摘要：A geographic information system (GIS) was used to analyze the effects of six physical variables (redwood sub-region, slope, aspect, elevation, distance from the coast, and moisture regime) on the natural fire rotation (NFR) of redwood ( Sequoia sempervirens ) forests between 1950 and 2003. NFR is defined as the years necessary for fires to burn over an area equal to that of the study area. This analysis relied on a spatial database of forest fire locations cataloged by California Department of Forestry and Fire Protection. The NFR for the California range of redwood forests was calculated as 778 years. The NFRs for north, central, and southern redwood sub-regions were 1,083, 717, and 551 years, respectively. The NFR of slope classes varied between 3,309 years for flat terrain and 423 years for steep slopes. The NFRs of north and south aspects were 796 years and 763 years, respectively. Elevation classes of 200 m illustrated a consistent decreasing trend in NFR values, 1,841 in the lowest elevation class and 53 years in the highest. Distance from the coast was classed in 5 km increments up to 50 km with NFR values of 648 years in the 5 km class and 1,148 years in the 50 km class. The NFRs of moisture regime classes were 1,183 years in the wettest class and 117 years for the driest class. Drier moisture regime classes were prevalent in the southern redwood range. The NFR calculated for redwood sub-regions, moisture regimes and elevation classes indicated that periodicity of fire in redwood stands decreased along a north-south, west-east gradient. The NFRs observed in these redwood variables substantiate results from previous work concerning the influence of a north-south, ocean-inland gradient on fire frequency in redwood forests.
