A year round vegetation and soil emissions module based on the BEIS3 biogenic emissions model has been developed. The model is designed to be part of the traditional deposition module found in photochemical models. Several reasons exist for this new comprehensive canopy modeling approach. Many air pollutants such as ammonia and formaldehyde have compensation points, which require that the traditional deposition modeling approach based on resistances be modified to include a ‘capacitance’ to reflect a process of uptake and re-emission. A second reason is operational in nature, the same meteorological, canopy, and land use conditions that are experienced by deposition must also be experienced by the emission processes, including terms for pollutant and water stress. The cycling of ammonia in a northeastern deciduous (oak-maple) and a northeastern pine forest is examined during the course of a year. CCEDM predictions for several typical seasonal days are examined in detail against data from Hubbard Brook and Harvard forests.