Notes: Significance levels of regression: ***p < 0.001, **p < 0.01, *p < 0.05, and †p < 0.1.
Compared to ignition source and fire weather, fuel composition and topography did not strongly impact tundra fire occurrence (Figure 2 a-b). Logistic regressions suggested that fractional covers of woody and herbaceous components were positively related to the fire occurrences (Table 1). Fires in the North Slope and the Seward Peninsula tended to occur in regions with more woody fuels. In contrast, those in Southwest Alaska show the opposite (Figure S6). Significantly higher coverage of nonvascular fuels was found when fires occurred in Southwest Alaska, while an inverse relationship existed for fires in the North Slope (Table S4). The significantly negative relationship between elevation fire occurrence (Table 1) also suggests that tundra fires are more common in flat areas.