Although northern temperate forests are generally not considered phosphorus (P) limited, ecosystem P limitation may occur on highly weathered or strongly acidic soils where bioavailable inorganic P is low. In such environments, soil organisms may compensate by increasing the utilization of organic P via the production of extracellular enzymes to prevent limitation. In this study, we experimentally increased available P and/or pH in several acidic eastern deciduous forests underlain by glaciated and unglaciated soils in eastern Ohio, USA. We hypothesized that where inorganic P is low; soil microbes are able to access organic P by increasing production of phosphatase enzymes, thereby overcoming biogeochemical P limitations. We measured surface soil for: available P pools, N mineralization and nitrification rates, total C and N, enzymes responsible for C, N, and P hydrolysis, and microbial community composition (PLFA). Increasing surface soil pH a whole unit had little effect on microbial community composition, but increased N cycling rates in unglaciated soils. Phosphorus additions suppressed phosphatase activities over 60% in the unglaciated soils but were unchanged in the glaciated soils. All treatments had minimal influence on microbial biomass, but available pools of P strongly correlated with microbial composition. Microbes may be dependent on sources of organic P in some forest ecosystems and from a microbial perspective soil pH might be less important overall than P availability. Although our sampling was conducted less than 1 year after treatment initiation, microbial community composition was strongly influenced by available P pools and these effects may be greater than short-term increases in soil pH.