treatment significantly increased soil microbial biomass carbon, nitrogen and P. The P addition exerted the specific influences on soil microbial community composition. The abundance of most groups of soil microbial community (bacteria, fungi, and arbuscular mycorrhizal fungi) increased in the HP treatment and the ratio of fungi to bacteria decreased in the LP and MP treatment, whereas the nonmetric multidimensional scaling ordination revealed no significant difference in the PLFA pattern between the P treatments and the control. Although soil P availability increased in all P treatments compared to the control, the dissolved organic carbon, indicative of soil carbon availability, was promoted only by the HP treatment. Besides, soil microbial biomass was positively correlated to soil carbon availability and pH. These results indicate that soil microbes are insensitive to the elevated P availability in this spruce plantation and P addition increases soil microbial biomass mainly through improving carbon availability and pH.