Latitudinal gradient of fire return interval in conifer forests of western North America

ABSTRACT Mean fire interval (MFI) is the average time between successive fires, influenced by environmental factors such as latitude, elevation, and vegetation type. This study evaluated the relationship between MFI and latitude in conifer forests of western North America. First, we obtained pre-fire-disruption MFI data from dendrochronology-based fire history studies in western Canada, the United States, and Mexico montane ranges. Then, we used generalized additive models (GAMs) to evaluate the relationship between MFI and latitude, considering elevation and conifer forest type as covariables. In addition, we mapped the spatial mean fire intervals (SMFIs) through inverse distance weighting (IDW). MFI increased significantly at higher latitudes, influenced by elevation and conifer forest type (R2 = 0.7). Furthermore, we found longer MFI in high elevations of the Madrean Archipelago, the Rocky Mountains, and the Alaska Range. Fire frequency also decreased in the boreal, Douglas-fir, and subalpine forests, with MFI longer than 20 yr. Moreover, the shortest SMFIs were found in the Mexican sierras and the Madrean Archipelago, with fire intervals between 4.1 and 5.6 yr. Our results showed a latitudinal gradient of MFI in conifer forests of western North America, which provides valuable information for fire management and the restoration of natural fire regimes.