EVects of Wre frequency on oak litter decomposition and nitrogen dynamics

Abstract Fire can alter a multitude of ecosystem proper-ties that have the potential to aVect rates of litter decompo-sition and nitrogen dynamics. In this study, we examined the eVect of long-term variation in Wre frequency in Minne-sota oak savanna on rates of litter mass loss of a common tree species (Quercus ellipsoidalis) to determine how site and intraspeciWc litter characteristics impacted by variation in Wre frequency aVect rates of decomposition, litter N dynamics, and litter microbial biomass. Although an increase in Wre frequency resulted in higher litter tempera-tures, lower litter moisture, and decreased soil N and P availability, site characteristics had no net eVect on rates of mass loss. Rather, litter C:N ratio, which increased with increased Wre frequency, was the dominant predictor of rates of decomposition and litter N dynamics. Increased lit-ter C:N led to decreased rates of decomposition and N immobilization, regardless of the characteristics of the site of decomposition. Therefore, it is the indirect eVects of long-term variation in Wre frequency on litter characteristics rather than Wre’s direct eVects on site characteristics that determine Wre eVects on decomposition and N dynamics in this system. Slower rates of decomposition and increased N immobilization of litter produced in frequently burned sites may enhance Wre-induced N losses, further decelerating rates of N cycling in frequently burned sites