Fire regimes of mixed conifer forests in the north-central Sierra Nevada at multiple spatial scales

Dendrochronology was used to quantify past fire regimes in mixed conifer forests in the north-central Sierra Nevada. Historic management activities, particularly railroad logging, severely limited the number of fire scar samples available. Fires were recorded between 1649 and 1921 and median point fire intervals, composite fire intervals at the 3-5 ha spatial scale, and composite fire intervals at the 9-15 ha spatial scale were 9-15, 6-14, and 5-10 yr. The seasonality of past fires in the north-central Sierra Nevada differs from that reported elsewhere, with the majority of fires occurring in latewood. There is a general trend of increasing latewood and growing season fires from the southern Cascades south to the southern Sierra Nevada. Superposed epoch analysis determined that widespread fires were significantly correlated to droughts the year of the fire, and in some cases, to a significantly wet year before the fire year. Fire return intervals are similar to those found in mixed conifer forests in the southern Cascades and southern Sierra Nevada but difference in the size of sampled areas complicates fire interval comparisons. In this study, we present fire statistics at several spatial scales and encourage others to do so. If all fire history research reported fire statistics at similar spatial scales it would allow for robust comparisons between diverse locations.