The objective of this work was to compare estimates of microbial and biogeochemical processes obtained from year round versus field season only data. We also aimed to capture the response of soils to simultaneous warming and nitrogen fertilization in both winter and summer months. Our research took place at the chronic Soil Warming and Nitrogen Fertilization experiment at the Harvard Forest Long Term Ecological Research site. The experiment includes four treatments in a completely randomized design: control, +heat, +N, and +heat +N. Heated plots are warmed to 5°C above ambient using buried heating cables, and N fertilization consists of monthly additions of NH₄NO₃ in doses equivalent to a rate of 5 g N m^-2 y^-1. To date, year-round measurements of C and N fluxes and the soil microbial community show that soils were active during the winter months, and that our experimental manipulations impacted soils outside of the growing season. Across all treatments, CO₂ flux underneath snowpack in January 2008 was approximately 10% of CO₂ flux in July of 2007. Annual flux estimates corroborated this finding, and indicated that winter respiration contributed between 17-18% of the total annual flux. In addition, CO₂ respiration in +heat and +heat +N plots was significantly higher than the control treatment both in winter and in summer months. Like CO₂ respiration, N mineralization occurred during the colder months of 2007, though rates in November and December were about 5% of those during the summer maximum in June. Total annual net N mineralization was significantly higher in the +heat and +heat +N plots, though most of the difference in N turnover among treatments appeared to occur during the summer months. Like the C and N fluxes, microbial community function, as quantified by extracellular enzyme activity, also showed a seasonal pattern. Phenol peroxidase activity was highest in winter for all experimental manipulations, with the highest rates occurring when assays are incubated at 0°C as compared to 25°C. In contrast, β-glucosidase activity peaked in July and October, and showed higher rates of activity at 25°C than at 0°C. Measurements of microbial community composition as PLFA also showed seasonal differences. To date, PLFA estimates of fungal and bacterial biomass showed significantly higher F:B ratios in January as compared to April and July. Together, the CO₂ respiration, N mineralization, and microbial community data suggest that soils are active in winter, and that microbial community composition and function differ between winter and the growing season. In addition, soil warming can accelerate CO₂ flux outside of the typical field season. Failure to measure this processes after the field season ends could result in incorrect estimates of annual CO₂ flux, and could also underestimate the impact of exogenous disturbances on ecosystem function.