Nitrogen mineralization characteristics of forest floor organic matter on slash-burned sites in coastal British Columbia

Nitrogen mineralization characteristics of the dominant types of organic matter in the forest floor of slash-burned sites were measured using a 26-week aerobic incubation. Six classes of forest floor material were distinguished on the basis of morphology and N mineralization characteristics. Fermentation layer materials, matted together with fungal hyphae, had a high content of total and potentially mineralizable N (N0) (7804 and 2816-mu-g/g, respectively) and mineralized the most N during incubation (1605-mu-g/g). Decayed wood had the lowest level of total N (1816-mu-g/g) and N0 (195-mu-g/g) and mineralized the least N (266-mu-g/g) despite a high inherent mineralization rate (k) (0.16). Humified materials (Hd and Hr) occupied a midrange, with the exception of those from thin residual horizons, which had high N0 values (2246-6009-mu-g/g) and low k-values (0.005-0.012). The significant differences in N mineralization among organic materials that are morphologically or ecologically distinct in the field suggest that it may be possible to assess site N fertility using intensive forest floor and soil survey data and information on the N characteristics of dominant horizon types.